Study on mitigation of ex-vessel release of fission products in severe accidents for Chinese two loops PWR

• Ex-vessel release of fission products in severe accidents for 600 MW PWR is analyzed.
• Mitigation effect of RCS depressurization on ex-vessel release is studied.
• Mitigation effect of wet cavity on ex-vessel release is studied.

In severe accidents of pressurized water reactor (PWR), after reactor pressure vessel (RPV) failure, ex-vessel release of fission products is occurred. In order to reduce radiological consequence, ex-vessel release of fission products should be mitigated. According to character of ex-vessel release, reactor cooling system (RCS) depressurization and wet cavity are studied. For RCS depressurization, the mitigation effect of typical severe accidents sequences on ex-vessel release is studied, and negative effect of RCS depressurization is also studied. For wet cavity, the mitigation effect of initial water in cavity and finite cavity injection are studied, in respectively.