Abstract | Three candidate intensity measures are compared in terms of efficiency and sufficiency for assessing the non-structural performance of nuclear powerplant components. These are the peak ground acceleration, the spectral acceleration at the fundamental period of the structure, and the average spectral acceleration in the range of short periods. To do so, single-degree-of-freedom non-structural components of different periods and capacities are considered at different locations within an AP 1000 reactor model. Incremental dynamic analysis is performed for a set of 30 records. The spectral floor accelerations of each SDOF component are monitored and capacity exceedances are recorded to assess the lognormal parameters of component fragility curves. The numerical results demonstrate that average spectral acceleration would be the most useful intensity measure in both efficiency and sufficiency, regardless of location, period or capacity, with the obvious exception of the ground surface. Nevertheless, the conventional choice of the peak ground acceleration remains a very close contender, as it leads to results of low dispersion and little bias for such stiff structures and short-period components.