While there are alternatives to vitrifying all low-activity radioactive waste at the Hanford Site in Washington state, the U.S. Energy Department should do more vetting before committing to one or more of those options, according to a new assessment from a National Academies of Sciences, Engineering, and Medicine panel.
The fiscal 2017 National Defense Authorization Act required the National Academies to review another study ordered by Congress, led by the Savannah River National Laboratory (SRNL) in South Carolina, into supplemental methods to treat the low-activity waste stored in underground tanks at Hanford.
That is because the Waste Treatment Plant (WTP) being built by Bechtel National lacks capacity to convert all 56 million gallons of radioactive tank waste at the former plutonium production complex into a stable glass-like substance.
The National Academies panel recently finished its review of the 278-page preliminary draft report issued in April by the Savannah River National Laboratory. The final SRNL report should be out in October.
While the 10% of Hanford’s waste is high-level radioactive waste (HLW) that will be made into glass, only one-third to half of the LAW will be vitrified during the plant’s 40 to 50 years of operation, the National Academies said in its assessment of the SRNL draft.
The remaining material is dubbed supplemental low-activity waste. Most of the supplemental LAW cannot be treated at WTP “without extension of processing and tank storage durations,” according to the SRNL document. The Energy Department has not made any decision on addressing the supplemental waste, and the cost for the various options could run from $2 billion to $36 billion.
The research and development center at SRNL identified three major options:
- Using additional vitrification technology could take 10 to 15 years to implement and cost $20 billion to $36 billion. Secondary waste from vitrification, including water, is currently expected to be grouted.
- Grouting the material into a concrete-like substance would cost $2 billion to $8 billion, and take eight to 13 years. Perma-Fix Environmental Services has conducted a successful pilot in which it grouted 3 gallons of LAW and shipped it to Waste Control Specialists in Texas. The company hopes to do a second phase this year involving 2,000 gallons, and subsequently a third phase with 100,000 gallons.
- Finally, using fluidized bed steam reforming technology could take 10 to 15 years and cost $6 billion to $17 billion. This would blend dry inorganic material with liquid supplemental waste to form dry granular material particles.
Vitrification is the most “technically mature” of the three options, according to SRNL. At the Savannah River Site in South Carolina, grouting has been used to immobilize low-level radioactive liquid. Steam reforming has the least developed track record, although it is intended to be used to immobilize sodium-bearing waste in the Idaho National Laboratory (INL) Integrated Waste Treatment Unit.
The supplemental LAW is described in the SRNL report as a “mixed” radioactive waste with a far lower radionuclide dose than the HLW stream. But the supplemental low-activity waste still contains long-lived radionuclides, such as technetium-99 and iodine-129.
The report from SRNL doe not list a preferred method, but is meant to provide data to help DOE planners make an informed choice.
The April preliminary study also says construction and testing lead times for one or more of the options would “require an immediate start” in order to meet the Energy Department’s 2034 target date for beginning treatment of the supplemental LAW that cannot be handled at the Waste Treatment Plant.
The National Academies review concludes that while the SRNL report “provides useful steps forward in assessing the options,” it does not yet provide a complete technical basis needed to support a final decision on a treatment approach. The cost estimates in the report are based on technologies that “for the most part” are not yet fully developed or tested, according to the expert panel.
But if one or more alternate technologies do pan out it could open the door to serious consideration of disposal site options that would include the Waste Control Specialists low-level waste site in Andrews County, Texas, and EnergySolutions’ operation near Clive, Utah. These sites are licensed to dispose of low-level radioactive waste.
Canisters of vitrified low-activity waste will be disposed of at Hanford’s Integrated Disposal Facility. Vitrified HLW would go to a national repository.
Hanford started making plutonium for the federal government’s Manhattan Project in 1944 and closed its last reactor in 1987. The site produced about two-thirds of the plutonium for U.S. nuclear weapons, the National Academies panel noted.
The National Academies will take comments on its report through Oct. 31, when the panel will hold its final public meeting in Richland, Wash., according to an Aug. 15 news release. The final report from the National Academies panel should be released in January 2020.
