The liquid waste contractor for the U.S. Department of Energy’s Savannah River Site double-stacked 191 canisters of treated liquid radioactive waste in fiscal 2019, and plans to stack another 300 containers in the current 2020 federal budget year.
Savannah River Remediation (SRR) says the project costs about $3 million annually and is freeing up space for the waste canisters, a longstanding issue that was the focus earlier this year of an audit from the agency’s inspector general.
The double-stacking campaign, which is expected to cost $23.3 million, began in August 2016 at the 310-square-mile Energy Department facility near Aiken, S.C. Savannah River Remediation has double-stacked 738 canisters to date. The project is expected to conclude in fiscal 2024 or 2025.
The treated waste is a byproduct of Cold War nuclear weapons production at Savannah River. Roughly 35 million gallons of liquid waste is stored on-site in more than 40 underground tanks, with salt waste accounting for 90 percent of the volume and sludge waste representing the other 10 percent.
The Defense Waste Processing Facility (DWPF) converts the sludge material into a glassy, less harmful form suitable for interim storage at SRS. That treated waste is poured into canisters and sent to Glass Waste Storage Buildings (GWSB) 1 and 2. Each canister is 10 feet tall and made of stainless steel.
The buildings have housed treated waste since DWPF operations began in 1996. While space was not an issue at the start of operations, the Energy Department has known for years that it would need to create more room in the Glass Waste Storage Buildings.
To accommodate the stacking in GWSB 1, Savannah River Remediation first ensured that there was adequate vertical space for the project and that it would not violate safety protocols. Then, the 21-foot-deep holding slots for the canisters had be modified by first removing the crossbar base support on which the canisters rest. Then, a thick concrete shield plug that guards against radiation was replaced by a thinner, denser cast-iron shield plug, which provides equivalent radiation shielding and structural support. During this process, 196 canisters in GWSB 1 were moved to the second building via a shielded transporter so the reconfiguration could be completed. It is unclear how many total canisters the building was housing at that time.
The DOE Inspector General’s Office reported in February that the agency’s Office of Environmental Management (EM) did not properly assess the viability of double-stacking at Savannah River. Specifically, the IG said double-stacking might not be sufficient to create adequate space for all the waste canisters, and that DOE needs another means to pair with the current mission. A solution to added storage space is needed sooner than later, the IG wrote.
The Energy Department is assessing other ways to generate more storage space at Savannah River Site. With double-stacking in Building 1, and normal storage in Building 2, the site will still need storage space for at least 1,310 more canisters.
One possible solution would be double-stacking canisters in GWSB 2. In GWSB 1, the 2,254 storage positions were doubled to 4,508. Savannah River Remediation is conducting a feasibility study regarding the potential cost and likelihood of success of another double-stacking campaign. A DOE spokesperson said via email the study should be completed by next summer. Factors that are being weighed include the structural design of the building, if it could sustain a seismic event following modifications, and other safety issues.
All told, the DWPF is expected to produce 8,170 waste canisters of waste, including the 4,207 canisters it has poured to date. Storage at SRS is temporary until the Energy Department identifies a permanent federal repository for the nation’s Cold War legacy waste.
