液态熔盐堆常用燃料盐增殖能力比较分析

Comparison and Analysis of Breeding Performance of Common Fuels for Molten Salt Reactor

熔盐堆作为第四代先进核能系统,具有中子经济性好、固有安全性高、在线换料、燃烧钍燃料等优点。本文针对熔盐快堆和熔盐热堆,采用MCNP5计算了熔盐堆中常用的9种燃料盐寿期初的临界性能和转换系数,并用中子平衡方法分析了影响转换系数的因素。从寿期初的计算数据分析,由于233 U具有较高的平均裂变中子数及较小的中子俘获截面,有利于提高反应堆增殖系数和燃料利用率。另外,熔盐中的23 Na相对于7 Li中子俘获截面更大,导致含23 Na燃料盐增殖系数相对较低,但对热堆的影响较小;而在快堆中,熔盐中采用Na元素相比采用Li元素更有利于中子能谱硬化,更适合快堆的增殖。

As the fourth generation advanced nuclear energy system,molten salt reactor has the advantages of good neutron economy,high intrinsic safety,on-line refueling and burn thorium fuel.For molten salt fast neutron reactor and molten salt thermal neutron reactor,the critical performance and conversion ratio of nine fuel salts commonly used in molten salt reactor at the beginning of cycle are calculated by MCNP5,and the factors affecting the conversion coefficient are analyzed by neutron balance method.According to the analysis of the calculated results at the beginning of cycle,233 U has higher average fission neutron number and smaller neutron capture cross section,which is conducive to improving the effective multiplication factor and fuel utilization.In addition,the neutron capture cross section of 23 Na in the reactor is larger than that of 7 Li,so the effective multiplication factor of fuel salt containing 23 Na is relatively low,but the influence of 23 Na in the thermal reactor is smaller,so 23 Na is more suitable for fast reactor.