Group cross section generation for MOX fuels with AMPX system

Abstract

Two revised procedures, the improved and the contracted conventional ones, are proposed to generate cross-section library suitable for the criticality safety analysis of Pu containing system. The AMPX code system is employed to produce the working library from 218 group CSRL-IV master library, and the KENO-IV to perform criticality calculation. The distinctive features of both procedures are the use of expanded group structure (51 neutron groups) for the final working library and heterogeneous modeling for the KENO calculation to treat the thermal resonances of Pu isotopes properly. Benchmark calculations have been carried out for six BPNL``s $UO_2$-2% $PuO_2$ (8% $Pu^240$) fueled critical experiments to verify the accuracy of the revised procedures. It is shown that both procedures predict the criticality with sufficient accuracy, the improved procedure with errors of -0.8-0.3 %Δk and the contracted conventional with errors of -0.3-1.3 %Δk. This is significant improvement over the conventional procedure which showed an error of about ±2%Δk for the same experiments. The improved procedure provides slightly better performance in terms of accuracy, but the contracted conventional would have more potential in the practical application because it requires less amount of cross section data and computer resources. Furthermore, although only feasibility is explored, the sensitivity study indicates that the modification of the energy spectrum and the Dancoff correction factor, if properly done, would make the contracted conventional more accurate.