The Department of Energy has been cleared to immediately begin stabilizing a Hanford tunnel storing highly radioactive waste that is at risk of collapse.
Filling the longer of two PUREX processing plant tunnels with concrete-like grout could start as soon as next week, according to DOE.
The risk of failure, based on DOE nuclear safety standards, was raised from “unlikely” to “anticipated” after a video inspection of the waste storage tunnel was completed earlier this year. The collapse also could be more severe than predicted, site officials said.
DOE told its Hanford regulator, the Washington State Department of Ecology, in July that it wanted to begin grouting the tunnel in August.
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It wanted to finish most, if not all, of the grouting before the worst of the winter weather. An unusually snowy winter may have contributed to the collapse of the first tunnel.
But the Department of Ecology said the public had a right to comment on a plan that would take irreversible action.
It had already scheduled public meetings and a 45-day public comment period, required by law unless waived in an emergency.
The public comment period ended Thursday night, and on Friday the state approved DOE’s request to do the work.
In May 2017 the older of the two PUREX radioactive waste storage tunnels partially collapsed.
Thousands of workers were ordered to take cover and local communities had some tense hours before Hanford officials could affirm that no radioactive particles had become airborne..
A day later the Department of Ecology ordered a structural evaluation of the second tunnel.
The tunnel that partially collapsed was completed in 1956 and stored eight rail cars loaded with failed and obsolete contaminated equipment in its 360-foot length. It was filled with grout by November under emergency regulatory approval without a public hearing.
The second tunnel was completed in 1964. It is 1,700 feet long and holds 28 rail cars.
The initial structural evaluation found that the second tunnel also was at risk of collapse. But concerns increased after a video inspection of the interior of the tunnel this spring.
The video inspection showed rusting metal, particularly near one end of the tunnel where filtered air was exhausted.
Steel beams were used to reinforce the tunnel after some initial construction problems, and corrosion was spotted both in the bolts used to anchor the beams to concrete arches and in the beams.
Corrosion increases the risk of failure, said Dan Wood, chief operating officer of CH2M Hill Plateau Remediation Co., the DOE contractor responsible for stabilizing the tunnel.
Engineers also are concerned that if one beam fails, there will be a “zipper” effect with more beams coming down, increasing the potential severity of a failure.
“Structural failure has to be anticipated. It is going to happen,” Wood said a a public meeting in late August. “It’s a 60-year-old facility. It is corroded. Sooner or later it is going to go.”
Airborne radioactive particles could be released into the air, particularly if a beam should puncture a waste package.
Mayors of the three Tri-Cities and West Richland urged the Department of Ecology in a letter at the end of July to skip additional public meetings on the topic.
“Delay on the state’s part puts our citizens at greater risk,” they said.
On Friday, Richland Mayor Bob Thompson said the state “made the right decision.”
Ecology went ahead with two public hearings and received 70 comments, reviewing them as they came in.
“Communities in Washington state have a right to review and weigh in on important Hanford decisions,” Alex Smith, manager for Ecology’s Nuclear Waste Program, said on Friday. “We needed to hear from the public to ensure that we made the best possible decision.”
Comments were thoughtful and raised some well-founded criticisms of grouting, she said.
“But in the end we must protect Hanford workers, and the surrounding communities and environment,” she said. “Grout is the best way to ensure the tunnel and its contents are safe until final decisions are made on how to deal with the waste.”
DOE says eventually the grout could be cut into large pieces based on the location of the rail cars and then the blocks of grout could be lifted out of the tunnel for permanent disposal.
Some critics of the plan said they feared that grouting would become the default permanent cleanup plan for the radioactive waste, with no future plan made to remove it.
Smith said that the ecology department’s approval on Friday should allow grouting to be well underway before winter, when snow and rain could increase the weight of the soil on top of the tunnel.
DOE also is concerned about completing the project before roads become snowy and icy. Nearly 5,000 truckloads of grout will be needed to fill the tunnel.
DOE earlier said it could be ready to grout by Sept. 6 and instead will start about a month later.
The Department of Ecology allowed DOE to proceed with work this summer to prepare for grouting at its own risk, warning that did not mean grouting would be approved.
CH2M, owned by Jacobs Engineering Group, has set up a mobile grout plant by the PUREX plant tunnel and has made test batches.
Workers also have installed equipment in six openings, called risers, along the top of the tunnel where grout will be added.
Plans call for adding an inch or two of grout at a time, allowing it to flow through the tunnel and dry, before another layer of grout is added.