Cooling Water Basins
The eight Cooling Tower Basins were all experiencing wall cracking and leaks. The initial cause of the cracking was determined to be inadequate horizontal reinforcing allowing shrinkage cracks to appear. A seismic event furthered the opening of the cracks.
There had been numerous attempts to address the problem by either patching or injection. These repairs had met with limited success for a variety of reasons with most of the cracks continuing to leak.
Apply CFRP composite materials to repair/stitch cracks and to strengthen walls in place of rebar. Engineering established the amount of materials needed for seismic and structural requirements. The repair included; clean and remove damaged concrete, seal leaks, treat and apply carbon fiber to crack areas, and finally, to apply carbon fiber to wall surfaces. The repaired system was then coated for UV protection.
The basins have been completely rehabilitated by this comprehensive repair. The solution brought each basin into compliance with seismic and structural requirements. The final result provides long term structural integrity and repairs leaks permanently.
Water Infiltration Repairs
Nuclear Generating Station
The Turbine Building Basement at a Nuclear Generating Station was plagued with leaks from leaking below grade piping. The water was seeping in through cracks in the concrete and creating water hazards and corrosion of rebar. The plant approached Next personnel to solve the problem.
Next personnel suggested a comprehensive approach to solving the problem including:
- Developed a repair plan to repair the below grade piping during a re-fueling shutdown.
- In the interim, Next proposed using urethane injection to stop the leaks until the more permanent repairs could be completed.
Due to the substantial thickness of the walls in the turbine basement, Next personnel utilized large drilling equipment with long bits. The plant was concerned about further damaging potentially degraded rebar so the location of all rebar in repair areas was Ground Penetrating Radar (GPR), mapped prior to beginning drilling. Additionally, drilling equipment was modified with grounding to provide automatic shutoff in case of contact with rebar.
The work proceeded for a period of four months. As leaks were sealed, new leaks would appear in adjacent areas. Some concrete reinforcement was required in areas of severe damage. Excessive cavities required pumping an enormous volume of hydrophobic urethane to ultimately seal cracks.
Next personnel were successful in stopping approximately 95 percent of active leaks in the basement. Because the water source (leaking below grade piping) was still active, there was some small scale seepage that remained until the piping repairs were completed