Power distribution investigation in the transition phase of the low moderation type MOX fueled LWR from the high conversion core to the breeding core

低減速型MOX燃料軽水炉の高転換炉心から増殖炉心への移行期における出力分布の検討

秋江 拓志  ; 中野 佳洋 ; 大久保 努

Akie, Hiroshi; Nakano, Yoshihiro; Okubo, Tsutomu

In the transition phase of Innovative Water Reactor for Flexible Fuel Cycle (FLWR) between high conversion (HC) and breeding (BR) type cores, there are two types of assemblies in the same core. Consequently, a region-wise spectrum difference is found which can lead to a large power peaking. For this reason, the power distribution of FLWR in this transition phase was studied by assembly and core calculations. Calculations on few assemblies geometries show large local power peakings can be effectively reduced by considering plutonium enrichment distribution in an assembly. In the whole core calculation, despite the power level mismatch between HC and BR assemblies, overall power distribution flattening is possible by optimizing fuel assemblies loading. The transition from HC to BR type FLWR seems feasible without difficulty.