易裂变材料运输临界安全评价要点分析

Critical Issues of Criticality Safety Evaluation for Transportation of Fissile Materials

目的分析探讨易裂变材料运输时核临界安全评价的重要关注点和技术要求,为易裂变材料运输货包的设计、安全评审提供参考和建议。方法基于易裂变材料核临界安全的相关评价标准要求,结合我国一些易裂变材料运输容器设计和评审的经验,从临界安全分析模型、临界安全分析方法、单货包和货包阵列等方面分析探讨临界安全分析重点关注的内容。结果临界安全分析必须考虑货包尺寸和易裂变材料成分、货包阵列情况及事故后对货包临界安全影响等因素,同时应用燃耗信用制和装载可燃毒物情况对货包临界安全分析也有重要影响。结论应用燃耗信用制得出的结果的不确定度对临界安全评估有比较大的影响,对含可燃中子毒物棒及不完整乏燃料组件的临界安全评估需要特别关注可燃中子毒物的影响及缺失燃料组件的影响。

The work aims to analyze and discuss the important concerns and technical requirements of nuclear criticality safety assessment during fissile material transportation,and to provide references and suggestions for the design and safety review of fissile material transportation packages.Based on the relevant evaluation standards of fissile material nuclear criticality safety,combined with some experience in the design and review of fissile material transport vessels in China,key concerns of criticality safety analysis were analyzed from the critical safety analysis model,critical safety analysis method,single package and package array.In the critical safety analysis,factors such as package size,fissile material composition,package array condition and the impact on the criticality safety of the package after the accident must be considered.At the same time,the application of burnup credit system and the loading of combustible poisons also had an important impact on the criticality safety analysis of the package.In conclusion,the uncertainty of the results obtained by the burnup credit system has a great impact on the critical safety assessment.The critical safety assessment of rods and incomplete spent fuel assemblies containing combustible poisons needs to pay special attention to the impact of combustible poisons and the impact of missing fuel assemblies.