A regulatory view of the seismic re-evaluation of existing nuclear power plants in the United Kingdom

The paper describes the background to the seismic re-evaluation of existing nuclear power plants in the United Kingdom. Nuclear installations in this country were not designed specifically to resist earthquakes until the nineteen-seventies, although older plants were robustly constructed. The seismic capability of these older installations is now being evaluated as part of the periodic safety reviews which nuclear licensees are required to carry out. The regulatory requirements which set the framework for these studies are explained and the approaches being adopted by the licensees for their assessment of the seismic capability of existing plants are outlined. The process of hazard appraisal is reported together with a general overview of UK seismicity. The paper then discusses the methodologies used to evaluate the response of plant to the hazard. Various other types of nuclear installation besides power plants are subject to licensing in the UK and the application of seismic evaluation to some of these is briefly described. Finally the paper provides some comments on future initiatives and possible areas of development. (author)