FBR type reactor

Regular corrugations are formed in the circumferential direction of a reactor container. Concrete walls of the reactor container are brought into contact with protrusions of the corrugation. Although seismic loads exerted on the reactor container have been supported so far only by a flange, they are supported by the entire outer surface of the reactor container in the structure as described above. Accordingly, even if great seismic loads are exerted, the reactor container causes only slight vibrations thereby enabling to prevent buckling upon earthquakes. Further, the difference of thermal expansion between the reactor container and the concrete walls is absorbed by the corrugation in the circumferential and occurrence of thermal stresses is prevented by causing free expansion without fixing the upper portion in the axial direction. (I.S.)