I'm calculating burnup of BWR fuel cell with option "set poi 1" to obtain 8-group XS.

In serpent 2.1.16 I got output in _res.m:

% Poison cross sections:

INF_XE135_MICRO_ABS - which, I believe, is cell-homogenised the 8-group microscopic XS of XE-135 absorption

INF_XE135_MACRO_ABS - which, I believe, is the same macro-XS

from _dep.m I got Xe-135 concentration in fuel. I re-normalised it by coefficient fuel_Volume/cell_Volume to get concentration in cell.

But if I multiply microXS on Xe-concentration I do not get macroXS - difference is about 20% in the thermal group.

That am I doing wrong?

Yuri

Update: I also defined the detector to get microXS for Xe-135:

Code: Select all

```
mat Xe135 1.0 Xe-135.09c 1.0
det flux8 du 0 de 8gr
det maXe du 0 dr -2 Xe135 de 8gr dt 3 flux8
```