Development of ex-vessel corium coolability analysis program(COCCA) with simplified models validated against FARO experiments

Molten corium may be discharged into the reactor cavity if the Reactor Pressure Vessel (RPV) fails during a severe accident. The cooling and stabilization of the discharged molten corium in the reactor cavity are crucial for preventing further accident progression. Pre-flooding the coolant into a reactor cavity is one of the strategies for ex-vessel corium cooling and stabilization. KAERI developed a module named Code of Ex-vessel Corium Coolability Analysis (COCCA) to perform meaningful risk analyses and make decisions in the field of accident management, mitigation measures and emergency procedures through the ex-vessel corium coolability analysis. COCCA code is a stand-alone, 1-D, and a fast running code to analyze the phenomena and sequences in the reactor cavity during postulated severe accidents. Here, the COCCA code is introduced with simplified models, and COCCA is validated against FARO experiment data. The particle debris mass of the FARO results were predicted well within an error of 20%. The temperature validation calculations showed that COCCA has reasonable agreement with FARO experiment data.