Dynamic analysis of AP1000 shield building for various elevations and shapes of air intakes considering FSI effects subjected to seismic loading

Abstract

The shield building of AP1000 was designed to protect the steel containment vessel of nuclear power plants. When an accident releases mass energy to containment, natural circulation of air outside containment cools steel containment vessel by air intake and water drains by gravity to enhance cooling with evaporation. However, the air intake in the original design located around the upper corner of shield building may not be the optimal position of shield building. In the previous study, the influence of various elevations and shapes of air intake on natural frequency considering fluid-structure effects under different water levels has been performed. In the present study, three elevations and two shapes (rectangle and circle) of air intakes with 71.3, 64.75 and 58.21 m are established and expressed as location I, II and III, respectively. The influences of various elevations and shapes of air intake on the structural response and stress distribution of shield building considering fluid-structure effects under seismic loading are also performed to identify the optimal design for stress analysis to improve the passive cooling system for AP1000 and CAP1400 (in China) in the future. The results of structural analyses indicated that the von Mises stress of both rectangular and circular air intakes at the lower location were greater than that of the higher location, and the stress for circular air intake was less than that of rectangular air intake under seismic loading. In addition, the simulation result also indicated that an optimal elevation of air intake should be implemented around the location II of shield building with circular shape, and the original design of air intake located around the upper corner of shield building may not be the optimal arrangement.