To expand interim storage of vitrified high-level radioactive waste at the Savannah River Site, the Department of Energy’s Office of Environmental Management and its liquid waste contractor Savannah River Mission Completion (SRMC) have double stacked 2,000 canisters in one of the site's two glass waste storage buildings (GWSB). GWSB 1 consists of a below-grade, seismically qualified concrete storage location containing support frames for the vertical storage of 2,262 10-foot-tall canisters.
The change: An evaluation in 2015 concluded that, with some minor changes to each vertical location, two canisters could be stored in an area previously used to store only one.
While combined storage space from the original design of both GWSBs would hold a total of 4,602 canisters, the modifications will allow for moving two canisters into each storage location, freeing the remaining existing space for future use. Doubling up on usage of the original space in the GWSBs has deferred—and potentially eliminated—the need for construction of another GWSB, according to the DOE, which saves approximately $100 million.
How it works: Double stacking was made possible by the removal of a steel crossbar at the bottom of each canister support and reducing the thickness of the plug that is used to seal each canister position. Modifying the metal support frame required workers to develop and test a cutting tool that could be operated from a distance to minimize workers’ potential exposure to radiation. A shielded canister transporter was used to move the canisters into modified underground storage locations.
The SRS Liquid Waste Program had previously filled nearly 4,400 cans with HLW, which now occupies a large percentage of the storage space in the two GWSBs, according to the DOE. Consolidating the existing stored canisters into the modified locations has effectively doubled the storage space available to hold canisters in the two facilities. Enough positions are planned to be converted to allow storage of all canisters produced at SRS.
Quotes: SRMC president and program manager Dave Olson said this innovative approach is solving a storage problem. “To reach this point has required rethinking, redesigning, and reconstructing our approach to the task of temporarily storing these waste canisters,” Olson said. “Achieving 2,000 double-stacked canisters exemplifies the dedication to continuous improvement that will help us disposition the remaining liquid waste at SRS and complete the overall mission. I am proud of this team’s effort.”
Jim Folk, DOE–Savannah River assistant manager for waste disposition, said the double-stack program is expected to provide enough storage space until a federal repository is established. “The double-stack program is making better use of the existing storage space we have, enabling us to keep the liquid-waste mission moving forward,” he said.