Abstract: In order to optimize the nuclear material accounting of spent fuel reprocessing facilities and find the main factors of the material unaccounted for (MUF), a numerical simulation model based on nuclear material accounting perspective is built, which includes the front-end process, PUREX process, uranium and plutonium back-end and MUF calculations. The material flow rate in the model can be changed easily by changing different process parameters to simulate different production scale. The simulated material measurement error comprising of random and system errors are simulated by normal distributed random variables and constant numbers respectively, which have the similar randomness and statistical features with the actual measurement uncertainty. When the model measurements are set to different random and system errors, the corresponding square error distribution and improvement direction can be obtained, by which a better measurements precision combination satisfying the uncertainty requirement can be found. The final results show that the system error of the 1AF measurement is the main source of the MUF.

Key words: spent fuel reprocessing, nuclear material accounting, material unaccounted for (MUF)

摘要： 为优化乏燃料后处理设施的核材料衡算，寻找核材料衡算不平衡差（MUF）的主要因素，采用基于数值模拟的系统仿真方法，以核材料衡算视角构建乏燃料后处理设施核材料衡算仿真模型。改变模型工艺参数仿真不同规模的后处理设施中各环节核材料的流通量，然后以正态分布随机变量模拟各铀钚衡算测量点的随机误差，将这些带有随机特征的测量值叠加相应测量的系统误差作为核材料的仿真测量值。仿真计算结果表明，1AF中Pu、U含量测量的系统误差的方差分别占整体MUF方差的50%、40%以上，是主要误差来源。1AF的体积测量误差较小，占比MUF方差小于15%。废液中U和Pu含量很低，U和Pu含量测量的误差分别为10%和30%，对MUF方差影响不大，占比MUF方差分别小于3%和1%，废液的体积测量误差较小，占比MUF方差小于1%。U和Pu产品测量误差的方差占比MUF方差界于1AF和废液的测量之间，不是MUF误差的主要来源。

关键词: 乏燃料后处理, 核材料衡算, 核材料衡算不平衡差（MUF）