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