AIKEN, S.C. – About 8,500 gallons of low-level liquid waste from an underground waste tank at Savannah River Site (SRS) have been treated and transferred to Saltstone Disposal Unit (SDU) 6, making this the first transfer of radioactive liquid waste to the mega-volume unit.
The low-level liquid waste, known as decontaminated salt solution (DSS), was treated at the Saltstone Production Facility and placed into SDU 6, the newly constructed disposal unit with a 32.8-million-gallon capacity.
SDU 6 was designed and built by SRS liquid waste contractor Savannah River Remediation (SRR) and will accommodate the large stream of DSS from the Salt Waste Processing Facility (SWPF), currently undergoing testing and commissioning. Until SWPF comes online, SDU 6 will be filled with the DSS processed by the site’s interim salt waste processing facility, the Actinide Removal Process/Modular Caustic Side Solvent Extraction Unit (ARP/MCU).
ARP/MCU removes the highly radioactive isotopes, primarily cesium, from the tank waste, which are then transferred to the Defense Waste Processing Facility to be turned to glass and safely stored at SRS, awaiting permanent disposal. The remaining waste stream — the DSS — is transferred to the Saltstone Production Facility for stabilization into a grout-like waste form. The waste is then pumped into the SDU, where it solidifies into saltstone, a non-hazardous waste form.
SDU 6 will also receive DSS from the recently installed Tank Closure Cesium Removal (TCCR) demonstration project. TCCR is designed to remove cesium from the high-level waste currently stored in H Tank Farm.
DOE is committed to safe and efficient waste removal at SRS, according to Jim Folk, DOE-Savannah River assistant manager for waste disposition.
“Significant work has been performed to advance the SRS liquid waste program,” Folk said. “The start of SDU 6 radioactive operations is another step toward safe disposal of decontaminated salt solution.”
Tom Foster, SRR president and project manager, said SDU 6 demonstrates that the mega-unit concept is an excellent addition to meet the needs of the liquid waste mission.
“The award-winning Saltstone Disposal Unit 6 project is instrumental to the liquid waste system,” Foster said. “Processing the first radioactive transfer is a significant milestone in the life of this project.”
The SDU 6 project won both the DOE Project of the Year Award for the Department’s EM sector and the 2018 DOE Project Management Excellence Award. Construction of SDU 6 was completed in July 2017, 16 months ahead of schedule and $25 million under budget.
SRR is currently constructing the second mega-unit, SDU 7. Excavation was completed this summer, and the foundational mud mats and protective liners are being installed. SDU 7 cell construction will begin later this fall.