压水堆内钍-铀增殖循环研究——乏燃料特性分析

利用ORIGENS程序对压水堆钍基乏燃料的特性进行分析，揭示了钍基乏燃料在放射性毒性、衰变热、γ射线等方面的特性，相关结果可为钍基乏燃料的贮存、后处理和地质处置提供必要的参考。研究的乏燃料是压水堆内钍-铀增殖循环堆芯设计方案中的4种，包括UOX（铀氧化物）、MOX（钚铀混合氧化物）、PuThOX（钚钍混合氧化物）和U3ThOX（工业级²³³U-钍混合氧化物）。研究结果表明：1）由于超铀核素的含量极低，在卸料后1 000年内，U3ThOX的放射性毒性显著低于超铀核素含量高的乏燃料；2）由于²³²U衰变链中²⁰⁸Tl的贡献，钍基乏燃料中2.6 MeV能量附近的γ射线强度明显高于铀基乏燃料，而这一能量附近的γ射线强度在卸料后约10年达到局部峰值，所以，钍基乏燃料的后处理最好避开此时间。

Spent Fuel Characteristics Analyses for Thorium-Uranium Breeding Recycle in PWRs

Spent fuel characteristics analyses of thorium-based fuel were investigated using ORIGEN-S code compared with uranium-based fuel.Such parameters as radio-activity,radiotoxicity,decay heat,and gamma ray were considered.Relative results in this work could provide some reference informations for storage,reprocessing and disposal of thorium-based spent fuel.Four type fuels,thorium-based fuel U3ThOX(mixed reactor grade 233U-thorium oxide),PuThOX(mixed reactor grade plutonium-thorium oxide),uranium-based fuel UOX(uranium oxide) and MOX(mixed reactor grade plutonium-uranium oxide),on the basis of core designs for thorium-uranium breeding recycle in PWRs were investigated.The calculated results show that: 1) Due to extremely low content of transuranic nuclides,the radiotoxicity of U3ThOX is dramatically lower than that of three other types of spent fuel in 1 000 years after discharge;2) In thorium-based spent fuel the intensity of gamma ray near 2.6 MeV mainly generated by 208Tl in 232U decay chain is much stronger than that in uranium-based fuel.The intensity of γ ray near 2.6 MeV reaches a local peak in about 10 years after discharge when the reprocessing should not be performed for thorium-based spent fuel.