The US Department of Energy (DOE) has authorised radioactive (hot) operations to begin at the Salt Waste Processing Facility (SWPF) at the Savannah River Site (SRS).
DOE’s Office of Environmental Management (EM) said the SWPF is the last major piece of the liquid waste treatment system to be completed at Savannah River. DOE’s approval of Critical Decision-4 (CD-4) and authorisation to operate the SWPF signals project completion and the transition from project phase to operations.
“This is a considerable achievement for EM's cleanup programme and will drive significant progress in treating the tank waste at SRS in the next decade,” said Senior Advisor for EM to the Under Secretary for Science William “Ike” White.
The SWPF 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 will be 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.
“SWPF provides the final piece enabling completion of tank closure activities at SRS,” said manager of DOE’s Savannah River Operations Office Mike Budney.
The approval comes five months ahead of the current baseline CD-4 completion date of 31 January 2021. Parsons Corporation, who designed and built the first-of-a-kind facility, will operate it for one year. The SWPF remains on track to start normal operations later this year following completion of hot commissioning. By 2030, it is expected that nearly all of the salt waste inventory at SRS will be processed.
Earlier, SRS said Savannah River Nuclear Solutions (SRNS) workers had assisted with the SWPF startup by supplementing the facility’s only water source. Personnel with SRNS Site Services organisation managed the design and installation of miles of water line, providing a critical second water source.
“Due to a history of leaks and other issues related to the original line, a second line was connected to the site domestic water loop,” said Randy Keenan, a facility manager with SRNS Site Services.
Crews installed several valves, pressure and flow sensors, and more than 4400 feet of four-inch pipe withinexcavated trenches. SRNS coordinated these activities with SWPF and Savannah River Remediation (SRR), the site’s liquid waste contractor, to comply with the facility startup testing schedule.
The project was completed despite several challenges,” Keenan said. Those hurdles ranged from an unusually high number of delays in the project due to rain to underground obstacles such as cables, pipes and metal conduits from past construction projects.
“When an unknown buried object of some kind that’s not on site drawings is discovered, everything comes to a stop until it can be identified. Then, a careful and thorough investigation begins. Is it active, dead, or contaminated? And that happens frequently in certain areas. We had a lot of those kind of stops,” said Mark Eberl, SRNS site services subcontracts manager.
Despite such setbacks, all work was completed safely and within budget.
When operational, SWPF will use technologies piloted by the Actinide Removal Process/Modular Caustic Side Solvent Extraction Unit to separate highly radioactive caesium and low-level radioactive nuclides from the contaminated salt solution transferred from the waste storage tanks. Once separated, each source of radioactive waste, both high and low level, will be treated separately for safe, long-term storage.
SRNS, a Fluor-led company with Newport News Nuclear and Honeywell, is responsible for the management and operations of SRS, including the Savannah River National Laboratory, located near Aiken, South Carolina.
Parsons Corporation said on 18 August that it had completed all necessary steps to begin the treatment of radioactive waste at the SWPF, which will process the site's salt waste at seven to eight times the current rate.
In 2002, the DOE selected Parsons to design, build, commission and operate SWPF with the goal of processing 31?million gallons of radioactive salt waste stored in underground tanks at SRS. Parsons finished building SWPF in April 2016, eight months ahead of schedule and more than $65?million under the target cost of the contract for construction activities.
"The startup of SWPF and the increased treatment capacity will save billions of dollars in overall operational costs by reducing the number of years needed to accomplish the nuclear remediation mission," said Chris Alexander, executive vice president and engineered systems market leader for Parsons.
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.
Photo: An aerial view of the Salt Waste Processing Facility (SWPF) at Savannah River (Photo: US DOE)