Controlling and cooling core melts outside the pressure vessel

For future reactors, the control and cooling of ex-vessel cerium melts is u nder consideration to increase the passive safety features even for very un likely severe accidents. In this context, different research activities are studying ex-vessel cerium behaviour and control, including the implementat ion of a core cooling device outside the reactor pressure vessel in order t o prevent basement erosion and to maintain the integrity of the containment . This paper describes current research on key phenomena which must be unde rstood and quantified to be finally controlled by the cooling device. These are the release of cerium melt from the pressure vessel, the temporary ret ention of the melt in the reactor cavity until melt through of the gate, sp reading of the melt on a large surface, and finally the cooling and solidif ication of the melt by direct water contact. The experiments use high tempe rature melts which are similar to corium melts. Where necessary, models are developed to transfer the results to reactor scale. (C) 2000 Elsevier Scie nce B.V. All rights reserved.