Volume 67, Issue 4

In view of an increasing age of nuclear power plants, many of which are planning or considering extending service life to 5060 years, ensuring the safety and reliability of ageing nuaclear power plants is an important task of the nuclear industry, national safety authorities, and international organizations such as the IAEA. This paper presents an overview of IAEA work on safety aspects of ageing nuclear power plants and indicates future direction aimed at strengthening capabilities of IAEA Member States in managing long-term nuclear power plant safety.

The OECD Nuclear Energy Agency (NEA) is a semi-autonomous body within the OECD established in 1958 with the mandate to promote co-operation among the governments of its participating countries in furthering the development of nuclear power as a safe, environmentally acceptable and economic energy source. While all of groups have detailed programmes involving important aspects, this paper will focus specifically on the work of Committee on Nuclear Regulatory Activities (CNRA) and the Committee on the Safety of Nuclear Installations (CSNI).

The Nuclear Regulatory Commission (NRC) issues licenses for commercial power reactors to operate for up to 40 years and allows these licenses to be renewed for additional periods of 20 years. In 1995 the Commission issued Part 54 of Title 10 of the Code of Federal Regulations (10 CFR Part 54) specifying the regulatory requirements for license renewal. The license renewal rule focuses on managing the adverse effects of ageing of plant structures and components. The NRC staff has developed license renewal rule implementation guidance documents. The NRC staff uses a systematic approach in evaluating the adequacies of ageing management programs. The NRC has approved several license renewal applications to date and will likely be asked to approve dozens more over the next 10 to 15 years.

Ageing surveillance programmes for Swiss nuclear power plants were started about ten years ago. The following contribution gives an overview of these programmes. They deal with ageing phenomena of materials of mechanical and electrical components, as well as civil structures. For each safety relevant component, the known ageing mechanisms are identified, and the maintenance, testing, inspection and monitoring programmes are then examined with respect to their suitability for detecting the ageing degradation. Programmes and procedures may be adjusted, or new ones introduced to ensure state of science and technology ageing surveillance. Documentation of the plant-specific ageing surveillance programmes is prepared by the nuclear power plant operators and given to the Swiss Federal Nuclear Safety Inspectorate for assessment. Experience with the ageing surveillance programmes over the last ten years shows favourable results for the monitoring of ageing and safe operation of the plants.

This paper summarizes ageing countermeasure program of the nuclear power plants performed by the Japanese Government and industries and related activities, and describes current research program and utilization of the research results for the aged nuclear power plants. Regulatory bodies (NISA of METI: Nuclear and Industrial Safety Agency of the Ministry of Economy, Trade and Industry') reviewed the ageing issues of nuclear power plants to enhance countermeasures for the aged plants. Nuclear Power Plant Life Engineering Center (PLEC) entrusted by NISA is carrying out the task relating to the aged plants.

Since the mid-90s, GRS has been dealing systematically with the assessment of the influences of ageing on the safety of nuclear power plants. This also involves the generic evaluation of operating experience. In the following, the procedure, methodological approaches and relevant results are presented in an exemplary manner for passive mechanical components. The results show that the number of events influenced by ageing phenomena that have so far occurred in German plants is low and that measures were taken where necessary to detect, monitor and control any changes due to ageing. As new insights may emerge over time concerning the assessment of the ageing behaviour of the components, it is considered necessary to continue with the ongoing generic evaluation of operating experience in order to obtain timely indications of any safety-relevant changes.

This paper gives a general view of the present state of ageing management in the Federal Republic of Germany, including the requirements set out in the set of rules and its handling within the plants. Moreover, it describes the requirements on ageing management and/or ageing monitoring in the area of materials ageing from the point of view of the expert and sets out in what way ageing processes have already manifested themselves in the area of mechanical and electrical engineering systems. And finally, it gives an outlook on current projects that, among other things, aim at making transparent the application of the methods of ageing management according to uniform requirements and rules and thus with a considerable depth.

This paper will discuss AECL’s approach in providing a comprehensive “full knowledge” support to plant ageing and ageing management. This requires the integration of research and development into safety, design, and service areas of the company. The paper will also explore how this integration is being accomplished through the initiatives of the PLiM program. The paper will examine several examples of how AECL is developing its understanding of ageing degradation, the engineered solutions, applying those solutions, improving those solutions, and finally incorporating these solutions into both the PLiM program and into new designs.

The present paper deals with the consideration of cases of degradation of the basic equipment (reactor pressure vessels and steam generators') of WWER-440 and WWER-1000 reactor plants, the degradation mitigation measures on the equipment of operating reactor plants as well on equipment being manufactured for newly designed reactor plants.

Electricit é de France is now operating 58 PWR nuclear power plants that produce 75 % of electricity in France. Besides maintaining safety and availability on a routine basis, it is outmost important to protect the investment. That is the reason why EDF is devoting important resources to implement ageing management concern as an integral part of operation and maintenance programs (for example through appropriate data collection and analysis, specific repair and replacement projects and important anticipation efforts, taking in account the high level of standardisation of the units). A particular organisation has been set up to continuously observe and analyse all activities so as to make sure that ageing concern is correctly taken in account in strategies and that no decisions are susceptible to impair plant lifetime. This “lifetime program” is paying attention to technical issues associated with main components but is also dealing with issues related to economics and industry situation.

British Energy has established a comprehensive suite of ageing/obsolescence asset management programmes. Through these programmes, the company has developed a thorough understanding of all the potentially significant degradation mechanisms which could affect the systems structures and components (SSCs) which are essential to the safe, reliable operation of their NPPs. The results from these ageing management programmes underwrite the existing design basis safety case, provide trending information for Safety System Reviews (SSRs) and Periodic Safety Reviews (PSRs) and provide data in support of extending the operating lifetimes of the NPPs. This paper describes te UK regulatory framework with respect to ageing management, British Energy’s overall approach to ageing management, The various ageing/obsolescence management programmes established by BEG, including examples of potentially significant ageing issues which have been successfully addressed by these programmes and the manner in which the results from the programmes are used in support of continued operation, SSRs, PSRs, lifetime extension and general performance enhancement.

Traditionally, evaluating the running behaviour of motor operated valves (MOV) is based upon a non-continuous and demand oriented method. Gundremmingen Nuclear Power Plants has improved this strategy over the last 3 years. At MOVs within the safety system, diagnostics modules were installed for an online monitoring of active power during every run on demand. In the near future, functionality will be further enhanced in order to increase the particular knowledge, as a basis for both a safety oriented, but optimised, condition-based preventive maintenance approach and a plant life management strategy. Furthermore, during spring outage of unit B in 2002, a benchmark was implemented at four MOVs, which includes both comparison between two different kinds of power monitoring as well as active control of one of the systems.

This paper is supposed to clarify the existing German utility integrity concept and is its sound application regarding ageing management issues covering the following key topics: requirements established in the German regulations and codes/standards, NPP safety relevance; NPP availability concerns, safety relevant systems to be considered, component ranking concerning safety significance, explanation of ageing management concept elements, examples for the application of ageing management concepts.

The deregulation of the power generation industry has resulted in increased competitive pressure and is forcing operators to improve plant operating economy while maintaining high levels of plant safety. A key factor to meeting this challenge is to apply a comprehensive plant life management (PLIM) approach which addresses all relevant ageing and degradation mechanisms regarding the safety concept, plant component structures and documentation, plant personnel, consumables, operations management system and administrative controls. For this reason, Framatome ANP GmbH has developed an integrated PLIM concept applicable for both new and operating plants and focusing on the safety concept, plant component structures and documentation.