Thermal fatigue of reactor components in OECD-NEA member countries: a three fold programme to enhance cooperation

The OECD Nuclear Energy Agency has 28 Member countries. Under the auspices of the Nuclear Safety Division are two senior committees dealing with regulatory aspects (CNRA) and technological aspects (CSNI). Under these two committees activities relevant to thermal fatigue in LWR piping are carried out under the two Working Groups (WG's): WG on Operating Experience, WG on Integrity of Components and Structures. There is also co-operation with the former task group on thermal hydraulics application. These groups make recommendations to the senior committees. WG on Operating Experience is mainly concerned with the analysis of safety significant incidents, but it undertakes special studies as well. WG on Integrity of Components and Structures (Integrity and Ageing, IAGE) has activities in fracture mechanics, Non-Destructive Examination and material degradation, as being the three aspects of structural integrity for metal reactor components. It also has sub-groups dealing with the ageing of concrete structures and the seismic behavior of structures. In the area of thermal fatigue, it currently has a three-fold program of work approved by CSNI: 1. A questionnaire completed by Member countries with the objective to find out how widespread a problem thermal fatigue is, to learn what kind of countermeasures have been taken by countries and to obtain a detailed view of countries' actions and regulations, if any, and to identify adequate corrective actions; 2. A benchmark to establish capabilities in thermal fatigue calculation supported by specific tests performed by CEA, France; 3. An active program of information exchange between experts worldwide through a biennial Conference on Fatigue of Reactors Components in association with the EPRI and the USNRC. This paper provides background on the Agency itself, while focusing on the thermal fatigue activities within NEA carried out mainly through the Committee on the Safety of Nuclear Installations and the groups of technical experts on operating experience, structural integrity, and thermal hydraulic. It presents recent accomplishments in each fold on the program and provides areas where efforts should be pursued. (authors)