IAEA activities on passive safety systems and overview of international development

Although a major focus of nuclear power reactor development efforts in indu strialised countries is on large evolutionary units and design modification s that take maximum advantage of successful proven features and components, consideration is also given to utilisation of passive safety systems and i nherent safety features. The various advanced reactor designs: evolutionary , large water-cooled reactor designs; evolutionary, medium size water-coole d reactor designs; concepts requiring substantial development; gas-cooled r eactor concepts; and liquid metal-cooled fast reactors, incorporate a wide variety of passive safety features for initiation of safety systems, for re sidual heat removal and for containment heat removal. Organizations have es tablished testing programmes to confirm their performance. A number of IAEA activities have lead to the conclusion that the use of passive safety feat ures can be a desirable method of achieving simplification and increasing t he reliability of the performance of essential safety functions. However, c are should be taken to evaluate possible new failure mechanisms, and both p assive and active systems should be assessed from the standpoint of reliabi lity and economics. Key technical issues include: the quantification of rel iability over a wide range of conditions: economics, speed of action, plant ageing, demonstration of technical feasibility, in-service testing, ease o f maintenance and minimization of personnel radiation exposure. Many member states conduct substantial work on the design, modelling, development and reliability assessments of passive safety systems. Continued information ex change can benefit the involved member states, and the IAEA is providing a forum for review of programmes, project directions, and the results achieve d. (C) 2000 Elsevier Science S.A. All rights reserved.