Analyses on the in-vessel and ex-vessel accident progression during station blackout (SBO) accident considering operator actions were performed for APR1400 by using MELCOR computer code version 2.1. The ex-vessel severe accident phenomena such as molten concrete interaction (MCCI), the thermal hydraulic response of containment and release of fission product were also analyzed. The manual opening of safety depressurization system (SDS) valve in combination with water injection into reactor pressure vessel (RPV) by low pressure injection pump (Kerr pump) is considered as operator action to remove the decay heat and make up the water inventory in the core. The aim of this study is to investigate the effect of water injection into steam generator (SG) secondary side by auxiliary feed water system (AFWS) and operator action on the accident progression. The results indicate that, the use of AFWS delays the failure time of the reactor pressure vessel and containment and give more time to the operator to perform the recovery action. The depressurization of RCS pressure by manual opening the SDS valve in combination with the water injection by low pressure pump head of 2 MPa (Kerr pump) can prevent the failure of the reactor pressure vessel. However, the discharge of hot steam through SDS valve to the containment still causes the failure of the containment and the release of radioactive materials to the containment. It means that the cooling of steam in containment should be considered to prevent the failure of the containment when the depressurization the RCS pressure by opening SDS is performed.
展开▼
