Byron Unit 1 high temperature chemical cleaning

The secondary side of the Byron Nuclear Station, Unit 1 steam generators were successfully chemically cleaned in September 1994, using the BWNT/Framatome high-temperature chemical cleaning process. This cleaning was the first North American application that used plant heat for process temperature control. The primary purpose of the cleaning was to remove bulk deposits and deposits from the drilled tube-to-tube support plate crevices of the Westinghouse D4 steam generators. Crevice deposit removal was targeted to mitigate initiation of new corrosion defects and the propagation of existing defects. The process application scenario and plant interface equipment were designed to maximize effectiveness while minimizing corrosion, waste volumes, and critical path time. A total of over 15,383 pounds (6,992 kilograms) of material was removed from the four steam generators during the chemical cleaning. Post-cleaning visual inspections showed the steam generators to be very clean. Some quantity (30% to 60%) of deposits remained in crevice areas. One indication of successful crevice magnetite removal was very clean and crisp eddy-current signals in the tube support plate region. Corrosion to steam generator materials resulting from the cleaning was less than 2.5 mils (63.5 microm) and consumed less than 20% of the available corrosion allowance