大型MOX燃料快堆钠空泡反应性微扰理论研究

钠空泡反应性效应是钠冷快堆核设计和安全分析的重要内容。本文基于多群节块扩散法，采用微扰理论推导出钠空泡反应性的计算方法，对1 000 MWe钠冷快堆MOX燃料堆芯的总钠空泡反应性、空间分布、物理分项进行了计算。结果表明，钠空泡反应性主要来源于中子泄漏的增加和能谱的硬化，两者一正一负，且空间分布规律相反，导致钠空泡反应性具有强烈的空间依赖性；对于所计算的MOX燃料堆芯钠空泡反应性高达3 $左右。计算和分析结果阐明了钠空泡反应性的产生机理和分布规律，可为低钠空泡的设计提供参考。

Research on Sodium Void Reactivity of Large MOX-fueled Sodium-cooled Fast Reactor by Perturbation Theory

The sodium void reactivity effect is one of the most important safety issues of sodium-cooled fast reactor (SFR) in nuclear design and safety analysis. In this paper, based on the nodal diffusion method and perturbation theory, a calculation method on sodium void reactivity was established, and the total sodium void reactivity, spatial distribution and physical components for MOX-fueled 1 000 MWe SFR were calculated. The results show that the main contributors to the sodium void reactivity lie in two aspects, the increasing of leakage and the hardening of spectrum, which are opposite both in sign and in spatial distribution, resulting in a strong dependence upon space. For the reference MOX-fueled core, the sodium void reactivity reaches approximately 3 $. The results reveal the mechanism of sodium void reactivity and its distribution, and provide reference for the design of low sodium void reactivity cores.