Intensity measures for the seismic assessment of non-structural components in nuclear power plants

Three candidate intensity measures are evaluated for their efficiency in assessing the fragility of non-structural components in a nuclear power plant. These are the peak ground acceleration, spectral acceleration at the fundamental period of a non-structural component, and average spectral acceleration across a range of short to moderate periods. Non-structural components with periods ranging from 0.05 to 0.90s, are analyzed at different locations within two structures of the EURATOM METIS project case study, comprising a VVER-1000 power plant: (a) the reactor building and (b) the diesel generator building. In both cases, moderate resolution models are considered with a simple (yet comprehensive) representation of soil-structure interaction (SSI). Using spectral acceleration at the fundamental period of each non-structural component yields the most efficient results at the cost of requiring a different intensity measure per component, which is not feasible in practice. Peak ground acceleration remains a close alternative, producing low dispersion results, particularly for stiff structures and short-period components. For broader applications, average spectral acceleration options that cover periods from 0.01s to 0.50s consistently perform better than, or at worst equally well to, peak ground acceleration across all non-structural components.