LAS VEGAS – The EM Nevada Program has finished removing an insulation material known as perlite from four tanks at Test Cell C (TCC) on the Nevada National Security Site (NNSS).
The tanks, also known as dewars, held spherical containers that stored liquid hydrogen. Perlite, meanwhile, is an amorphous volcanic glass dust that served as insulation to protect the inner spheres. A manager on the project, Jason Sofie, compared perlite to the foam pieces used to cushion fragile objects during everyday packing. It is not a hazardous material, but if released it could scatter and create obstacles for workers and wildlife.
“Perlite removal is in preparation for dewar demolition,” Sofie said. “So, when we approach the outer shell for size reduction, only residual perlite will have to be addressed and collected.”
In late November, workers performed “hot taps” on all four dewars, creating what are essentially controlled extraction points for perlite removal. The two larger dewars have an outer radius of 29 feet. The smaller tanks have a radius of 19 feet. Crew members made nine extraction points on each large dewar and seven each on the smaller pair.
"Exterior paint was removed and three-inch diameter holes were drilled through the outer shell at each hot tap extraction point," explained Site Supervisor Jason Brooks.
“The hot tap team welded on a four-inch nipple to the outer shell, attached a valve, then with the valve open, drilled through the outer shell,” Sofie added.
The removal work began on Dec. 22. A vacuum was used to pull perlite via a hose from the dewars and into containment bags held in roll-off canisters. Crew members filled about four to 10 bags a day. As each bag was filled, it was secured, processed through waste handlers and transported to a landfill at Area 9 at NNSS for disposal. On average each filled bag weighed about 5,000 pounds.
Built in 1961, TCC was used to ground test nuclear reactors and engines for rockets. The liquid hydrogen within the dewars was used to cool reactors after testing took place.
Workers filled more than 100 bags over the course of the extraction process, with a total of 550,000 pounds of perlite removed. By Feb. 15, they completed the removal process and demobilized the site, meaning all equipment and personnel associated with perlite work were taken offsite.
The successful removal will allow EM Nevada to move forward with demolition efforts at TCC. Four buildings within the TCC facility are scheduled for demolition this year.
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