Walls going up for new disposal unit at Savannah River Site

March 23, 2021, 9:30AMRadwaste Solutions
The first wall section of Saltstone Disposal Unit 8 is being constructed at the Savannah River Site. Source: DOE

The first wall section of Saltstone Disposal Unit 8 (SDU 8) at the Department of Energy's Savannah River Site in South Carolina was installed earlier this month.

SDU 8 will stand 43 feet tall and 375 feet in diameter, and have a 33-million-gallon capacity, just like two SDUs built recently at the site. The 25 wall sections of SDU 8 are being constructed using high-strength, reinforced concrete and will be wrapped with seven layers of more than 300 miles of steel cable for added strength.

The flooring of SDU 8 is more than halfway complete. The concrete floor sits on top of a multilayer foundation: a geosynthetic clay liner and high-density plastic liner sandwiched between two concrete layers called “mud mats.” The floor is being completed in 14 sections.

The disposal units are built to safely and permanently contain decontaminated salt solution processed at Savannah River, the DOE reported on March 9.

Savannah River Site continues to make progress on the next Saltstone Disposal Units being constructed to support the Salt Waste Processing Facility. Source: DOE

Also under construction: In parallel, work continues on SDU 9, where the lower mud mat is complete and the liner is being installed on top of it. Meanwhile, site prep design is ongoing for the final three units to be built, SDUs 10-12. The site prep design and excavation work for SDUs 7-12 were completed by BK All American Company, a locally owned small business.

Key roles: Shayne Farrell, the DOE's Savannah River SDU federal project director, said that waste tank cleanup is a priority for the DOE and that the SDUs play a key role in that mission, along with the Salt Waste Processing Facility (SWPF), which is now operational.

“The Salt Waste Processing Facility will greatly increase waste tank cleanup at the Savannah River Site,” Farrell said. “The liquid waste system relies on the capability to safely dispose of the saltstone onsite, and the Saltstone Disposal Units are required to fulfill this mission need.”

Treated waste: The SDUs are being built to support the increased decontaminated salt solution from the SWPF. Salt waste at SRS is decontaminated through processes that remove isotopes, such as cesium.

The treated solution is then sent to the Saltstone Production Facility, where it is mixed with dry materials to form a grout. The grout is pumped to the above-ground SDUs, where it hardens to a form called saltstone. The first unit, SDU 6, is already operational and receiving treated waste. SDU 7 is nearing completion and undergoing testing.

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