Accounting for environmental effects in fatigue has long been a necessity in Finland. This requirement was placed into the national regulatory guides in 2002 and the regulatory body, Radiation and Nuclear Safety Authority (STUK) required the license holders of operating reactors to respond by 2004.

At that time, the international state-of-the-art was reviewed and found not mature. However, reasonable approaches for accounting environmental effects were developed and adopted by both utilities, Fortum and TVO. Adoption of the proposed new design curves was considered impractical and calculation of Fen factors was preferred. This placed the Finnish utilities among the first industries, who brought environment assisted fatigue (EAF) into practice. At the same time, fatigue design of the new EPR design (OL3) was also subject of the requirement. The experimental work and approaches developed by Areva have been widely discussed in previous PVP Conferences.

A high number of PVP papers in these ‘ENVIRONMENTAL FATIGUE ISSUES’ sessions reveals that work remains to be done before the state-of-the-art in EAF is mature and an international consensus can be reached. Follow-up of evolving state-of-the-art is a part of the safety culture for Finnish utilities and regulator. Therefore, we encourage the researchers and engineers together to find solutions, which can be justified by sound arguments and brought into practice to reduce confusion and bias in fatigue management.

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