SRS preps for dissolution of stainless-steel-clad spent fuel

June 21, 2021, 12:00PMRadwaste Solutions
A train pushes a container full of old equipment from H Canyon to a Savannah River Site disposal facility to make way for a new spent nuclear fuel dissolving campaign. (Photo: DOE)

The Department of Energy is preparing for an upcoming campaign to dissolve stainless-steel-clad spent nuclear fuel at its Savannah River Site in South Carolina by installing a new dissolver and an additional double-sized tank for storing dissolved material.

Workers with site contractor Savannah River Nuclear Solutions (SRNS) are making room for the new equipment by disposing of old equipment at Savannah River’s H Canyon, the only operating production-scale chemical separations facility in the United States.

“The upcoming dissolving campaign will add a third electrolytic dissolver to the complement of equipment already in use in the canyon and will provide the capability to dissolve stainless-steel fuel,” said Wyatt Clark, SRNS senior vice president of Environmental Management Operations. “The current chemical dissolvers are designed to dissolve aluminum-clad fuel, so they are not adequate to support the upcoming mission.”

SRS spent fuel: Savannah River’s stainless-steel-clad spent fuel is currently stored in the site’s K Area and will be shipped to H Canyon for processing. Once the fuel is dissolved in the electrolytic dissolver, the resulting solution will be transferred to the liquid waste tank farms. The material will then be transferred to the Defense Waste Processing Facility, where it will be vitrified and placed in an SRS facility for interim storage.

According to the U.S. Nuclear Waste Technical Review Board, Savannah River holds approximately 20 metric tons (about 2,000 fuel assemblies) of non-aluminum-based spent fuel, including zirconium-alloy-clad, stainless-steel-clad, and de-clad thorium oxide and uranium oxide or uranium-zirconium alloy. The spent nuclear fuel is primarily from research and test reactors.

Out with the old: In preparation for the processing mission, crews at H Canyon recently finished removing the first of three shipments of legacy equipment to make room for the new campaign.

According to Richard Brown, an SRNS project manager, the old equipment is placed in large, engineered packages, called burial boxes, using the canyon’s remote cranes. “Once that box is full, we secure the package, verify it is free of any radioactive contamination, and transfer it to the SRS Solid Waste Management Facility for disposal,” he said.

To minimize the number of burial boxes required to remove the equipment, SRNS purchased a special cutting tool and a grapple system. These tools will be used to remotely reduce the size of large equipment to maximize the amount of equipment loaded into a burial box.

Other work: Preparations for the new campaign also include preparing and calibrating the double-sized tank and new dissolver with the use of a bladder tank and pump system. The use of the bladder tank and pump system speeds up the calibration process by pumping water versus using a domestic water hose to fill the 50- and 150-gallon prover tanks, which are vessels used to add a specific volume of water to the tanks being calibrated.

Once a calibration run is complete, the water is pumped from the vessel back to the bladder tank, using recycled water instead of fresh water for each of the four minimum calibration runs per vessel.

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