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镤(Pa233)是钍铀燃料转换链中的重要核素,有着较长的半衰期(27.4 d)和较大的中子吸收截面,对于Th232到U233的转换率、钍铀燃料堆芯的运行都有着重大影响。在已有的使用钍燃料的热堆设计中,普遍对Pa233的这一特性作出了反应堆运行上的调整。该文利用基于Monte-Carlo方法的MCBurn程序系统,研究了Pa233核素在快中子能谱条件下的表现和对反应堆物理性能的影响,得到了Pa233核素在快谱和热谱下的不同性能对比,说明了Pa233对燃料转换比、反应堆开堆和停堆后反应性变化的重要影响,为钍基快堆及长寿命堆的设计提供了参考依据。
(Pa233) is an important nuclide in the thorium-uranium fuel conversion chain and has a long half-life (27.4 d) and a large neutron absorption cross section. For the conversion rate of Th232 to U233, the operation of the thorium-uranium fuel core Has a significant impact. In the existing thermal reactor design using thorium fuel, it is common to adjust reactor operation for this characteristic of Pa233. In this paper, MCBurn program system based on Monte-Carlo method is used to study the effect of Pa233 nuclide on the fast neutron spectrum and its effect on the physical properties of the reactor. The performance comparison shows that Pa233 has an important influence on the fuel conversion ratio, reactor reactivity and reactor reactivity after shutdown, and provides a reference for the design of thorium-based fast reactor and long-life reactor.