A tunnel was damaged on Tuesday at a plutonium handling facility at the Hanford Nuclear Reservation in Washington state, leading authorities to evacuate some workers at the site and instruct others to take cover, federal officials said.
There had been a shelter-in-place directive for 3,000 workers at the entire Hanford Site, but that was lifted for most of the area hours later.
The U.S. Department of Energy activated the Hanford Emergency Operations Center at 8:26 a.m. Tuesday morning following a cave-in that created a 20-by-20-foot hole [pictured below] in the roof of the tunnel.
Crews are now surveying the area near the PUREX tunnels for contamination.
The Department of Energy says a 20-foot-by-20-foot section of soil caved in where two underground tunnels meet next to the Plutonium Uranium Extraction Facility, known as the PUREX plant. The waste produced at the site has been the subject of a major cleanup project since 1989, and now 11,000 employees are involved in the operation.
The collapse was discovered during a routine surveillance of the area by workers.
No spent nuclear fuel is stored in the tunnel, Energy Department officials said.
Hanford is the largest depository of radioactive waste, containing 56 million gallons of it, mostly in underground tanks.
In 2016, in an advisory letter to Department of Energy officials, the Hanford Advisory Board asked officials to "expeditiously investigate whether the PUREX tunnels pose a high risk and, if so, to then negotiate milestones to begin planning for their remediation".
Its last reactor closed down in 1987 but millions of gallons of leftover waste are contained in tanks at the site. Efforts were bolstered by about $2 billion in federal stimulus funds authorized several years ago, but decades of work remain.
Beginning in 1943 and lasting for more than 40 years, Hanford made plutonium for nuclear weapons, including for the bomb that was dropped on Nagasaki.
"Between 1960 and 1965, eight rail cars were pushed inside one tunnel, full of radioactive waste. The Department will continue to monitor this closely and provide information and updates as they become available", said a statement from the Department of Energy Tuesday.
Hanford was constructed during the Manhattan Project and was the source for plutonium used in the first nuclear bomb.
Carpenter said he expects total cleanup costs could reach $300 billion to $500 billion.
Workers demolish a decommissioned nuclear reactor during the cleanup operations at the nuclear site in Hanford, Wash., in 2011.