乏燃料容器设计中组件包壳的氢脆特性影响分析

Influence of Hydrogen Ductile-brittle Transition Characteristics of Cladding on Design of Spent Fuel Transport Container

目的针对高燃耗乏燃料在干法运输条件下存在的包壳脆性变化,探讨其对我国现阶段乏燃料运输及容器安全研究中以“组件结构保持完整”作为设计基准所带来的影响和考虑。方法结合锆包壳氢化物韧脆转变的机理,针对乏燃料离堆和运输过程对包壳性能变化进行分析,并根据美国“ISG-11”等技术导则中提出的判别准则,探讨事故载荷下高燃耗乏燃料包壳结构性能的变化。结果通常认为2G乏燃料不需要考虑其材料氢脆影响问题,而高燃耗的3G乏燃料则必须综合评价离堆及后续干法运输过程中各种因素变化对其性能的影响,以判断包壳的峰值温度、韧脆转变温度和温度变化幅度等是否会对事故工况下“其结构始终保持完整”的设计基准造成影响。结论随着我国进入3G高燃耗乏燃料密集运输的时代,在乏燃料运输容器设计及运输安全分析时更应充分考虑包壳材料氢脆特性影响下的乏燃料结构在事故载荷下的保持能力。

Aiming at the change of cladding brittleness of high burnup spent fuel under dry transportation condition,the work aims to discuss the influence and consideration of''keeping the assembly structure intact''as the design basis in current spent fuel transportation and container safety research in China.Based on the mechanism of ductile-brittle transition of zircon cladding,the work analyzed the performance changes of spent fuel in off pile and transportation,and discussed the structural and performance changes of spent fuel cladding with high burnup under accident load according to the criteria proposed in''ISG-11''and other technical guidelines of the United States.It was generally considered that 2G spent fuel did not need to consider the impact of hydrogen embrittlement of its material;while 3G spent fuel with high burnup must be evaluated according to the influence of various factors during the process of spent fuel leaving the reactor and subsequent dry transportation.It can be judged whether the peak temperature,ductile brittle transition temperature and temperature change range of the cladding would affect the design basis of"keeping the structure intact"under accident conditions.As China enters the period of large amount of high burnup spent fuel transportation,the influence of hydrogen embrittlement characteristics of cladding materials under accident load on the structural retention capacity of spent fuel must be fully considered in design and transportation safety analysis of spent fuel transportation containers.It is hoped that the conclusion of the work can provide some reference and impetus to the research on the design of spent fuel transport container and the analysis of transport accidents in China.