Type of initiating event Time when fuel damage occurs (related to the IE) Amount of water surrounding the fuel Status of the containment protection and mitigation systems Recovery of fuel cooling Amount of water in Refuelling Water Storage Tank (RWST) (PWR specific) Amount of water in the condensation pool (BWR specific) Primary system pressure boundary integrity, e.g. Primary system intact Primary system open but RPV head still mounted RPV head dismounted Primary system pressure Status of high pressure and low pressure safety injection system. The PDSs are grouped based on the POSs of the plant at power operation and during refuelling outage [47], e.g. Group 0 Full power operation – Group 1 POSs similar to full power operation. Both the RCS and the containment are normally closed. – Group 2 POSs in which the RCS is closed but the containment is open. – Group 3 POSs in which both the RCS and containment are open. The fuel is located in the reactor – vessel. Group 4 POSs which is a special case because the fuel is relocated to the SFP. – SHUTDOWN STATES L2 PSA This section on guidance for shutdown states is focusing on the RPV and the reactor core and complement to the existing ASAMPSA2 guidance [1] for L2 PSA. Obviously, the spent fuel pool is of interest in shutdown states, but the SFP is addressed separately in section 3 of this report below. In general, shutdown states are subdivided into two main groups based on the primary system integrity: states with closed RPV head and states with open RPV head. These states might also be subdivided in different subgroups, the number of which depends on reactor type and operational instructions. These sub-states are defined based on their impact on the core damage (L1 criteria) or fuel damage during shutdown and are associated to different plant configurations (barriers of retention and boundary conditions) and mitigation systems availability during the refuelling process. For L2 PSA, also the source term confinement into the containment should be taken into account and new sub-states need to be included when the containment at full power is modified into the plant configuration during the refuelling. If primary system integrity is given up for maintenance works before opening of RPV head, this period can be separated in a new sub-state or integrated into the states with open RPV head.
Type of initiating event Time when fuel damage occurs (related to the IE) Amount of water surrounding the fuel Status of the containment protection and mitigation systems Recovery of fuel cooling Amount of water in Refuelling Water Storage Tank (RWST) (PWR specific) Amount of water in the condensation pool (BWR specific) Primary system pressure boundary integrity, e.g. Primary system intact Primary system open but RPV head still mounted RPV head dismounted Primary system pressure Status of high pressure and low pressure safety injection system. The PDSs are grouped based on the POSs of the plant at power operation and during refuelling outage [47], e.g. Group 0 – Full power operation Group 1 – POSs similar to full power operation. Both the RCS and the containment are normally closed. Group 2 – POSs in which the RCS is closed but the containment is open. Group 3 – POSs in which both the RCS and containment are open. The fuel is located in the reactor vessel. Group 4 – POSs which is a special case because the fuel is relocated to the SFP. SHUTDOWN STATES L2 PSA This section on guidance for shutdown states is focusing on the RPV and the reactor core and complement to the existing ASAMPSA2 guidance [1] for L2 PSA. Obviously, the spent fuel pool is of interest in shutdown states, but the SFP is addressed separately in section 3 of this report below. In general, shutdown states are subdivided into two main groups based on the primary system integrity: states with closed RPV head and states with open RPV head. These states might also be subdivided in different subgroups, the number of which depends on reactor type and operational instructions. These sub-states are defined based on their impact on the core damage (L1 criteria) or fuel damage during shutdown and are associated to different plant configurations (barriers of retention and boundary conditions) and mitigation systems availability during the refuelling process. For L2 PSA, also the source term confinement into the containment should be taken into account and new sub-states need to be included when the containment at full power is modified into the plant configuration during the refuelling. If primary system integrity is given up for maintenance works before opening of RPV head, this period can be separated in a new sub-state or integrated into the states with open RPV head.
ASAMPSA_E-WP40-D40-7-vol4-L2PSA-RD-and-SFP-1.docx