International Conference Nuclear Energy for New Europe 2005 ATWS Thermal-Hydraulic Analysis for Krško Full Scope Simulator Validation

ABSTRACT The purpose of this analysis was to simulate Anticipated Transient without Scram transient for Krško NPP. The results of these calculations were used for annual ANSI/ANS validation of reactor coolant system thermal-hydraulic response predicted by Krško Full Scope Simulator. For the thermal-hydraulic analyses the RELAP5/MOD3.3 code and the input model for NPP Krško, delivered by NPP Krško, was used. In the presented paper the most severe ATWS scenario has been analyzed, starting with the loss of Main Feedwater at both steam generators. Thus, gradual loss of secondary heat sink occurred. On top of that, control rods were not supposed to scram, leaving the chain reaction to be controlled only by inherent physical properties of the fuel and moderator and eventual actions of the BOP system. The primary system response has been studied assuming AMSAC availability