Study on burnup characteristics of actinide burnable poisons in plate-type fuel assembly

In order to study the burnup characteristics of actinide burnable poisons in plate-type fuel assembly and the feasibility of actinide burnable poisons in extending core lifetime, the burnable poison loading, burnup depth and utilization of ²³⁵U in plate-type fuel assemblies with different enrichments but same initial k_inf were calculated and analyzed in this paper. The results show that, in the case of low enrichment (4% ∼ 7%), ²⁴⁰Pu burnable poison exhibits a good conversion effect during the lifetime, and the utilization of ²³⁵U is high, which plays a role in extending lifetime. In the case of medium enrichment (25% ∼ 40%), the conversion effect of the ²⁴⁰Pu burnable poison is weakened. The ²³¹Pa burnable poison exhibits a better conversion effect during the lifetime. In the case of high enrichment (70% ∼ 97%), the assemblies containing ²³¹Pa can achieve the deepest burnup and its utilization of ²³⁵U is also the highest, although the conversion effect of the ²³¹Pa burnable poison is weakened. It can be concluded that, ²⁴⁰Pu can be used as the burnable poisons for the low enrichment fuel for long lifetime purpose. However, ²³¹Pa is preferred for the circumstances of medium and high enrichment fuels. (authors)