BUILDING FOR NUCLEAR REACTOR

PURPOSE: To increase the capacity of a wet well air chamber with no increase of containment vessel by installing a shell inside the wet well, extending into a wet well pool, and partitioning a dry gap. CONSTITUTION: In a wet well 26 a wet well pool 26a is partitioned, and thereover a suppression chamber 26b is installed. The well 26 and a containment vessel 12 for nuclear reactor partition a dry well 40 which surrounds the pressure vessel 16 of the nuclear reactor. A plurality of vents 42 are provided in the pool 26a in communication with the dry well 40. A shell 46 is installed inside the well 26 and extended into the pool 26a so that a dry gap 48 is formed. The gap 48 does not contain wet well water 36 and is arranged in communication with the suppression chamber 26b. The roof 34 of the well 26 is formed by installing slabs 54 on a plurality of supporting beams 56 arranged at a certain spacing, wherein the beams 56 bound an auxiliary chamber. The gap 48 and aux. chamber give an additional volume to the suppression chamber 26b so that the pressure margin is improved.