Study On The Utilization And Conversion Characteristics Of Thorium In A Thorium-based Molten Salt Reactor

In 2011,aiming at the major national strategic requirements in the field of nuclear energy,the Chinese academy of sciences launched the strategic pilot technology project of"future advanced nuclear fission energy-thorium Molten Salt Reactor nuclear energy system",and is building a 2MW Thorium Molten Salt Reactor?Thorium Molten Salt Reactor?.Due to the energy spectrum of the experimental reactor is thermal neutron energy spectrum,its design power is small,and it does not have the ability of large-scale use of thorium and thorium uranium proliferation.However,on the basis of the existing design scheme,we can carry out the demonstration of thorium uranium conversion experiment,carry out relevant theoretical analysis and the verification of radiochemical sampling detection and analysis method.It can also provide technical support for the design of high power thorium uranium breeder.Therefore,this paper is based on a thorium-based molten salt reactor model,it is very necessary and of great application value to study the utilization ratio of different Th additives to Th in fuel.In this paper,the Monte Carlo N Particle Transport Code?MCNP5?was used to model the reactor core,and the burnup Code coupled with MCNP and ORIGEN2 using BATch language?MOBAT?developed by Dr.Zhu guifeng was used to analyze the burnup calculation.The MOBAT program has been verified by thermal reactor and fast reactor,and is used for the design and optimization of fluorine-cooled hot bed reactor,fluorine-cooled plate-shaped hot reactor and solid-fuel molten salt cooled fast reactor.In this paper,a thorium based molten salt reactor model with power of 2MW is used as the background,the utilization and transformation of Th with different Th additives in fuel are studied in this paper.Firstly,the influence of the two groups of experimental groups on core parameters was analyzed.In group A,the single variable was Th addition under different masses,and the initial effective proliferation factor was keff?1.02.In group B,Li F-UF₄ was added to meet certain residual reactivity?Keff?1.02?after adding Th of different mass.By analyzing the mole ratio,reactivity,density of heavy metals and the loading capacity of LiF-UF₄ with added salt of different Th additives in the two groups of experimental groups,it is concluded that in order to meet certain Th consumption and utilization,Th additives in fuel are not too large,and should be selected at the level of 100 kg.Through further study on group B,the burnup of the group was calculated for 300 days of full power operation,and the CR,Th consumption rate,Th relative consumption rate and ²³⁵U loading capacity were analyzed.The conclusion was drawn that to realize the further effective use of Th in fuel,the Th addition amount should be less than 100kg.In order to study the transformation characteristics of Th additives below 100 kg,5 groups of experiments were selected in this paper:10kg,20kg,50kg,80kg and 100kg Th additives.The evolution of key nuclides on Th-U chain,¹³⁵Xe and ¹⁴⁹Sm concentration,neutron energy spectrum,the burnup and radioactivity were studied.The results show that with the increase of Th addition:the concentration of ¹³⁵Xe and ¹⁴⁹Sm equilibrium will increase.Neutron energy spectrum is harder which is conducive to the proliferation and transformation of Th.The major fission products and actinide nuclides had little change in their evolution curves,and the Th addition of different masses had little influence on the evolution of FP and Actinides.The total radioactive activity of AP?activated products?decreased,the total radioactive activity of actinide products increased,and the total radioactive activity of fission products remained unchanged.The comparative analysis shows that the higher the amount of Th added within 100kg,the better the performance of Th utilization and transformation..