The desirability of nuclear power plants (NPPs) fulfilling a common minimum level of safety holds for NPPs designed to earlier standards, as well as for modern plants. Many utilities and regulators are now seeking additional assurance that NPPs are continuously operated at the highest reasonable levels of safety compared with the safety standards which would apply to an NPP designed and constructed today. The paper presents a discussion, based upon the experience of European utilities on the safety objectives, safety re-evaluations and main safety issues of NPPs designed to earlier standards. The question of whether the design and operation of a specific NPP still fulfils basic safety objectives and standards should be addressed periodically. Guidelines on how to take stock using all suitable sources of potential information as a basis for a periodic safety re-evaluation have been addressed by the regulators, by the European Commission and by the IAEA. The paper looks at this issue from the viewpoint of the operator. Many of the conclusions, however, are in line with those of the other studies. A generic approach required to conduct a satisfactory safety re-evaluation, taking into account these guidelines, is presented. In principle, this approach can be followed worldwide for all NPPs regardless of their design or age. The overall goal of the process outlined in the
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