To control loss-of-coolant accidents (LOCA), Generation III+ reactors (e.g. AP1000, CAP1000) retain the melt in the reactor pressure vessel instead of an external core catcher.
This concept is based on in-vessel retention (IVR) and is a severe accident management strategy that is based on the external flooding of the reactor pressure vessel and aims to stop the downward progression of an assumed core meltdown accident.
The failure criterion for the passive IVR concept is the occurrence of film boiling when the critical heat flux is reached. Within the SIMA project, experimental investigations of the IVR concept are carried out to analyze the boiling crisis.