慢化剂氢化锆与氢化钇参数对TOPAZ-II反应堆功率分布的影响研究

Study on the Effects of Zirconium Hydride and Yttrium Hydride Parameters on TOPAZ-II Reactor Power Distribution

摘要: TOPAZ-II反应堆是使用固体金属氢化物为慢化剂的微型空间堆，常用的慢化剂材料是氢化锆。近年来，由于金属钇的制造成本降低，氢化钇逐渐成为TOPAZ-II反应堆慢化剂材料的新选择。使用MCNP程序对TOPAZ-II反应堆进行功率分布计算，分别研究氢化锆和氢化钇在不同条件下对反应堆功率的影响。计算结果表明：改变金属氢化物慢化剂的氢含量和温度参数时，堆芯径向功率峰因子的变化趋势决定了功率不均匀系数的变化趋势；慢化剂的氢含量和温度参数的改变会导致堆芯热中子分布发生变化，进而影响反应堆功率分布，低能热中子占中子群份额越高，堆芯径向功率峰因子越小；慢化剂周围的CO₂气体环境导致氢损失速率较小，对反应堆功率分布的影响很小；两种慢化剂呈正温度效应，氢化钇的温度系数比氢化锆的温度系数小，且以氢化钇为慢化剂的反应堆k_eff更高。

Abstract: The TOPAZ-II reactor is a micro-space reactor that uses solid metal hydride as the moderator, with zirconium hydride being the commonly used moderator material. In recent years, the reduced manufacturing cost of yttrium has led to yttrium hydride gradually becoming a new choice of moderator material for the TOPAZ-II reactor. The MCNP program was used to calculate the power distribution of the TOPAZ-II reactor and research the influence of zirconium hydride and yttrium hydride on the reactor power under different conditions. The calculation results show that the trend of the variation in radial power peak factor determines the trend of the variation in power inhomogeneous coefficient when changing the hydrogen content and temperature parameters of the metal hydride moderator. Changes in hydrogen content and temperature parameters of the moderator can cause changes in the thermal neutron distribution in the core, thereby affecting the reactor power distribution. The higher the proportion of low-energy thermal neutrons in the neutron group, the smaller the radial power peak factor in reaction core. The CO₂ gas environment surrounding the moderator causes a lower rate of hydrogen loss, resulting in minimal impact on the reactor power distribution. Both moderators exhibit positive temperature effects, with the temperature coefficient of hydrogenated yttrium being smaller than that of hydrogenated zirconium, and the k_eff of the reactor with hydrogenated yttrium as the moderator is higher.