Preliminary Analysis of Hydrogen Distribution and Risk under Severe Accident Conditions for QINSHAN NPP Unit 2 Containment

Severe accident sequences induced by large-break loss-of-coolant accident（LB-LOCA）,small-break loss-of-coolant accident（SB-LOCA） and station blackout（SBO） are calculated by using an integral systems analysis computer code for QINSHAN NPP Unit2.Hydrogen concentration distributions in the containment atmosphere and their potential deflagration risk are investigated,according to the hydrogen control and risk analysis standard of US 10 CFR.The results show that the average hydrogen concentration un-der LB-LOCA severe accident is nearly 10%,which means large scale hydrogen deflagration might occur.In spite of the possibility of local deflagration,such large scale deflagration under SB-LOCA and SBO severe accidents maybe cease.The analysis provides a reference for hydrogen control and severe accident management of QINSHAN NPP Unit 2.