SPOKANE, Wash. (AP) — Some workers at a nuclear weapons production site in Washington state were ordered to stay inside Friday because steam escaped from a tunnel with radioactive waste as it was being filled with cement, officials said.
There no indication that the steam seen at the Hanford Nuclear Reservation contained radiation or any other hazardous material, and the workers were ordered inside as a precaution, the U.S. Department of Energy said in a statement.
The site near the Columbia River in eastern Washington is half the size of Rhode Island and for decades produced plutonium for use in nuclear weapons.
The steam came out of a tunnel that stores nuclear waste in railroad cars left over from the Cold War and is in danger of collapsing. The cement was being used to stabilize it.
The tunnel is about 1,700 feet (518 meters) long and has 28 rail cars filled with nuclear waste.
Last year, a different tunnel at Hanford partially collapsed and workers were ordered to stay inside for several hours. There was no airborne release of radiation, and no workers were injured. Work to fill that tunnel with cement was completed last November.
An analysis found that the tunnel from which steam emerged Friday did not meet structural integrity codes, prompting the decision to fill it with cement.
Hanford was created during the Manhattan Project in World War II and made most of the nation's plutonium, including the plutonium for the atomic bomb that was dropped on Nagasaki, Japan.