Comparison of Plant Life Management Approaches for Long Term Operations

Abstract

Many Member States of the International Atomic Energy Agency (IAEA) have given high priority to long term operation of nuclear power plants beyond the timeframe originally anticipated (e.g. 30 or 40 years). Out of a total of 445 (369 GWe) operating nuclear power plants, 349 units (297 GWe) have been in operation for more than 20 years (as of November 2011) and many are engaged in investigations and studies aimed at prolonging the plant service life. The need for engineering support to operation, maintenance, safety review and life management for long term operation as well as education and training on LTO issues is increasingly evident. Plant life management (PLiM) techniques that can be defined as the integration of ageing and economic planning, have been used in operating nuclear power plants to maintain a high level of safety, optimize performance and justify long term operation (LTO) beyond the plant design life. In addition, as a follow up to the Fukushima accident, operators have become even more attentive to beyond design basis measures in the preparation of their plants for operation beyond their design life. In many countries, the safety performance of NPPs is periodically assessed and characterized via the periodic safety review (PSR) process. Regulatory review and acceptance of PSRs constitutes for these countries the licensing requirement for continued operation of the plant to the following PSR cycle (usually 10 years). In the USA and in other countries operating US designed plants, instead of a PSR process, a license renewal application (LRA) process is followed, which requires certain pre-requisites such as ageing management programmes, particularly for passive irreplaceable systems structures and components (SSCs). Active components are normally addressed via the maintenance rule (MR) requirements and other established regulatory processes. A third group of Member States have adopted a combined approach that incorporates elements of both the PSR process and selected LRA specific requirements, such as time limited ageing analysis. Taking into account this variety of approaches, the IAEA initiated work to collect and share information among Member States on good practices in plant life management for long term operation in nuclear power plants, by comparing the various approaches to the PSR reference and by drawing lessons learned from relevant applications and experiences.