Project:     Humboldt Bay Power Station, Unit 3 – Caisson Inleakage Chemical Injection
Location:  Eureka, California
Owner:     Pacific Gas & Electric
GC:           Morrison Knudsen Corporation


One of the first nuclear power plants built in the U.S., Humboldt Bay Station, was shutdown in the late 1970′s and was undergoing final stage decommissioning.  This could not proceed until a large underground water leak 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-up involved polyurethane foam products, which were rejected due to excessive pressure caused by the expansion of the foam.  At this time, Marathon Coations (MC) contacted Jean’s Waterproofing, Inc. (JWI), about a line of non-toxic, water-based acrylic-ester products specifically designed to seal various types of water leaks.  Testing was conducted until the perfect combination and spacing concluded with favorable results.  After testing was complete, it was time to commence site work in the Suppression Chamber at elevation -66 feet.

Once all the holes were drilled and documented, the injection packers were installed.  Then the resins were pumped into the injection packers.  Since the resins do not foam or expand, there were no pressure problems.  Injection was done in sections by forming “Dams” using a two-component, polyurethane waterstop resin with elastomeric properties and an acrylate resin for the stabilization of soils and rock.  In all, eight sections were injected.  After the eighth and last section was complete, the leak, which was constantly monitored, had gone from a high of 10,000 gallons per day to 10 gallons per month.  The chemical injection resins performed as expected.  The success of the project insured final decommissioning could proceed.


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