project: caisson inleakage chemical
in leakage unit 3
humboldt bay power station
Eureka, California
Owner: Pacific Gas & Electric Co.
Completed: September 1997
Engineer: Westinghouse
GC: Morrison Knudsen Corp.
Agent: Marathon Coatings Corp.
One of the first nuclear power plants built in the U. S., Humboldt Bay Station, was shutdown in the late 1970's and is undergoing final stage decommissioning. This could not proceed until a large underground water inleakage beneath the reactor caisson suppression chamber was drastically reduced. To solve this problem, mock-ups were conducted to devise a procedure as well as to determine the type of product to be used.
The first mock-ups involved polyurethane foam products, which were rejected due to excessive pressure caused by the expansion of the foam, gassing and the toxicity of the urethane and its cleaners. At this time, agent Marathon Coatings (MC), contacted JWI to help solve the problem. A team formed from PG & E, Westinghouse, Morrison Knudsen and JWI conducted several more mock-ups using several injection resins. Testing proceeded until the perfect combination of products, injection packer placement and spacing concluded with favorable results. After testing was complete, it was time to commence site work in the Suppression Chamber at elevation -66'.
Once all holes were drilled and documented, the injection packers were installed. At this time injection resins were now pumped into the injection packers. Since the injection resins chosen for this portion of the project do not foam or expand, there were no pressure problems. Injection was done in sections by forming “dams” using urethane followed by the injection of acrylic resins. In all, eight sections were injected. After the eighth and last section was complete, the inleakage, which was constantly monitored, had gone from a high of 10,000 gallons per day to 10 gallons per month. The success of the project insured final decommissioning could proceed.