Pre-test simulation and a scoping test for dryout and remelting phenomena of an in-vessel debris bed

Abstract

The present study is intended to investigate the dryout and remelting phenomena of a debris bed during the late phase of an in-vessel severe accident progression. The SIMECO-2 facility at KTH is adapted to conduct the experimental investigation. For selection of an appropriate debris bed in the facility, pre-test simulations are performed by using the COCOMO code to determine: (i) simulant materials of debris particles; (ii) debris bed particle diameters; (iii) configuration and geometry of the debris bed (e.g., shape, layers, dimensions). Candidate particulate beds packed with different mixtures of particles are identified and simulated to obtain their thermal hydraulics in the hemispherical slice test section with radius of 500 mm and width of 120 mm. Based on the simulation results, a particulate bed is chosen and loaded in the SIMECO-2 facility for a scoping investigation. FBG probes with multiple measurement points of each probe are employed to acquire the temperature field of the particulate bed inductively heated. A video recording is applied to detect the dryout and remelting phenomena. In the scoping test, the dryout phenomenon occur first at the elevation of 5 cm from the bed surface under the induction heating power of 14.8 kW, which are comparable with the data predicted by the COCOMO code (6 cm from the bed surface under the heating power of 13.8 kW) in the pre-test simulations.