Aging Evaluation for the Extension of Qualified Life of Nuclear Power Plant Equipment

Abstract

In recent decades, the aging of nuclear power plants, the upgrading of safety systems and the concern for life extension of licensed plants close to completing 40 years of operation have been considered by regulatory agencies. The extension of operating licenses for power reactors over 40 years has been a viable option for operators of nuclear power plants to ensure the adequacy of future capacity of power generation, in terms of economic benefits, compared with the construction of new power reactors. Routine reviews of nuclear power plant operation (including modifications to hardware and procedures, significant events, operating experience, plant management and personnel competence) and special reviews following major events of safety significance are the primary means of safety verifications. Rereviews include an assessment of plant design and operation against current safety standards and practices, and they aim at ensuring a high level of safety throughout the plant’s operating lifetime. They are complementary to the routine and special safety reviews and do not replace them (IAEA, 2009). In 1991, the US Nuclear Regulatory Commission (NRC) issued rules and associated documentation describing how the licensee must demonstrate that the unit can continue operating for 20 years following the expiration of the 40-year license. These rules were established in 10CFR51 (NRC, 2007a), environmental protection requirements, and 10CFR54 (NRC, 2010a), technical requirements. In 1994, the International Atomic Energy Agency (IAEA) issued recommendations, guidance and associated documentation describing how the licensee must demonstrate that the unit can continue operating through a systematic safety reassessment, named periodic safety review (PSR) (IAEA, 1994, 2003). The safety guide has the purpose of providing recommendations and guidance on the conduct of a PSR each 10 years for an existing nuclear power plant, and it is directed at plant operating organizations and regulators. In addition, some member states have initiated this reassessment to evaluate the cumulative effects of plant aging and plant modifications, operating experience, technical developments and siting aspects.