芯体多孔结构对单片式燃料元件辐照热-力耦合行为的影响研究  

Effects of porous fuel structure on the irradiation-induced thermo-mechanical coupling behavior in monolithic fuel plates

作　　者：严峰 孔祥喆 丁淑蓉 何大明[2] 李垣明[2] 陈平[2] 周毅[2] YAN Feng;KONG XiangZhe;DING ShuRong;HE DaMing;LI YuanMing;CHEN Ping;ZHOU Yi(Institute of Mechanics and Computational Engineering,Department of Aeronautics and Astronautics,Fudan University,Shanghai 200433,China;Science and Technology on Reactor System Design Technology Laboratory,Nuclear Power Institute of China,Chengdu 610213,China)

机构地区：[1]复旦大学航空航天系,力学与工程仿真研究所,上海200433 [2]中国核动力研究设计院,核反应堆系统设计技术重点实验室,成都610213

出　　处：《中国科学：物理学、力学、天文学》2019年第11期62-77,共16页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家自然科学基金(编号:11572091,11772095);国家重点研发计划(编号:2016YFB0700103);中国核动力研究设计院核反应堆系统设计技术重点实验室项目资助

摘　　要：在中子辐照的环境中,由于裂变气体产物的产生,UMo燃料芯体将演化为多孔结构,孔隙率和孔压随着燃耗增长而不断变化,促使单片式燃料元件内产生复杂的多尺度辐照热力耦合行为.本文针对UMo/Al单片式燃料元件,基于考虑芯体亚晶化及外界静水压力相关性的裂变气体肿胀模型,建立了芯体孔隙率随燃耗演化的理论模型,进一步考虑孔隙率及孔压影响建立了芯体/包壳界面微观正应力计算模型.将芯体孔隙率演化模型引入燃料元件多尺度辐照热力耦合行为的三维有限元模拟,实现了温度和孔隙率与芯体热传导率的实时关联,获得了辐照过程中燃料元件内热-力学场量的分布及演化规律,计算分析了孔隙率对燃料元件温度、变形、芯体/包壳界面微观正应力所产生的影响,并考察了燃料元件表面热交换系数对其辐照热-力耦合行为的影响,获得了芯体/包壳界面破坏的重要影响因素.A UMo/Al monolithic fuel plate is composed of UMo fuel meat and Al cladding.These fuel plates with a high uranium density have a promising prospect to be used in advanced research and test reactors.Under the neutron irradiation environments,nuclear fissions occur to result in heat generation in the fuel meat;accumulation of fission-induced solid and gaseous products will lead to irradiation swelling;irradiation creep of UMo will affect the mechanical interactions between the fuel meat and the cladding.Especially,intragranular and intergranular gas bubbles will make the fuel meat evolve into a porous structure,and the fuel porosity and pore pressure will change continuously with the irradiation time.As a result,a complex irradiation-induced multi-scale thermo-mechanical coupling behavior needs to be simulated for optimal design and safety evaluation of UMo/Al monolithic fuel plates.In this study,a theoretical model for fuel porosity evolution is developed,based on a fission gas swelling model with the grain recrystallization,the resolution of intergranular gas atoms and the dependence of hydrostatic pressure involved.Moreover,the computation method of microscopic interfacial normal stress is established,with consideration of fuel porosity and pore pressure.The evolution model of fuel porosity is introduced into three-dimensional finite element simulation of the irradiation-induced multiscale thermo-mechanical coupling behavior,which correlates the current thermal conductivity of UMo fuel with the fuel temperature and porosity.The distribution and evolution disciplines of thermo-mechanical variables in the fuel plate are obtained at different irradiation time.In addition,the effects of fuel porosity on the temperature,the main deformation and microscopic interfacial normal stresses are investigated.Simultaneously,the effects of surface heat transfer coefficient on the thermo-mechanical behavior are analyzed.The research results indicate that the porous fuel structure and fission-gas induced pore pressure become the

关 键 词：单片式燃料元件 中子辐照 裂变气体肿胀 辐照蠕变 多孔结构 界面破坏机理 

分 类 号：TB3[一般工业技术—材料科学与工程]