Verification of SAMGs in SBO sequences with Seal LOCA. Multiple damage domains

• ISA methodology allows verifying the SAMGs taking into account all damage indicators.
• Multiple damage domains (MDD) shows the effect of human actions during severe accident sequences.
• The comparison of several MDD allows to graduate efficiency of SAMG.

The Integrated Safety Assessment (ISA) methodology, developed by the Spanish Nuclear Safety Council, has been applied to PWR Station Blackout (SBO) sequences in the context of the IDPSA (Integrated Deterministic-Probabilistic Safety Assessment) network. The ISA methodology allows obtaining the Damage Domain (DD), the region of the uncertain parameters space where the damage limit is exceeded, for each sequence of interest as a function of the operator actuation times. Several damage limits have been taken into account within this analysis: cladding embrittlement criteria (Peak cladding temperature >1477 K); Inadequate core cooling conditions (Core Exit Thermocouples temperature >922 K); local fuel melting (fuel temperature >2499 K); fuel relocation in lower plenum and vessel failure. Other continuous damages, such as percentage of relocated fuel are also studied. Every one of these damage variables provides a specific DD. The application to the severe accident management (SAM) actions shows the capability of a methodology such as ISA in order to analyze the impact of different SAM strategies and to obtain the available times for different operator actions.