A Minimal-Content Gadolinia in Above-5wt Enrichment Fuel for Criticality Safety in Next-Generation LWR

摘要

An above-5wt% enrichment UO_2 fuel with "minimal-content gadolinia (MCG)" is proposed for next generation light water reactors (LWRs). The fuel features super high burnup of 70GWd/t and criticality safety for the front-end scene of a fuel cycle such as UO2 fuel fabrication facility, fresh fuel transport and storage. The MCG fuel realizes a super high burnup fuel without its reactivity penalty at the end of operating cycle (EOC).This study has revealed that gadolinia content ranging from ～50 to ～300 ppm is required for a BWR fuel of UO_2 enriched to 6 to 10 wt%. A next generation BWR core without MCG was selected as a reference core. Nuclear characteristics of MCG for the BWR core were analyzed through 3-D core simulation. While the MCG fuels, introduced in the reference core, suppressed the hot excess reactivity by 0.4%Ak at the beginning of operating cycle (BOC), the MCG core reactivity recovered at 2~3GWd/t. Thermal performances such as maximum linear heat generation rate (MLHGR) and minimum critical power ratio (MCPR) were comparable with those of the reference core.