Patent Number: 051924943
Section: description

FIG. 1 shows schematically an example of a reactor containment. The reactor vessel is indicated schematically by 1 and is located above a pool 2 which, in the event of an accident, is filled with water 3 to a level indicated by 31. Molten core material running down from the reactor vessel 1 will granulate in the water 3 and form a bed 4 of granulate, the highest expected level of which is indicated by 41. A vertical penetration 51 is shown extending through the floor 21 of the pool 2, and a horizontal penetration 52 is shown extending through the side wall 22 of the pool 2. A pipe 60 surrounds the penetration 51 and is provided with a water inlet 61 located at a level between the levels 41 and 31, and an outlet 62 located in the lower part of the pool 2, in the bed 4. A conical screen 71 covers the upper end of the gap 64 between the penetration 51 and the pipe 60 in order to prevent granulate on its way down from entering directly into the gap 64. The outlet 62 may be in the form of slits in the lower end of the pipe 60, said slits being shaped to prevent particles from entering the gap, or being covered by a suitably fine-meshed net. The pipe 60 prevents direct contact between the bed 4 and the penetration 51 and, together with the penetration 51, forms an annular gap through which water flows in downward direction, leaving through the outlet 62 to be vaporized in the bed 4. The steam produced in the cooling process rises and condenses in the water layer 3 above the bed 4. The horizontal penetration 52 is surrounded in the pool 2 by a horizontal pipe 60 provided with outlets 62 close to the wall 22. Particles from the bed 4 are prevented from entering the outlets 62 by a covering ring 163. The other end of the pipe 60 is connected to a vertical riser 165 emerging between the levels 41 and 31. The inlet to pipe 165 is provided by a cowl 166 preventing granulate from flowing directly in. FIG. 2 shows schematically an alternative or a supplement to one or both the protective arrangements shown in FIG. 1. The protective arrangement according to FIG. 2 comprises a tubular sheet metal casing covering the side wall 22 of the pool from the bottom 21 up to a level above the level of the granulate 41, forming a gap 64. The tubular casing 60 is provided with an inlet 61 between the levels 41 and 31, and an outlet 62 at the floor of the pool. The gap 64 is also protected by a conical sheet-metal screen 72 which prevents granulate from directly entering the gap. Granulate is also prevented from entering the outlet 62. In a further development of the invention the floor of the pool 21 is covered by a bottom plate 81 with outlets 82 for water to the bed 4. Together with the bottom 21 of the pool, the plate 81 forms a gap 84. The plate 81 may be supported by beams or supports 87, indicated schematically, raising it from the floor 21. The gap 84 can be supplied with water through the gap 64, the water flowing out through the openings 82 to cool the particle bed and the plate 81 preventing direct contact between the particle bed and the floor 21 of the pool. As shown in FIG. 3, the water outlets through the floor plate 81 may be formed by upwardly directed pipe connections 83 provided with one or more openings 86 through their walls and covered by a lid 85, the free edge of which is at a level below the level from the opening 86, thus forming a labyrinth which prevents particles from the bed 4 from entering the water gap 84.