The Hanford Site, in Washington State, currently stores radioactive waste in underground storage tanks. The waste was generated, in part, by the prior reprocessing of spent nuclear fuel during the Manhattan Project and Cold War eras, for defense-related nuclear research, development and weapons-production activities.
In accordance with plans for cleanup and remediation of the waste, the Department of Energy (DOE) has decided to separate the tank waste into a low-activity waste steam and a high-level radioactive waste stream.
Their plans for treatment of the low-activity waste and secondary waste was published in a report, released to the public on January 31. 2023, Final Waste Incidental to Reprocessing Evaluation for Vitrified Low-Activity Waste and Secondary Waste at the Hanford Site, Washington. In this report they disclose the following:
- Vitrified low-activity waste (VLAW) and secondary waste are waste incidental to the reprocessing of spent nuclear fuel and are not high-level radioactive waste, therefore they can be safely managed and disposed of as low-level waste (LLW).
- Some of this waste can be transported and treated at an off-site commercial treatment facility.
The DOE plans to use the direct-feed low-activity waste (DFLAW) approach. The DFLAW approach is a two-phased process that will separate and pretreat supernate (essentially the upper-most layer of tank waste that contains low concentrations of long-lived radionuclides) from some of the Hanford tanks, to generate a LAW stream.
During Phase 1 the DFLAW approach will entail the following: in-tank settling; separation (removal by decanting) of the supernate (including dissolved saltcake and interstitial liquids); filtration and then cesium removal using ion exchange columns in a tank-side cesium removal (TSCR) unit.
During Phase 2, the DOE plans to treat additional supernate (including dissolved saltcake and interstitial liquids) using the same processes and will deploy either an additional TSCR unit or a filtration and cesium removal facility. The DFLAW approach is expected to remove more than 99% of the cesium, and also other key radionuclides.
After pretreatment, the LAW stream will be sent by transfer lines to the Low-Activity Waste Vitrification Facility at the Hanford Site, where it will be vitrified (immobilized in borosilicate glass) beginning no later than December 31, 2023. Approximately 13,500 containers of vitrified waste will be produced using the DFLAW approach. DOE plans to dispose of the pretreated and vitrified LAW in the onsite Integrated Disposal Facility, but some of the waste will be transported and disposed of at the Waste Control Specialists (WCS) Federal Waste Facility in Andrews, Texas. Up to 350 cubic meters of solidified secondary waste, via the vitrification process, will be disposed of at the WCS annually.
To learn more regarding DOE’s decisions go to Hanford’s Vitrified Low-Activity Waste program webpage https://www.hanford.gov/page.cfm/VitrifiedLowActivityWaste.