노외 증기폭발에 대한 원자로 공동의 건전성 분석 방법론 제시

Abstract

An Ex-vessel steam explosion might occur when hypothetical severe reactor accident causes reactor vessel fails and the molten core pours into the water in the reactor cavity. A steam explosion is a fuel coolant interaction process where the heat transfer from the melt to water is so intense and rapid that the time scale for heat transfer is shorter than the time scale for pressure relief. A steam explosion is a complex, highly nonlinear, coupled multi-component, multi-phase phenomenon. For the last several decades several computational models have been developed to evaluate the steam explosion energetics. The models have been verified with a number of experiment data and recently successfully analyzed in-vessel and ex-vessel steam explosions in new and advanced reactor designs. The TEXAS-V code is one of the models that have a unique feature employing the jet breakup model for the mixing phase and explosion models for the explosion triggering and propagation in one-dimensional fashion. The one-dimensional approach to analyze the steam explosion in this model, however, has a limitation to simulate the reactor case that has multi-dimension in nature. Therefore, in this work, the limitation of the TEXA-V code is supplemented by employing a commercial CFD code, like CFX, that evaluates the dynamic steam explosion pressure propagation from the FCI mixing zone to the reactor cavity wall. Furthermore, to assess the integrity of nuclear reactor cavity by the dynamic loadings from ex-vessel steam explosion, the ANSYS FE code is used for its analysis, and finally, in this study, the new methodology for the analysis on reactor cavity structure from ex-vessel steam explosion using TEXAS-V, CFX, and ANSYS FE is suggested. The developed model for the simulation of underwater shock propagation using CFX is validated by comparing its result with the correlation for underwater TNT explosion, and the result matches with the correlation with an error range of 5%. The structure analysis is performed considering the inertial effect of dynamic loading by shock wave propagation.