Workers at the Hanford Nuclear Reservation have started injecting grout into a partially collapsed tunnel that contains radioactive wastes left over from the production of nuclear weapons.
The grout is intended to improve the stability of the 360-foot-long tunnel, which dates to 1956, and help prevent any radioactivity from escaping into the environment.
The U.S. Department of Energy said it will take an estimated 650 truckloads of grout to fill the tunnel adjacent to the closed Plutonium Uranium Extraction Plant, which produced most of the plutonium for the nation's nuclear arsenal. The department said it will take the rest of the year to fill the tunnel with grout.
The tunnel, sealed in 1965, partially collapsed on May 9, forcing some 3,000 workers to shelter in place for several hours.