Mass/Energy Release Influence to Thermal Hydraulics of Accident Localisation System at Ignalina NPP in Case of MDBA Available to Purchase

The maximal loads on ALS structures could be reached during Maximum Design Basis Accident (MDBA). MDBA for Ignalina NPP is defined as guillotine rupture of the pressure header of main circulation pumps (MCP). In this paper the influence of calculated mass and energy release in case of MCP pressure header rupture on behavior of thermal hydraulic parameters in ALS compartments is presented. The performed analysis demonstrated the importance of mass/energy release for the calculated highest pressure in ALS. Nevertheless, the maximal calculated pressures in ALS compartments are below the design pressures even in case of most conservative mass/energy release through the break.