During a visit by Energy Secretary Rick Perry, the Savannah River Site broke ground Thursday on a multimillion-dollar disposal unit for radioactive salt waste.
Saltstone Disposal Unit (SDU) 7 will be a 32-million-gallon concrete structure designed and built by Savannah River Remediation (SRR), the liquid waste contractor for the Energy Depatrtment site near Aiken, S.C. Once complete, it will be a permanent disposal unit for saltstone, a low radioactive salt waste found in the SRS storage tanks.
Savannah River Remediation began preparing for construction of SDU 7 in October by clearing out the designated area at the site’s saltstone facilities. Workers also rerouted above- and below-ground utilities located within the SDU 7 footprint. That will enable them to excavate more than 170,000 cubic yards of soil, making way for the unit.
An Energy Department press release did not include SDU 7 cost projections or a timeline for completion. But the site did include figures for SDU 6, a similar megavolume structure that was completed in April 2016. That unit cost $118 — $25 million less than the initial estimate. It was also completed 16 months ahead of the November 2018 projection because SRS padded the schedule to account for potential setbacks, such as weather delays or construction concerns.
“The template created by the liquid waste team from safely completing Saltstone Disposal Unit 6 will continue as we begin construction on Saltstone Disposal Unit 7,” SRR President Tom Foster said in the press release.
The site’s other saltstone disposal facilities include Vaults 1 and 4, along with SDUs 2, 3, and 5. Each of the three units consists of two tanks, all able to hold up to 2.9 million gallons of waste. Saltstone Disposal Units 6 and 7 are the firsts of their kind at SRS, and the site says it will require another seven megavolume units to complete the liquid waste mission, with SDU 7 projected to be needed by fiscal 2021.
“The SDUs are an important part of our cleanup mission and underscore the Department of Energy’s continued commitment to furthering progress on the closure of the high-level waste tanks at SRS,” DOE Savannah River Site Manager Jack Craig said in prepared comments.
All told, about 35 million gallons of radioactive salt and sludge waste are held in more than 40 storage tanks at Savannah River. The waste, a byproduct of Cold War nuclear weapons production, is 90 percent salt waste and 10 percent sludge waste. The salt waste is processed on-site through the Modular Caustic Solvent Extraction Unit (MCU), while the sludge goes to the Defense Waste Processing Facility.
In late 2018, the site is expected to start up the larger Salt Waste Processing Facility to treat more salt waste. That will boost waste processing from 1.5 million gallons a year to 6 million. Ultimately, the final salt waste solution is placed in the SDUs for permanent disposition, while the sludge waste is temporarily stored on site until DOE names a permanent repository.
