Sensitivity of piping seismic responses to input factors

This report summarizes the sensitivity of peak dynamic seismic responses to input parameters. The responses have been modeled and calculated for the Zion Unit 1 plant as part of a seismic probabilistic risk assessment (PRA) performed by the US NRC Seismic Safety Margins Research Program (SSMRP). The SSMRP was supported by the US NRC Office of Nuclear Regulatory Research. Two sensitivity topics motivated the study. The first is the sensitivity of piping response to the mean value of piping damping. The second is the sensitivity of all the responses to the earthquake and model input parameters including soil, structure and piping parameters; this information is required for another study, the sensitivity of the plant system response (in terms of risk) to these dynamic input parameters and to other input factors. We evaluate the response sensitivities by performing a linear regression analysis (LRA) of the computer code SMACS. With SMACS we have a detailed model of the Zion plant and of the important dynamic processes in the soil, structures and piping systems. The qualitative results change with the location of the individual response. Different responses are in locations where the many potential influences have different effectiveness. The results give an overview of the complexity of the seismic dyanmic response of a plant. Within the diversity trends are evident in the influences of the input variables on the responses