Studies on advanced LWR cores for effective use of plutonium and analysis of MOX physics experiments

Basic design studies of high moderation cores have been performed with the abject of higher plutonium consumption in advanced light water reactors (LWRs). Studied fuel assemblies have a hydrogen to heavy metal atom number ratio (H/HM) of 6 with additional water rods and 7 with a reduced fuel diameter for ABWRs, and H/HMs of 5 and 6 with reduced fuel diameters for APWRs. The design and analysis of equilibrium cores show that nuclear and thermal hydraulic parameters satisfy design criteria, and a fissile Pu consumption rate increases up to 20% for ABWRs and 50% for APWRs. Safety and stability analyses for the LWR plants with the high moderation cores have been also performed, and it was found that the high moderation cores are feasible from a viewpoint of safety. Study has also conducted for multiple recycling of Pu in the high moderation cores. In this study, recycling of depleted plutonium from spent MOX fuel was supplemented by that from spent UO₂ fuel. This paper also shows the analyses of the MOX critical experiments of MISTRAL and EPICURE programs. It was shown that analytical accuracy for the MOX cores was almost the same as that for the UO₂ cores in the programs and no significant difference was found in analytical accuracy between the cores with an H/HM of 3.7 and 5 for the MOX and UO₂ cores