The slope of the criticality curve calculated by CASMO4 is steeper than that obtained by MCODE. There are two reasons for this disagreement: 1. Differences in the number of fission products and actinides tracked in MCODE. One hundred fission products and 29 actinides were tracked in the MCODE calculation while about two hundred fission products and over 35 actinides were considered in the CASMO4 depletion calculations. 2. Differences in libraries between these two codes. MCODE utilized primarily ENDF-VI cross-section data. CASMO4 cross-section data are based on data files JEF-2.2 and ENDF/B-VI that are processed by NJOY-91.91 to generate libraries in 70 energy groups in CASMO4 format. Also to be noted is that CASMO4 has higher recoverable energy per fission than ORIGEN2.1 but exhibits faster burnup rate, i.e. against the expectations based on fission energy difference. Thus, the effect of differences in fission products and cross sections is more important than the differences in recoverable energy per fission.
PWR Lattice Calculations This part of the benchmark was performed in order to assure the capability of CASMO-4 and MCODE computer codes to manage assembly level 2D transport calculations with fuel depletion. As in the first part of the benchmark, the results obtained with CASMO-4 and MCODE will be compared to the results obtained by the participants of the IAEA Coordinative Research Program. The calculations were performed for a 17x17 PWR fuel assembly with octant symmetry. The assembly included 25 water hole positions without guide tubes. The assembly cans were not considered. The calculations were carried out at a constant specific power of 37.7 kW/kg of initial HM and with zero buckling. The assembly and fuel pin geometry as well as the material compositions are described in details in [Ruetten H.-J. et al., 2000] and [MacDonald P. et al., 2002].
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