MELCOR simulation of the SBLOCA induced severe accident for the SMR in a floating nuclear power plant

A floating nuclear power plant (FNPP) is a kind of nuclear power plant on a barge moored specifically in an area of the sea. This study focuses on a severe accident induced by cold leg small break loss of coolant accident (SBLOCA) occurring in a small modular reactor (SMR) in a FNPP of 100 MWt 2-loop pressurized water reactor (PWR) type. The severe accident was modeled using MELCOR computer code. A MELCOR model was developed for the primary and secondary systems, the engineered safety features, and the containment of the SMR. Three severe accident mitigation measures were analyzed using the model, namely the pressurizer (PZR) relief extension, the external vessel reactor cooling (EVRC), and the passive autocatalytic recombiners (PARs). The progression of the severe accident and the effects of three mitigation measures against the severe accident were analyzed. The simulation results indicated that the reactor core was exposed and heat up due to the coolant leakage and finally melted down due to high-pressure and lower-pressure injection failure. However, with the mitigation measures against the severe accident, the reactor pressure vessel (RPV) and containment integrity were maintained, thus preventing the large release of radioactive products into other cabins and the environment. Comparative analysis results also showed that all the three measures performed their scheduled functions and were significant in mitigating the accident. The study is useful in gaining insights into the processes of the severe accident induced by cold leg SBLOCA and can be used to identify appropriate mitigation strategies and countermeasures to deal with the severe accident in the FNPP.