组件型熔盐堆燃料组件的设计研究

Design of fuel assembly for molten-salt-cooled reactors

熔盐堆是第四代核反应堆的六种构型之一,具有良好的经济性和固有安全性。以球形包覆颗粒燃料元件为基本单元设计了可用于熔盐冷却高温堆的燃料组件,并在此燃料组件模型下构建了组件型熔盐堆堆芯,研究了组件容器材料的种类、密度、厚度以及球形燃料元件中包覆颗粒填充率、FLi Be熔盐中7Li富集度对无限介质增殖因数K_(inf)、冷却剂反应性温度系数(Reactivity Temperature Coefficient,RTC)、排空反应性(Void Reactivity,VR)的影响。结果表明,作为组件材料,碳材料明显优于碳化硅材料;提高包覆颗粒(Tristructural Isotropic,TRISO)填充率、7Li富集度有利于提高堆芯的中子经济性和安全性。

Background： Molten salt reactor （MSR）, a fourth generation reactor, possesses good economy and inherent safety properties. By using the fuel assembly in molten-salt-cooled reactor, it is expected that the fuel load and release can be easier and reliable, which is similar to that widely used in LWR （Light Water Reactor）. Purpose： Based on spherical TRISO （Tristmctural Isotropic） coated particle fuel elements, this study aims to design a fuel assembly model for the high-temperature molten-salt-cooled reactor. Methods： The MCNP （A Monte Carlo N-Particle Transport Code） is employed to investigate the feasibility and behavior of the fuel assembly by analyzing the infinite multiplication factor Kinf, the reactivity temperature coefficient （RTC） and the void reactivity （VR） of the FLiBe coolant as a function of the composition, density and wall thickness of the assembly material, the TRISO coated particles packing factor and the enrichment of 7Li in FLiBe salt. Results and Conclusion： The results show that carbon-based materials are significantly better than silicon-carbide-based materials for fuel assembly. Increasing the TRISO packing factor and enrichment of 7Li helps to improve neutron economy and security properties of the reactor.