Analysis of In-Vessel Melt Retention for KONVOI PWR for selected severe accident scenarios

In the framework of the EU H2020 IVMR project, the applicability and technical feasibility of In-Vessel Melt Retention (IVMR) for high power reactors is assessed. HZDR contribution to the project was the investigation of the IVMR strategy for German Pressurized Water Reactor of type Konvoi (high power reactor with 1300 MWe). Four different severe accident scenarios with core material relocation to the lower head have been studied with the severe accident code ATHLET-CD, including Station Blackout (SBO), and Loss-of-Coolant accidents (LOCA) of various leak sizes in combination with SBO. The molten corium pool formed in the lower head and the ablation of vessel wall have been studied. The observed maximum heat flux on the outer surface of the wall is in the range between 1.47 MW/m² (SBO) and 1.67 MW/m² (LOCA). The corresponding minimum wall thickness is 25 mm and 21 mm, respectively. The simulations showed that with the assumptions made, IVMR seems to be possible for the investigated accident scenarios without vessel failure.