RICHLAND (AP) — The U.S. Department of Energy has decided a partially collapsed tunnel containing radioactive waste will be filled with a concrete-like grout.

The tunnel is located on the Hanford Nuclear Reservation in Washington state, and contains wastes left over from the production of plutonium for nuclear weapons.

On May 9, workers discovered that a portion of the tunnel roof had collapsed.

The Tri-City Herald said an emergency was declared and steps were taken to stabilize the 360-foot-long tunnel, which dates to the 1950s. The breach was filled with soil and a layer of heavy plastic was pulled over the length of the tunnel.

No radioactivity was released.

The Energy Department said Wednesday that most of the tunnel will be filled with grout, which will stabilize the tunnel and help contain radioactivity.

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