From 4ec05c643fef40fd66b1681fe36771504eae8c85 Mon Sep 17 00:00:00 2001
From: Sterling Harper <smharper@mit.edu>
Date: Mon, 18 Apr 2016 14:41:22 -0400
Subject: [PATCH] Add collision-estimated scattering derivatives

---
 src/tally.F90 | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/src/tally.F90 b/src/tally.F90
index 9f2bdc4a3a..0a6603f39b 100644
--- a/src/tally.F90
+++ b/src/tally.F90
@@ -3068,6 +3068,16 @@ contains
               score = score * deriv % flux_deriv
             end if
 
+          case (SCORE_SCATTER)
+            if (materials(p % material) % id == deriv % diff_material &
+                 .and. material_xs % total - material_xs % absorption /= ZERO) &
+                 then
+              score = score * (deriv % flux_deriv + ONE &
+                   / materials(p % material) % density_gpcc)
+            else
+              score = score * deriv % flux_deriv
+            end if
+
           case (SCORE_ABSORPTION)
             if (materials(p % material) % id == deriv % diff_material &
                  .and. material_xs % absorption /= ZERO) then
@@ -3146,6 +3156,22 @@ contains
               score = score * deriv % flux_deriv
             end if
 
+          case (SCORE_SCATTER)
+            if (i_nuclide == -1 .and. &
+                 materials(p % material) % id == deriv % diff_material .and. &
+                 material_xs % total - material_xs % absorption /= ZERO) then
+              score = score * (deriv % flux_deriv &
+                   + (micro_xs(deriv % diff_nuclide) % total &
+                   - micro_xs(deriv % diff_nuclide) % absorption) &
+                   / (material_xs % total - material_xs % absorption))
+            else if (scoring_diff_nuclide .and. &
+                 (micro_xs(deriv % diff_nuclide) % total &
+                 - micro_xs(deriv % diff_nuclide) % absorption) /= ZERO) then
+              score = score * (deriv % flux_deriv + ONE / atom_density)
+            else
+              score = score * deriv % flux_deriv
+            end if
+
           case (SCORE_ABSORPTION)
             if (i_nuclide == -1 .and. &
                  materials(p % material) % id == deriv % diff_material .and. &
@@ -3178,7 +3204,6 @@ contains
             if (i_nuclide == -1 .and. &
                  materials(p % material) % id == deriv % diff_material .and. &
                  material_xs % nu_fission /= ZERO) then
-              write(*, *) micro_xs(deriv % diff_nuclide) % nu_fission
               score = score * (deriv % flux_deriv &
                    + micro_xs(deriv % diff_nuclide) % nu_fission &
                    / material_xs % nu_fission)