Washington state officials were cool this week to a new government report that could point toward an alternative method for treating radioactive waste stored at the Department of Energy’s Hanford Site.
Grouting holds promise to effectively treat a portion of the millions of gallons of low-activity radioactive waste stored in tanks at Hanford, the Government Accountability Office said Wednesday. It also could allow waste to be treated sooner, according to the GAO report.
Congressional auditors recommended the Department of Energy and Congress take steps to make grouting a possibility for as much as a half to two-thirds of Hanford’s low-activity waste.
Grouting involves combining nuclear waste with a cement mixture for stable storage. The current plan at Hanford involves using a massive plant being built by Bechtel National to convert the waste into a storable glass form – a process known as vitrification.
Washington state has been adamant that any tank waste disposed of at Hanford must be vitrified to best protect the state’s environment, and DOE cannot dispose of treated tank waste at a Hanford landfill without a state permit.
“We’re still evaluating the GAO report, but we remain firm in our conviction that vitrification, or glass, is the superior process,” said Alex Smith, manager of the state Department of Ecology’s Nuclear Waste Program. “A succession of studies have verified that conclusion, based both on long-term protection of the environment and cost-effectiveness, which is why glass became the chosen technology to treat Hanford’s tank waste.”
The state additionally is concerned that if DOE pursues grouting, it could direct critical funding away from starting treatment of waste at Hanford’s Waste Treatment Plant, adding to the history of delays on the project.
“We can’t afford to distract from the job at hand,” Sen. Maria Cantwell (D-Wash.) said.
The Department of Energy is continuing efforts to begin vitrifying low-activity waste at the Waste Treatment Plant as soon as 2022 and also is working to resolve technical issues to allow full operation of the facility, including treatment of high-level radioactive waste, by a federal court consent decree deadline of 2036. “Future cleanup decisions must be consistent with the Tri-Party Agreement and consent decree, and guided by the best science,” Cantwell said, referring to the documents governing remediation of Hanford’s Cold War plutonium production legacy.
Roughly 90 percent of the 56 million gallons of waste stored in Hanford’s underground tanks is low-activity waste. The large volume of material holds just 10 percent of the total radioactivity of the high-level waste. Current plans call for as much as possible of the low-activity waste to be treated at the vitrification plant.
The plant was not planned to be large enough to treat all of the waste in a reasonable length of time. Plans must be made for the remainder, which initially was estimated at half to two-thirds of the low-activity waste. However, the current plan to begin treating low-activity waste earlier than high-level waste at the vitrification plant, plus potential ways being investigated to load more low-activity waste into each canister of glass, could significantly increase the amount of low-activity waste that could be treated at the vitrification plant.
When DOE decided 25 years ago to vitrify much of Hanford’s low-activity waste, the best available knowledge at the time showed vitrification was better at encapsulating the mix of radioactive and hazardous chemicals held in Hanford tanks, the GAO report said. “Since that time, DOE has experienced significant technical challenges at Hanford, unforeseen when it made the treatment decision, and has spent more than $19 billion on tank management and plant construction without yet treating any waste,” according to the GAO. “Conversely, at its Savannah River Site, DOE has successfully treated about 4 million gallons of (low-activity waste) with grout at a substantially lower cost than Hanford’s estimated costs for vitrification.”
The GAO acknowledged, though, that because of the many processing methods once used at Hanford, its tank waste is more complex than the waste at Savannah River.
A panel of 21 experts convened for the GAO by the National Academies of Sciences, Engineering, and Medicine agreed that both vitrification and grouting could effectively treat Hanford’s low-activity tank waste, the GAO said. Grouting technologies have matured in the last 25 years and new scientific information is available about its ability to encapsulate waste, the report said. Earlier assumptions regarding grout no longer appear accurate, particularly considering the dry climate at Hanford and that the facility’s disposal site for the waste would be engineered to keep precipitation from infiltrating and leaching any waste, the report said. One expert said that if waste did leach from the landfill, it would take 2,000 years for it to enter the groundwater, according to the GAO report.
Several experts said grouting would likely be less expensive than vitrification, with one estimating savings of 20 to 50 percent, according to the GAO report. If waste were removed from tanks sooner, which would shorten the time that the tanks must be managed, significant funds could be saved, other experts said. Extracting waste from Hanford’s leak-prone single-shell tanks sooner also could have environmental benefits, preventing more of the radioactive material from leaking into the soil underneath.
The GAO report recommended that Congress clear the way toward grouting by specifically authorizing DOE to classify some of Hanford’s low-activity waste based on risk. In 2004, Congress passed similar legislation for the Savannah River Site. However, Washington state would retain authority over how tank waste must be treated for disposal at Hanford.
The GAO report also recommended that DOE develop updated information on the effectiveness of treating Hanford low-activity waste with alternate methods, such as grouting. It called for an independent study of the life-cycle costs of treating and disposing of some of Hanford’s low-activity waste with alternate methods or at alternate disposal sites.
The Department of Energy agreed with both recommendations and has already commissioned a study, which will include a cost benefit analysis for treatment and disposal alternatives. It will be independently reviewed by the National Academy of Sciences.
