The International Atomic Energy Agency’s (IAEA’s) Safety Aspects of Long-Term Operation (SALTO) programme provides advice and assistance to Member States on enhancing the safety of nuclear power plants embarking on long-term operation (see ‘A peer review for long term operation’, Nuclear Engineering International, July 2014). Long-term operation, also referred to as life extension, is defined as operation beyond an established time frame set by, for example, licence term, design, standards, licence or regulations, which has been justified by safety assessment with consideration given to life limiting processes.

Careful design and high quality of construction are prerequisites for a safe nuclear power plant. However, a plant’s safety depends ultimately on the ability and conscientiousness of the operating personnel and on the plant programmes, processes and working methods. This applies also to life extension activities. A SALTO peer review evaluates a facility’s life extension related activities and programmes against IAEA Safety Standards and proven international practices.

SALTO peer reviews are available to all Member States with plants considering life extension. Many Member States have participated in the programme by hosting one or more SALTO missions or by making experts available to participate.

Preparedness for safe life extension can also be reviewed as a part of an Operational Safety Review Team (OSART) mission when a dedicated life extension module is included in the mission scope. Follow-up missions are a standard part of the SALTO programme and are conducted 18 to 24 months after the SALTO mission.

Many of the challenges faced by those responsible for ensuring the safe operation of plants are common throughout the world. The results of a SALTO peer review service are, therefore, of interest and possible application to many plants. The primary objective of
this article is to enable organisations that operate, regulate or provide technical support to nuclear plants to benefit from experience gained in the course of SALTO missions during a period from 2005 to the mid-2015.

The SALTO review is performed in line with the SALTO Guidelines, ‘Service Series 26’, published in 2014. SALTO teams consist of senior expert reviewers from nuclear plants, technical support organisations and regulatory authorities in the various disciplines relevant to the mission. During technical discussions between reviewers and plant staff, life extension and ageing management programmes are examined in detail and their performance checked; strengths are identified and listed as good practices and weaknesses are listed as recommendations or suggestions in issues.

The criteria used by the teams as they formulate their conclusions are based on IAEA Safety Standards and the best prevailing international practices. They may be more stringent than national requirements. SALTO reviews are not regulatory inspections nor design reviews. Rather, SALTO reviews consider the effectiveness of life extension and ageing management programmes and are more oriented to process and management issues than to hardware. The performance or outcome of the various programmes is given particular attention. SALTO teams do not assess the adequacy of plant designs or compare the safety performance of different plants.

The SALTO peer review service has the following elements:

  • A workshop on IAEA safety standards and the SALTO review method;
  • one or more pre-SALTO missions, at least two years before entering life extension;
  • the SALTO mission (less than two years before entering life extension); and
  • a follow-up mission 18-24 months later.

Between 2005 and mid-2015 there were 22 SALTO missions reviewing plants around the world. The first nine were pilot SALTO missions, with narrow scope. They also helped develop the SALTO peer review service methodology. At two plants the safety aspects of life extension were reviewed in the frame of an OSART mission that included the life extension module.

While the nuclear industry has made significant advances in safety, there is always room for further improvement. SALTO peer review teams have identified many safety aspects of life extension where improvements are still needed. At the same time the assessment teams and plants reviewed have provided the IAEA with valuable feedback that has helped improve IAEA services aimed at life extension. In most plants the level of preparation for the review, the openness of the counterpart teams and their readiness to cooperate impressed the SALTO peer review teams.

Trends and achievements

The IAEA evaluated the general trends and achievements derived from these SALTO and OSART missions.

Organisation and functions, current licensing basis, configuration/modification management:

  • In three plants there is an indication that regulatory requirements specific to life extension are not available or too general.
  • In three plants the missing life extension specific requirements are compensated for by the IAEA life extension and ageing management guidance or US NRC requirements.
  • In three plants a decision on life extension has been taken but the related organisational actions are not established.
  • In five plants the plant life extension policy is not clearly defined and established, resulting in problems related to strategy, tasks, roles, responsibilities, organisational structure, familiarity of the staff, etc.
  • In five plants the plant life extension implementation programme is established but the actions to ensure its implementation are not in place.
  • In three plants deficiencies were noted in the pre-SALTO mission in the Final Safety Analyses Report and other Current Licensing Basis documents, but these deficiencies no longer appear.
  • In five plants deficiencies in the configuration/modification management including design basis documentation were identified, indicating a gap between the life extension needs and actual status.

Scoping, screening and plant programmes relevant to life extension:

  • In four plants there is an indication that the scoping and screening methodology does not properly address non-safety related items, failure of which may affect safety functions or result in an incomplete scope for life extension.
  • In three plants there is an indication that the scoping and screening methodology used does not address active components adequately.
  • In seven plants there is an indication that the existing plant programmes relevant for life extension have not been evaluated at a proper time and with the correct scope to demonstrate they are adequate for safe life extension.

Review of ageing management programmes and revalidation of time limited ageing analyses for mechanical components:

  • In four plants deficiencies in the area of specific scoping and screening were observed.
  • In four plants operating experience is not sufficiently covered in the ageing management review.
  • In five plants ageing management programmes (AMPs) do not meet the nine attributes of an effective AMP and were not revised as applicable.
  • In two plants the proactive obsolescence management programme is not yet fully implemented.
  • In two plants codes and standards of different origin were applied selectively or inconsistently without prudent reconciliation.

Review of ageing management programmes and revalidation of time limited ageing analyses for electrical and I&C components:

  • In four plants actual environmental conditions are not monitored to ensure that ageing analyses are based on conservative data, or there are no inspections and tests aimed at preserving qualification and functionality for the life extension period.
  • In three plants the environmental qualification is incomplete or missing.
  • In four plants the environmental qualification is not revalidated for life extension.

Review of ageing management programmes and revalidation of time limited ageing analyses for civil structures:

  • In three plants scoping and screening of civil structures was not performed thoroughly to facilitate ageing management for life extension.
  • In seven plants the ageing management review for civil structures was not implemented in a comprehensive way to facilitate ageing management for life extension.
  • In three plants the AMP for civil structures does not meet the nine attributes of an effective AMP and is not effective.
  • In three plants time-limited ageing analyses revalidation of civil structures was not completed.

Human resources, competence and knowledge management for life extension:

  • This issue was reviewed at only five plants.
  • In two of them the human resources strategy is not implemented consistently or is missing completely.
  • In two plants competence management and staffing is inadequate to support the life extension programme.
  • In two plants knowledge management is not adequate to support safe life extension.

Both SALTO and OSART follow-up missions are an integral part of the service that take place 18-24 months after the main missions. Between 2005 and mid-2015 there were six follow-up missions. For two plants, a life extension module was included in an OSART mission.

The following are the results of the follow- up missions regarding the resolution of the findings (total 77 issues).

The results of the follow-up missions demonstrate the effectiveness of the SALTO service and in particular the commitment
of the plants to implement improvements identified by SALTO teams. The number of issues is similar across the review areas,
with the exception of mechanical components where there were more recommendations and suggestions.

The peer review has proven to be an extremely effective mechanism for safety reviews of complex issues. The SALTO peer review service has been established as an effective tool to review the compliance with IAEA standards and international
best practices, to provide opportunity for plant staff to discuss their practices with experienced experts, to strengthen the public confidence in nuclear plants and to support licence renewal.

The SALTO service is of growing interest to Member States which has led to an increase in missions. From just one or two per year in 2007 to 2011, numbers rose to between three and five missions per year in 2012-2015. In 2016 and 2017 there are as many as eight to ten missions scheduled per year.

There has been a growing demand for SALTO workshops since they were introduced in 2012. Now there are between ten and 12 organised annually.

The IAEA is encouraging all Member States with operating plants to invite missions from the SALTO peer review service. This service for reviewing ageing management and other activities relevant to life extension can be carried out at any time during the lifetime of
a plant but is strongly recommended prior to entering life extension period.

 

If you would like to discuss the possibility of arranging a mission you should contact Robert Krivanek, IAEA project manager for life extension, operational safety section at the Department of Nuclear Safety and Security, Vienna International Centre, P.O. Box 100, 1400 Vienna, Austria.