From 5c5d120220cdf26eb555a8affbbce957f535f886 Mon Sep 17 00:00:00 2001
From: Bryan Herman <bherman@mit.edu>
Date: Sat, 14 Jan 2012 16:54:19 -0500
Subject: [PATCH] added zero flux trap

---
 src/cmfd_execute.F90 | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/src/cmfd_execute.F90 b/src/cmfd_execute.F90
index 01b10a73dc..9bb137274a 100644
--- a/src/cmfd_execute.F90
+++ b/src/cmfd_execute.F90
@@ -129,6 +129,21 @@ contains
             flux = t % scores(score_index,1) % val
             cmfd % flux(h,i,j,k) = flux
 
+            ! detect zero flux
+            if ((flux - 0.0D0) < 1.0D-10) then
+              if (.not. allocated(cmfd%coremap)) then
+                write(*,*) 'Fatal: detected zero flux without coremap'
+                stop
+              else
+                write(*,*) 'Warning: detected zero flux at:',i,j,k
+                flux = 99999.0D0
+                if (.not. cmfd%coremap(i,j,k) == 99999) then
+                  write(*,*) 'Fatal: need to check core map with zero flux'
+                  stop
+                end if
+              end if
+            end if
+ 
             ! get total rr and convert to total xs
             cmfd % totalxs(h,i,j,k) = t % scores(score_index,2) % val / flux