XGPT example

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Example on calculation of reaction-wise reactivity temperature coefficients using xGPT.

Input

% --- Infinite homogeneous critical U235, U238, H1, B10 mixture

surf 1  inf

cell 1  0  fuel   -1
cell 2  0  outside 1

mat fuel         sum
 92235.03c  1.12633E-03
 92238.03c  2.18178E-02
  1001.03c  4.58880E-02
  5010.03c  8.61741e-5

% --- Cross section library

set acelib "/home/tpvtuomas/xsdata/xsss2-beta/sss_endfb71.xsdata"

% --- Neutron population

set pop 10000 100000 20 1 50 50

% --- Neutron and event buffer sizes

set nbuf 3 3

% --- The response we are interested in is k-effective

sens resp keff

% --- Use custom perturbations

%     For example:
%     CPT.txt contains relative difference of fuel material macroscopic capture XSs
%     in 300 K and 301 K (Sig_301 - Sig_300)/Sig_300
%     The value is scored when interactions happen in material "fuel"
%     and the sampled reaction is a capture reaction "capt", i.e. any reaction with
%     total neutron yield of 0.0

% --- This should yield the temperature reactivity effect of these three
%     (sum) reaction types

sens pert custom DopCPT  efunc "CPT.txt"  matlist fuel realist capt
sens pert custom DopFISS efunc "FISS.txt" matlist fuel realist fiss
sens pert custom DopELA  efunc "ELA.txt"  matlist fuel realist ela

% --- Number of latent generations to use

sens opt latgen 14

% --- Score perturbations directly to a result array (do not store events)

sens opt direct 0.20

% --- Define energy grid to be used (one that covers whole neutron energy range)

sens opt egrid myGrid

ene myGrid 1 1e-11 2e1

Each of the three files CPT.txt, FISS.txt and CPT.txt have a similar structure

lin-lin
96219
E1 f1
E2 f2
...
E96219 f96219

where the E and f are energy-value pairs. To calculate the values for the energy dependent functions at each point, the user needs to obtain the material macroscopic cross sections at temperatures of 300 K and 301 K, based on which the relative difference between the two can be then calculated. The cross sections can be obtained, e.g. via the use of the set xsplot.