### Bug in PN scattering cross sections and diffusion parameters

Posted:

**Thu Sep 02, 2010 11:41 pm**There is a bug in the calculation of PN scattering cross sections (SCATT0, SCATT1, SCATT2 ... SCATT5) and P1 diffusion parameters (P1_TRANSPXS, P1_DIFFCOEF, P1_MUBAR). The problem has been identified before (see description) and corrected in update 1.1.3 for all the other group constants.

The magnitude of the problem can be estimated by comparing the values of SCATT0 and SCATTXS. They should be the same within statistics, but in many cases there is a clear difference when there are void regions in the geometry. The problem can be avoided by replacing void regions with low-density gas, but this usually results in large statistical errors.

I'll try to fix the problem in update 1.1.14.

The magnitude of the problem can be estimated by comparing the values of SCATT0 and SCATTXS. They should be the same within statistics, but in many cases there is a clear difference when there are void regions in the geometry. The problem can be avoided by replacing void regions with low-density gas, but this usually results in large statistical errors.

I'll try to fix the problem in update 1.1.14.