Reactor vault of reinforced concrete has ring of blocks - surrounding vessel to form thermal shield containing ion chambers

A nuclear reactor vault, comprising a reinforced concrete shield wall surrounding the reactor vessel and containing ionisation chambers, is constructed as follows. An internal protective or thermal shield is composed of a series of prefabricated reinforced concrete blocks; these are arranged to form a continuous cylinder or ring around the reactor vessel, except for radial gaps between the blocks to permit expansion and movement. The ring of blocks is supported on a ledge in the surrounding reinforced concrete shield wall, the blocks thus being arranged in a continuous recess above the shoulder of the wall and below an overhang or corbel. The blocks are pref. of heat-resistant concrete. The protective shield is remote from the wall of the reactor, thus improving conditions in the event of an earthquake. Access inside the shield wall for direct inspection of the vessel wall is possible. Prefabrication reduces construction time by 60-80 days.