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| Here, the first 160,000-pound segment of the above-ground ducts is maneuvered away from the fan house and lowered to the ground. |
In July, the first sections of above-ground ductwork were removed from the Brookhaven Graphite Research Reactor, signalling the start of a second major phase in the decommissioning effort.
The U.S. Department of Energy (DOE) recently issued an Action Memorandum that documented the decision to remove the above-ground ducts. The Action Memorandum is available in local libraries and on the web at http://www.bgrr.bnl.gov/docs.html.
These concrete ducts have deteriorated since their construction in the late 1940s, necessitating their removal. The ducts were erected during the complex's original construction, and are showing the effects of more than 50 years of aging and weathering. Small, fist-sized chunks of concrete have flaked off, and there is evidence of previous rainwater intrusion into the ducts. Moreover, the original exterior coating contains lead, asbestos, and PCBs.
Preparations ensure safety
Brookhaven National Laboratory requested bids for the removal project earlier this year. Contract bids were evaluated for their safety procedures and operating techniques, as well as cost. The Laboratory awarded the contract to URS/US Ecology, and initial preparations began in May 2000.
Before actual work could begin, contract workers had to complete the Laboratory's training requirements. The contractors also had to submit formal written plans for environment, health, and safety protection, as well as technical work documents for cutting and segmentation of the concrete ducts, containment of contamination, lifting the duct segments using an overhead crane, and waste management and disposal.
An Operational Readiness Review, including DOE, Suffolk County Department of Health Services and the BGRR Decommissioning Project team, was completed before work began. Laboratory personnel from Plant Engineering, and the Environmental Safety, Health & Quality Directorate were also involved in this review.
The ducts come down
After all plans and training were completed and equipment and materials collected, work began. Two diamond-wire saw stations were set up on top of the fan house, and barriers were installed to isolate the above-grade ducts. Workers applied a fixative to the expansion joints and a strippable fixative to the duct interior surfaces to prevent the spread of radiological contamination during cutting, lifting, and transport of the concrete. Then, the methodical process of cutting the ductwork apart with diamond-wire saws began.
As the sections above the fan house were cut free, they were lowered by crane to a staging area. There, they will be cut into thirds and securely sealed and packaged before being shipped off site for decontamination, waste volume reduction and disposal.
The decontamination will be performed at a licensed off-site facility using a chemical/vacuum extraction process. This three-part process is particularly effective with hard, porous materials such as bricks and concrete. A base, then an acid, and then a cleaner will be applied to the surface of the concrete. The chemicals draw the radionuclides to the porous surface of the concrete, where they are vacuumed out. The small volume of chemicals containing the radionuclides will be sent for hazardous materials processing.
After decontamination, the concrete should be clean enough to meet release
criteria and be sent to an industrial landfill.