反应性引入事故下芯块高温塑性对包壳的影响

Influence of High Temperature Plasticity of Pellet on Cladding During Reactivity-initiated Accident

芯块包壳机械相互作用(PCMI)是高燃耗压水堆核燃料棒在反应性引入事故(RIA)下失效的主要原因,现有燃料性能瞬态分析程序在考虑PCMI行为时忽略了芯块的高温塑性,但UO2陶瓷芯块在1200℃以上温度时会呈现明显塑性。为研究RIA事故下芯块高温塑性对包壳变形的影响,本文通过ABAQUS/Explicit建立PCMI分析模型,分别计算刚体芯块与理想弹塑性芯块导致的包壳变形,定量说明RIA事故下芯块高温塑性对包壳变形的影响。研究结果表明:ABAQUS/Explicit能够较好求解RIA事故下PCMI行为中的应力集中问题;模拟RIA事故时,芯块高温塑性对于包壳的内径变化影响较小,但对包壳环脊的形成影响较明显。

Pellet-cladding mechanical interaction(PCMI) is one of the main reason for high burnup nuclear fuel rod failure in pressurized water reactor during reactivity-initiated accident(RIA). The high temperature plasticity of pellet is ignored in the current transient analysis program of fuel performance, but UO2ceramic pellet show obvious plasticity when temperature above 1200℃. In order to study the influence of high temperature plasticity of pellet on cladding deformation during RIA, a PCMI model was established by ABAQUS/Explicit to calculate the cladding deformation caused by rigid pellet and ideal elastic-plastic pellet respectively, and quantitatively illustrate the influence of high temperature plasticity of pellet on cladding deformation during RIA. The results show that ABAQUS/Explicit can solve the stress concentration problem in PCMI behavior during RIA;In the simulation of RIA, the influence of high temperature plasticity on the inner diameter of cladding is small, but the influence of high temperature plasticity on the formation of cladding hoop ridge is obvious.