Transient Parameter Analysis of Non-scrammed Local Melting Accidents—A VVER 1000 Case Study

The first stage of a core degradation—based on the defense-in-depth concept nuclear power plant (NPP) safety—is prone to fuel melting due local blockage. flow blockage accidents with no SCRAM happening can lead fuel-clad failure, consequently affecting safety NPP. present study provides an analysis Anticipated Transient Without (ATWS), which might condition burning out. related ATWS scenarios, detailed in case VVER-1000/V446 reactor FSAR (Final Safety Analysis Report), include pump blockage, relative increase, and combination these transients. In this research, first, drawing upon MCNPX 2.7 COBRA-EN codes, coupling framework is developed then validated using authentic reference point. obtained results reveal that does not occur while are being investigated as there 10% difference mass rate reduction, 470 kPa channel pressure drop, 204°K clad temperature, constitute limitations under most pessimistic scenarios. However, conditions, 70% void fraction over 12 min observed certain channels. Hence, burnout could normal operational circumstances. According uncertainty analyses, occurrence above zero locally definite. transient outputs be deployed monitoring system inputs exploited for identifying weak points system.