The radioactive waste tunnels at Hanford’s PUREX
The Department of Energy wants to start stabilizing a Hanford tunnel filled with highly radioactive waste that is at risk of collapse without waiting for more public comments.
Work needs to start in a few weeks to finish before winter, the department said.
DOE has asked the Washington Department of Ecology, a Hanford nuclear reservation regulator, if it can proceed with filling the nearly 1,700-foot-long storage tunnel with concrete-like grout in August.
DOE held a public comment period on the plan, but the state planned its own 45-day comment period and public meetings starting next month.
Ecology officials will review DOE’s request made Thursday, but still plans to go on with its own public process, said spokesman Randy Bradbury.
The older of the two waste storage tunnels at the PUREX processing plant partially collapsed in May 2017, causing thousands of workers across the Hanford site to take cover.
The concern was that radioactive contamination could have spread from the open tunnel roof. No radioactive material is believed to have escaped but DOE is trying to prevent further collapses of the aging tunnels.
DOE wants to start filling the longer tunnel in August to get some, if not all, of the tunnel stabilized with grout before ice and snow make roads slippery this winter.
Dozens of daily truckloads will be needed to bring supplies to a batch plant near the tunnel to mix the grout. Trucks then will deliver the grout to spots along the length of the tunnel, where it will be inserted.
In addition, video shot of the inside of the tunnel in April raised concerns about the condition of the tunnel. The videos found corrosion of bolts and weld plates.
“While not an indication of imminent collapse, the fact that some components are stressed above design capacity and are also corroding is a concern,” DOE said.
After the tunnel collapse last year, Hanford officials determined that the soil covering the tunnel had fallen in, covering the waste and preventing radioactive particles from becoming airborne.
Within six weeks, DOE injected 521 truckloads of grout into that tunnel to surround and cover the waste with emergency permission from the state.
The Department of Energy also conducted an analysis of the second waste storage tunnel, in part to meet conditions of a Washington Department of Ecology order. It found the tunnel was at high risk of a collapse.
The first tunnel, built of creosoted timber in 1956, holds eight rail cars loaded with obsolete equipment contaminated with waste from the chemical separation plutonium for the nation’s nuclear weapons project from uranium fuel irradiated at Hanford reactors.
The second tunnel, built of steel in 1964, holds 28 rail cars loaded with highly contaminated equipment.
Some members of the public told DOE at public comment sessions that filling the tunnel with grout could make eventual permanent cleanup of the tunnel and its contents difficult or impossible.
DOE has said it has experience using grout to contain contamination until final cleanup actions are taken. A panel of experts also agreed that grouting was the best near-term option after looking at multiple methods of stabilization.
One option for eventual permanent disposition of the tunnel could be cutting up the grout within the tunnel with water jets, and wire saws for excavation equipment — both guided by a detailed excavation plan with specific locations for cuts, according to a DOE contractor assessment included in a proposed changes to a state permit required for the work.
Another final alternative that could be considered is leaving the grouted waste in place and building a barrier over the tunnel to prevent water from coming in and pushing waste into the soil underneath.
Ecology officials plan a public hearing on grouting the second tunnel at 5:30 p.m. Aug. 27 at the Richland Library. A meeting, yet to be scheduled, also will be held in Seattle.
DOE asked the state for an answer by July 23 on whether it can start putting grout in the tunnel in August.
Ecology says regulations require its director to approve or deny temporary authorization as quickly as practical, but there is no set timeline.