Abstract

A steam explosion can occur when molten corium falls from the reactor vessel into the water in the reactor cavity. While various research studies have been conducted on steam explosions following the free fall of molten corium in air before entering the water, steam explosions following submerged corium discharge under the ex-vessel cooling condition have received relatively little analysis. The aim of this paper is to compare the progress and consequences of a steam explosion in experiments and simulations for the partially flooded cavity and ex-vessel cooling conditions. Three steam explosion tests carried out in the TROI (Test for Real cOrium Interaction with water) experimental facility were simulated by the TEXAS-V code. Experimental tests were first modeled, followed by a comparison of the experimental and simulation results. The effect of the molten corium mass involved in the steam explosion under water at the moment of triggering on the strength of the explosion was higher than that of the corium composition in the tests and simulations for the condition of a partially flooded cavity. In the test and simulations of different corium injection modes to the water, the maximum pressure and impulse of the steam explosion appeared in the partially flooded cavity condition. In the simulations for the partially flooded cavity condition, the mass of the molten corium fragmented by Rayleigh-Taylor instability (RTI) was higher than that fragmented by Kelvin-Helmholtz instability (KHI). Modeling of KHI fragmentation caused solidification of the fragmented corium particles, and the impulses reduced accordingly. In the simulations for the ex-vessel cooling condition, as melt jet breakup did not occur before the triggering time, simulations with only RTI fragmentation underestimated the impulse of the steam explosion. Otherwise, modeling of KHI fragmentation increased the impulse of the steam explosion due to fragmentation on the side of the corium jet. Steam explosion simulations in the ex-vessel cooling condition require more detailed modeling of the melt jet and premixing area, as well as variable adjustment for the fragmentation by KHI.

摘要

当熔融的钄从反应堆容器落入反应堆腔体中的水中时，就会发生蒸汽爆炸。虽然已经对熔融的真皮在进入水中之前在空气中自由下落后发生的蒸汽爆炸进行了各种研究，但在船外冷却条件下浸没的真皮排放后的蒸汽爆炸得到的分析相对较少。本文的目的是比较蒸汽爆炸在部分淹没腔和容器外冷却条件下的实验和模拟中的进展和后果。TEXAS-V 代码模拟了在 TROI（真正的钴与水相互作用的测试）实验设施中进行的三个蒸汽爆炸试验。首先模拟实验测试，然后比较实验和模拟结果。在部分淹没腔体条件下的测试和模拟中，触发时刻参与水下蒸汽爆炸的熔融真皮对爆炸强度的影响高于真皮成分。在对水中不同注入模式的测试和模拟中，蒸汽爆炸的最大压力和冲量出现在部分淹没的腔体条件下。在部分淹没腔条件的模拟中，瑞利-泰勒不稳定性 (RTI) 破碎的熔融真皮的质量高于开尔文-亥姆霍兹不稳定性 (KHI) 破碎的质量。KHI 碎片的建模导致碎片化的真皮颗粒凝固，并且脉冲相应地减少。在对船外冷却条件的模拟中，由于熔体喷射破裂在触发时间之前没有发生，仅使用 RTI 碎裂的模拟低估了蒸汽爆炸的冲量。否则，由于真皮射流一侧的碎片，KHI 碎片的建模增加了蒸汽爆炸的冲动。容器外冷却条件下的蒸汽爆炸模拟需要对熔体喷射和预混区域进行更详细的建模，以及 KHI 对破碎的可变调整。