An independent team of experts on Friday said more homework is needed before the Department of Energy can pick a reliable and cost-effective means to treat low-activity tank waste at the Hanford Site in Washington state that cannot be accommodated through vitrification.
A National Academies of Sciences, Engineering, and Medicine panel issued its fourth and final study on possible supplement options for treating low-activity waste held in 177 underground tanks at the former plutonium production complex. The last report was released in August 2019.
Low-activity waste (LAW) comprises about 90% of the 56 million gallons of radioactive waste inside the Hanford tanks. The other 10% is more radioactive high-level waste. The Waste Treatment Plant being built by Bechtel is expected to start converting LAW into a stable glass-like substance in 2023 — but the facility only has capacity to handle perhaps half of that material.
The fiscal 2017 National Defense Authorization Act called on the National Academies to review another congressionally mandated study, prepared by the Savannah River National Laboratory (SRNL) in South Carolina, on what to do with Hanford’s leftover LAW.
The SRNL research indicates vitrification of the supplemental waste could take 10 to 15 years to implement and cost $20 billion to $36 billion. Grouting it into a concrete-like substance would cost $2 billion to $8 billion and take up to 13 years. Use of fluidized bed steam reforming technology could take 10 to 15 years and cost $6 billion to $17 billion. The final draft report did not pick a favored approach.
The state of Washington and other advocates have urged the NAS panel to ensure any treatment option is as “good as glass.” However, that term is “not defined in law, regulation or agreement, and is only tentatively defined by its advocates,” the 131-page report says.
More research would allow DOE and its stakeholders to use “a holistic approach” to selecting a treatment technology, the panel said. The committee acknowledged the clock is ticking given that any treatment option will take years to implement, increasing the potential for leaks or structural failure of underground tanks.
The committee’s mission did not include recommending any preferred option for treatment of the supplemental waste. The panel also noted in the report that it was not charged with evaluating issues such as tank management or high-level waste at Hanford.
The Savannah River National Laboratory draft report, issued last April, taken alone lacks the technical basis needed to make a final decision on picking an approach to treatment, the National Academies said in its Friday report. It added the SRNL study can form the basis for further work.
The panel recommended using the SRNL report “as a pilot or scoping study” for a full comparative analysis of alternatives for treatment of supplemental low-activity waste.
The options, which the experts said should be studied in more depth, include:
- Vitrification, grouting, and steam reforming;
- Pre-treatment to remove certain long-lived radionuclides such as iodine-129 and technetium-99, to ensure the waste could legally be disposed of on land or in near-surface facilities;
- Pre-treatment of strontium-90, if it is not removed via other pre-treatment efforts; and ultimate disposal at one of three low-level waste sites – Hanford’s Integrated Disposal Facility, the Waste Control Specialists site in Andrews County, Texas, and possibly the EnergySolutions site in Clive, Utah.
The canisters filled at WTP are expected to go to the Hanford Integrated Disposal Facility, the NAS study notes.
The Committee on Supplemental Treatment of Low-Activity Waste at the Hanford Nuclear Reservation has 13 members comprised of university professors, researchers, engineers, researchers, an economist, consultant, and others with a background in nuclear radiation and cleanup issues. The panel reports to the NAS Nuclear and Radiation Studies Board.
This final NAS report builds on the prior analyses and also looks at all comments filed with the panel between Aug. 15, 2019, and Nov. 20, 2019.
