Seismic evaluations of reactor structure for tank type-fast breeder reactor

Tank type fast breeder reactors are those of the type that the primary sodium directly cooling the core and the primary equipment such as a pump and an intermediate heat exchanger are contained in a reactor vessel of about 20 m diameter and 20 m depth. In the tank type reactors, the pressure during the operation is low, therefore, it is the structural feature that reactor vessels become large, thin-walled shells, and consequently, the development of the techniques for evaluating the aseismatic soundness of reactor structures seems to be one of the important technical subjects. In this paper, the techniques of analyzing the earthquake response for carrying out the aseismatic design of tank type fast breeder reactors and the techniques of evaluating buckling behavior are reported about their state of development. Moreover, it is discussed that as the results of having applied these evaluating techniques to the structure of tank type fast breeder reactors, the prospect that the structure is usable under the severe condition of aseismatic design in Japan was obtained. In the structure of tank type reactors, the strength reliability against thermal stress using a thin-walled structure and the aseismatic reliability using a thick-walled structure must be compatible. (Kako, I.)