一体化小型氟盐冷却高温堆瞬态特性分析

Transient analysis of the integral small modular fluoride molten salt cooled high temperature reactor

根据下一代核能系统的发展目标,提出了采用自然循环的一体化小型氟盐冷却高温堆的概念。利用修改后的RELAR5-MS系统分析程序,建立了一体化小型氟盐冷却高温堆模型,并得到其稳态特性参数。在此基础上,对其在满功率运行状态下的反应性引入事故和失热阱事故进行了分析。分析计算表明,在反应性事故工况下,由于自然循环的存在,堆芯冷却剂流量随着堆芯温度发生动态变化,最终达到新的稳态,燃料棒和冷却剂温度均处于安全限值范围内。在失热阱事故下,反应堆负反馈的特性使得堆芯功率逐渐降低并实现自动停堆,即使不考虑余热排出系统的作用,燃料组件和冷却剂温度上升缓慢,在140 h内,燃料棒和冷却剂温度均处于全限值范围内。结果表明,一回路采用自然循环冷却的一体化小型氟盐冷却高温堆具有良好的固有安全性。

Background： Safety and economy is the goal of the next generation of nuclear power system as important indexes in the development of nuclear power system. According to the characteristics of fluoride molten salt reactor, the concept of the integral small modular fluoride molten salt cooled high temperature reactor which uses natural circulation for residual heat removal is proposed. Purpose： This study aims to analyze the transient characteristics under two kinds of incidents： the reactivity insertion incident and the heat sink loss incident. Methods： Based on the basis of the steady state simulation, modified RELAP5-MS software is employed to analyze the two kinds of incidents. Results： In the case of the reactivity insertion incident, as a result of the existence of natural circulation, the coolant flow rate of core changes dynamically with the core temperature, and reaches a new steady state eventually. The power of the core reduces gradually because of the negative feedback, and the reactor shutsdown eventually under the circumstance of heat trap loss incident. Taking no account of the residual heat removal system conservatively, the fuel assembly and the coolant temperature rise slowly. Fuel and coolant temperature are within safe limits within 140 h. Conclusion： The results show that natural circulation for residual heat removal in the first loop will guarantee the great safety features of the fluoride molten salt cooled high temperature reactor.