燃料包壳破损条件下裂变气体释放模拟实验研究  

Simulation experiment study on release of fission gas at fuel cladding failure

作　　者：李磊豪 董冰[1] 李晨悦 尹俊连[1] 王德忠[1] LI Leihao;DONG Bing;LI Chenyue;YIN Junlian;WANG Dezhong(Shanghai Jiao Tong University,Shanghai 201100,China)

机构地区：[1]上海交通大学

出　　处：《核技术》2019年第12期64-70,共7页Nuclear Techniques

基　　金：国家自然科学基金(No.11675105、No.11535009)资助~~

摘　　要：反应堆燃料包壳破损发生时需要判断其破损程度,为系统及时作出响应提供参考依据。目前使用逃脱率系数表征压水堆燃料包壳的破损程度,但对于裂变气体释放机理缺乏研究。本文采用实验方法研究燃料包壳破损时,非稳态过程中冷却剂压力和温度对裂变气体释放的影响。实验装置基于几何相似性、流动相似性以及闪蒸相变相似性设计,考察了在子通道内冷却剂压力与温度对裂变气体释放的影响,以及闪蒸对非稳态过程中裂变气体逃脱率的影响。实验结果表明:在选取的0.5 mm破口尺寸下,非稳态过程对于气体释放速率没有明显影响,实验中长期逃逸率保持稳定,释放过程符合一级动力学方程。同样冷却剂压力下,冷却剂温度从90℃增长到110℃时,长期逃逸率增长。同样冷却剂温度下,回路压力从0.3 MPa增长到0.5 MPa,长期逃逸率则下降。长期逃逸率与过冷度负相关,表明燃料包壳破口处的液膜对于裂变气体释放有影响。[Background]When fuel rod cladding failure occurs,the defect needs to be determined and information needs to be provided for system response in time.Escape rate of fission gas is adopted to reflect the defect size.However,there is hardly researches on mechanisms of gas release.[Purpose]This paper studies the effect of unsteady process,the pressure and temperature of the coolant on the instantaneous escape rate of the rod cladding breach by experimental simulation.[Methods]First of all,the experimental apparatus was designed on the base of geometric similarity,flow similarity and flashing similarity.Then,influence of coolant pressure and temperature in a subchannel was investigated by using computational fluid dynamics(CFD)methods.Effect of flashing on unsteady process and escape rate in short-term were analysed.[Results]The results indicate that unsteady process has no distinct effect on release of gas at defect size of 0.5 mm.Long-term escape rate remains steady during experiments and release process can be described by first-order kinetics.At the same coolant pressure,long-term escape rate increases when coolant temperature changes from 90℃ to 110℃.At the same coolant temperature,long-term escape rate decreases when coolant pressure changes from 0.3 MPa to 0.5 MPa.[Conclusions]A negative correlation is found between long-term escape rate and subcooled temperature,which indicates that liquid layer formed on the defect has impact on fission gas release.

关 键 词：包壳破损 非稳态过程 逃脱率系数 

分 类 号：TL99[核科学技术—核技术及应用]