Savannah River Site completes large disposal unit

14 July 2023

The US Department of Energy’s (DOE’s) Environmental Management Office (EM) has authorised operation of a new large-size disposal unit at the Savannah River Site (SRS). The Saltstone Disposal Unit (SDU) 8, which was completed three years ahead of schedule, can now begin to receive decontaminated material for disposal.

EM’s liquid waste contractor at SRS, Savannah River Mission Completion, manages the construction and operation of the SDUs. Subcontractors Quality Plus Services, US FUSION & Specialty Construction and DN Tanks completed the site preparation.

The SDUs are the end of the salt waste processing path. The Salt Waste Processing Facility (SWPF) produces decontaminated material that is sent to the Saltstone Production Facility, where it is mixed with dry materials to make a cement-like grout. The grout is pumped into the SDUs, where it solidifies into a monolithic, non-hazardous form.

SDU 8 is the third mega-size unit built at SRS and can hold up to 33m gallons of saltstone. These larger SDUs are designed to support the increased material production from SWPF. The new SDUs result in more than $500m in cost savings over the life of the SRS liquid waste programme because they require less infrastructure and materials than the previously planned 80 smaller SDUs.

Achieving significant construction milestones, such as SDU 8, is an EM priority part of the 10-year Strategic Vision, according to Jim Folk, DOE-Savannah River assistant manager for waste disposition.

“DOE-Savannah River is proud to play a critical role in EM’s commitment to tackling one of the largest environmental clean-up efforts in the world,” Folk said. “The mega-size Saltstone Disposal Units are key in our ability to safely dispose of legacy liquid waste and underscore DOE’s commitment to complete the SRS Liquid Waste Programme.”

Construction and testing of the next unit, SDU 9, is slated for completion in autumn 2024. SRMC is also in various stages of constructing the final SDUs needed at SRS – 10, 11 & 12.

SRS was built in the 1950s to produce materials for nuclear weapons, primarily tritium and plutonium-239. Five reactors were built on the site along with two chemical separations plants, a water extraction plant, nuclear fuel and target fabrication facility and waste management facilities. Savannah River faces a massive legacy waste clean-up task.

The SWPF, which began operation in 2021, will process the majority of the SRS’s salt waste inventory by separating the highly radioactive waste – mostly caesium, strontium, actinides, and waste slurry – from the less radioactive salt solution. After the initial separation process is completed, the concentrated high-activity waste will be sent to the nearby Defence Waste Processing Facility (DWPF), where it will be immobilised in glass and stored in vaults until it can be placed in a geological repository. The decontaminated salt solution is mixed with cement-like grout at the nearby Saltstone Facility for disposal on site. Removing salt waste, which fills over 90% of tank space in the SRS tank farms, is a major step toward emptying and closing the site’s remaining 43 high-level waste tanks.

Image: Saltstone Disposal Unit 8 project team members stand in front of the newest mega-size disposal unit completed at the Savannah River Site

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