CHF trend:

In the USA, the NRC issues initial licences for commercial power reactors to operate for a maximum term of 40 years and allows these licences to be renewed for an additional 20 years through the LRA system. The maximum licence term of 40 years was selected on the basis of economic and antitrust considerations, not technical limitations.

There is no limit on the number of licence renewals, as long as the plant can be shown to continue to be run safely and in accordance with environmental requirements. The decision whether to seek a licence renewal rests entirely on the nuclear power plant owners, and is typically based on economic factors and safety considerations.

An LRA may be submitted to the NRC as early as 20 years after first operation and no later than 35 years of operation. This 15 year window of opportunity was set by the NRC to allow enough time for the owner/operators to develop their long term business plans and to allow the NRC staff enough time, at least 5 years, to perform a proper review of the LRA. A typical NRC review takes anywhere from 22 to 30 months. When significant intervention is involved, the review may take even longer than 5 years, due to the adjudicatory process, but the plant is allowed to continue operation. The licence renewal process proceeds along two tracks: one focused on the review of safety

AMP

Technical primary area

system

Technical mechanicalarea

Technical electricalarea

Technical I&Carea

Technical structurearea

Technical nuclear area

fuel Primary 

system Mechanical Electrical I&C Structures Nuclear

fuel

Sub­programmes within Ringhals ageing management programme

Equipment qualification

In­service inspection programmes

Surveillance

programmes Maintenance

programmes Environmental programmes

Obsolescence programmes

FIG. 54. AMP structure of Ringhals nuclear power plant, Sweden.

Code 10 CFR 54.21 [73] describes the licence renewals, and requires each renewal application to include:

— An integrated plant assessment;

— An evaluation of the changes to the current licensing basis;

— An evaluation of TLAAs;

— An FSAR supplement.

The NRC has issued regulatory guides and NUREG documents to address details and questions regarding the regulatory process for an LRA. In addition, the NEI has developed, in support of its members, an industry guidance document, NEI 95-10, Revision 3 [7], on how to best prepare an LRA. The NEI report has been endorsed by the NRC in its regulatory guide 1.188 [74]. All regulations, guidance documents and background information on the licence renewal process are available to the public on the NRC web site at www.nrc.gov. The standard review plan for the licence renewal sections is keyed to the regulatory guide 1.188 format [74], namely the sections are numbered according to the section numbers of the guide.

In the LRA, the applicant provides the information needed to demonstrate that any changes to the safety and performance envelope, including the effects of ageing, will meet the licence renewal requirements during the entire LTO period. In order to fulfil this goal, an applicant should analyse the effects of ageing on the plant SSCs to ensure that actions have been or will be taken to:

— Show the effectiveness of the long term management of ageing during the period of extended operation. This determination should be based on the functionality of all SSCs subject to an ageing management review and on the effectiveness of their ageing programmes during the LTO.

— Perform and incorporate any changes (either in hardware or in administration, programmes and procedures) implied by the TLAA on all components requiring it.

The GALL report [9] is treated as an approved topical report. The NRC reviewers do not repeat their review of a matter described in the GALL report. They usually find an application that references the GALL report and confirm its acceptance if the evaluation of the matter in the GALL report applies to the plant. If the applicants rely on the report for licence renewal, the staff seeks only to ensure that the material presented in the GALL report is applicable to the specific plant and that the applicants have identified specific programmes as described and evaluated in the GALL report. The results of the GALL effort are presented in a table format in the GALL report, Revision 2. The table column headings include:

— Item;

— Link;

— Structure and/or component;

— Material;

— Environment;

— Ageing effect/mechanism;

— AMPs;

— Further evaluation.

The terms of how the NRC reviews are conducted are spelled out in the NRC standard review plan for LRAs (SRP-LR) of nuclear power plants (NUREG-1800) [75]. The SRP-LR is divided into four major topics:

— Administrative information;

— Scoping and screening methodology for identifying structures and components subject to ageing management review, and implementation results;

— Ageing management review;

— Time limited ageing analyses.

The SRP-LR addresses various site conditions and plant designs, and provides complete procedures for all of the areas of review pertinent to each of the SRP-LR sections. For any specific application, NRC reviewers may

select and emphasize particular aspects of each SRP-LR section, as appropriate for the application. For these and similar reasons, the NRC reviewers need not carry out in detail all of the steps listed in each SRP-LR section in the review of every application. The subsections are:

— Areas of review: This describes the scope of review, that is, what is being reviewed by the branch that has primary review responsibility. It contains a description of the SSCs, analyses, data or other information that are reviewed as part of the LRA. It also contains a discussion on the information needed or the review expected from other branches to permit the primary review branch to complete its review.

— Acceptance criteria: This contains a statement on the purpose of the review, an identification of applicable NRC requirements, and the technical basis for determining the acceptability of programmes and activities within the area of review of the SRP-LR section. The technical bases consist of specific criteria, such as NRC regulatory guides, codes and standards, and branch technical positions. Consistent with the approach described in NUREG-0800 [76], the technical bases for some sections of the SRP-LR can be provided in branch technical positions or appendices as they are developed and can be included in the SRP-LR.

— Review procedures: This discusses the manner in which the review is accomplished. It is generally a step by step procedure that the reviewer follows to provide reasonable verification that the applicable acceptance criteria have been met.

— Evaluation findings: This presents the type of conclusion that is sought for the particular review area. For each section, a conclusion of this type is included in the safety evaluation report, in which the reviewers publish the results of their review. The safety evaluation report also contains a description of the review, including:

● Which aspects of the review were selected or emphasized;

● Which matters were modified by the applicant, or required additional information, will be resolved in the future, or remain unresolved;

● Where the applicant’s programme deviates from the criteria provided in the SRP-LR;

● The bases for any deviations from the SRP-LR or exemptions from the regulations.

— Implementation: This discusses the plans of the NRC staff in using the SRP-LR section.

— References: This gives a list of the references used in the review process.

These analyses need to include:

— The effects of ageing on the SSCs;

— A consideration of the effects of time limited assumptions, defined by the current operating licence and determined to be relevant to safety;

— A justification for the presumed capability of the SSCs to perform their intended functions;

— All calculations contained or incorporated by reference in the current licensing basis.

A screening of SSCs involving TLAAs needs to be conducted. The TLAAs then need to be evaluated to ensure the following:

— The analyses remain valid for the period of extended operation;

— TLAAs are projected to the end of the licence renewal period;

— Ageing can and will be managed adequately for the period of extended operation.

An example of TLAAs submitted by Exelon to the NRC is shown in Table 5.

7.3.1.1. Organizational structure

The organization of PLiM in the USA varies widely from plant to plant. For example, some plants may have a dedicated PLiM organization that coordinates the PLiM activities and provides the PLiM study results to the appropriate plant organizations (e.g. maintenance, engineering or operations) for implementation. Other plants may not have a dedicated PLiM organization, but rely on various organizations (e.g. design engineering, system

by component groups (e.g. piping, cables or transformers) or by individual components (e.g. turbine generators or steam generator).

The organizational structure for preparing an LRA varies from utility to utility, but a typical structure is based on creating a project team to address each major discipline of the needed studies. The team members may be from utility organizations, contracted consultants who specialize in preparing LRAs or a combination of the two groups, which is most common. A typical organizational structure is shown in Fig. 55.

The team typically consists of 10–20 full time members, with several other part time support members from various expert organizations (utilities and contracted consultants) needed to perform the engineering, ageing management and environmental studies, and to prepare the supporting documentation for the LRA project.