From adfa0288ce22a01c1cfe3220cb4713638357ff68 Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Mon, 28 Sep 2015 16:54:48 +0700
Subject: [PATCH] Update all geometry.xml files to use 'region'

---
 examples/xml/basic/geometry.xml               |  6 +-
 examples/xml/lattice/nested/geometry.xml      | 16 ++--
 examples/xml/lattice/simple/geometry.xml      | 14 ++--
 examples/xml/pincell/geometry.xml             |  8 +-
 tests/test_basic/geometry.xml                 |  2 +-
 tests/test_confidence_intervals/geometry.xml  |  2 +-
 tests/test_density_atombcm/geometry.xml       |  2 +-
 tests/test_density_atomcm3/geometry.xml       |  2 +-
 tests/test_density_kgm3/geometry.xml          |  2 +-
 tests/test_density_sum/geometry.xml           |  2 +-
 .../test_eigenvalue_genperbatch/geometry.xml  |  2 +-
 .../test_eigenvalue_no_inactive/geometry.xml  |  2 +-
 tests/test_energy_grid/geometry.xml           |  2 +-
 tests/test_entropy/geometry.xml               |  2 +-
 tests/test_filter_cell/geometry.xml           | 56 ++++++-------
 tests/test_filter_cellborn/geometry.xml       | 56 ++++++-------
 .../case-1/geometry.xml                       |  6 +-
 .../case-2/geometry.xml                       | 18 ++---
 .../case-3/geometry.xml                       | 56 ++++++-------
 .../case-4/geometry.xml                       |  8 +-
 tests/test_filter_energy/geometry.xml         | 56 ++++++-------
 tests/test_filter_energyout/geometry.xml      | 56 ++++++-------
 tests/test_filter_group_transfer/geometry.xml | 56 ++++++-------
 tests/test_filter_material/geometry.xml       | 56 ++++++-------
 tests/test_filter_mesh_2d/geometry.xml        | 56 ++++++-------
 tests/test_filter_mesh_3d/geometry.xml        | 56 ++++++-------
 tests/test_filter_universe/geometry.xml       | 56 ++++++-------
 tests/test_fixed_source/geometry.xml          |  2 +-
 tests/test_infinite_cell/geometry.xml         |  4 +-
 tests/test_lattice/geometry.xml               | 72 ++++++++---------
 tests/test_lattice_hex/geometry.xml           | 28 +++----
 tests/test_lattice_mixed/geometry.xml         | 28 +++----
 tests/test_lattice_multiple/geometry.xml      | 56 ++++++-------
 tests/test_many_scores/geometry.xml           | 56 ++++++-------
 tests/test_natural_element/geometry.xml       | 66 +++++++--------
 tests/test_output/geometry.xml                |  2 +-
 .../test_particle_restart_eigval/geometry.xml |  2 +-
 .../test_particle_restart_fixed/geometry.xml  |  2 +-
 tests/test_plot_background/geometry.xml       |  2 +-
 tests/test_plot_basis/geometry.xml            |  6 +-
 tests/test_plot_colspec/geometry.xml          |  2 +-
 tests/test_plot_mask/geometry.xml             |  6 +-
 tests/test_ptables_off/geometry.xml           |  2 +-
 tests/test_reflective_cone/geometry.xml       |  2 +-
 tests/test_reflective_cylinder/geometry.xml   |  2 +-
 tests/test_reflective_plane/geometry.xml      |  2 +-
 tests/test_reflective_sphere/geometry.xml     |  2 +-
 tests/test_resonance_scattering/geometry.xml  |  2 +-
 tests/test_rotation/geometry.xml              |  4 +-
 tests/test_salphabeta/geometry.xml            |  6 +-
 tests/test_salphabeta_multiple/geometry.xml   | 66 +++++++--------
 tests/test_score_MT/geometry.xml              | 56 ++++++-------
 tests/test_score_absorption/geometry.xml      | 56 ++++++-------
 tests/test_score_current/geometry.xml         | 56 ++++++-------
 tests/test_score_events/geometry.xml          | 56 ++++++-------
 tests/test_score_fission/geometry.xml         | 56 ++++++-------
 tests/test_score_flux/geometry.xml            | 56 ++++++-------
 tests/test_score_flux_yn/geometry.xml         | 56 ++++++-------
 tests/test_score_kappafission/geometry.xml    | 56 ++++++-------
 tests/test_score_nufission/geometry.xml       | 56 ++++++-------
 tests/test_score_nuscatter/geometry.xml       | 56 ++++++-------
 tests/test_score_nuscatter_n/geometry.xml     | 56 ++++++-------
 tests/test_score_nuscatter_pn/geometry.xml    | 56 ++++++-------
 tests/test_score_nuscatter_yn/geometry.xml    | 56 ++++++-------
 tests/test_score_scatter/geometry.xml         | 56 ++++++-------
 tests/test_score_scatter_n/geometry.xml       | 56 ++++++-------
 tests/test_score_scatter_pn/geometry.xml      | 56 ++++++-------
 tests/test_score_scatter_yn/geometry.xml      | 56 ++++++-------
 tests/test_score_total/geometry.xml           | 56 ++++++-------
 tests/test_score_total_yn/geometry.xml        | 56 ++++++-------
 tests/test_seed/geometry.xml                  |  2 +-
 tests/test_source_angle_mono/geometry.xml     |  2 +-
 tests/test_source_energy_maxwell/geometry.xml |  2 +-
 tests/test_source_energy_mono/geometry.xml    |  2 +-
 tests/test_source_file/geometry.xml           |  2 +-
 tests/test_source_point/geometry.xml          |  2 +-
 tests/test_sourcepoint_batch/geometry.xml     |  2 +-
 tests/test_sourcepoint_interval/geometry.xml  |  2 +-
 tests/test_sourcepoint_latest/geometry.xml    |  2 +-
 tests/test_sourcepoint_restart/geometry.xml   |  2 +-
 tests/test_statepoint_batch/geometry.xml      |  2 +-
 tests/test_statepoint_interval/geometry.xml   |  2 +-
 tests/test_statepoint_restart/geometry.xml    |  2 +-
 tests/test_statepoint_sourcesep/geometry.xml  |  2 +-
 tests/test_survival_biasing/geometry.xml      |  2 +-
 tests/test_tally_assumesep/geometry.xml       | 56 ++++++-------
 tests/test_tally_nuclides/geometry.xml        |  4 +-
 tests/test_trace/geometry.xml                 |  2 +-
 tests/test_track_output/geometry.xml          | 80 +++++++++----------
 tests/test_translation/geometry.xml           |  4 +-
 .../test_trigger_batch_interval/geometry.xml  |  4 +-
 .../geometry.xml                              |  4 +-
 tests/test_trigger_no_status/geometry.xml     |  4 +-
 tests/test_trigger_tallies/geometry.xml       |  4 +-
 tests/test_uniform_fs/geometry.xml            |  2 +-
 tests/test_union_energy_grids/geometry.xml    |  2 +-
 tests/test_universe/geometry.xml              |  4 +-
 tests/test_void/geometry.xml                  | 30 +++----
 98 files changed, 1186 insertions(+), 1186 deletions(-)

diff --git a/examples/xml/basic/geometry.xml b/examples/xml/basic/geometry.xml
index e9483306c..b7de2c134 100644
--- a/examples/xml/basic/geometry.xml
+++ b/examples/xml/basic/geometry.xml
@@ -2,9 +2,9 @@
 <geometry>
 
   <!-- Definition of Cells -->
-  <cell id="1" universe="0" fill="37" surfaces="-2" />
-  <cell id="100" universe="37" material="40" surfaces="-1" />
-  <cell id="101" universe="37" material="41" surfaces="1" />
+  <cell id="1" universe="0" fill="37" region="-2" />
+  <cell id="100" universe="37" material="40" region="-1" />
+  <cell id="101" universe="37" material="41" region="1" />
   <cell id="2" universe="0" material="41" surfaces = "2 -3" />
 
   <!-- Defition of Surfaces -->
diff --git a/examples/xml/lattice/nested/geometry.xml b/examples/xml/lattice/nested/geometry.xml
index 9df9b9e93..324f71cb3 100644
--- a/examples/xml/lattice/nested/geometry.xml
+++ b/examples/xml/lattice/nested/geometry.xml
@@ -1,14 +1,14 @@
 <?xml version="1.0"?>
 <geometry>
 
-  <cell id="1"                fill="6" surfaces="1 -2 3 -4" />
-  <cell id="2"   universe="5" fill="4" surfaces="1 -2 3 -4" />
-  <cell id="101" universe="1" material="1" surfaces="-5" />
-  <cell id="102" universe="1" material="2" surfaces="5" />
-  <cell id="201" universe="2" material="1" surfaces="-6" />
-  <cell id="202" universe="2" material="2" surfaces="6" />
-  <cell id="301" universe="3" material="1" surfaces="-7" />
-  <cell id="302" universe="3" material="2" surfaces="7" />
+  <cell id="1"                fill="6" region="1 -2 3 -4" />
+  <cell id="2"   universe="5" fill="4" region="1 -2 3 -4" />
+  <cell id="101" universe="1" material="1" region="-5" />
+  <cell id="102" universe="1" material="2" region="5" />
+  <cell id="201" universe="2" material="1" region="-6" />
+  <cell id="202" universe="2" material="2" region="6" />
+  <cell id="301" universe="3" material="1" region="-7" />
+  <cell id="302" universe="3" material="2" region="7" />
 
   <!-- 4 x 4 assembly -->
   <lattice id="4">
diff --git a/examples/xml/lattice/simple/geometry.xml b/examples/xml/lattice/simple/geometry.xml
index c1f8d7864..bda7246c7 100644
--- a/examples/xml/lattice/simple/geometry.xml
+++ b/examples/xml/lattice/simple/geometry.xml
@@ -1,13 +1,13 @@
 <?xml version="1.0"?>
 <geometry>
 
-  <cell id="1" fill="5" surfaces="1 -2 3 -4" />
-  <cell id="101" universe="1" material="1" surfaces="-5" />
-  <cell id="102" universe="1" material="2" surfaces="5" />
-  <cell id="201" universe="2" material="1" surfaces="-6" />
-  <cell id="202" universe="2" material="2" surfaces="6" />
-  <cell id="301" universe="3" material="1" surfaces="-7" />
-  <cell id="302" universe="3" material="2" surfaces="7" />
+  <cell id="1" fill="5" region="1 -2 3 -4" />
+  <cell id="101" universe="1" material="1" region="-5" />
+  <cell id="102" universe="1" material="2" region="5" />
+  <cell id="201" universe="2" material="1" region="-6" />
+  <cell id="202" universe="2" material="2" region="6" />
+  <cell id="301" universe="3" material="1" region="-7" />
+  <cell id="302" universe="3" material="2" region="7" />
 
   <lattice id="5">
     <dimension>4 4</dimension>
diff --git a/examples/xml/pincell/geometry.xml b/examples/xml/pincell/geometry.xml
index 53cb2f15d..f67f9e74c 100644
--- a/examples/xml/pincell/geometry.xml
+++ b/examples/xml/pincell/geometry.xml
@@ -19,9 +19,9 @@
   <surface id="6" type="y-plane" coeffs="-0.62992" boundary="reflective" />
   <surface id="7" type="y-plane" coeffs=" 0.62992" boundary="reflective" />
 
-  <cell id="1" material="1" surfaces="  -1" />        <!-- UO2 Fuel -->
-  <cell id="2" material="2" surfaces="1 -2" />        <!-- Helium gap -->
-  <cell id="3" material="3" surfaces="2 -3" />        <!-- Zircaloy cladding -->
-  <cell id="4" material="4" surfaces="3 4 -5 6 -7" /> <!-- Borated water -->
+  <cell id="1" material="1" region="  -1" />        <!-- UO2 Fuel -->
+  <cell id="2" material="2" region="1 -2" />        <!-- Helium gap -->
+  <cell id="3" material="3" region="2 -3" />        <!-- Zircaloy cladding -->
+  <cell id="4" material="4" region="3 4 -5 6 -7" /> <!-- Borated water -->
 
 </geometry>
diff --git a/tests/test_basic/geometry.xml b/tests/test_basic/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_basic/geometry.xml
+++ b/tests/test_basic/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_confidence_intervals/geometry.xml b/tests/test_confidence_intervals/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_confidence_intervals/geometry.xml
+++ b/tests/test_confidence_intervals/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_density_atombcm/geometry.xml b/tests/test_density_atombcm/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_density_atombcm/geometry.xml
+++ b/tests/test_density_atombcm/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_density_atomcm3/geometry.xml b/tests/test_density_atomcm3/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_density_atomcm3/geometry.xml
+++ b/tests/test_density_atomcm3/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_density_kgm3/geometry.xml b/tests/test_density_kgm3/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_density_kgm3/geometry.xml
+++ b/tests/test_density_kgm3/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_density_sum/geometry.xml b/tests/test_density_sum/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_density_sum/geometry.xml
+++ b/tests/test_density_sum/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_eigenvalue_genperbatch/geometry.xml b/tests/test_eigenvalue_genperbatch/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_eigenvalue_genperbatch/geometry.xml
+++ b/tests/test_eigenvalue_genperbatch/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_eigenvalue_no_inactive/geometry.xml b/tests/test_eigenvalue_no_inactive/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_eigenvalue_no_inactive/geometry.xml
+++ b/tests/test_eigenvalue_no_inactive/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_energy_grid/geometry.xml b/tests/test_energy_grid/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_energy_grid/geometry.xml
+++ b/tests/test_energy_grid/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_entropy/geometry.xml b/tests/test_entropy/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_entropy/geometry.xml
+++ b/tests/test_entropy/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_filter_cell/geometry.xml b/tests/test_filter_cell/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_filter_cell/geometry.xml
+++ b/tests/test_filter_cell/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_filter_cellborn/geometry.xml b/tests/test_filter_cellborn/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_filter_cellborn/geometry.xml
+++ b/tests/test_filter_cellborn/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_filter_distribcell/case-1/geometry.xml b/tests/test_filter_distribcell/case-1/geometry.xml
index 507559615..34e636e9f 100644
--- a/tests/test_filter_distribcell/case-1/geometry.xml
+++ b/tests/test_filter_distribcell/case-1/geometry.xml
@@ -1,9 +1,9 @@
 <?xml version="1.0"?>
 <geometry>
 
-  <cell id="1" fill="5" surfaces="1 -2 3 -4" />
-  <cell id="201" universe="2" material="1" surfaces="-5" />
-  <cell id="202" universe="2" material="2" surfaces="5" />
+  <cell id="1" fill="5" region="1 -2 3 -4" />
+  <cell id="201" universe="2" material="1" region="-5" />
+  <cell id="202" universe="2" material="2" region="5" />
   <cell id="301" universe="3" material="2"/>
 
   <lattice id="5">
diff --git a/tests/test_filter_distribcell/case-2/geometry.xml b/tests/test_filter_distribcell/case-2/geometry.xml
index b6797d65d..e3aeedd64 100644
--- a/tests/test_filter_distribcell/case-2/geometry.xml
+++ b/tests/test_filter_distribcell/case-2/geometry.xml
@@ -1,15 +1,15 @@
 <?xml version="1.0"?>
 <geometry>
 
-  <cell id="1" fill="5" surfaces="1 -2 3 -4" />
-  <cell id="201" universe="21" material="1" surfaces="-5" />
-  <cell id="202" universe="21" material="2" surfaces="5" />
-  <cell id="203" universe="22" material="1" surfaces="-5" />
-  <cell id="204" universe="22" material="2" surfaces="5" />
-  <cell id="205" universe="23" material="1" surfaces="-5" />
-  <cell id="206" universe="23" material="2" surfaces="5" />
-  <cell id="207" universe="20" material="1" surfaces="-5" />
-  <cell id="208" universe="20" material="2" surfaces="5" />
+  <cell id="1" fill="5" region="1 -2 3 -4" />
+  <cell id="201" universe="21" material="1" region="-5" />
+  <cell id="202" universe="21" material="2" region="5" />
+  <cell id="203" universe="22" material="1" region="-5" />
+  <cell id="204" universe="22" material="2" region="5" />
+  <cell id="205" universe="23" material="1" region="-5" />
+  <cell id="206" universe="23" material="2" region="5" />
+  <cell id="207" universe="20" material="1" region="-5" />
+  <cell id="208" universe="20" material="2" region="5" />
 
   <lattice id="5">
     <dimension>2 2</dimension>
diff --git a/tests/test_filter_distribcell/case-3/geometry.xml b/tests/test_filter_distribcell/case-3/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_filter_distribcell/case-3/geometry.xml
+++ b/tests/test_filter_distribcell/case-3/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_filter_distribcell/case-4/geometry.xml b/tests/test_filter_distribcell/case-4/geometry.xml
index 4c2a7fd5e..c835218bc 100644
--- a/tests/test_filter_distribcell/case-4/geometry.xml
+++ b/tests/test_filter_distribcell/case-4/geometry.xml
@@ -1,9 +1,9 @@
 <?xml version='1.0' encoding='utf-8'?>
 <geometry>
-    <cell fill="5" id="1" name="Cell 1" surfaces="1 -2 3 -4" universe="0" />
-<cell id="101" material="1" name="cell 2" surfaces="-5" universe="1" />
-<cell id="102" material="2" name="cell 3" surfaces="5" universe="1" />
-<cell id="500" material="2" name="cell 4" surfaces="" universe="3" />
+    <cell fill="5" id="1" name="Cell 1" region="1 -2 3 -4" universe="0" />
+<cell id="101" material="1" name="cell 2" region="-5" universe="1" />
+<cell id="102" material="2" name="cell 3" region="5" universe="1" />
+<cell id="500" material="2" name="cell 4" region="" universe="3" />
 <hex_lattice id="5" n_rings="2">
         <pitch>1.0</pitch>
     <outer>3</outer>
diff --git a/tests/test_filter_energy/geometry.xml b/tests/test_filter_energy/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_filter_energy/geometry.xml
+++ b/tests/test_filter_energy/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_filter_energyout/geometry.xml b/tests/test_filter_energyout/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_filter_energyout/geometry.xml
+++ b/tests/test_filter_energyout/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_filter_group_transfer/geometry.xml b/tests/test_filter_group_transfer/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_filter_group_transfer/geometry.xml
+++ b/tests/test_filter_group_transfer/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_filter_material/geometry.xml b/tests/test_filter_material/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_filter_material/geometry.xml
+++ b/tests/test_filter_material/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_filter_mesh_2d/geometry.xml b/tests/test_filter_mesh_2d/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_filter_mesh_2d/geometry.xml
+++ b/tests/test_filter_mesh_2d/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_filter_mesh_3d/geometry.xml b/tests/test_filter_mesh_3d/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_filter_mesh_3d/geometry.xml
+++ b/tests/test_filter_mesh_3d/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_filter_universe/geometry.xml b/tests/test_filter_universe/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_filter_universe/geometry.xml
+++ b/tests/test_filter_universe/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_fixed_source/geometry.xml b/tests/test_fixed_source/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_fixed_source/geometry.xml
+++ b/tests/test_fixed_source/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_infinite_cell/geometry.xml b/tests/test_infinite_cell/geometry.xml
index e3f63354c..90bd2233b 100644
--- a/tests/test_infinite_cell/geometry.xml
+++ b/tests/test_infinite_cell/geometry.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0"?>
 <geometry>
   <cell id="11" universe="11" material="1"/>
-  <cell id="12" universe="12" material="2" surfaces=""/>
+  <cell id="12" universe="12" material="2" region=""/>
 
   <lattice id="21" dimension="2 2" lower_left="-2.0 -2.0"
     pitch="2.0 2.0" outer="12">
@@ -13,5 +13,5 @@
 
 
   <surface id="101" type="z-cylinder" coeffs="0.0 0.0 5.0" boundary="vacuum"/>
-  <cell id="101" universe="0" fill="21" surfaces="-101"/>
+  <cell id="101" universe="0" fill="21" region="-101"/>
 </geometry>
diff --git a/tests/test_lattice/geometry.xml b/tests/test_lattice/geometry.xml
index 89af5f196..809cd6fbb 100644
--- a/tests/test_lattice/geometry.xml
+++ b/tests/test_lattice/geometry.xml
@@ -40,11 +40,11 @@
 
 
   <!-- overall geometry -->
-  <cell id="1" material="4" surfaces="21 23 -25 1   -2" /> <!-- Bottom and Top Refl -->
-  <cell id="2" material="5" surfaces="21 23 -25 2   -4" /> <!-- Aluminum Plate -->
-  <cell id="3" fill="11"    surfaces="21 23 -25 4  -12" /> <!-- Core Lattice -->
-  <cell id="4" material="6" surfaces="21 23 -25 12 -14" /> <!-- Lead Shield -->
-  <cell id="5" material="4" surfaces="21 23 -25 14 -15" /> <!-- Bottom and Top Refl -->
+  <cell id="1" material="4" region="21 23 -25 1   -2" /> <!-- Bottom and Top Refl -->
+  <cell id="2" material="5" region="21 23 -25 2   -4" /> <!-- Aluminum Plate -->
+  <cell id="3" fill="11"    region="21 23 -25 4  -12" /> <!-- Core Lattice -->
+  <cell id="4" material="6" region="21 23 -25 12 -14" /> <!-- Lead Shield -->
+  <cell id="5" material="4" region="21 23 -25 14 -15" /> <!-- Bottom and Top Refl -->
 
   <!-- Cube cell filled Fuel -->
   <lattice id="11">
@@ -85,38 +85,38 @@
   </lattice>
 
   <!-- fuel cell universe -->
-  <cell id="21" universe="1" material="3" surfaces="-6     -36" />                 <!-- Bottom Clad -->
-  <cell id="22" universe="1" material="2" surfaces=" 6  -7 -35" />                 <!-- UO2 layer -->
-  <cell id="23" universe="1" material="1" surfaces=" 7 -11 -35" />                 <!-- MOX -->
-  <cell id="24" universe="1" material="3" surfaces=" 6 -11  35 -36" />             <!-- Middle Clad -->
-  <cell id="25" universe="1" material="3" surfaces="11     -36" />                 <!-- Top clad -->
-  <cell id="26" universe="1" material="4" surfaces="-5  36" />                     <!-- Moderator below bottom egg-crate -->
-  <cell id="27" universe="1" material="5" surfaces=" 5  -8 -37" />                 <!-- Bottom Al Egg-Crate Left -->
-  <cell id="28" universe="1" material="5" surfaces=" 5  -8  38" />                 <!-- Bottom Al Egg-Crate Right -->
-  <cell id="29" universe="1" material="5" surfaces=" 5  -8 -39  37 -38" />         <!-- Bottom Al Egg-Crate Top -->
-  <cell id="30" universe="1" material="5" surfaces=" 5  -8  40  37 -38" />         <!-- Bottom Al Egg-Crate Bottom -->
-  <cell id="31" universe="1" material="4" surfaces=" 5  -8  37 -38  39 -40 36" />  <!-- Moderator within bottom egg-crate -->
-  <cell id="32" universe="1" material="4" surfaces=" 8  -9  36" />                 <!-- Moderator in middle -->
-  <cell id="33" universe="1" material="5" surfaces=" 9 -10 -37" />                 <!-- Top Al Egg-Crate Left -->
-  <cell id="34" universe="1" material="5" surfaces=" 9 -10  38" />                 <!-- Top Al Egg-Crate Right -->
-  <cell id="35" universe="1" material="5" surfaces=" 9 -10 -39  37 -38" />         <!-- Top Al Egg-Crate Top -->
-  <cell id="36" universe="1" material="5" surfaces=" 9 -10  40  37 -38" />         <!-- Top Al Egg-Crate Bottom -->
-  <cell id="37" universe="1" material="4" surfaces=" 9 -10  37 -38  39 -40 36" />  <!-- Moderator within top egg-crate -->
-  <cell id="38" universe="1" material="4" surfaces="10      36" />                 <!-- Moderator above top egg-crate -->
+  <cell id="21" universe="1" material="3" region="-6     -36" />                 <!-- Bottom Clad -->
+  <cell id="22" universe="1" material="2" region=" 6  -7 -35" />                 <!-- UO2 layer -->
+  <cell id="23" universe="1" material="1" region=" 7 -11 -35" />                 <!-- MOX -->
+  <cell id="24" universe="1" material="3" region=" 6 -11  35 -36" />             <!-- Middle Clad -->
+  <cell id="25" universe="1" material="3" region="11     -36" />                 <!-- Top clad -->
+  <cell id="26" universe="1" material="4" region="-5  36" />                     <!-- Moderator below bottom egg-crate -->
+  <cell id="27" universe="1" material="5" region=" 5  -8 -37" />                 <!-- Bottom Al Egg-Crate Left -->
+  <cell id="28" universe="1" material="5" region=" 5  -8  38" />                 <!-- Bottom Al Egg-Crate Right -->
+  <cell id="29" universe="1" material="5" region=" 5  -8 -39  37 -38" />         <!-- Bottom Al Egg-Crate Top -->
+  <cell id="30" universe="1" material="5" region=" 5  -8  40  37 -38" />         <!-- Bottom Al Egg-Crate Bottom -->
+  <cell id="31" universe="1" material="4" region=" 5  -8  37 -38  39 -40 36" />  <!-- Moderator within bottom egg-crate -->
+  <cell id="32" universe="1" material="4" region=" 8  -9  36" />                 <!-- Moderator in middle -->
+  <cell id="33" universe="1" material="5" region=" 9 -10 -37" />                 <!-- Top Al Egg-Crate Left -->
+  <cell id="34" universe="1" material="5" region=" 9 -10  38" />                 <!-- Top Al Egg-Crate Right -->
+  <cell id="35" universe="1" material="5" region=" 9 -10 -39  37 -38" />         <!-- Top Al Egg-Crate Top -->
+  <cell id="36" universe="1" material="5" region=" 9 -10  40  37 -38" />         <!-- Top Al Egg-Crate Bottom -->
+  <cell id="37" universe="1" material="4" region=" 9 -10  37 -38  39 -40 36" />  <!-- Moderator within top egg-crate -->
+  <cell id="38" universe="1" material="4" region="10      36" />                 <!-- Moderator above top egg-crate -->
 
   <!-- radial reflector cell universe -->
-  <cell id="41" universe="2" material="4" surfaces="-5" />                     <!-- Moderator below bottom egg-crate -->
-  <cell id="42" universe="2" material="5" surfaces="5  -8 -37" />              <!-- Bottom Al Egg-Crate Left -->
-  <cell id="43" universe="2" material="5" surfaces="5  -8  38" />              <!-- Bottom Al Egg-Crate Right -->
-  <cell id="44" universe="2" material="5" surfaces="5  -8 -39  37 -38" />      <!-- Bottom Al Egg-Crate Top -->
-  <cell id="45" universe="2" material="5" surfaces="5  -8  40  37 -38" />      <!-- Bottom Al Egg-Crate Bottom -->
-  <cell id="46" universe="2" material="4" surfaces="5  -8  37 -38  39 -40" />  <!-- Moderator within bottom egg-crate -->
-  <cell id="47" universe="2" material="4" surfaces="8  -9" />                  <!-- Moderator in middle -->
-  <cell id="48" universe="2" material="5" surfaces="9 -10 -37" />              <!-- Top Al Egg-Crate Left -->
-  <cell id="49" universe="2" material="5" surfaces="9 -10  38" />              <!-- Top Al Egg-Crate Right -->
-  <cell id="50" universe="2" material="5" surfaces="9 -10 -39  37 -38" />      <!-- Top Al Egg-Crate Top -->
-  <cell id="51" universe="2" material="5" surfaces="9 -10  40  37 -38" />      <!-- Top Al Egg-Crate Bottom -->
-  <cell id="52" universe="2" material="4" surfaces="9 -10  37 -38  39 -40" />  <!-- Moderator within top egg-crate -->
-  <cell id="53" universe="2" material="4" surfaces="10" />                     <!-- Moderator within top egg-crate -->
+  <cell id="41" universe="2" material="4" region="-5" />                     <!-- Moderator below bottom egg-crate -->
+  <cell id="42" universe="2" material="5" region="5  -8 -37" />              <!-- Bottom Al Egg-Crate Left -->
+  <cell id="43" universe="2" material="5" region="5  -8  38" />              <!-- Bottom Al Egg-Crate Right -->
+  <cell id="44" universe="2" material="5" region="5  -8 -39  37 -38" />      <!-- Bottom Al Egg-Crate Top -->
+  <cell id="45" universe="2" material="5" region="5  -8  40  37 -38" />      <!-- Bottom Al Egg-Crate Bottom -->
+  <cell id="46" universe="2" material="4" region="5  -8  37 -38  39 -40" />  <!-- Moderator within bottom egg-crate -->
+  <cell id="47" universe="2" material="4" region="8  -9" />                  <!-- Moderator in middle -->
+  <cell id="48" universe="2" material="5" region="9 -10 -37" />              <!-- Top Al Egg-Crate Left -->
+  <cell id="49" universe="2" material="5" region="9 -10  38" />              <!-- Top Al Egg-Crate Right -->
+  <cell id="50" universe="2" material="5" region="9 -10 -39  37 -38" />      <!-- Top Al Egg-Crate Top -->
+  <cell id="51" universe="2" material="5" region="9 -10  40  37 -38" />      <!-- Top Al Egg-Crate Bottom -->
+  <cell id="52" universe="2" material="4" region="9 -10  37 -38  39 -40" />  <!-- Moderator within top egg-crate -->
+  <cell id="53" universe="2" material="4" region="10" />                     <!-- Moderator within top egg-crate -->
 
 </geometry>
diff --git a/tests/test_lattice_hex/geometry.xml b/tests/test_lattice_hex/geometry.xml
index 8b5915dcd..cfe39849c 100644
--- a/tests/test_lattice_hex/geometry.xml
+++ b/tests/test_lattice_hex/geometry.xml
@@ -14,29 +14,29 @@
   <surface id="015" type="sphere" coeffs="0.0 0.0 -2.5639 2.0"/>
   <surface id="016" type="sphere" coeffs="0.0 0.0 2.5639 2.0"/>
 
-  <cell id="011" universe="011" material="void" surfaces="-011"/>
-  <cell id="012" universe="011" material="13" surfaces="011 -012 015 016"/>
-  <cell id="013" universe="011" material="void" surfaces="011 -012 -015"/>
-  <cell id="014" universe="011" material="void" surfaces="011 -012 -016"/>
-  <cell id="015" universe="011" material="void" surfaces="012 -013"/>
-  <cell id="016" universe="011" material="21" surfaces="013 -014"/>
-  <cell id="017" universe="011" material="01" surfaces="014"/>
+  <cell id="011" universe="011" material="void" region="-011"/>
+  <cell id="012" universe="011" material="13" region="011 -012 015 016"/>
+  <cell id="013" universe="011" material="void" region="011 -012 -015"/>
+  <cell id="014" universe="011" material="void" region="011 -012 -016"/>
+  <cell id="015" universe="011" material="void" region="012 -013"/>
+  <cell id="016" universe="011" material="21" region="013 -014"/>
+  <cell id="017" universe="011" material="01" region="014"/>
 
 
   <!-- Universe 051: Central guide tube -->
     <surface id="051" type="z-cylinder" coeffs="0.0 0.0 0.44"/>
     <surface id="052" type="z-cylinder" coeffs="0.0 0.0 0.515"/>
-    <cell id="051" universe="051" material="01" surfaces="-051"/>
-    <cell id="052" universe="051" material="21" surfaces="051 -052"/>
-    <cell id="053" universe="051" material="01" surfaces="052"/>
+    <cell id="051" universe="051" material="01" region="-051"/>
+    <cell id="052" universe="051" material="21" region="051 -052"/>
+    <cell id="053" universe="051" material="01" region="052"/>
 
 
   <!-- Universe 055: Cluster tube -->
     <surface id="155" type="z-cylinder" coeffs="0.0 0.0 0.55"/>
     <surface id="156" type="z-cylinder" coeffs="0.0 0.0 0.63"/>
-    <cell id="155" universe="055" material="01" surfaces="-155"/>
-    <cell id="156" universe="055" material="22" surfaces="155 -156"/>
-    <cell id="157" universe="055" material="01" surfaces="156"/>
+    <cell id="155" universe="055" material="01" region="-155"/>
+    <cell id="156" universe="055" material="22" region="155 -156"/>
+    <cell id="157" universe="055" material="01" region="156"/>
 
 
 
@@ -194,6 +194,6 @@
   <surface id="1008" type="z-plane" coeffs="177.4" boundary="vacuum"/>
 
   <cell id="1001" universe="0" fill="101"
-      surfaces="-1001 -1002 -1003 -1004 -1005 -1006 1007 -1008"/>
+      region="-1001 -1002 -1003 -1004 -1005 -1006 1007 -1008"/>
 
 </geometry>
diff --git a/tests/test_lattice_mixed/geometry.xml b/tests/test_lattice_mixed/geometry.xml
index 524e4d928..41aa05d41 100644
--- a/tests/test_lattice_mixed/geometry.xml
+++ b/tests/test_lattice_mixed/geometry.xml
@@ -15,29 +15,29 @@
   <surface id="015" type="sphere" coeffs="0.0 0.0 -2.5639 2.0"/>
   <surface id="016" type="sphere" coeffs="0.0 0.0 2.5639 2.0"/>
 
-  <cell id="011" universe="011" material="void" surfaces="-011"/>
-  <cell id="012" universe="011" material="13" surfaces="011 -012 015 016"/>
-  <cell id="013" universe="011" material="void" surfaces="011 -012 -015"/>
-  <cell id="014" universe="011" material="void" surfaces="011 -012 -016"/>
-  <cell id="015" universe="011" material="void" surfaces="012 -013"/>
-  <cell id="016" universe="011" material="21" surfaces="013 -014"/>
-  <cell id="017" universe="011" material="01" surfaces="014"/>
+  <cell id="011" universe="011" material="void" region="-011"/>
+  <cell id="012" universe="011" material="13" region="011 -012 015 016"/>
+  <cell id="013" universe="011" material="void" region="011 -012 -015"/>
+  <cell id="014" universe="011" material="void" region="011 -012 -016"/>
+  <cell id="015" universe="011" material="void" region="012 -013"/>
+  <cell id="016" universe="011" material="21" region="013 -014"/>
+  <cell id="017" universe="011" material="01" region="014"/>
 
 
   <!-- Universe 051: Central guide tube -->
     <surface id="051" type="z-cylinder" coeffs="0.0 0.0 0.44"/>
     <surface id="052" type="z-cylinder" coeffs="0.0 0.0 0.515"/>
-    <cell id="051" universe="051" material="01" surfaces="-051"/>
-    <cell id="052" universe="051" material="21" surfaces="051 -052"/>
-    <cell id="053" universe="051" material="01" surfaces="052"/>
+    <cell id="051" universe="051" material="01" region="-051"/>
+    <cell id="052" universe="051" material="21" region="051 -052"/>
+    <cell id="053" universe="051" material="01" region="052"/>
 
 
   <!-- Universe 055: Cluster tube -->
     <surface id="155" type="z-cylinder" coeffs="0.0 0.0 0.55"/>
     <surface id="156" type="z-cylinder" coeffs="0.0 0.0 0.63"/>
-    <cell id="155" universe="055" material="01" surfaces="-155"/>
-    <cell id="156" universe="055" material="22" surfaces="155 -156"/>
-    <cell id="157" universe="055" material="01" surfaces="156"/>
+    <cell id="155" universe="055" material="01" region="-155"/>
+    <cell id="156" universe="055" material="22" region="155 -156"/>
+    <cell id="157" universe="055" material="01" region="156"/>
 
 
 
@@ -151,6 +151,6 @@
   <surface id="1008" type="z-plane" coeffs="177.4" boundary="vacuum"/>
 
   <cell id="1001" universe="0" fill="103"
-      surfaces="-1001 -1002 -1003 -1004 -1005 -1006 1007 -1008"/>
+      region="-1001 -1002 -1003 -1004 -1005 -1006 1007 -1008"/>
 
 </geometry>
diff --git a/tests/test_lattice_multiple/geometry.xml b/tests/test_lattice_multiple/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_lattice_multiple/geometry.xml
+++ b/tests/test_lattice_multiple/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_many_scores/geometry.xml b/tests/test_many_scores/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_many_scores/geometry.xml
+++ b/tests/test_many_scores/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_natural_element/geometry.xml b/tests/test_natural_element/geometry.xml
index 2d427d8cb..b6b4bd817 100644
--- a/tests/test_natural_element/geometry.xml
+++ b/tests/test_natural_element/geometry.xml
@@ -45,50 +45,50 @@
 
 
   <!-- Beryllium Reflector -->
-  <cell id="1"  material="2" surfaces=" 1  -2 -30" />
-  <cell id="2"  material="2" surfaces="28 -29 -30" />
+  <cell id="1"  material="2" region=" 1  -2 -30" />
+  <cell id="2"  material="2" region="28 -29 -30" />
 
   <!-- Duralumin base and top -->
-  <cell id="3"  material="4" surfaces=" 2  -4 -30  31" />
-  <cell id="4"  material="4" surfaces="25 -28 -30  31" />
+  <cell id="3"  material="4" region=" 2  -4 -30  31" />
+  <cell id="4"  material="4" region="25 -28 -30  31" />
 
   <!-- Duralumin top cylindrical shell -->
-  <cell id="6"  material="5" surfaces="15 -28 -31  32" />
+  <cell id="6"  material="5" region="15 -28 -31  32" />
 
   <!-- Duralumin bottom cylindrical shell -->
-  <cell id="7"  material="6" surfaces=" 2 -14 -31  32" />
+  <cell id="7"  material="6" region=" 2 -14 -31  32" />
 
   <!-- Steel Cover -->
-  <cell id="8"  material="3" surfaces=" 2  -3 -33" />
-  <cell id="9"  material="3" surfaces=" 5  -6 -33" />
-  <cell id="10" material="3" surfaces=" 7  -8 -33" />
-  <cell id="11" material="3" surfaces=" 9 -10 -33" />
-  <cell id="12" material="3" surfaces="11 -12 -33" />
-  <cell id="13" material="3" surfaces="13 -14 -33" />
-  <cell id="14" material="3" surfaces="15 -16 -33" />
-  <cell id="15" material="3" surfaces="17 -18 -33" />
-  <cell id="16" material="3" surfaces="19 -20 -33" />
-  <cell id="17" material="3" surfaces="21 -22 -33" />
-  <cell id="18" material="3" surfaces="23 -24 -33" />
-  <cell id="19" material="3" surfaces="26 -27 -33" />
-  <cell id="20" material="3" surfaces=" 2 -14  33 -32" />
-  <cell id="21" material="3" surfaces="15 -27  33 -32" />
+  <cell id="8"  material="3" region=" 2  -3 -33" />
+  <cell id="9"  material="3" region=" 5  -6 -33" />
+  <cell id="10" material="3" region=" 7  -8 -33" />
+  <cell id="11" material="3" region=" 9 -10 -33" />
+  <cell id="12" material="3" region="11 -12 -33" />
+  <cell id="13" material="3" region="13 -14 -33" />
+  <cell id="14" material="3" region="15 -16 -33" />
+  <cell id="15" material="3" region="17 -18 -33" />
+  <cell id="16" material="3" region="19 -20 -33" />
+  <cell id="17" material="3" region="21 -22 -33" />
+  <cell id="18" material="3" region="23 -24 -33" />
+  <cell id="19" material="3" region="26 -27 -33" />
+  <cell id="20" material="3" region=" 2 -14  33 -32" />
+  <cell id="21" material="3" region="15 -27  33 -32" />
 
   <!-- Plutonium -->
-  <cell id="22" material="1" surfaces=" 3  -5 -33" />
-  <cell id="23" material="1" surfaces=" 6  -7 -33" />
-  <cell id="24" material="1" surfaces=" 8  -9 -33" />
-  <cell id="25" material="1" surfaces="10 -11 -33" />
-  <cell id="26" material="1" surfaces="12 -13 -33" />
-  <cell id="27" material="1" surfaces="16 -17 -33" />
-  <cell id="28" material="1" surfaces="18 -19 -33" />
-  <cell id="29" material="1" surfaces="20 -21 -33" />
-  <cell id="30" material="1" surfaces="22 -23 -33" />
-  <cell id="31" material="1" surfaces="24 -26 -33" />
+  <cell id="22" material="1" region=" 3  -5 -33" />
+  <cell id="23" material="1" region=" 6  -7 -33" />
+  <cell id="24" material="1" region=" 8  -9 -33" />
+  <cell id="25" material="1" region="10 -11 -33" />
+  <cell id="26" material="1" region="12 -13 -33" />
+  <cell id="27" material="1" region="16 -17 -33" />
+  <cell id="28" material="1" region="18 -19 -33" />
+  <cell id="29" material="1" region="20 -21 -33" />
+  <cell id="30" material="1" region="22 -23 -33" />
+  <cell id="31" material="1" region="24 -26 -33" />
 
   <!-- Void -->
-  <cell id="32" material="void" surfaces="14 -15 -31" />
-  <cell id="33" material="void" surfaces=" 4 -25  31 -30" />
-  <cell id="34" material="void" surfaces="27 -28 -30" />
+  <cell id="32" material="void" region="14 -15 -31" />
+  <cell id="33" material="void" region=" 4 -25  31 -30" />
+  <cell id="34" material="void" region="27 -28 -30" />
 
 </geometry>
diff --git a/tests/test_output/geometry.xml b/tests/test_output/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_output/geometry.xml
+++ b/tests/test_output/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_particle_restart_eigval/geometry.xml b/tests/test_particle_restart_eigval/geometry.xml
index 52fea4df6..c86e016c6 100644
--- a/tests/test_particle_restart_eigval/geometry.xml
+++ b/tests/test_particle_restart_eigval/geometry.xml
@@ -4,6 +4,6 @@
   <!-- Sphere with no boundary condition -->
   <surface id="1" type="sphere" coeffs="0.0 0.0 0.0 80.0" />
   <surface id="2" type="sphere" coeffs="0.0 0.0 0.0 10000.0" boundary="vacuum" />
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
 
 </geometry>
diff --git a/tests/test_particle_restart_fixed/geometry.xml b/tests/test_particle_restart_fixed/geometry.xml
index 52fea4df6..c86e016c6 100644
--- a/tests/test_particle_restart_fixed/geometry.xml
+++ b/tests/test_particle_restart_fixed/geometry.xml
@@ -4,6 +4,6 @@
   <!-- Sphere with no boundary condition -->
   <surface id="1" type="sphere" coeffs="0.0 0.0 0.0 80.0" />
   <surface id="2" type="sphere" coeffs="0.0 0.0 0.0 10000.0" boundary="vacuum" />
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
 
 </geometry>
diff --git a/tests/test_plot_background/geometry.xml b/tests/test_plot_background/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_plot_background/geometry.xml
+++ b/tests/test_plot_background/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_plot_basis/geometry.xml b/tests/test_plot_basis/geometry.xml
index ac00ebaf5..83619d9f7 100644
--- a/tests/test_plot_basis/geometry.xml
+++ b/tests/test_plot_basis/geometry.xml
@@ -6,8 +6,8 @@
   <surface id="3" type="z-cylinder" coeffs="0 0 10" boundary="vacuum" />
   <surface id="4" type="y-plane" coeffs="5" boundary="vacuum" />
 
-  <cell id="1" material="1" surfaces="  -1 -4" />
-  <cell id="2" material="3" surfaces="1 -2 -4" />
-  <cell id="3" material="2" surfaces="2 -3 -4" />
+  <cell id="1" material="1" region="  -1 -4" />
+  <cell id="2" material="3" region="1 -2 -4" />
+  <cell id="3" material="2" region="2 -3 -4" />
 
 </geometry>
diff --git a/tests/test_plot_colspec/geometry.xml b/tests/test_plot_colspec/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_plot_colspec/geometry.xml
+++ b/tests/test_plot_colspec/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_plot_mask/geometry.xml b/tests/test_plot_mask/geometry.xml
index ac00ebaf5..83619d9f7 100644
--- a/tests/test_plot_mask/geometry.xml
+++ b/tests/test_plot_mask/geometry.xml
@@ -6,8 +6,8 @@
   <surface id="3" type="z-cylinder" coeffs="0 0 10" boundary="vacuum" />
   <surface id="4" type="y-plane" coeffs="5" boundary="vacuum" />
 
-  <cell id="1" material="1" surfaces="  -1 -4" />
-  <cell id="2" material="3" surfaces="1 -2 -4" />
-  <cell id="3" material="2" surfaces="2 -3 -4" />
+  <cell id="1" material="1" region="  -1 -4" />
+  <cell id="2" material="3" region="1 -2 -4" />
+  <cell id="3" material="2" region="2 -3 -4" />
 
 </geometry>
diff --git a/tests/test_ptables_off/geometry.xml b/tests/test_ptables_off/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_ptables_off/geometry.xml
+++ b/tests/test_ptables_off/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_reflective_cone/geometry.xml b/tests/test_reflective_cone/geometry.xml
index 5453e1615..f5499fbb6 100644
--- a/tests/test_reflective_cone/geometry.xml
+++ b/tests/test_reflective_cone/geometry.xml
@@ -2,6 +2,6 @@
 <geometry>
 
   <surface id="1" type="z-cone" coeffs="0 0 0 5" boundary="reflective"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_reflective_cylinder/geometry.xml b/tests/test_reflective_cylinder/geometry.xml
index ce1082f3d..e6aed65da 100644
--- a/tests/test_reflective_cylinder/geometry.xml
+++ b/tests/test_reflective_cylinder/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- cylinder with radius 10 -->
   <surface id="1" type="z-cylinder" coeffs="0 0 10" boundary="reflective"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_reflective_plane/geometry.xml b/tests/test_reflective_plane/geometry.xml
index 454441436..0dc5c29ab 100644
--- a/tests/test_reflective_plane/geometry.xml
+++ b/tests/test_reflective_plane/geometry.xml
@@ -8,6 +8,6 @@
   <surface id="4" type="y-plane" coeffs="5" boundary="reflective"/>
   <surface id="5" type="z-plane" coeffs="-5" boundary="reflective"/>
   <surface id="6" type="z-plane" coeffs="5" boundary="reflective"/>
-  <cell id="1" material="1" surfaces="1 -2 3 -4 5 -6" />
+  <cell id="1" material="1" region="1 -2 3 -4 5 -6" />
     
 </geometry>
diff --git a/tests/test_reflective_sphere/geometry.xml b/tests/test_reflective_sphere/geometry.xml
index 5f36d2396..0dc98eba6 100644
--- a/tests/test_reflective_sphere/geometry.xml
+++ b/tests/test_reflective_sphere/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="reflective"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_resonance_scattering/geometry.xml b/tests/test_resonance_scattering/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_resonance_scattering/geometry.xml
+++ b/tests/test_resonance_scattering/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_rotation/geometry.xml b/tests/test_rotation/geometry.xml
index 7306dabde..222617877 100644
--- a/tests/test_rotation/geometry.xml
+++ b/tests/test_rotation/geometry.xml
@@ -5,7 +5,7 @@
   <surface id="2" type="z-plane" coeffs="-100" />
   <surface id="3" type="z-plane" coeffs="100" />
 
-  <cell id="1" fill="2" rotation="45 45 45" surfaces="-1" />
-  <cell id="2" universe="2" material="1" surfaces="2 -3" />
+  <cell id="1" fill="2" rotation="45 45 45" region="-1" />
+  <cell id="2" universe="2" material="1" region="2 -3" />
 
 </geometry>
diff --git a/tests/test_salphabeta/geometry.xml b/tests/test_salphabeta/geometry.xml
index ef0598842..f9caa6c88 100644
--- a/tests/test_salphabeta/geometry.xml
+++ b/tests/test_salphabeta/geometry.xml
@@ -6,8 +6,8 @@
   <surface id="3" type="x-plane" coeffs="5" />
   <surface id="4" type="x-plane" coeffs="10" boundary="vacuum"/>
 
-  <cell id="1" material="1" surfaces="1 -2" />
-  <cell id="2" material="2" surfaces="2 -3" />
-  <cell id="3" material="3" surfaces="3 -4" />
+  <cell id="1" material="1" region="1 -2" />
+  <cell id="2" material="2" region="2 -3" />
+  <cell id="3" material="3" region="3 -4" />
     
 </geometry>
diff --git a/tests/test_salphabeta_multiple/geometry.xml b/tests/test_salphabeta_multiple/geometry.xml
index 63f69f743..13eb60166 100644
--- a/tests/test_salphabeta_multiple/geometry.xml
+++ b/tests/test_salphabeta_multiple/geometry.xml
@@ -45,52 +45,52 @@
 
 
   <!-- Bottom Beryllium Reflector -->
-  <cell id="1"  material="2" surfaces=" 1  -2 -30" />
+  <cell id="1"  material="2" region=" 1  -2 -30" />
 
   <!-- Top ZrH Reflector -->
-  <cell id="2"  material="7" surfaces="28 -29 -30" />
+  <cell id="2"  material="7" region="28 -29 -30" />
 
   <!-- Duralumin base and top -->
-  <cell id="3"  material="4" surfaces=" 2  -4 -30  31" />
-  <cell id="4"  material="4" surfaces="25 -28 -30  31" />
+  <cell id="3"  material="4" region=" 2  -4 -30  31" />
+  <cell id="4"  material="4" region="25 -28 -30  31" />
 
   <!-- Duralumin top cylindrical shell -->
-  <cell id="6"  material="5" surfaces="15 -28 -31  32" />
+  <cell id="6"  material="5" region="15 -28 -31  32" />
 
   <!-- Duralumin bottom cylindrical shell -->
-  <cell id="7"  material="6" surfaces=" 2 -14 -31  32" />
+  <cell id="7"  material="6" region=" 2 -14 -31  32" />
 
   <!-- Steel Cover -->
-  <cell id="8"  material="3" surfaces=" 2  -3 -33" />
-  <cell id="9"  material="3" surfaces=" 5  -6 -33" />
-  <cell id="10" material="3" surfaces=" 7  -8 -33" />
-  <cell id="11" material="3" surfaces=" 9 -10 -33" />
-  <cell id="12" material="3" surfaces="11 -12 -33" />
-  <cell id="13" material="3" surfaces="13 -14 -33" />
-  <cell id="14" material="3" surfaces="15 -16 -33" />
-  <cell id="15" material="3" surfaces="17 -18 -33" />
-  <cell id="16" material="3" surfaces="19 -20 -33" />
-  <cell id="17" material="3" surfaces="21 -22 -33" />
-  <cell id="18" material="3" surfaces="23 -24 -33" />
-  <cell id="19" material="3" surfaces="26 -27 -33" />
-  <cell id="20" material="3" surfaces=" 2 -14  33 -32" />
-  <cell id="21" material="3" surfaces="15 -27  33 -32" />
+  <cell id="8"  material="3" region=" 2  -3 -33" />
+  <cell id="9"  material="3" region=" 5  -6 -33" />
+  <cell id="10" material="3" region=" 7  -8 -33" />
+  <cell id="11" material="3" region=" 9 -10 -33" />
+  <cell id="12" material="3" region="11 -12 -33" />
+  <cell id="13" material="3" region="13 -14 -33" />
+  <cell id="14" material="3" region="15 -16 -33" />
+  <cell id="15" material="3" region="17 -18 -33" />
+  <cell id="16" material="3" region="19 -20 -33" />
+  <cell id="17" material="3" region="21 -22 -33" />
+  <cell id="18" material="3" region="23 -24 -33" />
+  <cell id="19" material="3" region="26 -27 -33" />
+  <cell id="20" material="3" region=" 2 -14  33 -32" />
+  <cell id="21" material="3" region="15 -27  33 -32" />
 
   <!-- Plutonium -->
-  <cell id="22" material="1" surfaces=" 3  -5 -33" />
-  <cell id="23" material="1" surfaces=" 6  -7 -33" />
-  <cell id="24" material="1" surfaces=" 8  -9 -33" />
-  <cell id="25" material="1" surfaces="10 -11 -33" />
-  <cell id="26" material="1" surfaces="12 -13 -33" />
-  <cell id="27" material="1" surfaces="16 -17 -33" />
-  <cell id="28" material="1" surfaces="18 -19 -33" />
-  <cell id="29" material="1" surfaces="20 -21 -33" />
-  <cell id="30" material="1" surfaces="22 -23 -33" />
-  <cell id="31" material="1" surfaces="24 -26 -33" />
+  <cell id="22" material="1" region=" 3  -5 -33" />
+  <cell id="23" material="1" region=" 6  -7 -33" />
+  <cell id="24" material="1" region=" 8  -9 -33" />
+  <cell id="25" material="1" region="10 -11 -33" />
+  <cell id="26" material="1" region="12 -13 -33" />
+  <cell id="27" material="1" region="16 -17 -33" />
+  <cell id="28" material="1" region="18 -19 -33" />
+  <cell id="29" material="1" region="20 -21 -33" />
+  <cell id="30" material="1" region="22 -23 -33" />
+  <cell id="31" material="1" region="24 -26 -33" />
 
   <!-- Void -->
-  <cell id="32" material="void" surfaces="14 -15 -31" />
-  <cell id="33" material="void" surfaces=" 4 -25  31 -30" />
-  <cell id="34" material="void" surfaces="27 -28 -30" />
+  <cell id="32" material="void" region="14 -15 -31" />
+  <cell id="33" material="void" region=" 4 -25  31 -30" />
+  <cell id="34" material="void" region="27 -28 -30" />
 
 </geometry>
diff --git a/tests/test_score_MT/geometry.xml b/tests/test_score_MT/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_MT/geometry.xml
+++ b/tests/test_score_MT/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_score_absorption/geometry.xml b/tests/test_score_absorption/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_absorption/geometry.xml
+++ b/tests/test_score_absorption/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_score_current/geometry.xml b/tests/test_score_current/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_current/geometry.xml
+++ b/tests/test_score_current/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_score_events/geometry.xml b/tests/test_score_events/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_events/geometry.xml
+++ b/tests/test_score_events/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_score_fission/geometry.xml b/tests/test_score_fission/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_fission/geometry.xml
+++ b/tests/test_score_fission/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_score_flux/geometry.xml b/tests/test_score_flux/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_flux/geometry.xml
+++ b/tests/test_score_flux/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_score_flux_yn/geometry.xml b/tests/test_score_flux_yn/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_flux_yn/geometry.xml
+++ b/tests/test_score_flux_yn/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_score_kappafission/geometry.xml b/tests/test_score_kappafission/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_kappafission/geometry.xml
+++ b/tests/test_score_kappafission/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_score_nufission/geometry.xml b/tests/test_score_nufission/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_nufission/geometry.xml
+++ b/tests/test_score_nufission/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_score_nuscatter/geometry.xml b/tests/test_score_nuscatter/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_nuscatter/geometry.xml
+++ b/tests/test_score_nuscatter/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_score_nuscatter_n/geometry.xml b/tests/test_score_nuscatter_n/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_nuscatter_n/geometry.xml
+++ b/tests/test_score_nuscatter_n/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_score_nuscatter_pn/geometry.xml b/tests/test_score_nuscatter_pn/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_nuscatter_pn/geometry.xml
+++ b/tests/test_score_nuscatter_pn/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_score_nuscatter_yn/geometry.xml b/tests/test_score_nuscatter_yn/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_nuscatter_yn/geometry.xml
+++ b/tests/test_score_nuscatter_yn/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_score_scatter/geometry.xml b/tests/test_score_scatter/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_scatter/geometry.xml
+++ b/tests/test_score_scatter/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_score_scatter_n/geometry.xml b/tests/test_score_scatter_n/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_scatter_n/geometry.xml
+++ b/tests/test_score_scatter_n/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_score_scatter_pn/geometry.xml b/tests/test_score_scatter_pn/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_scatter_pn/geometry.xml
+++ b/tests/test_score_scatter_pn/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_score_scatter_yn/geometry.xml b/tests/test_score_scatter_yn/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_scatter_yn/geometry.xml
+++ b/tests/test_score_scatter_yn/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_score_total/geometry.xml b/tests/test_score_total/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_total/geometry.xml
+++ b/tests/test_score_total/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_score_total_yn/geometry.xml b/tests/test_score_total_yn/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_score_total_yn/geometry.xml
+++ b/tests/test_score_total_yn/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_seed/geometry.xml b/tests/test_seed/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_seed/geometry.xml
+++ b/tests/test_seed/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_source_angle_mono/geometry.xml b/tests/test_source_angle_mono/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_source_angle_mono/geometry.xml
+++ b/tests/test_source_angle_mono/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_source_energy_maxwell/geometry.xml b/tests/test_source_energy_maxwell/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_source_energy_maxwell/geometry.xml
+++ b/tests/test_source_energy_maxwell/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_source_energy_mono/geometry.xml b/tests/test_source_energy_mono/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_source_energy_mono/geometry.xml
+++ b/tests/test_source_energy_mono/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_source_file/geometry.xml b/tests/test_source_file/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_source_file/geometry.xml
+++ b/tests/test_source_file/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_source_point/geometry.xml b/tests/test_source_point/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_source_point/geometry.xml
+++ b/tests/test_source_point/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_sourcepoint_batch/geometry.xml b/tests/test_sourcepoint_batch/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_sourcepoint_batch/geometry.xml
+++ b/tests/test_sourcepoint_batch/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_sourcepoint_interval/geometry.xml b/tests/test_sourcepoint_interval/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_sourcepoint_interval/geometry.xml
+++ b/tests/test_sourcepoint_interval/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_sourcepoint_latest/geometry.xml b/tests/test_sourcepoint_latest/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_sourcepoint_latest/geometry.xml
+++ b/tests/test_sourcepoint_latest/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_sourcepoint_restart/geometry.xml b/tests/test_sourcepoint_restart/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_sourcepoint_restart/geometry.xml
+++ b/tests/test_sourcepoint_restart/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_statepoint_batch/geometry.xml b/tests/test_statepoint_batch/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_statepoint_batch/geometry.xml
+++ b/tests/test_statepoint_batch/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_statepoint_interval/geometry.xml b/tests/test_statepoint_interval/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_statepoint_interval/geometry.xml
+++ b/tests/test_statepoint_interval/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_statepoint_restart/geometry.xml b/tests/test_statepoint_restart/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_statepoint_restart/geometry.xml
+++ b/tests/test_statepoint_restart/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_statepoint_sourcesep/geometry.xml b/tests/test_statepoint_sourcesep/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_statepoint_sourcesep/geometry.xml
+++ b/tests/test_statepoint_sourcesep/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_survival_biasing/geometry.xml b/tests/test_survival_biasing/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_survival_biasing/geometry.xml
+++ b/tests/test_survival_biasing/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_tally_assumesep/geometry.xml b/tests/test_tally_assumesep/geometry.xml
index b85dd04df..f6f067aad 100644
--- a/tests/test_tally_assumesep/geometry.xml
+++ b/tests/test_tally_assumesep/geometry.xml
@@ -21,50 +21,50 @@
   <surface id="39" type="z-plane" coeffs="223.0" boundary="vacuum" />
 
   <!-- All geometry on base universe -->
-  <cell id="1"  fill="200"    surfaces="  -6 34 -35" /> <!-- Lower core -->
-  <cell id="2"  fill="201"    surfaces="  -6 35 -36" /> <!-- Upper core -->
-  <cell id="3"  material="8"  surfaces="  -7 31 -32" /> <!-- Lower core plate region -->
-  <cell id="4"  material="9"  surfaces="  -5 32 -33" /> <!-- Bottom nozzle region -->
-  <cell id="5"  material="12" surfaces="  -5 33 -34" /> <!-- Bottom FA region -->
-  <cell id="6"  material="11" surfaces="  -5 36 -37" /> <!-- Top FA region -->
-  <cell id="7"  material="10" surfaces="  -5 37 -38" /> <!-- Top nozzle region -->
-  <cell id="8"  material="7"  surfaces="  -7 38 -39" /> <!-- Upper plate region -->
-  <cell id="9"  material="4"  surfaces="6 -7 32 -38" /> <!-- Downcomer -->
-  <cell id="10" material="5"  surfaces="7 -8 31 -39" /> <!-- RPV -->
-  <cell id="11" material="6"  surfaces="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
-  <cell id="12" material="7"  surfaces="5 -6 36 -38" /> <!-- Top of radial reflector -->
+  <cell id="1"  fill="200"    region="  -6 34 -35" /> <!-- Lower core -->
+  <cell id="2"  fill="201"    region="  -6 35 -36" /> <!-- Upper core -->
+  <cell id="3"  material="8"  region="  -7 31 -32" /> <!-- Lower core plate region -->
+  <cell id="4"  material="9"  region="  -5 32 -33" /> <!-- Bottom nozzle region -->
+  <cell id="5"  material="12" region="  -5 33 -34" /> <!-- Bottom FA region -->
+  <cell id="6"  material="11" region="  -5 36 -37" /> <!-- Top FA region -->
+  <cell id="7"  material="10" region="  -5 37 -38" /> <!-- Top nozzle region -->
+  <cell id="8"  material="7"  region="  -7 38 -39" /> <!-- Upper plate region -->
+  <cell id="9"  material="4"  region="6 -7 32 -38" /> <!-- Downcomer -->
+  <cell id="10" material="5"  region="7 -8 31 -39" /> <!-- RPV -->
+  <cell id="11" material="6"  region="5 -6 32 -34" /> <!-- Bottom of radial reflector -->
+  <cell id="12" material="7"  region="5 -6 36 -38" /> <!-- Top of radial reflector -->
 
   <!-- Fuel pin, cladding, cold water -->
-  <cell id="21" universe="1" material="1" surfaces="-1"   />
-  <cell id="22" universe="1" material="2" surfaces="1 -2" />
-  <cell id="23" universe="1" material="3" surfaces="2"    />
+  <cell id="21" universe="1" material="1" region="-1"   />
+  <cell id="22" universe="1" material="2" region="1 -2" />
+  <cell id="23" universe="1" material="3" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="24" universe="2" material="3" surfaces="-3"   />
-  <cell id="25" universe="2" material="2" surfaces="3 -4" />
-  <cell id="26" universe="2" material="3" surfaces="4"    />
+  <cell id="24" universe="2" material="3" region="-3"   />
+  <cell id="25" universe="2" material="2" region="3 -4" />
+  <cell id="26" universe="2" material="3" region="4"    />
 
   <!-- Fuel pin, cladding, hot water -->
-  <cell id="27" universe="3" material="1" surfaces="-1"   />
-  <cell id="28" universe="3" material="2" surfaces="1 -2" />
-  <cell id="29" universe="3" material="4" surfaces="2"    />
+  <cell id="27" universe="3" material="1" region="-1"   />
+  <cell id="28" universe="3" material="2" region="1 -2" />
+  <cell id="29" universe="3" material="4" region="2"    />
 
   <!-- Instrumentation guide tube -->
-  <cell id="30" universe="4" material="4" surfaces="-3"   />
-  <cell id="31" universe="4" material="2" surfaces="3 -4" />
-  <cell id="32" universe="4" material="4" surfaces="4"    />
+  <cell id="30" universe="4" material="4" region="-3"   />
+  <cell id="31" universe="4" material="2" region="3 -4" />
+  <cell id="32" universe="4" material="4" region="4"    />
 
   <!-- cell for water assembly (cold) -->
-  <cell id="50" universe="5" material="4" surfaces="34 -35" />
+  <cell id="50" universe="5" material="4" region="34 -35" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="60" universe="6" fill="100"   surfaces="34 -35" />
+  <cell id="60" universe="6" fill="100"   region="34 -35" />
 
   <!-- cell for water assembly (hot) -->
-  <cell id="70" universe="7" material="3" surfaces="35 -36" />
+  <cell id="70" universe="7" material="3" region="35 -36" />
 
   <!-- containing cell for fuel assembly -->
-  <cell id="80" universe="8" fill="101"   surfaces="35 -36" />
+  <cell id="80" universe="8" fill="101"   region="35 -36" />
 
   <!-- Fuel Assembly (Lower Half) -->
   <lattice id="100">
diff --git a/tests/test_tally_nuclides/geometry.xml b/tests/test_tally_nuclides/geometry.xml
index 65954a785..7c3aefe88 100644
--- a/tests/test_tally_nuclides/geometry.xml
+++ b/tests/test_tally_nuclides/geometry.xml
@@ -4,7 +4,7 @@
   <surface id="1"  type="sphere" coeffs="0. 0. 0. 1.4" />
   <surface id="2"  type="sphere" coeffs="0. 0. 0. 5.35" boundary="vacuum" />
 
-  <cell id="1"  material="void" surfaces="-1" />      <!-- cavity -->
-  <cell id="2"  material="1"    surfaces=" 1  -2" />  <!-- Pu Core -->
+  <cell id="1"  material="void" region="-1" />      <!-- cavity -->
+  <cell id="2"  material="1"    region=" 1  -2" />  <!-- Pu Core -->
 
 </geometry>
diff --git a/tests/test_trace/geometry.xml b/tests/test_trace/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_trace/geometry.xml
+++ b/tests/test_trace/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_track_output/geometry.xml b/tests/test_track_output/geometry.xml
index 3b5a49311..5b16fe26c 100644
--- a/tests/test_track_output/geometry.xml
+++ b/tests/test_track_output/geometry.xml
@@ -15,22 +15,22 @@
     <!-- pin-cell construction -->
 
       <!-- Water pin-cell -->
-      <cell id="11" universe="1" material="1" surfaces="-99"/>
-      <cell id="12" universe="1" material="1" surfaces=" 99"/>
+      <cell id="11" universe="1" material="1" region="-99"/>
+      <cell id="12" universe="1" material="1" region=" 99"/>
 
       <!-- Fuel Rod -->
-      <cell id="21" universe="2" material="2" surfaces="  -1"/>  <!-- fuel  -->
-      <cell id="22" universe="2" material="3" surfaces="1 -2"/>  <!-- clad  -->
-      <cell id="23" universe="2" material="1" surfaces="   2"/>  <!-- water -->
+      <cell id="21" universe="2" material="2" region="  -1"/>  <!-- fuel  -->
+      <cell id="22" universe="2" material="3" region="1 -2"/>  <!-- clad  -->
+      <cell id="23" universe="2" material="1" region="   2"/>  <!-- water -->
 
       <!-- Pyrex Rod -->
-      <cell id="31" universe="3" material="4" surfaces="  -3"/>  <!-- pyrex -->
-      <cell id="32" universe="3" material="1" surfaces="   3"/>  <!-- water -->
+      <cell id="31" universe="3" material="4" region="  -3"/>  <!-- pyrex -->
+      <cell id="32" universe="3" material="1" region="   3"/>  <!-- water -->
 
   <!-- Assembly construction -->
 
     <!-- Dummy Water Assembly Universe -->
-      <cell id="99" universe="999" fill="1" surfaces="-99"/>
+      <cell id="99" universe="999" fill="1" region="-99"/>
 
     <!-- Central Fuel Assemblies -->
 
@@ -56,7 +56,7 @@
           2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
         </universes>
       </lattice>
-      <cell id="111" universe="111" fill="11" surfaces=""/>
+      <cell id="111" universe="111" fill="11" region=""/>
       
       <!-- North Fuel Assembly -->      
       <lattice id="22" dimension="15 15">
@@ -80,10 +80,10 @@
           2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
         </universes>
       </lattice>
-      <cell id="222" universe="222" fill="22" surfaces=""/>                     <!-- north -->
-      <cell id="444" universe="444" fill="222" surfaces="" rotation="0 0 90"/>  <!-- west  -->
-      <cell id="555" universe="555" fill="222" surfaces="" rotation="0 0 180"/> <!-- south -->
-      <cell id="666" universe="666" fill="222" surfaces="" rotation="0 0 270"/> <!-- east  -->
+      <cell id="222" universe="222" fill="22" region=""/>                     <!-- north -->
+      <cell id="444" universe="444" fill="222" region="" rotation="0 0 90"/>  <!-- west  -->
+      <cell id="555" universe="555" fill="222" region="" rotation="0 0 180"/> <!-- south -->
+      <cell id="666" universe="666" fill="222" region="" rotation="0 0 270"/> <!-- east  -->
       
       <!-- Northeast Fuel Assembly -->      
       <lattice id="33" dimension="15 15">
@@ -107,10 +107,10 @@
           2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
         </universes>
       </lattice>
-      <cell id="333" universe="333" fill="33" surfaces=""/>                     <!-- northeast -->
-      <cell id="777" universe="777" fill="333" surfaces="" rotation="0 0 90"/>  <!-- northwest -->
-      <cell id="888" universe="888" fill="333" surfaces="" rotation="0 0 180"/> <!-- southwest -->
-      <cell id="998" universe="998" fill="333" surfaces="" rotation="0 0 270"/> <!-- southeast -->
+      <cell id="333" universe="333" fill="33" region=""/>                     <!-- northeast -->
+      <cell id="777" universe="777" fill="333" region="" rotation="0 0 90"/>  <!-- northwest -->
+      <cell id="888" universe="888" fill="333" region="" rotation="0 0 180"/> <!-- southwest -->
+      <cell id="998" universe="998" fill="333" region="" rotation="0 0 270"/> <!-- southeast -->
 
     <!-- Surrounding Driver Assemblies -->
 
@@ -136,7 +136,7 @@
           2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
         </universes>
       </lattice>
-      <cell id="240" universe="240" fill="24" surfaces="-99"/>
+      <cell id="240" universe="240" fill="24" region="-99"/>
 
       <!-- North Edge -->
       <lattice id="14" dimension="15 15">
@@ -160,10 +160,10 @@
           2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
         </universes>
       </lattice>
-      <cell id="140" universe="140" fill="14" surfaces=""/>                     <!-- north -->
-      <cell id="410" universe="410" fill="140" surfaces="" rotation="0 0 90"/>  <!-- east  -->
-      <cell id="740" universe="740" fill="140" surfaces="" rotation="0 0 180"/> <!-- south -->
-      <cell id="470" universe="470" fill="140" surfaces="" rotation="0 0 270"/> <!-- west  -->
+      <cell id="140" universe="140" fill="14" region=""/>                     <!-- north -->
+      <cell id="410" universe="410" fill="140" region="" rotation="0 0 90"/>  <!-- east  -->
+      <cell id="740" universe="740" fill="140" region="" rotation="0 0 180"/> <!-- south -->
+      <cell id="470" universe="470" fill="140" region="" rotation="0 0 270"/> <!-- west  -->
 
       <!-- Northeast Edge Corner -->
       <lattice id="15" dimension="15 15">
@@ -187,10 +187,10 @@
           2 2 2 1 1 1 1 1 1 1 1 1 1 1 1
         </universes>
       </lattice>
-      <cell id="150" universe="150" fill="15" surfaces=""/>                     <!-- northeast -->
-      <cell id="130" universe="130" fill="150" surfaces="" rotation="0 0 90"/>  <!-- northwest -->
-      <cell id="510" universe="510" fill="150" surfaces="" rotation="0 0 180"/> <!-- southwest -->
-      <cell id="570" universe="570" fill="150" surfaces="" rotation="0 0 270"/> <!-- southeast -->
+      <cell id="150" universe="150" fill="15" region=""/>                     <!-- northeast -->
+      <cell id="130" universe="130" fill="150" region="" rotation="0 0 90"/>  <!-- northwest -->
+      <cell id="510" universe="510" fill="150" region="" rotation="0 0 180"/> <!-- southwest -->
+      <cell id="570" universe="570" fill="150" region="" rotation="0 0 270"/> <!-- southeast -->
 
       <!-- Northeast Top Steps -->
       <lattice id="25" dimension="15 15">
@@ -214,10 +214,10 @@
           2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
         </universes>
       </lattice>
-      <cell id="250" universe="250" fill="25" surfaces=""/>                     <!-- northeast -->
-      <cell id="320" universe="320" fill="250" surfaces="" rotation="0 0 90"/>  <!-- northwest -->
-      <cell id="630" universe="630" fill="250" surfaces="" rotation="0 0 180"/> <!-- southwest -->
-      <cell id="560" universe="560" fill="250" surfaces="" rotation="0 0 270"/> <!-- southeast -->
+      <cell id="250" universe="250" fill="25" region=""/>                     <!-- northeast -->
+      <cell id="320" universe="320" fill="250" region="" rotation="0 0 90"/>  <!-- northwest -->
+      <cell id="630" universe="630" fill="250" region="" rotation="0 0 180"/> <!-- southwest -->
+      <cell id="560" universe="560" fill="250" region="" rotation="0 0 270"/> <!-- southeast -->
 
 
       <!-- Northeast Middle Corner -->
@@ -242,10 +242,10 @@
           2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 
         </universes>
       </lattice>
-      <cell id="260" universe="260" fill="26" surfaces=""/>                     <!-- northeast -->
-      <cell id="220" universe="220" fill="260" surfaces="" rotation="0 0 90"/>  <!-- southeast -->
-      <cell id="620" universe="620" fill="260" surfaces="" rotation="0 0 180"/> <!-- southwest -->
-      <cell id="660" universe="660" fill="260" surfaces="" rotation="0 0 270"/> <!-- northwest -->
+      <cell id="260" universe="260" fill="26" region=""/>                     <!-- northeast -->
+      <cell id="220" universe="220" fill="260" region="" rotation="0 0 90"/>  <!-- southeast -->
+      <cell id="620" universe="620" fill="260" region="" rotation="0 0 180"/> <!-- southwest -->
+      <cell id="660" universe="660" fill="260" region="" rotation="0 0 270"/> <!-- northwest -->
 
       <!-- Northeast Bottom Steps -->
       <lattice id="36" dimension="15 15">
@@ -269,10 +269,10 @@
           2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
         </universes>
       </lattice>
-      <cell id="360" universe="360" fill="36" surfaces=""/>                     <!-- northeast -->
-      <cell id="230" universe="230" fill="360" surfaces="" rotation="0 0 90"/>  <!-- southeast -->
-      <cell id="520" universe="520" fill="360" surfaces="" rotation="0 0 180"/> <!-- southwest -->
-      <cell id="650" universe="650" fill="360" surfaces="" rotation="0 0 270"/> <!-- northwest -->
+      <cell id="360" universe="360" fill="36" region=""/>                     <!-- northeast -->
+      <cell id="230" universe="230" fill="360" region="" rotation="0 0 90"/>  <!-- southeast -->
+      <cell id="520" universe="520" fill="360" region="" rotation="0 0 180"/> <!-- southwest -->
+      <cell id="650" universe="650" fill="360" region="" rotation="0 0 270"/> <!-- northwest -->
 
 
   <!-- Core construction -->
@@ -299,7 +299,7 @@
     </lattice>
 
     <!-- Core Bounding Cell -->
-    <cell id="1111" universe="0" fill="99"   surfaces="10 -20 -30"/>
-    <cell id="1112" universe="0" material="3" surfaces="10 -20 30 -40"/>
+    <cell id="1111" universe="0" fill="99"   region="10 -20 -30"/>
+    <cell id="1112" universe="0" material="3" region="10 -20 30 -40"/>
 
 </geometry>
diff --git a/tests/test_translation/geometry.xml b/tests/test_translation/geometry.xml
index 1390691dc..e2cdf2391 100644
--- a/tests/test_translation/geometry.xml
+++ b/tests/test_translation/geometry.xml
@@ -5,7 +5,7 @@
   <surface id="2" type="z-plane" coeffs="-100" />
   <surface id="3" type="z-plane" coeffs="100" />
 
-  <cell id="1" fill="2" translation="2.3 5.0 -10.0" surfaces="-1" />
-  <cell id="2" universe="2" material="1" surfaces="2 -3" />
+  <cell id="1" fill="2" translation="2.3 5.0 -10.0" region="-1" />
+  <cell id="2" universe="2" material="1" region="2 -3" />
 
 </geometry>
diff --git a/tests/test_trigger_batch_interval/geometry.xml b/tests/test_trigger_batch_interval/geometry.xml
index 65954a785..7c3aefe88 100644
--- a/tests/test_trigger_batch_interval/geometry.xml
+++ b/tests/test_trigger_batch_interval/geometry.xml
@@ -4,7 +4,7 @@
   <surface id="1"  type="sphere" coeffs="0. 0. 0. 1.4" />
   <surface id="2"  type="sphere" coeffs="0. 0. 0. 5.35" boundary="vacuum" />
 
-  <cell id="1"  material="void" surfaces="-1" />      <!-- cavity -->
-  <cell id="2"  material="1"    surfaces=" 1  -2" />  <!-- Pu Core -->
+  <cell id="1"  material="void" region="-1" />      <!-- cavity -->
+  <cell id="2"  material="1"    region=" 1  -2" />  <!-- Pu Core -->
 
 </geometry>
diff --git a/tests/test_trigger_no_batch_interval/geometry.xml b/tests/test_trigger_no_batch_interval/geometry.xml
index 65954a785..7c3aefe88 100644
--- a/tests/test_trigger_no_batch_interval/geometry.xml
+++ b/tests/test_trigger_no_batch_interval/geometry.xml
@@ -4,7 +4,7 @@
   <surface id="1"  type="sphere" coeffs="0. 0. 0. 1.4" />
   <surface id="2"  type="sphere" coeffs="0. 0. 0. 5.35" boundary="vacuum" />
 
-  <cell id="1"  material="void" surfaces="-1" />      <!-- cavity -->
-  <cell id="2"  material="1"    surfaces=" 1  -2" />  <!-- Pu Core -->
+  <cell id="1"  material="void" region="-1" />      <!-- cavity -->
+  <cell id="2"  material="1"    region=" 1  -2" />  <!-- Pu Core -->
 
 </geometry>
diff --git a/tests/test_trigger_no_status/geometry.xml b/tests/test_trigger_no_status/geometry.xml
index 65954a785..7c3aefe88 100644
--- a/tests/test_trigger_no_status/geometry.xml
+++ b/tests/test_trigger_no_status/geometry.xml
@@ -4,7 +4,7 @@
   <surface id="1"  type="sphere" coeffs="0. 0. 0. 1.4" />
   <surface id="2"  type="sphere" coeffs="0. 0. 0. 5.35" boundary="vacuum" />
 
-  <cell id="1"  material="void" surfaces="-1" />      <!-- cavity -->
-  <cell id="2"  material="1"    surfaces=" 1  -2" />  <!-- Pu Core -->
+  <cell id="1"  material="void" region="-1" />      <!-- cavity -->
+  <cell id="2"  material="1"    region=" 1  -2" />  <!-- Pu Core -->
 
 </geometry>
diff --git a/tests/test_trigger_tallies/geometry.xml b/tests/test_trigger_tallies/geometry.xml
index 65954a785..7c3aefe88 100644
--- a/tests/test_trigger_tallies/geometry.xml
+++ b/tests/test_trigger_tallies/geometry.xml
@@ -4,7 +4,7 @@
   <surface id="1"  type="sphere" coeffs="0. 0. 0. 1.4" />
   <surface id="2"  type="sphere" coeffs="0. 0. 0. 5.35" boundary="vacuum" />
 
-  <cell id="1"  material="void" surfaces="-1" />      <!-- cavity -->
-  <cell id="2"  material="1"    surfaces=" 1  -2" />  <!-- Pu Core -->
+  <cell id="1"  material="void" region="-1" />      <!-- cavity -->
+  <cell id="2"  material="1"    region=" 1  -2" />  <!-- Pu Core -->
 
 </geometry>
diff --git a/tests/test_uniform_fs/geometry.xml b/tests/test_uniform_fs/geometry.xml
index b9b880d08..90cf35461 100644
--- a/tests/test_uniform_fs/geometry.xml
+++ b/tests/test_uniform_fs/geometry.xml
@@ -8,6 +8,6 @@
   <surface id="4" type="y-plane" coeffs="10" boundary="vacuum"/>
   <surface id="5" type="z-plane" coeffs="-10" boundary="vacuum"/>
   <surface id="6" type="z-plane" coeffs="10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="1 -2 3 -4 5 -6" />
+  <cell id="1" material="1" region="1 -2 3 -4 5 -6" />
 
 </geometry>
diff --git a/tests/test_union_energy_grids/geometry.xml b/tests/test_union_energy_grids/geometry.xml
index 612e46132..bc56030e1 100644
--- a/tests/test_union_energy_grids/geometry.xml
+++ b/tests/test_union_energy_grids/geometry.xml
@@ -3,6 +3,6 @@
 
   <!-- Sphere with radius 10 -->
   <surface id="1" type="sphere" coeffs="0 0 0 10" boundary="vacuum"/>
-  <cell id="1" material="1" surfaces="-1" />
+  <cell id="1" material="1" region="-1" />
     
 </geometry>
diff --git a/tests/test_universe/geometry.xml b/tests/test_universe/geometry.xml
index a0b8b2f4f..03f507bec 100644
--- a/tests/test_universe/geometry.xml
+++ b/tests/test_universe/geometry.xml
@@ -5,7 +5,7 @@
   <surface id="2" type="z-plane" coeffs="-100" />
   <surface id="3" type="z-plane" coeffs="100" />
 
-  <cell id="1" fill="2" surfaces="-1" />
-  <cell id="2" universe="2" material="1" surfaces="2 -3" />
+  <cell id="1" fill="2" region="-1" />
+  <cell id="2" universe="2" material="1" region="2 -3" />
 
 </geometry>
diff --git a/tests/test_void/geometry.xml b/tests/test_void/geometry.xml
index 99b78586a..48a72c7c3 100644
--- a/tests/test_void/geometry.xml
+++ b/tests/test_void/geometry.xml
@@ -21,20 +21,20 @@
   <surface id="17" type="z-plane"    coeffs="-14.15" boundary="vacuum" />
   <surface id="18" type="z-plane"    coeffs="14."    boundary="vacuum" />
 
-  <cell id="1"  material="void" surfaces="-1" />                  <!-- cavity -->
-  <cell id="2"  material="1"    surfaces=" 1  -3" />              <!-- Pu Core -->
-  <cell id="3"  material="void" surfaces=" 3  -4  12" />
-  <cell id="4"  material="void" surfaces=" 3  -5  11 -12" />
-  <cell id="5"  material="2"    surfaces=" 3  -7 -16" />          <!-- Bottom Reflector -->
-  <cell id="6"  material="2"    surfaces=" 4   6  -8  12" />      <!-- top reflector -->
-  <cell id="7"  material="void" surfaces=" 3  10 -11 -15" />
-  <cell id="8"  material="3"    surfaces=" 5  11 -12 -15" />      <!-- diaphragm -->
-  <cell id="9"  material="void" surfaces=" 7 -10  13 -15  17" />
-  <cell id="10" material="void" surfaces=" 8  12 -15 -18" />
-  <cell id="11" material="4"    surfaces=" 7  -9 -13 -10" />      <!-- copper cup -->
-  <cell id="12" material="3"    surfaces=" 9 -10 -14  17" />      <!-- shaft -->
-  <cell id="13" material="void" surfaces=" 9 -10 -13  14  17" />
-  <cell id="14" material="void" surfaces=" 3  -7 -10  16" />
-  <cell id="15" material="void" surfaces=" 4  -6  -8  12" />      <!-- polar hole in Top Reflector -->
+  <cell id="1"  material="void" region="-1" />                  <!-- cavity -->
+  <cell id="2"  material="1"    region=" 1  -3" />              <!-- Pu Core -->
+  <cell id="3"  material="void" region=" 3  -4  12" />
+  <cell id="4"  material="void" region=" 3  -5  11 -12" />
+  <cell id="5"  material="2"    region=" 3  -7 -16" />          <!-- Bottom Reflector -->
+  <cell id="6"  material="2"    region=" 4   6  -8  12" />      <!-- top reflector -->
+  <cell id="7"  material="void" region=" 3  10 -11 -15" />
+  <cell id="8"  material="3"    region=" 5  11 -12 -15" />      <!-- diaphragm -->
+  <cell id="9"  material="void" region=" 7 -10  13 -15  17" />
+  <cell id="10" material="void" region=" 8  12 -15 -18" />
+  <cell id="11" material="4"    region=" 7  -9 -13 -10" />      <!-- copper cup -->
+  <cell id="12" material="3"    region=" 9 -10 -14  17" />      <!-- shaft -->
+  <cell id="13" material="void" region=" 9 -10 -13  14  17" />
+  <cell id="14" material="void" region=" 3  -7 -10  16" />
+  <cell id="15" material="void" region=" 4  -6  -8  12" />      <!-- polar hole in Top Reflector -->
 
 </geometry>