Post-Test Calculations of the IAEA-SPE4

In the Research Center Rossendorf post test calculations of the SPE4 were performed using the thermohydraulic code ATHLET. The SPE-4 experiment was a small break loss of coolant accident in the cold leg with unavailable high pressure injection system. For the prevention of core damage the secondary side bleed and feed was used. The experiment was performed at the Hungarian PMK-2 test facility, modelling the Paks VVER-440 reactor. In the calulations different nodalizations were tested for modelling the hydroaccumulators and the horizontal steam generator. Deviations between calculation and experiment were observed especially in the primary pressure decay and consequently in the behaviour of accumulator injection. It was found, that the prediction of observed core dry out depends on the correct calculation of the low pressure injection setpoint.