Workers at the Department of Energy’s Hanford Site in Washington state on Monday completed filling with grout the PUREX Plant tunnel that was discovered partially collapsed on May 9.
The tunnel holds eight railcars loaded with highly radioactively contaminated equipment from the shuttered plutonium extraction plant. “Since a portion of the tunnel’s roof collapsed last spring, the tunnel has posed a threat of further collapse and the potential release of radiation into the environment,” said Alex Smith, Nuclear Waste Program manager for the state Department of Ecology.
Hanford cleanup contractor CH2M Hill Plateau Remediation Co. and subcontractor Intermech Inc., which has a location in nearby Richland, hauled about 521 truckloads of grout to the tunnel starting Oct. 3. Cameras in the tunnel were used to ensure that each layer of grout added flowed to the ends of the tunnel and surrounded the equipment and railcars. After an initial problem with a further collapse of some of the sand and soil used to fill the breach in the top of the tunnel, the project advanced safely and quickly, according to Hanford officials. Most of the work was done at night as a safety measure to keep heavy truck traffic off the site during work hours.
“Our contractors not only completed this work safely, but also ahead of the department’s projected completion timeframe of late December,” said Doug Shoop, manager of the DOE Richland Operations Office.
The grout protects the tunnel, constructed of timbers in 1956, from further collapse, Smith said. It also protects people and the environment from the highly radioactive contents of the tunnel, she said. A final remediation plan for the tunnel has not been developed, but the grout and equipment it surrounds could be cut out in pieces for permanent disposal.
“Although we recognize that grouting the tunnel may make eventual removal of the material in the tunnel more challenging, it was the best solution available to mitigate the short-term dangers posed by the aging timbers holding up Tunnel 1,” Smith said.
The second tunnel holding PUREX waste on 28 railcars is also at risk of collapse, DOE has said. The department is still developing a stabilization plan for that tunnel.
