Post Test Calculations for a Small Break LOCA Experiment at the Integral Test Facility ISB-VVER Using the Thermalhydraulic Code ATHLET

The ISB-VVER facility of the Elektrogorsk Research and Engineering Center is currently the only operating integral test facility for the thermal hydraulic behaviour of the Russian pressurized water reactor VVER-1000. In 1993 it was decided, to perform a test for a small break at the upper plenum with locked rotor of all circulating pumps as the 1st Russian Standard Problem. The experimental results were made available to the Research Center Rossendorf, where post test calculations were carried out using the GRS-code ATHLET. The main results of these calculations are presented in this paper.