PUREX tunnel collapse structural integrity analysis press conference
A second tunnel storing highly radioactive waste at Hanford is at serious risk of a cave-in.
The Department of Energy made the announcement Friday morning following a review of the sturdiness of the two tunnels at the former Plutonium Uranium Extraction Facility (PUREX).
The smaller of the two waste storage tunnels was discovered to be partially collapsed on May 9, leading to the declaration of a sitewide emergency at the nuclear reservation. Thousands of workers took cover indoors for hours.
The state of Washington, a regulator on the project, immediately ordered a review of the structural soundness of both tunnels by Saturday.
The DOE review, released a day early, showed neither tunnel meets current codes for structural integrity.
Tunnel 2 is identified as presenting a high potential for localized collapse.
Department of Energy statement
While temporary measures have been taken to stabilize the first tunnel, the second, longer tunnel also may not be able to bear the weight of the eight feet of soil covering it, the report found.
The tunnel has a “high potential for localized collapse,” according to a DOE statement.
At a news conference Friday, the state said the second tunnel — made of metal and concrete — is “structurally deficient by almost every measure.”
“This makes it clear that the second tunnel may also pose a risk to human health and the environment,” said Alex Smith, nuclear waste program manager for the state Department of Ecology.
“We took quick action in response to the Tunnel No. 1 collapse because of the potential for additional structural failures,” he added.
The breach in the first tunnel has been filled with sand and gravel and its 360-foot length covered by heavy plastic. Preparations are being made to fill it with concrete-like grout by the end of the year at a cost of $4 million to $7 million. The grout is meant to further stabilize the tunnel until its waste is permanently cleaned up.
The second tunnel also should be stabilized as soon as possible, said Doug Shoop, manager of the DOE Richland Operations Office.
However, there are not immediate plans to cover it with heavy plastic, as was done with the first tunnel. The second tunnel is about four and a half times as long, Shoop said.
“We’re closely monitoring the situation to make sure (DOE) finds an effective solution,” Smith said.
For Tunnel No. 2, we were not surprised to find that it is also at risk of collapsing. But it is very concerning to us.
Alex Smith, state Department of Ecology nuclear waste program manager
DOE faces a second deadline under the state order to deliver a draft plan by Aug. 1 to ensure the safe storage of waste in both tunnels, as an interim measure before final cleanup of the tunnels. DOE plans to hold a public meeting in July to discuss possible options.
The tunnel that partially collapsed was built in 1956 of Douglas fir timbers coated with creosote to help preserve the wood. The timbers formed the sides and the flat top of the tunnel.
The second tunnel was built in 1964, with initial construction of corrugated metal formed into a semicircle, somewhat like a Quonset hut, Shoop said.
As eight feet of soil were placed on top of the tunnel, it collapsed twice, Shoop said. In response, cement girders were added to the outside and large steel beams were added to the inside.
The tunnel was built long enough for 40 rail cars holding radioactive waste from the PUREX plant, which chemically processed irradiated uranium fuel to remove plutonium for the nation’s nuclear weapons program.
However, by the time the tunnel was closed in the mid-1990s, only 28 rail cars of waste had been pushed inside.
Hanford officials have been studying historical documents covering construction of the tunnel, trying to learn more, including the compaction of the soil that covers it.
We’re overseeing Energy’s response to the situation as it searches for solutions.
Alex Smith, state Department of Ecology nuclear waste program manager
“The records, as you might imagine, 50 years ago might not have been as good as we would like them,” Shoop said.
To compensate for the uncertainty, the engineering evaluation is conservative, he said.
The risk of collapse is considered high, based both on the stress, or loads, on its components and what engineers know about its construction, he said. At more than 50 years old, it is beyond the age for which it was designed to last.
Hanford officials are investigating ways to place and maneuver a video camera within the tunnel to take a look at the condition of its interior and to take radiological readings, Shoop said. The tunnel has been too radioactive to enter since waste was first placed within it.
Monitoring has been stepped up at both the tunnels. Daily walk-downs are done and cameras have been installed with views of both tunnels that can be accessed remotely.
“We’re overseeing Energy’s response to the situation as it searches for solutions,” Smith said.
No airborne radioactive contamination was detected after the May 9 partial collapse of the smaller tunnel.
But the initially gaping 20-by-20-foot cave-in at the first PUREX tunnel drew state and national concern as just one symptom of the aging structures at the DOE site.
“For Tunnel No. 2, we were not surprised to find that it is also at risk of collapsing,” Smith said. “But it is very concerning to us.”
The issues highlight the importance of having adequate federal funding for the Hanford nuclear reservation, she said.
8rail cars holding waste stored in Tunnel No. 1
28 rail cars holding waste stored in Tunnel No. 2
360 feet length of Tunnel No. 1
1,700 feet length of Tunnel No. 2
DOE is working with its contractor for central Hanford, CH2M Hill Plateau Remediation Co., to take a close look at all of the Hanford infrastructure since the partial tunnel collapse. Some of it dates to World War II.
DOE has developed a list of high-priority projects it will discuss with its regulators — the state Department of Ecology and the U.S. Environmental Protection Agency — and then make public, Shoop said.
The Department of Ecology is looking at whether some cleanup deadlines should be reassessed at high-risk facilities. It also is considering whether the permits it issues to DOE should include requirements for more frequent assessments, Smith said.
The two PUREX tunnels, which are the only waste-storage tunnels at Hanford, are covered by legal deadlines in the Tri-Party Agreement that require a date to be set in 2036 for all PUREX facilities to be cleaned up. Central Hanford cleanup of buildings and waste sites is required to be completed in 2042.
The order issued by the state in May required DOE to investigate the cause of the breach of the first tunnel, but it could not be determined with the information available, Smith said.
There were multiple stresses on the tunnel that could have contributed. They include its construction materials or design, deterioration of the wooden beams from radiation, and an usually wet and cold winter this year.
The order also requires DOE to submit a draft plan by Oct. 1 for permanently cleaning up the waste in the tunnels