Wolf Creek Feedwater Heater Repair

Since 1990, an increasing number of the 304 SST feedwater heater tubes in the number 1 and 2 feedwater heaters (six heaters total) at the Wolf Creek Nuclear Power Plant have experienced failure due to fretting wear within the drain cooler region. Tube damage was due to thin end plate design resulting in tube wear at the end plate and support plate locations. Despite performing extensive eddy current inspections and preventative plugging on the heaters, the damage mechanism is powerful enough that tube leaks were continuing to occur while at power, resulting in the forced shutdown of a string of heaters for plugging. As an option to feedwater heater replacement, a method of reducing the tube-to-end plate gap, by expanding the tube into very close contact with the end plate, and sleeving tubes with wear indications was evaluated. Based on an evaluation of outage schedule time and cost, it was decided that the option of repairing the feedwater heaters, rather than replacing them, would be pursued. During Wolf Creek’s September 2000 refueling outage, Framatome ANP performed feedwater heater tube plug removal, tube expansions at the end plate, and sleeving. All work on-site was performed within the outage scheduling constraints.