²³⁷Np替换可燃毒物对压水堆BEAVRS模型安全性的影响

The Effect of ²³⁷Np Partial Substitution for Burnable Poison on Safety of PWR BEAVRS Model

摘要: 次锕系元素是压水堆乏燃料放射性的重要来源之一，²³⁷Np在乏燃料次锕系元素中质量占比为50%左右。BEAVRS模型是麻省理工学院计算反应堆物理小组2013年基于商用压水堆建立的全堆芯高精度模型，具有丰富的堆芯细节和实测数据。本文基于BEAVRS模型引入了三种方案，用²³⁷NpO₂部分替换原堆芯可燃毒物B₂O₃，使用MCNP5模拟计算得出：同等体积下使用²³⁷NpO₂替换可燃毒物B₂O₃均会使堆芯有效增殖因数减小，随着替换质量的增加，减小的趋势趋缓。三种方案对堆芯燃料温度系数几乎没有影响，但会使慢化剂温度系数绝对值增大，有利于堆芯安全性。

Abstract: Minor actinide is one of the most important radioactive sources of Pressurized Water Reactor (PWR) spent fuel; the mass fraction of ²³⁷Np in minor actinide is about 50%. BEAVRS model is a Bench mark for Evaluation And Validation of Reactor Simulations published by MIT Computational Reactor Physics Group. BRAVRS is a full-core PWR benchmark based on a commercial nuclear power plant that provides a detailed description of components in reactor core and measured value of operating parameters. Based on BEAVRS model, we introduce three patterns of ²³⁷NpO₂ partial substitution for burnable poison B₂O₃. The simulation results of MCNP5 indicate that ²³⁷NpO₂ partial substitution for burnable poison B₂O₃ will decrease effective multiplication factor; the trend of decrease will slowdown when the substitution mass increase. All three substitution patterns almost have no effect on fuel temperature coefficient, but will increase the absolute value of moderator temperature coefficient, that will enhance the safety of reactor.