License renewal (LR) in the USA is based on the pre-requisite that ageing management of active components and systems is adequately addressed by the maintenance rule (MR) [26] requirements (10 CFR Part 50.65) and other established regulatory processes. This assumption is validated by the nuclear regulatory commission (NRC)’s regulatory oversight of the current licensing basis (CLB), which includes regulatory oversight to ensure implementation of continuous performance monitoring of active system functions in accordance with the MR, on-going compliance with operation technical specifications and regular updating of the so-called final safety analysis report (FSAR).

LR provides NPPs with the regulatory option to continue to operate beyond the 40-year term of the original licence, whilst the final decision to continue operation will depend on economic analyses of individual NPPs. Obviously, if the plant becomes uneconomical to operate, it may be shutdown and decommissioned at any time.

LR focuses primarily on the following three areas:

• Integrated plant assessment to evaluate the AM of passive, long lived SSCs, to ensure that they can support continued safe plant operation beyond the 40-year term of the original operating license and remain within the safety evaluation and requirements;

• Assessment of time-limited ageing analyses (TLAA) (e. g. fatigue, neutron embrittlement, environmental qualification analysis) to address the additional twenty years of operation; and

• Environmental impact assessment of the additional twenty years of operation.

The primary bases for determining the adequacy of passive SSC ageing management are operating experience, research results, and material sciences. Considerable documentation of operating experience is available in published reports, such as NRC regulatory guides, generic ageing lessons learned reports (e. g. NUREG-1801, [27]), and industry reports (e. g. NEI 95­10, [28]). NPPs must have at least 20 years of operating experience to demonstrate the adequacy of existing AMPs prior to submitting an application for LR.

The LR process typically takes about 4 to 5 years to complete. The utility takes about 2 years to do the engineering and environmental assessment work needed to prepare an application, and the NRC takes about 22 months (range of 17 to 30 months based on experience so far) to review the application and prepare a safety evaluation report (SER) and environmental impact statement. The overall cost of the LR process is $10 to $20 million (including utility costs and regulatory review fees) over this 4 to 5 year period. Fig.3 shows the review process of LR application.