Concepts for Inconel 690 as a steam generator tube material

Corrosion related failures in heat transfer tubing used in PWR steam generators is of great utility concern, considering the sizeable loss of generating power due to tube failures and the consequential expense associated with remedial actions. For successful operation, the tubing used must be resistant to various types of corrosion under a variety of adverse environmental conditions, while having desirable heat transfer characteristics. Inconel 690 thermally treated tubing has proven superior corrosion resistant to Inconel 600 in laboratory tests. Although there is not a significant amount of operating experience, the significant amount of laboratory and model testing, involving several organizations, clearly leads to the conclusion that Inconel 690 is the best selection for heat transfer tubing material. Since the thermal resistance of Inconel 690 is greater than that of Inconel 600, the heat transfer coefficient has been lessened by the change in material. Thus design concepts associated relatively poor heat transfer characteristics of Inconel 690 as a steam generator tube material was studied in this paper. The study concluded that Inconel 690 could be adopted within manufacturing constraints with the same design basis thermal hydraulic parameters as those of Inconel 600 steam generator without seriously impacting interfacing system design