Work is moving ahead to remove radioactive capsules at Hanford from storage in a water-filled pool that could be at risk in a severe earthquake.
CH2M Hill Plateau Remediation Co. has awarded a $23 million contract to have casks designed and built to hold the 1,936 capsules of cesium and strontium on an outdoor pad in central Hanford.
The capsules contain about 94 million curies of radioactivity, or about a third of the radioactivity at the Hanford nuclear reservation.
The dry-storage system would be much like those used by nuclear power plants, including the outdoor storage pad and casks used at Energy Northwest’s Columbia Generating Station near Richland, according to CH2M, the Department of Energy contractor in charge of managing the Hanford capsules.
Hanford’s 1,335 cesium capsules and 601 strontium capsules are stored under 13 feet of water at the Waste Encapsulation and Storage Facility, or WESF, adjoining the B Plant processing facility in central Hanford. The water protects workers from radioactivity and helps keep the capsules cool.
The cesium and strontium were removed from the waste in Hanford’s underground storage tanks in the ’70s to reduce the temperature of the waste in the tanks, which hold 56 million gallons of waste from the past production of weapons plutonium at Hanford.
The radioactive material was packaged in stainless steel, double-wall capsules that are about 22 inches long.
A previous plan to move the capsules to dry storage by 2006 was put aside to use the Hanford budget for cleanup projects that Hanford officials thought were more pressing a decade ago.
But the focus on moving the capsules received renewed attention in 2014 when DOE’s Office of the Inspector General said they needed to be moved to dry storage as soon as possible, in part because of the potential risk of a severe earthquake.
NAC International, a Georgia-based company with experience in storage of used nuclear fuel, was awarded the contract for design and fabrication of the cask storage system for the capsules.
“Dry storage would be a better, safer option, so we’re happy to see this process begin,” said Alex Smith, nuclear waste program manager for the Washington State Department of .Ecology’s Nuclear Waste Program manager.
Construction of the first cask should begin in fiscal 2019, according to CH2M, and the capsules could begin to be moved to dry storage as soon as 2022.
The original WESF ventilation system needed to be updated, to support continued storage of the capsules until they are moved and the transfer of the capsules to dry storage. The filters deteriorated after they were used longer than planned and the system had been contaminated by work done with radioactive material, according to a DOE report.
Work to update the ventilation system was completed in September and the system is operating extremely well, said Connie Simiele, CH2M vice president for waste and fuels management.
Ventilation duct work that is no longer needed has been filled with grout and final preparation work has been done to start filling six unneeded hot cells at WESF with grout after Thanksgiving.
Most of the WESF hot cells measure about 8 feet long and 8 feet high and up to 13.5 feet tall. The floors and walls are lined with stainless steel. Workers would look through 25-inch-thick lead glass windows and operate manipulators inside the cells that handled the radioactive materials.
The largest of the seven cells will be retained. It is on standby if one of the underwater capsules develops a leak or other issue that would require a capsule to be pulled from the water for work. The remaining hot cell also may be used to process waste for transfer to dry storage.
The planned outdoor dry storage is a temporary measure until the capsules can be disposed of permanently.
Among options that may be considered is a 3-mile-deep borehole, although DOE has yet to find a site in the nation for a test borehole to be drilled.