氟锂铍熔盐热中子散射效应对熔盐堆中子学性能的影响  

Influence of thermal neutron scattering effect of FLiBe molten salt on neutronic performance of molten salt reactors

作　　者：张志成 胡继峰[1,3] 陈金根[1,2,3] 蔡翔舟 ZHANG Zhicheng;HU Jifeng;CHEN Jingen;CAI Xiangzhou(Shanghai Institute of Applied Physics,Chinese Academy of Sciences,Shanghai 201800,China;University of Chinese Academy of Sciences,Beijing 100049,China;CAS Innovative Academy in TMSR Energy System,Chinese Academy of Sciences,Shanghai 201800,China)

机构地区：[1]中国科学院上海应用物理研究所,上海201800 [2]中国科学院大学,北京100049 [3]中国科学院先进核能创新研究院,上海201800

出　　处：《核技术》2023年第7期118-124,共7页Nuclear Techniques

基　　金：国家自然科学基金(No.12135019)资助。

摘　　要：氟锂铍(FLiBe)熔盐作为液态熔盐堆的冷却剂和载体盐,具有一定的慢化性能,其热中子散射数据影响熔盐堆的中子学性能,进而影响熔盐堆物理设计和安全运行。基于通用蒙特卡罗粒子输运程序分析了液态FLiBe熔盐的热中子散射数据对65 MW熔盐堆堆芯中子能谱、不同能谱下有效增殖因数k_(eff)、核素反应率、温度反应性系数等中子学性能的影响。研究结果表明:考虑FLiBe熔盐热散射效应,堆芯中子能谱变硬,导致~(235)U裂变反应率和k_(eff)变小,燃料的温度反应性系数中多普勒系数减小0.28×10~(-5) K~(-1),而密度反应性系数几乎无变化。当堆芯由热谱转变为相对较快的中子能谱时,FLiBe熔盐热散射效应导致~(235)U裂变率减少的变化量降低,k_(eff)的下降幅度从9.2×10~(-4)变为2×10~(-4)。因此,熔盐堆堆芯物理计算需开展FLiBe熔盐的热中子散射数据影响的量化。[Background]FLiBe is commonly used as the coolant and carrier salt in liquid molten salt reactors(MSRs).Its certain moderating properties and thermal neutron scattering attributes affect the neutronic performance of the MSR,and this in turn influences the physical design and safe operation of the reactor.Consequently,studying FLiBe's thermal neutron scattering data is essential for MSRs.[Purpose]This study aims to analyze the influence of of FLiBe thermal neutron scattering on neutronic performances of a 65-MW MSR.[Methods]First,according to the requirements,a core model of a 65-MW MSR was established by using the general Monte Carlo procedure.Then,the neutronics performance of the MSR was calculated by considering the scattering cross-section of the free gas model and FLiBe thermal neutron scattering data(e.g.,the neutron spectrum,effective multiplication factor,and nuclide reactivity rate).Finally,the changes in the influence of FLiBe thermal neutron scattering effect on neutronic properties under different energy spectra were compared.[Results]The computation results show that,by considering the thermal scattering effect of FLiBe molten salt,the neutron energy spectrum in the core of the MSR becomes harder,235U fission rate decreases,the keff value of the reactor decreases,but the density coefficient in the temperature reaction coefficient of the fuel keeps almost unchanged,and the Doppler coefficient decreases by 0.28×10-5 K-1.With the hardening of the energy spectrum,the variation in the 235U fission rate reduction decreases,and the decrease in keff caused by thermal neutron scattering changs from 9.2×10-4 to 2×10-4.[Conclusions]Therefore,it is necessary to incorporate FliBe's thermal neutron scattering data into the physical calculations for the MSR core.

关 键 词：熔盐堆 氟锂铍熔盐 热中子散射截面 有效增殖因数 

分 类 号：TL99[核科学技术—核技术及应用]