Nuclear class equipment should be assessed for seismic safety before they are used in nuclear power plant. According to nuclear safety codes and regulations, all seismic category I equipments shall be designed enduring safety shutdown earthquake (SSE). That is, the stress evaluation needs to be accomplished for those structures. For some components, the deformation evaluation needs to be performed as well to assure the function integrity of the equipment. In this paper, the seismic analysis for an explosion-proof valve used in nuclear power plant, which exactly belongs to seismic category I equipment, has been conducted based on finite element method. The natural frequency, vibration mode and seismic response of the structure have been obtained through calculation, and the stress and deformation under the combined loadings of gravity, internal pressure, blast and seismic load have been evaluated according to ASME AG-1. The bolts of the structure have been qualified according to ASME III-NF as well. The results show that the design of the explosion-proof valve is in compliance with the requirement of corresponding nuclear safety standards.
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