WASTE MANAGEMENT | HANFORD’S TBI
● Will be managed to meet safety requirements comparable to the performance objectives set out in 10 CFR 61, Subpart C, Performance Objectives
● Will be incorporated in a solid physical form at a concentration that does not exceed the applicable concentration limits for Class C low-level waste. In fact the material will be well below the concentration limits for Class C LLW and is expected to meet concentration limits for Class A LLW.
The three step TBI demonstration The first step was pre-treating approximately 2,000 gallons (7500 litres) of waste retrieved from double-shell Tank SY- 101, in order to produce a low-activity waste liquid safe for transport. For the TBI Demonstration, 2,000 gallons of the Tank SY-101 supernate was pre-treated to remove 99.99% of the caesium and other radionuclides. The supernate is the uppermost liquid layer of the tank, which contains low levels of insoluble, long-lived radionuclides. The liquid was decanted, filtered, and processed through ion exchange media. The decanting (pumping without disturbing the underlying saltcake layer), filtering and ion exchange pre- treatment took place in an in-tank system. The treated waste was shipped in US Department of
Above top: Removing radioactive waste materials from Hanford’s 177 large tanks is now the site’s primary mission
Above bottom: The waste in most of the Hanford tanks has three phases: supernate, saltcake and sludge
Below: The 580 square mile (150,000 Ha) Hanford site was left with large amounts of radioactive waste
Treatment and transport
The proposed TBI Demonstration was opened up for public comment in 2022. It could not go ahead without meeting the requirements of the National Environmental Policy Act (NEPA), which comprise a Final Waste Incidental to Reprocessing (WIR) Evaluation, a WIR Determination, and analysis and documentation. The WIR Evaluation had to ensure the waste is incidental
to the reprocessing of spent nuclear fuel, is not high- level radioactive waste and may be managed as low-level radioactive waste under DOE criteria.
The evaluation found that the wastes: ● Have been processed, or will be processed, to remove key
radionuclides to the maximum extent that is technically and economically practical. Pre-treatment removed 98.8% of the key radionuclides (including Cs-137 and its daughter, Ba-137) from supernate. About 1.8 curies remains in the pre-treated waste.
Transportation (DOT)-compliant robust double-walled steel containers referred to as totes (a general term for a pallet-mounted, industrial-grade reusable intermediate bulk container used to transport bulk liquids and powders). Each Type A shipment consisted of three of the double-contained shipping packages of up to 1,000 gallons (less than 5 tonnes), compliant with all applicable regulations for highway transport of radioactive material. The DOE Office of Packaging and Transportation provided oversight to ensure that safe and DOT-compliant transportation processes and procedures were followed. TBI totes are certified to meet DOT requirements for the shipment of radioactive liquid, but in fact, because Hanford removed more than 98% of the radioactivity from the waste before shipment, the radioactive inventory of each tote would be only about 10% of that allowed by the package type. The DOE’s Motor Carrier Evaluation Program evaluates the safety and practices of commercial vendors and drivers transporting hazardous materials. Shipments were made in a fully enclosed trailer transported by a commercial carrier approved by the Carrier Evaluation Program. In planning the transfer, the DOE said it assessed severe
accident scenarios and found that the probability of a severe accident during the transport to Utah was calculated at less than one in 1 million, while the probability of a severe accident during transport to the Texas site was less than three in 1 million. It found that, in the event of such an accident, the certified totes might spill their full contents 0.4% of the time. The highest potential radiation exposure for an individual would be less than that from a single abdominal x-ray. In the next phases the pre-treated liquid is being solidified into a grout form at the two licensed, permitted commercial waste disposal facilities. It will then undergo final disposal in the two facilities. “Implementation of this technology on an industrial scale
has the potential to safely treat low-activity waste from Hanford tanks, solidify the waste in grout, and dispose of it offsite in a manner that would reduce risks to workers, the public and the environment consistent with industry standards,” said Harkins. ■
12 | July 2025 |
www.neimagazine.com
Source for all images: DOE
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