Severe accident mitigation measure and severe accident sequence of SMR

Interest in evaluation of reactor response and off-site consequences following beyond design basis accidents has significantly increased after Fukushima. MELCOR is an advanced computational aid that has been widely used and adapted to various reactor designs for severe core damage analyses. This paper summarizes the core thermal hydraulic response for a hypothetical severe accident caused by station blackout at a small modular reactor using MELCOR. The results show that: After a severe accident in SMRs, the passive core cooling system can cool the core by the natural circulation of water, extend the time of core uncover. The time of bottom head failed delays nearly 64000s. So the passive core cooling system have great mitigation effect on the severe accident induced by station blackout. The analyses are focused on safety assessment of the reactor core for severe accidents and are part of the overall evaluation of safety features of the small modular reactor for residual risk posed by severe accidents. (author)