Passive containment cooling system with hydrogen recombiner for prolonged station blackout

Beyond design basis accident scenario, where station blackout could lead to severe accident with hydrogen release, has become important after accident at Fukushima Daiichi nuclear plant. Here a passive containment cooling system (PCCS) combined with hydrogen mitigation system is suggested that will passively remove containment heat load as well as mitigate hydrogen gas generated and accumulated in the containment atmosphere during prolonged station blackout. It is proposed to make use of atmosphereic air as ultimate heat sink to reject the PCCS heat, which in turn transfers heat from the containment. In the proposed design a finned vertical tube type PCCS system submersed in pool water is considered with supply of pool water lasting three days following which airflow cools PCCS tubes for long term. The PCCS inlet flow path has a catalytic recombiner that is effective during first few days should there be any hydrogen generation and accumulation in the containment.