ASTEC is an integral computer code jointly developed by Institut de
Radioprotection et de Sûreté Nucléaire (IRSN, France) and Gesellschaft für Anlagenund
Reaktorsicherheit (GRS, Germany) to assess nuclear power plant behaviour
during a severe accident (SA). The ASTEC code was used to model and to simulate
NPP behaviour during a postulated station blackout accident in the NPP Krško.
The accident analysis was focused on containment behaviour; however the complete
integral NPP analysis was carried out in order to provide correct boundary
conditions for the containment calculation. During the accident, the containment
integrity was challenged by release of reactor system coolant through degraded
coolant pump seals, molten corium concrete interaction and direct containment
heating mechanisms. Impact of those processes on relevant containment
parameters, such as compartments pressures and temperatures, is going to be
discussed in the paper