Application of artificial rare earth compound (RE2O3) based neutron absorber in a PWR spent fuel cask

Abstract

In previous research, a new concept of a neutron absorption material (artificial rare earth compound, RE2O3) was introduced for criticality control in a spent fuel storage system, and its neutron absorption cross-section, effective lifetime etc. were analyzed to investigate its possibility as a neutron absorption material. In this study, some calculations based on the KSC-4 cask were performed to evaluate the practical applicability of the RE2O3 compound, and its required amount and radiation effect was analyzed using the MCNPX 2.7.0 code. In these calculations, the WH 17 x 17 assembly with 3.5 w/o enrichment, 35 GWD/MTU burnup, and 10-year cooling time was considered to perform a bounding analysis. As a result, the criticality is continually decreased with increasing mass of RE2O3 compound filled in neutron absorber, and the criticality in the original design is achieved by using the rod-type RE2O3 absorbers of 205 kg similar with the total mass of the Boral (TM) plates. In addition, the radiation emitted from the RE2O3 compound has a little effect on the radiation dose rates around the KSC-4 cask. Therefore, it is expected that the efficiency of radioactive waste management can be significantly improved by simultaneously keeping the RE2O3 compound and spent nuclear fuels in a compact space.