Abstract: A corium protection assembly includes a perforated base grid disposed below a pressure vessel containing a nuclear reactor core and spaced vertically above a containment vessel floor to define a sump therebetween. A plurality of layers of protective blocks are disposed on the grid for protecting the containment vessel floor from the corium.

Abstract: A penetration (51) through the bottom of a pool in the reactor containment below a reactor vessel is protected against the effects of a core meltdown, by the penetration (51) being surrounded by a pipe (60) having an inlet (61) located below the surface (31) of the water and above the highest level (41) which the bed (4) of granulate formed by the descending molten core material could be expected to reach. The pipe (60) has an outlet (62) at its lower end, located in the bed (4). The gap (64) between the penetration (51) and the pipe (60) is covered by a screen (7) which prevents granulate from entering. Granulate is also prevented from entering the outlet (62). The pool water flows in through the inlet (61), down through the gap (64), out through the outlet (62) and into the particle bed (4) where the water is vaporized and rises through the bed without obstructing the flow of water through the gap for cooling the penetration.

Abstract: The device is constituted by a metal structure (10) resting on the bottom of the reactor pit (3) and submerged in a mass of water filling the lower portion of the reactor pit (3). The metal structure (10) comprises a central chimney (11), a recovery wall (12) constituted by juxtaposed dihedra (22) made from metal sheet, and a peripheral wall (13) fixed to the external edges of the dihedra (22) and providing water passages at the periphery of the reactor pit. When the molten core of the reactor spreads into the reactor pit, following an accident, the structure (10) ensures its recovery and prevents contact between the molten core and the bottom of the reactor pit. The molten core flows onto the wall (12) in such a manner as to constitute a layer of small thickness which is cooled over its upper surface and over its lower surface and which solidifies rapidly.