Validation of ASTEC2.1 using QUENCH-12 for VVER-Reactors

Abstract

Russian VVER-type reactors are one of the most common used commercial reactors in the world. The validation of severe accident codes using experimental data is focused in core degradation both in-vessel and ex-vessel phenomena such as the QUENCH-12 tests performed at the Karlsruhe Institute of Technology (KIT). This step is needed before integral codes are applied to evaluate the behavior of VVER-plants under severe accident conditions. The main goal of the QUENCH-12 test was to evaluate the hydrogen generation resulting from the injection of cold quench water into an overheated and oxidized bundle of fuel rod simulators representing the VVER-fuel rods. Such phenomena are expected to occur during a severe accident sequence e.g. LOCA or as part of an accident management measure. This paper describes the investigations done to simulate the QUENCH-12 test using the ASTEC V2, which is developed by IRSN to simulate all physical and chemical phenomena during severe accident condition. A model of the QUENCH-12 test facility was developed for ASTEC first time taking into account the specific material data, geometry and boundary conditions. The evaluation of the results have shown, that ASTEC V2 is able to predict the main trends of key-parameters during the all test phases in good agreement with the measured data. The integral hydrogen generation is only over-predicted during the quench phase. As next steps, the model will be improved by taking into account the real material properties of the ZrNb-cladding typical of Russian reactors instead of the ones of Zr. Also the sensitivity studies regarding the electrical heater resistance will be carried out.