新型熔盐快堆的物理优化设计及^(99)Mo产量分析

Physical optimal design and analysis of^(99)Mo production in new type molten salt fast reactor

为提高新型熔盐快堆的堆芯中子经济与安全性能,并利用^(235)U的裂变反应进行^(99)Mo同位素生产,应用SCALE6.1程序进行了堆芯几何参数优化,基于优化后的堆芯对^(99)Mo同位素的生产进行相关分析。结果表明:适当增加燃料元件半径、减小燃料栅元半径可提高有效增殖因子,同时降低冷却剂温度系数;当燃料元件容器壁厚为0.1 cm、燃料元件半径为3.5 cm、栅元半径为5 cm、活性区半径和反射层厚度分别为63 cm和100 cm时,堆芯运行寿期满足32个月,此时总反应性温度系数为−1.615×10^(−5)K^(−1),保证了堆芯的固有安全性;选最外层燃料元件作为^(99)Mo生产的燃料靶件可提高^(99)Mo的产量,当燃料靶件提取周期为7 d时,^(99)Mo出堆年产量达到6.25×10^(16)Bq,比活度为2.77×10^(15)Bq∙g^(-1)。

[Background]^(99)Mo has important applications in nuclear medicine field.It can be produced in a ^(235)U fission reactor with high yield and specific activity.[Purpose]This study aims to optimize the core parameters of new type molten salt fast reactor,and then analyze the production of^(99)Mo based on the optimized core.[Methods]The Standardized Computer Analyses for Licensing Evaluation Version 6.1(SCALE6.1)was used to perform the critical calculations,by analyzing the influence of geometry parameters on k_(eff)(effective proliferation factor)and temperature coefficient of reactivity,the geometry parameters of the core were determined,and then the extraction position of fuel target in the production of^(99)Mo was determined by analyzing the neutron energy spectrum and mean microscopic fission cross sections of ^(235)U.Finally,the output of^(99)Mo in fuel target was calculated.[Results]The results show that the k_(eff) can be increased while the coolant temperature coefficient be decreased by increasing the radius of fuel element and reducing the radius of fuel cell appropriately.When the fuel element container wall thickness is 0.1 cm,fuel element radius is 3.5 cm,fuel cell radius is 5 cm,active area radius and reflector thickness are 63 cm and 100 cm respectively,the operating life of core reaches 32 months and the temperature coefficient of reactivity is−1.615×10^(−5)K^(−1),which ensure the inherent safety of reactor core.Selecting the outermost fuel element as the fuel target for^(99)Mo production can increase the yield of^(99)Mo.The^(99)Mo annual output exceeds 6.25×10^(16)Bq and specific activity exceeds 2.77×10^(15)Bq∙g^(-1)when the extraction cycle of fuel target is 7 days.[Conclusions]Therefore,the high yield and purity of^(99)Mo can be obtained by producing^(99)Mo in the new type molten salt fast reactor.