From f72eda7f282f2d79de8466090a6d1bb342a99105 Mon Sep 17 00:00:00 2001
From: Will Boyd <wbinventor@gmail.com>
Date: Mon, 19 Oct 2015 10:25:45 -0400
Subject: [PATCH] The ScatterMatrixXS now optionally creates tallies for P0
 transport correction

---
 openmc/mgxs/library.py |  4 ++++
 openmc/mgxs/mgxs.py    | 52 ++++++++++++++++++++++++++++++++++--------
 2 files changed, 46 insertions(+), 10 deletions(-)

diff --git a/openmc/mgxs/library.py b/openmc/mgxs/library.py
index 8680e726ac..85cfaad3b0 100644
--- a/openmc/mgxs/library.py
+++ b/openmc/mgxs/library.py
@@ -244,6 +244,10 @@ class Library(object):
                 if self.tally_trigger:
                     mgxs.tally_trigger = self.tally_trigger
 
+                # Specify whether to use a transport ('P0') correction
+                if isinstance(mgxs, openmc.mgxs.ScatterMatrixXS):
+                    mgxs.correction = self.correction
+
                 mgxs.create_tallies()
                 self.all_mgxs[domain.id][mgxs_type] = mgxs
 
diff --git a/openmc/mgxs/mgxs.py b/openmc/mgxs/mgxs.py
index d4e368af5d..aa2abb0de5 100644
--- a/openmc/mgxs/mgxs.py
+++ b/openmc/mgxs/mgxs.py
@@ -1603,13 +1603,35 @@ class NuScatterXS(MGXS):
 
 
 class ScatterMatrixXS(MGXS):
-    """A scattering matrix multi-group cross section."""
+    """A scattering matrix multi-group cross section.
+
+    Attributes
+    ----------
+    correction : 'P0' or None
+        Apply the P0 correction to scattering matrices if set to 'P0'
+
+    """
 
     def __init__(self, domain=None, domain_type=None,
                  groups=None, by_nuclide=False, name=''):
         super(ScatterMatrixXS, self).__init__(domain, domain_type,
                                               groups, by_nuclide, name)
         self._rxn_type = 'scatter matrix'
+        self._correction = 'P0'
+
+    def __deepcopy__(self, memo):
+        clone = super(ScatterMatrixXS, self).__deepcopy__(memo)
+        clone._correction = self.correction
+        return clone
+
+    @property
+    def correction(self):
+        return self._correction
+
+    @correction.setter
+    def correction(self, correction):
+        cv.check_value('correction', correction, ('P0', None))
+        self._correction = correction
 
     def create_tallies(self):
         """Construct the OpenMC tallies needed to compute this cross section.
@@ -1625,8 +1647,12 @@ class ScatterMatrixXS(MGXS):
         energyout = openmc.Filter('energyout', group_edges)
 
         # Create a list of scores for each Tally to be created
-        scores = ['flux', 'scatter', 'scatter-P1']
-        filters = [[energy], [energy, energyout], [energyout]]
+        if self.correction == 'P0':
+            scores = ['flux', 'scatter', 'scatter-P1']
+            filters = [[energy], [energy, energyout], [energyout]]
+        else:
+            scores = ['flux', 'scatter']
+            filters = [[energy], [energy, energyout]]
 
         estimator = 'analog'
         keys = scores
@@ -1648,7 +1674,7 @@ class ScatterMatrixXS(MGXS):
         """
 
         # If using P0 correction subtract scatter-P1 from the diagonal
-        if correction == 'P0':
+        if self.correction == 'P0':
             scatter_p1 = self.tallies['scatter-P1']
             scatter_p1 = scatter_p1.get_slice(scores=['scatter-P1'])
             energy_filter = openmc.Filter(type='energy')
@@ -1924,16 +1950,22 @@ class NuScatterMatrixXS(ScatterMatrixXS):
 
         """
 
-        # Create a list of scores for each Tally to be created
-        scores = ['flux', 'nu-scatter', 'scatter-P1']
-        estimator = 'analog'
-        keys = ['flux', 'scatter', 'scatter-P1']
-
         # Create the non-domain specific Filters for the Tallies
         group_edges = self.energy_groups.group_edges
         energy = openmc.Filter('energy', group_edges)
         energyout = openmc.Filter('energyout', group_edges)
-        filters = [[energy], [energy, energyout], [energyout]]
+
+        # Create a list of scores for each Tally to be created
+        if self.correction == 'P0':
+            scores = ['flux', 'nu-scatter', 'scatter-P1']
+            estimator = 'analog'
+            keys = ['flux', 'scatter', 'scatter-P1']
+            filters = [[energy], [energy, energyout], [energyout]]
+        else:
+            scores = ['flux', 'nu-scatter']
+            estimator = 'analog'
+            keys = ['flux', 'scatter']
+            filters = [[energy], [energy, energyout]]
 
         # Intialize the Tallies
         super(ScatterMatrixXS, self).create_tallies(scores, filters,