DEVELOPMENT OF DEEP HOLE DRILLING TECHNOLOGY FOR TUBE SHEET OF STEAM GENERATOR

摘要

Advanced PWR nuclear power plant has very-large steam generators of which tube-sheet is diameter 5000mm / thickness 500 mm / weight 100 ton or larger. Drilling of very thick tube sheet needs deep-hole drilling technique with strict dimensional tolerance control. In addition, the tube sheet has 10,000 or more tube holes, which means that stable drilling operation is mandatory for productivity control. Upon such background, steam generator tube sheet drilling operation needs precise dimensional control technique with highly efficient productivity. In this study, authors did (1) feasibility-study and development of deep hole drilling machine with the Boring and Trepanning Association (BTA) method, (2) cutting parameter evaluation such as feed rate and cutting velocity, (3) tube hole measurement system development, and (4) drill exchange program development with monitoring drilling machine motor loads and setting alarm level for the loads. Based on techniques developed by this study, IHI has achieved high-accuracy and stable deep-hole drilling technology for very-thick tube sheets applicable to the very-large steam generators.