Investigation of seismic limit states for LWR containments

An in-depth analytical study was conducted by Sargent and Lundy Engineers under contract to Sandia in order to determine typical values for seismic capacities and plausible seismic failure modes of LWR containments. This was a scoping study to determine if seismic events pose a significant threat to containment integrity. The seismic capacities of the containment buildings of four nuclear power plants located in the eastern United States were investigated for four different conditions of internal pressure and temperature. Sixteen potential limit states were postulated and structural calculations were conducted to identify the critical limit states for each containment. In this investigation, load combinations well beyond the original design basis were considered. The results are interpreted in the context of generic seismic hazard curves, which are subject to large uncertainty, especially for the strong ground motion corresponding to levels beyond the SSE. Therefore, careful exercise of engineering judgment is required to evaluate seismic threat. This paper provides only a very brief summary of the results and a Sandia/NRC perspective of seismic threat to containment integrity. 4 refs., 1 fig., 4 tabs.