Collapsed tunnel sealed at site of nuclear accident

SPOKANE, Wash. — Workers at a Washington state nuclear site where a tunnel filled with nuclear waste in railroad cars partially collapsed have safely sealed off a large sinkhole that emerged as a result of the collapse, U.S. Energy Secretary Rick Perry said Thursday.

Authorities also revealed the 400-square-foot sinkhole they filled with soil could have been there since last weekend before it was discovered Tuesday. That’s because the area around the Hanford Nuclear Reservation’s waste-filled tunnels is not observed every day by workers who patrol the site’s sprawling grounds.

Authorities have detected no signs that radiation emanated from the collapsed tunnel, and the hole was filled with 53 truckloads of dirt delivered by workers wearing protective gear, Perry said.

Tuesday’s discovery of the sinkhole prompted the evacuation of some nearby Hanford workers and an order for thousands more to stay inside buildings for several hours at the 500-square-mile expanse in Washington state’s remote interior. No one was injured.

The plugging of the sinkhole “was accomplished swiftly and safely to help prevent any further complications,” Perry said in a statement. “Our next step is to identify and implement longer-term measures to further reduce risks.”

Hanford, created during the Manhattan Project to build an atomic bomb during World War II, for decades made plutonium for nuclear weapons. Now it is engaged in cleaning up the radioactive waste.

The cause of the partial roof cave-in of the tunnel is under investigation, said Mark Heeter, a spokesman for the Energy Department at the site in southcentral Washington state.

“We’re not sure how long that will take,” he said.

Also under investigation is when the cave-in happened. There is a massive volume of nuclear waste stored at the Hanford site, about the size of the U.S. state of Rhode Island, and not all of the storage sites are inspected daily, Heeter said.

Authorities believe the cave-in could have happened as many as four days before the hole was found, and Heeter said they “don’t know exactly when it occurred.”

But the agency said there was no sign that radiation escaped from the hole.