A settlement agreement for cleaning up underground tank waste at the Department of Energy’s Hanford Site in Washington state, still subject to public comment and submission to a federal court, lays out a path for using grout to stabilize some less-radioactive liquid waste.
The so-called “holistic” agreement, in the works since 2019 and announced Monday by DOE, the U.S. Environmental Protection Agency and the Washington Department of Ecology, chiefly concerns itself with plans to solidify tank waste into a glass form at the Waste Treatment and Immobilization Plant built by Bechtel.
But parts of the document lay out how the agencies could go about solidifying part of the low-level waste into a concrete-like grout.
If DOE wants to build an on-site grout treatment facility it should file plans with the state no later than Dec. 31, 2028, according to the settlement agreement.
All grouted low-level tank waste must ultimately be disposed of off-site, according to the settlement document.
Likewise, the grouted waste should not pile up at Hanford while awaiting shipment. The agreement said grouted tank waste temporarily stored at Hanford should never exceed what DOE reasonably expects it can ship out in a three-month period.
Research by DOE and the National Academies of Science has identified grout as a doable and cheaper option than vitrifying all Hanford’s low-level waste into glass.
Hanford has about 56 million gallons of liquid waste left from decades of plutonium production. Low-level waste accounts for most of the volume, while high-level waste accounts for most of the radionuclides.
All the high-level waste is expected to be solidified into glass at Bechtel’s vitrification plant. That plant, however, might accommodate only 60% of the low-level waste, according to research by the National Academies and the Savannah River National Laboratory.
DOE has said in public filings the ultimate disposal sites for grouted waste would be EnergySolutions in Utah or Waste Control Specialists in Texas. As a result, those two states should also be part of public comment on the settlement proposal, said Nikolas Peterson, executive director of Hanford Challenge, in a Wednesday email to Exchange Monitor.
Eventually, much of the settlement agreement will be submitted to the U.S. District Court for the Eastern District of Washington as the sixth amended consent decree between DOE and the state of Washington.
Other parts of the agreement will be used to update milestones under the Tri-Party Agreement on Hanford cleanup between DOE, the state and EPA.
