How sturdy are Hanford’s radioactive tunnels? Initial report due Friday

The Department of Energy will release the results of an evaluation of the structural integrity of two tunnels storing radioactive waste at the Hanford nuclear reservation.

The oldest of the two processing plant tunnels partially collapsed May 9.

The gaping 20-by-20-foot hole at the former Plutonium Uranium Extraction Facility (PUREX) drew state and national concern as just one symptom of the aging structures at the Department of Energy site.

No airborne radioactive contamination was detected from the breach by either federal or state monitors but the state issued an administrative order requiring three corrective actions.

On Friday, Doug Shoop, manager of the Richland Operations Office for DOE, and Alexandra Smith, manager of the nuclear program for the Washington Department of Ecology, plan to speak to the media at 10:30 a.m.

Check tricityherald.com for full coverage of the news conference.

The tunnel that partially collapsed was about 360 feet long and built of creosoted timbers and some concrete. Since the ’60s it has stored eight railcars holding 780 cubic yards of contaminated equipment. Doors to the tunnel were sealed in the ’90s.

DOE considered several ways to immediately stabilize the hole, settling on filling it rather than covering the breach with a tarp or building a structure over it, according to the state order.

A day after the collapse, clean sand and soil was dropped into the hole to help prevent the release of any radioactive material into the air, according to DOE.

A layer of thick plastic then was pulled over the tunnel as another temporary measure, with plans being made to fill the tunnel with grout to prevent a further collapse before permanent disposal of the waste.

The state order required DOE to determine the cause of the breach and do a structural integrity analysis of both PUREX tunnels by July 1.

DOE’s next deadline, Aug. 1, is to develop a draft plan of corrections to ensure the safe storage of waste in both tunnels.

By Oct. 1 it must propose modifications to an existing dangerous waste permit for the tunnels, which would include a plan for permanently cleaning up the waste in the tunnels.

According to the state, a study prepared by a past Hanford contractor in 1991 concluded that the wood would lose strength because of radiation from the waste within the tunnel. It estimated that the timber would have about 60 percent of its original strength in 2001.

It recommended a study of the structural integrity of the wood in 2001, but it is not clear if that was done.

DOE has said that the unusually wet and harsh winter also may have contributed to deterioration of the tunnel.

This story was originally published June 29, 2017 at 4:15 PM with the headline "How sturdy are Hanford’s radioactive tunnels? Initial report due Friday."