燃料棒包壳氧化层溶解失效准则研究

Failure Criterion of Cladding Oxide Layer in Dissolution Mechanism

为确定严重事故条件下燃料棒包壳温度达到金属锆的熔点后包壳氧化层的失效时间、再定位熔融物的成分以及氧化层失效对堆芯熔化进程的影响,本文基于熔融锆同时溶解UO_2和ZrO_2动力学模型及燃料棒包壳水侧氧化层的受力分析建立了氧化层在熔融锆中溶解失效的准则。以FPT-0实验结果验证后发现该失效准则可以较准确地预测包壳氧化层的溶解失效。为增加该准则在严重事故计算程序中的适用性,在燃料棒设计结构一定的条件下,进一步将该准则量化为温度的函数,分析表明包壳氧化程度和燃料棒温度上升速率是影响包壳氧化层失效温度的主要因素。利用该失效准则可以同时获得包壳氧化层失效后再定位的熔融物的质量及成分含量。

A new failure criterion of cladding oxide layer dissolved by molten zircaloy is given based on the kinetics of molten zircaloy dissolve UO2and ZrO2simultaneously and its load conditions. The criterion was successfully validated against FPT-0 test. For a given structure of the fuel rod in nuclear reactors, the failure criterion can be simplified by temperature, which is a function of oxide scale and heat-up rate of the cladding. The relocation of melt in the flow path will be influenced by the new criterion predictions concerning mass and composition of relocated U-Zr-O mixture. © 2015, Editorial Office of Nuclear Power Engineering. All right reserved.