熔盐实验堆备用停堆方案及其可行性分析

Standby shutdown modes and feasibility analysis of molten salt experimental reactor

反应性控制系统的设计是反应堆物理设计的主要内容之一。熔盐堆采用熔融的氟化盐混合物作为燃料,由于核燃料的特殊性,熔盐堆在反应堆设计方面与传统固体燃料反应堆有着较大区别。本文鉴于熔盐堆的特殊性,针对2MW液态燃料钍基熔盐堆(Thorium Molten Salt Reactor-Liquid Fuel,TMSR-LF1),提出多种停堆方式,包括排燃料盐、套管中注中子毒物、改变燃料盐成分、改变堆芯石墨栅元数,并进行了计算分析。分析结果表明:往套管中注入中子毒物是在控制棒失效的情况下很好的替换停堆方式;燃料盐成分可调,是熔盐堆本身具有的特点,因此往燃料盐中添加BF3、LiF-BeF2-ZrF4、LiF-ThF4,是调节堆芯反应性很好的方式;改变石墨栅元数也可以使反应堆停堆。本研究分析可以为熔盐堆停堆方式提供技术储备和理论参考。

[Background] Reactivity control design is one of the main contents of reactor neutronics design. Molten fluoride mixture was used as fuel in molten salt reactor (MSR). Due to the particularity of nuclear fuel, molten salt reactor is different from traditional solid fuel reactor in reactor design.[Purpose] This study aims at feasibility analysis of shutdown modes with emphasis on the standby scheme.[Methods] The shutdown modes includes discharging fuel salt, injecting neutron poison into the core tube, changing the composition of fuel salts, changing the number of graphite cells. The 2 MW thorium molten salt reactor-liquid fuel (TMSR-LF1) model was taken as the reference reactor, and the calculation was completed by using Monte Carlo N particle transport code (MCNP).[Results] The analysis results show that injection of neutron poison into the core tube was a good alternative to shutdown the reactor when the control rod cannot be inserted into the core. The adjustable composition of fuel salts was the characteristic of MSR itself, thus, adding BF3, LiF-BeF2-ZrF4, LiF-ThF4 to fuel salts was a good way to adjust the reactivity. Changing the number of graphite cells could also shutdown the reactor.[Conclusion] The analysis of this study can provide technical reserves and theoretical reference for the shutdown modes of molten salt reactor.