Journal of Nuclear Science and Technology ( IF 1.2 ) Pub Date : 2021-01-04 , DOI: 10.1080/00223131.2020.1858989 Ayumi Itoh 1 , Nathan C. Andrews 2 , David L. Luxat 2 , Randall O. Gauntt 3 , Masaki Kurata 4 , Yoshinao Kobayashi 5
ABSTRACT
Degradation mechanism involving the interaction between the U-Zr-O phase from molten fuel cladding and steel was investigated at the lower structure of core region of the boiling water reactor, which could take place at low temperatures compared to the failure conditions typically assumed in the current severe accident codes. The non-isothermal interaction was simulated by the heat and mass transport equations with possible chemical reactions estimated by thermodynamic database and the following potential mechanisms were identified: (1) the U-Zr-O melt dissolves steel leading to serious damage, (2) the reaction results in partial solidification of U-Zr-O melt near the reaction surface forming (U, Zr)O2-x phase and U-Fe-rich metallic phase and (3) unsolidified U-Zr-O melt could drain to the lower plenum through the lower structure of core support plate. These mechanisms will propose new hypothesis in which the timing of core support plate degradation could get earlier due to liquefaction of U-Fe-rich metallic phase or the timing of lower head failure of the reactor pressure vessel could be affected by drained U-Zr-O melt.
中文翻译:
BWR严重事故堆芯降解过程中U-Zr-O熔融混合物对不锈钢的降解机理
摘要
在沸水反应堆堆芯中心区域的下部结构上研究了涉及熔融燃料熔覆层中的U-Zr-O相与钢之间相互作用的降解机理,该结构可能会在低温下发生,与通常假定的失效条件相比。当前的严重事故代码。通过热和质量输运方程模拟了非等温相互作用,并通过热力学数据库估计了可能的化学反应,并确定了以下可能的机理:(1)U-Zr-O熔体溶解钢导致严重损坏,(2)反应导致反应表面附近形成的U-Zr-O熔体部分凝固(U,Zr)O2-x相和富U-Fe的金属相以及(3)未固化的U-Zr-O熔体可以通过堆芯支撑板的下部结构排到下部气室。这些机制将提出新的假设,其中由于富含U-Fe的金属相的液化,堆芯支撑板退化的时间可能会更早,或者反应堆压力容器的较低水头故障的时间可能会受到U-Zr-排放的影响。融化。