International Conference Nuclear Energy for New Europe 2005 Loss of Normal Feedwater Analyses for Krško Full Scope Simulator Validation

ABSTRACT The purpose of this analysis was to perform Loss of Normal Feedwater reference calculations for Krško Full Scope Simulator validation. In addition, the thermal-hydraulic response of the reactor coolant system was studied in detail. 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. The analyses performed to study the response of RCS to the Loss of FW accident consist of two scenarios, starting with the same initiating event that is loss of normal feedwater to both steam generators. In both cases the turbine driven auxiliary feedwater pump was unavailable by assumption. While in the first scenario credit has been taken for motor driven auxiliary feedwater pumps, the second scenario was broadened and accounted also for unavailability of the motor driven auxiliary feedwater pumps, which is a beyond-design assumption and leads unavoidably to severe accident scenario including core over-heating