From fb9f7e2d42345b68fdac1020728ca61fc59fb1da Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Tue, 25 Apr 2017 15:55:29 -0500
Subject: [PATCH] Check for elastic scattering with isotropic mu.

This apparently happens for Sm150 in JEFF 3.2.
---
 src/physics.F90 | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/physics.F90 b/src/physics.F90
index a946c161b2..d1e9921ef6 100644
--- a/src/physics.F90
+++ b/src/physics.F90
@@ -481,7 +481,11 @@ contains
     ! Sample scattering angle
     select type (dist => rxn % products(1) % distribution(1) % obj)
     type is (UncorrelatedAngleEnergy)
-      mu_cm = dist % angle % sample(E)
+      if (allocated(dist % angle % energy)) then
+        mu_cm = dist % angle % sample(E)
+      else
+        mu_cm = TWO*prn() - ONE
+      end if
     end select
 
     ! Determine direction cosines in CM