Earthquake response analysis of a BWR-type nuclear reactor building in regard to base mat flexibility

The effects of base-mat flexibility are discussed on the earthquake-response characteristics of a BWR-type nuclear reactor building. First, the experimental and analytical literature focusing on base mat flexibility is reviewed. Second, earthquake response analysis is conducted, where, as an example, a typical BWR-type nuclear reactor building is idealized by a finite element method. In order to check the effects of base mat flexibility, studies are made under the following two conditions: (1) base-mat flexibility is taken into account, (2) base mat flexibility is not considered. As for soil condition of supporting layer, two conditions--500 m/sec and 1,000 m/sec, respectively--of shear wave velocity are considered. As the results, the reaction stress distribution of the supporting soil and the stress distribution of aseismic walls are compared between models (1) and (2), and the quantitative effects of base mat flexibility on these models are determined. (author)