The buckling strength of a steel containment vessel with discontinuous stiffening rings of a nuclear power plant

Abstract

A steel containment vessel of PWR (Pressurized Water Reactor) has a circular cylindrical body and a hemispherical head. Since the containment vessel is a thin-walled shell structure, shear and bending buckling might occur in the cylindrical part under the seismic load which exceeds the design load. In the conformity assessment of existing nuclear power plants to the new regulatory standards established by NRA (Nuclear Regulation Authority) of government of Japan in 2013, the assessment of structural strength becomes more severe than that before construction due to the increase of design basis earthquake ground motion. If the existing power plant does not have sufficient structural strength against the seismic load, a countermeasure with reinforcements is required. In this study, the stiffened steel containment vessel is proposed by using the partial stiffening rings which has discontinuous, to avoid the interference with penetrations such as equipment hatch, air lock and piping. A series of buckling tests and elasto-plastic buckling analysis of scaled containment vessel model were conducted to verify the effectiveness of this reinforced structure. Through the buckling tests, it is confirmed that the buckling strength of steel containment vessel was improved by the partial stiffening rings as well as continuous rings. Moreover, the buckling behavior and the buckling load estimated by the elasto-plastic buckling analysis considering the material stress–strain relationship and the initial imperfection shape in test vessel suitably agreed with corresponding test results.

Keywords

• steel containment vessel
• circular cylinder
• discontinuous stiffning ring
• buckling test
• elasto-plastic buckling analysis