Comparison of nuclear parameters for a LMFBR heterogenous Benchmark core. Influence of different basic data sets and processing codes

A LMFBR heterogenous core model was a few years ago proposed by CEA as a Benchmark core for comparative calculations. The geometrical RZ model consists of three radial fissile zones of the same enrichment divided at the midplane by an axial slice of internal breeder material. The fissile zones are separated by three internal breeder zones, one central zone and two breeder rings. The core has been studied with 2D diffusion codes in 10 to 25 energy groups. Comparisons have been made between CEA (CARNAVAL III) INTERATOM (KEKINR) and STUDSVIK (ENDF IV) solutions. THe spread in k (sub)eff is 1.7 percent with the lowest value for STUDSVIK (ENDF IV) and the highest value for INTERATOM (KFKINR). The spread in breeding ratio is 0.03 with the highest value for STUDSVIK and lowest for INTERATOM. This spread in k (sub) eff and BR is of the same magnitude as for homogenous benchmark core. The variations in the sodium void effect between CARNAVAL III, KFKINR and ENDF IV solutions are rather similar for the heterogenous and homogenous benchmark cores. Comparison of one-group core fission and capture cross sections indicate a dominating influence of the processing codes. The influence on k (sub) eff seem to be smaller due to cancelling effects. (author)