This paper presents the main design and fabrication improvements that were included in the new steam generators that were installed at Nuclear Power Plant Krsko in Slovenia in 2000. These improvements were a result of an on-going R & D effort associated with steam generator technology, aimed at increased reliability and better maintainability of new steam generators. The paper also provides basic information related to 20 years of operation of NPP Krsko with an emphasis on subjects related to steam generator performance and degradation. These include inservice inspection results on steam generators up to replacement, corrective actions, corrosion-erosion counter-measures, and replacement of condenser and moisture spearator reheaters with improved material. The paper also provides data regarding changes in feedwater and steam generator water chemistry, with water chemistry results before and after steam generator replacement. This paper shows that materials issues are very important for steam generator reliability, and it gives the reasons why specific materials were selected for replaced components. Finally, the paper demonstrates how the strategy used at NPP Krsko prolonged the useful life of the old steam generators until replacement steam generators could be designed, fabricated, and installed.

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