The US Department of Energy (DOE), Washington State Department of Ecology (Ecology), and US Environmental Protection Agency (EPA) have announced a “landmark agreement” proposing “a realistic and achievable course for cleaning up millions of gallons of radioactive and chemical waste from large, underground tanks at the Hanford Site.”

A legacy of nuclear weapons development and nuclear energy research during World War II and Cold War, Hanford is home to 177 underground waste storage tanks: 149 single-shell tanks (SST), and 28 double-shell tanks (DST), ranging from 55,000 to 1.265m gallons in capacity. Those tanks are organised into 18 different groups called farms. Currently, the site's underground tanks store approximately 56m gallons of radioactive and chemical waste. As part of an existing plan for Hanford cleanup, crews must remove at least 99% of the all of the high-level waste and an estimated 40-60% of the low-activity waste in every tank on the Site, or at least as much waste as can be removed based on available technology. This waste will be immobilised in glass at the plant. Under this new agreement, the agencies have now decided to immobilise a large portion of the low-activity (liquid) tank waste in grout after it’s been treated to remove radioactive cesium and solids.

Following voluntary, mediated negotiations that began in 2020, also known as Holistic Negotiations, the agencies have now signed a settlement agreement and are also proposing new and revised clean-up deadlines. The proposed changes uphold a shared commitment to the safe and effective cleanup of tank waste.

Highlights of the proposed modifications include the following:

  • Maintaining existing timeframes for starting treatment of both low-activity and high-level waste by immobilising it in glass via vitrification;
  • Using a direct-feed approach for immobilising high-level waste in glass, similar to the Direct-Feed Low-Activity Waste Program;
  • Building a vault storage system and second effluent management facility to support treating high-level waste;
  • Retrieving waste from 22 tanks in Hanford’s 200 West Area by 2040, including grouting the low-activity portion of the waste for offsite disposal;
  • Designing and constructing 1 million gallons of additional capacity for multi-purpose storage of tank waste; and
  • Evaluating and developing new technologies for retrieving waste from tanks.

Under the settlement agreement, DOE has also committed to refrain from applying its interpretation of what constitutes “high-level waste” when disposing of treated waste or closing tank systems at Hanford.

The proposed changes will go out for a 60-day public comment period on 30 May. During the comment period, the three agencies will hold regional public meetings in Washington and Oregon. Detailed information on these meetings will be available when the comment period begins.

DOE says changes to milestones and deadlines are not final until the public comment period is complete, a response to comments is issued, the federal district court accepts the proposed amendments to the consent decree, and the agencies implement the proposed revisions.

“We have alignment on a plan that lays out a realistic and achievable path forward for Hanford’s tank waste mission,” said Brian Vance, Hanford’s DOE manager of the River Protection and Richland Operations offices. “Our One Hanford team is ready to get down to the business of more fully conducting the tank waste mission resulting in benefits for the environment, the people of Washington state and the nation.”

Ecology Director Laura Watson said: “We’ve negotiated a durable framework that aligns our agencies and accelerates work while maintaining a robust and safe clean-up. The communities we all serve deserve no less,” said. “This agreement will get more tank waste retrieved, treated, and disposed of on schedule and gives us a roadmap for Hanford cleanup through 2040 and beyond.”

EPA Region 10 Administrator Casey Sixkiller said the disposal of tank waste is a critical component of the complex, site-wide clean-up efforts at Hanford. “This agreement builds on decades of work and collaboration between the Department of Energy, State of Washington, and the EPA, and will guide the tank waste mission as it enters a new phase of operation. We encourage all impacted Tribes, community members, and other stakeholders to participate in the public review process.”

Image courtesy of US Department of Energy