The agency says it has until August 1 to develop plans to prevent the collapse of yet another tunnel at Hanford.
The facility was built in the 1950s and for decades produced plutonium for the US nuclear weapons arsenal. In 1988, production stopped and the site became a burying ground for radioactive waste.
The tunnels were used to get rid of nuclear material and equipment, such as rail cars that transported the fuel rods from nuclear reactors to the processing facility.
One such tunnel partially collapsed on May 9, prompting the Department of Energy to declare an emergency at Hanford. Some 3,000 workers sought shelter and were advised to temporarily refrain from eating and drinking.
No workers were injured in the collapse, and officials have detected no release of radiation, Washington state Department of Ecology spokesman Randy Bradbury told AP in May.
“In the ’60s, spent fuel rods were put in railroad cars and, once filled, the railroad cars were wheeled into a tunnel dug into the side of a hill,” Bradbury said. “Twenty-eight rail cars in all fill this particular tunnel.”
However, the facility itself, which has been vacant for decades, “remains highly contaminated,” according to the Hanford website.
It still contains roughly 53 million gallons – over 2,600 rail cars – worth of high-level nuclear waste, left from the production of plutonium.
A number of current and former Hanford workers suffer from serious medical conditions as a result of exposure to toxic waste leaks and “burps” of radiation at the complex, RT America reported last year.
In a study published in May, researchers warned that the US authorities are underestimating the risks to nuclear safety. If spent fuel at one of the dozens of US nuclear sites sets alight, it “could dwarf the horrific consequences of the Fukushima accident [in Japan],” said researchers from Princeton University and the Union of Concerned Scientists.