Two years ago, the U.S. Department of Energy was warned that two tunnels containing radioactive waste at the Hanford Nuclear Reservation were vulnerable to collapse.
On Tuesday, part of one tunnel failed, triggering an emergency at the nuclear site that required Hanford employees to shelter in place while workers checked for radiation releases.
No one was hurt and no radiation leaks were detected. But problems related to the tunnel’s deteriorating wood timbers from exposure to radioactivity had been identified in a 2015 risk assessment commissioned by the Energy Department.
The tunnel that partially collapsed is near Hanford’s PUREX plant, a nuclear fuel processing facility as large as a cruise ship that operated until 1990.
When the plant was built in the 1950s, it included an unusual feature for disposing of large pieces of radioactive waste, including old equipment.
A 360-foot rail extension was built onto the tunnel that brought irradiated slugs to the PUREX plant. Between 1960 and 1965, eight flat-bed rail cars with radioactive equipment were pushed into the tunnel by a remote-controlled engine.
The tunnel’s rectangular walls and ceiling were built with pressure-treated Douglas fir timbers. A second storage tunnel wasn’t affected by the collapse. Built in 1964 with steel beams and concrete arches, it holds 28 rail cars filled with radioactive waste.
The rail cars were stored for safekeeping until a final cleanup plan could be figured out, officials said.
Vanderbilt University led the preliminary “risk review,” which looked at potential dangers from delaying clean up at various areas of Hanford. The review said both tunnels were at risk from an earthquake, which could lead to their collapse and releases of radiation.
The report also said the timbers in the wood-framed tunnel were deteriorating because of exposure to gamma rays from radioactive material stored in the tunnel. But the report also said the likelihood of collapse was about 30 years away.
Last year, the Energy Department was given a September 2017 deadline for starting an assessment of the tunnels’ structural integrity, the Tri-City Herald reported.
Oregon State University Professor Kathryn Higley was part of the team that worked on the risk assessment.
“I think they’re being extremely cautious,” Higley, who heads OSU’s School of Nuclear Science and Engineering, said of the preventive measures being taken Tuesday. “It seems unlikely that you’d have a radiation release.”
No spent fuel rods were put in the tunnels, which contain “big, bulky things,” such as equipment, she said. Though there is radioactive dust and debris in the tunnels, they are contained in glove boxes, Higley added.
Glove boxes are sealed containers that allowed Hanford workers to remotely manipulate radioactive materials. Workers reached into the containers through heavy, rubberized long-sleeve gloves.
Hanford engineers were working Tuesday on plans to deal with the cave-in.
“We are developing plans to get that hole filled up. That our immediate concern,” said Mark Heeter, a spokesman for the U.S. Department of Energy’s Richland operations office.
About 70,000 tons of uranium fuel rods were processed at PUREX, which was Hanford’s largest plutonium processing plant.
“I think Hanford was lucky there weren’t workers hurt, or an off-site release of radiation,” said Tom Carpenter, executive director of the watchdog group Hanford Challenge.
“In our view this is a wakeup call,” he added. “You’ve got other dangers and risks at Hanford that are much worse than these tunnels.”
If a tank with high-level nuclear waste had collapsed, Carperter said there could have been serious consequences for workers’ health and safety and the potential for off-site releases.
“We’re impatient with the government for not leaping onto these issues and not managing these risks better,” he said.