Earthquake response spectra for seismic design of nuclear power plants in the UK

► Seismic design of UK nuclear power plants usually based on PML response spectra. ► We review derivation of PML spectra in terms of earthquake data used and procedure. ► The data include errors and represent a small fraction of what is now available. ► Seismic design loads in current practice are derived as mean uniform hazard spectra. ► The need to capture epistemic uncertainty makes use of single equation indefensible. Earthquake actions for the seismic design of nuclear power plants in the United Kingdom are generally based on spectral shapes anchored to peak ground acceleration (PGA) values obtained from a single predictive equation. Both the spectra and the PGA prediction equation were derived in the 1980s. The technical bases for these formulations of seismic loading are now very dated if compared with the state-of-the-art in this field. Alternative spectral shapes are explored and the options, and the associated benefits and challenges, for generating uniform hazard response spectra instead of fixed shapes anchored to PGA are discussed.