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Hanford site
Crews inspected the area around a tunnel at the Hanford Nuclear Reservation that contains nuclear waste. (Department of Energy Photo)

Workers at the Hanford Nuclear Reservation in southeastern Washington state were told to take cover for several hours today when steam was seen escaping from a tunnel where radioactive waste is being stored.

The take-cover order was lifted at about 12:15 p.m. PT when inspectors confirmed that there was no radiological release from Tunnel 2 at Hanford’s Plutonium Uranium Extraction facility, or PUREX, the U.S. Department of Energy’s Richland Operations Office reported in an update.

For the past few weeks, Hanford workers have been filling the 1,688-foot-long tunnel with thousands of cubic yards of grout to guard against the tunnel’s collapse. The tunnel, which dates back to 1964, houses a set of 28 rail cars that contain contaminated equipment. The last rail car was placed inside in 1996.

The Department of Energy’s update said steam was spotted coming from an opening in a structure on the north end of the tunnel, where equipment used to open a large access door is kept.

Based on imagery from cameras placed inside the tunnel, the steam arose from the curing of recently placed grout, according to the update. “When the warm moist air left the tunnel and interacted with the cool early-morning atmosphere, steam was visible,” the operations office said. The opening was sealed, and inspection crews are checking the integrity of the seal.

The crews reported that radiological conditions inside the tunnel have remained stable, and that the surrounding area has no contamination above background levels. Once the seal on the opening in the tunnel structure has been evaluated, efforts to stabilize the tunnel with still more grout will resume, the Department of Energy said.

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