An experimental study on fuel-coolant interaction characteristics on ZrO2 and UO2/ZrO2 melt

TROI experiments performed at KAERI aim at identifying fuel-coolant interactions (FCI) using real reactor material melts and water. In these experiments, ZrO2 or mixture of UO2 and ZrO2 was used as a molten reactor material, and the mass of the material was 5 ∼ 10kg. In the future, the mass will be increased up to 20 kg. This reactor material was melted in a cold crucible applying the induction heating method. Steam explosions occurred twice ans did not occur once in the TROI tests with ZrO2. Meanwhile, a steam explosion happened in the test with the mixture of UO2 and ZrO2. The data acquired in the tests were static pressures and temperatures in the pressure vessel and the interaction vessel. Also, in case of a steam explosion, dynamic pressures and dynamic loads to the bottom were obtained. The mean diameter of debris obtained in the FCI test with ZrO2 was about about 5 cm, while that with the mixture of UO2 and ZrO2 was about 2 ∼ 5 mm. The concentration of hydrogen which is thought to suppress a steam explosion was measured but it is negligible