Simulant Melt Experiments on Thermal and Metallurgical Performance of the In-Vessel Core Catcher

LAVA-GAP experiments were performed to investigate the thermal and mechanical performance of the in-vessel core catcher, which was proposed to improve in-vessel retention for high-power reactors. In the LAVA-GAP experiments, alumina melt was used as a core material simulant. The hemispherical in-vessel core catcher made of carbon steel was installed inside the lower head vessel maintaining a uniform gap of 10 mm from the inner surface of the lower head vessel. Two types of in-vessel core catchers were used in this study. The first one is a single-layered in-vessel core catcher without an internal coating, and the other one is a two-layered in-vessel core catcher with a 0.5-mm-thick ZrO₂ internal coating. LAVA-GAP experimental results indicate that an internally coated in-vessel core catcher has better thermal performance compared with an uncoated in-vessel core catcher. For the precise investigations on the thermal and mechanical response of the in-vessel core catcher, thermal analyses using the LiLAC code and metallurgical inspections were performed. LiLAC calculation results suggest that the coating layer could lessen the thermal attack transferred to the core catcher and result in improving the integrity of the core catcher in the LAVA-GAP experiments. Metallurgical inspection results indicate that the carbon steel showed stable and pure chemical compositions without any oxidation and interaction with the coating layer. In terms of the material aspects, these metallurgical inspection results suggest that the ZrO₂ coating performed well.