Key Elements of the R&D Activity Supporting the Steam Generator Ageing Management Program

The steam generator (SG) tubing degradation caused by stress corrosion cracking, fretting, vibration induced fatigue and other age-related mechanisms continues to be a significant safety and cost concern for many steam generators, even for some of the replacement steam generators with improved materials and designs. Therefore, systematic SG ageing management programs (AMP) are needed at all NPPs. The understanding of SG ageing is derived from the steam generator baseline data, the operating and maintenance histories, and external experience. External experience consists of the operating and maintenance experience of: steam generators of similar design, materials of construction and fabrication, steam generators operated under similar water chemistry or with similar tube alloy material, even if the steam generator designs are different and relevant research results and relevant R&D results. The paper aims to present the Steam Generator R&D Program, developed in the Institute for Nuclear Research Pitesti since 2000. During this period a lot of experimental results were obtained, in the paper being presented only one example of experimental research regarding the steam generator tubing corrosion behaviour. The purpose of the experimental research consists in the assessment of the Incoloy 800 corrosion behaviour at the normal secondary circuit parameters (260 °C, 5.1 MPa). The testing environment was the demineralised water, at pH = 9.5 regulated by All Volatile Treatment. The results are presented like micrographs and graphics representing the loss of metal through corrosion, corrosion rate, total corrosion products, adherent corrosion product, released corrosion products and the release of the metal. (author).