KIT-JIMEC Experiments to Investigate Jet Impingement on the Ablation of Core Catcher Bottom

In 2019, the research activities of KIT in the field of experimental severe accident research on fast reactors were concentrated on the European ESFR-SMART project. Within this project two large-scale JIMEC (Jet Impingement of Metallic Core-Catcher) experiments have been performed to investigate the thermal ablation kinetics of an internal core catcher material in a SFR (Sodium-Cooled Fast Reactor). Besides this, the planning work for LIVEESFR tests to study the interaction between the corium simulant and the sacrificial simulant of the core catcher started. It has been decided to construct and build a new test vessel with downscaled geometries similar to SFR core catcher design. The actual safety design of a SFR in the case of a postulated severe accident includes removing the corium from the core by corium transfer tubes and collecting the corium in a core catcher in the lower head. One threat scenario of the core-catcher integrity is a high ablation rate by the impingement of a metallic corium jet on the core catcher surface. Experimental data is needed to simulate this ablation behaviour under prototypical conditions including a long impinging duration and high jet temperature. Under such conditions, the insights of a yet insufficiently studied behaviour when a molten pool is created ("pool effect") at the impact point could be obtained. Therefore, the ITES-SAR (Institute for Thermal Energy Technologies and Safety - Severe Accident Research Group) team has adapted the existing MOCKA test facility to perform two JIMEC experiments in the frame of the European ESFR-SMART project. JIMEC-1 and JIMEC-2 tests are two large-scale tests with 1 ton of metallic mass. The objectives of the experiments are to deliver experimental data on the interaction of melt jet parameter and erosion dynamics in prototypical materials and conditions. The melt jet parameters such as jet temperature, jet velocity and jet diameter, and the erosion dynamics including the erosion velocity and the timing of pool effect are obtained. The experimental results will be used for developing new correlations which could be used in codes for simulation of the ablation kinetics for SFR core catcher concepts.