Savannah River begins test of saltstone disposal mega unit

August 16, 2023, 12:00PMRadwaste Solutions
An October 2022 photo showing various SDUs at SRS. (Photo: DOE)

The Department of Energy’s Savannah River Site in South Carolina will begin a leak tightness test on what it called “the fourth megavolume saltstone disposal unit (SDU)” at the site.

The test will qualify the newly constructed unit for use, verifying that it is safe to store up to 33 million gallons of solidified, decontaminated salt solution produced at SRS.

The test: Beginning on August 18, SRS liquid waste contractor Savannah River Mission Completion will begin filling SDU 9 with water to check for visible signs of leakage on the exterior of the unit. It will take three to four weeks to fill the unit with about 33 million gallons, equivalent to the amount of water that would fill approximately 55 Olympic-sized swimming pools, the DOE said.

After about four feet of water is added to the unit, roughly 400 gallons of dye/tracer will be introduced to the tank as an additional means to confirm leak tightness and will assist in leak detection. The fluorescent yellow-green dye, which is commonly used in dye/tracer tests, is certified for use in drinking water by NSF International, an independent public health and safety organization, according to the DOE.

The test is expected to take six to eight weeks. Once complete, SDU 9 will be drained, and the dyed water will be discharged to drainage basins on-site for a controlled release to the environment. When discharged, the water will traverse over land and empty into an on-site tributary to the Savannah River. Because the dye is safe for the environment, there are no health, safety, or environmental concerns with discharging this water in the SRS ecosystem or the Savannah River, the DOE noted.

The DOE added that the SDUs are a critical part of the liquid waste system, as they are permanent disposal units that will hold solidified, decontaminated salt solution at SRS.

The megaunits: SDU 9 is the fourth SDU at SRS. SDUs 6 and 7 are in operation, while SDU 8 has been approved for operation. Leak tightness tests were performed on SDUs 6-8 using the same method that will be used for SDU 9.

About SRS: The Savannah River Site, a 310-square-mile-site in Aiken, S.C., focused on the production of plutonium and tritium for national defense purposes from its inception in the early 1950s until the end of the Cold War. In 1992, the site's focus turned to environmental cleanup, nuclear materials management, and research and development activities, according to the DOE.

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