The condensing unit at a northeast nuclear power plant has six outlet water boxes and attached discharge pipes leading to an underground discharge tunnel. The area of concern was the discharge piping which runs from the expansion joint immediately downstream of the water box into the discharge tunnel. Each of the six discharge pipes are made of 0.375 inch wall rolled carbon steel plate and are approximately 21 feet in length and 8 feet in diameter. Over the last 30 years of operation the carbon steel substrate had shown substantial signs of base metal loss including through wall failures. The plant identified that the through wall failures have affected the function of vacuum within the discharge pipe that is vital to cooling capacity during peak energy demand. Worse, if the wearing and erosion were to remain unmitigated the potential for complete pipe failure was imminent.
Confronted with the logistics of limited time, environmental concerns, and space restrictions, the determination was made that the discharge pipes could not be replaced in kind. This led to a search for an alternative solution.
CSI utilizing Carbon Fiber Reinforced Polymers (CFRP) performed the rehabilitation of the discharge pipes to meet the challenges of this project. This repair method restored original structural design levels of the discharge pipe and arrested any future erosion or corrosion concerns. Due to extremely high flow conditions, the termination of the CFRP repair was finished at each end with an internal seal .