Investigations on in-vessel severe accident phenomena

The in-vessel evolution of a severe accident in nuclear reactors is characterised by core uncovery and heat-up, core material oxidation and melting, molten material relocation, and debris behaviour in the lower plenum up to vessel failure. The report summarises recent results of FZK research on mitigation of severe accidents with emphasis on the reflood of an overheated reactor core for the purpose of early termination of the accident and fuel coolant interactions in the lower plenum of the pressure vessel and its consequences. (orig.)