Framatome steam generator units for plant life extension

From 1975 up to now, Framatome has developed a large SGs product line for new plants and, more recently, for replacement units. All these equipments benefit from a continuous effort in design, materials and manufacturing areas, to improve the reliability, operation flexibility and especially tube bundle resistance. First design and research effort was applied to 68/19 model (1050 MWth type, used in 4 loops 1350 MWe plant such as Paluel plants). Improvements were backfitted on 51B model (950 MWth type used in 3 loops 950 MWe French plants and on 55/19 model (1000 MWth type used in 3 loops 1000 MWe plant such as Chinese Daya Bay nuclear Units). More recently FRA has designed the 73/19E model (with axial mixing preheater, 1100 MWth type for new 4 loops 1450 MWth plant such as Chooz B) and finally, different replacement models destined to foreign and domestic market. Design, materials and manufacturing features will be presented. In case of tube bundle corrosion on primary or secondary side of the tube, and after some years of difficult operation with many inspection and plugging, the main choice appears between some various repair methods and the replacement operation. A short list of repair methods (shot peening or roto peening, local heat treatment, nickel electrolytic coating, mechanical or welded sleeving) gives many possibilities to extend SG units life. A combination of various repair methods is possible and the total life time extension is very difficult to predict. A replacement operation requires a decision to be taken 3 or 4 years before the replacement operation itself, for designing and manufacturing the units and for on site work preparation