Seismic Design and Qualification for Nuclear HVAC System

This paper proposes an efficient seismic qualification method for representative HVAC systems in nuclear power plants, following the guidelines of US NRC Regulatory Guide 1.10, IEEE-344, and ASME Section III. Through structural and geometrical similarity analysis, candidate items for qualification were grouped using dynamic similarity principles, significantly streamlining the process. For large-scale equipment where seismic testing is impractical, a combined approach of seismic analysis and testing was employed. Seismic analysis included modal analysis and response spectrum analysis, while seismic tests were conducted on active components such as driving motors, fans, compressors, and control panels. Input seismic loadings accounted for response amplification due to the equipment’s modal properties, incorporating specified margins to ensure conservative qualifications. The combined stresses derived from these procedures were confirmed to be below allowable limits, with a stress ratio under 0.8. Additionally, no mechanical or electrical failures were observed in the seismic analyses or tests. Consequently, the authors verified the safety and reliability of the HVAC system for use in safety-related nuclear applications.