The APR1400 SOARCA study: Insights into the evolution of severe accidents and fission product source term analysis results

Abstract

The Korean utility, KHNP (Korea Hydro and Nuclear Power Co.), carried out a three-year research study in July 2016 (named the Korean SOARCA: K-SOARCA), which is similar with the United State (US) SOARCA (State-of-the-Art Reactor Consequence Analysis) study. One of the two reference reactors designated for the study was Advanced Power Reactor of 1400 MWe (APR1400). To consider the integral response of the reactor, steam generators, and containment to severe accidents initiated by the representative accident sequences selected from the plant-specific Probabilistic Safety Assessment (PSA) results, dedicated modeling was performed for a broad spectrum of plant safety/mitigation systems and relevant phenomena influencing the evolution of the accident. The influence of dedicated accident mitigation strategies on the evolution of accident progression and fission product source terms was also investigated to assess their effectiveness in coping with relevant severe accident sequences. Especially, relating to the APR1400 SOARCA, the latest versions of two severe accident analysis codes, MELCOR 2.2 and MAAP5.04, were used to compare the analysis results of interest. This paper presents best-practice analysis results for the evolution of key accidents and plant response including the environmental release of radiological fission product Cs (cesium), as implemented through the APR1400 SOARCA study, and relevant insights.