An emergency has been declared in central Hanford in Eastern Washington state Tuesday after the roof of a tunnel used to store highly radioactively contaminated waste collapsed.
Several thousand workers at the Hanford nuclear reservation were told to take shelter in buildings.
An aerial survey mid-morning Tuesday showed an opening about 20 feet by 20 feet into one of two tunnels, which had been covered with about eight feet of soil.
The breach at the defunct Purex processing plant tunnel could expose the highly radioactive material in the tunnel to the atmosphere.
No airborne radiation had been detected as of about noon. Radiological surveys were continuing.
All workers have been accounted for and none were injured, according to the Department of Energy.
The tunnels are about 25 miles northwest of the center of Richland in the Hanford nuclear reservation’s 200 East Area.
Instructions for Hanford workers to shelter in place were expanded from central Hanford to all federally controlled portions of Hanford, including the LIGO observatory and the reactor areas along the Columbia River, after the aerial survey.
The order was partially lifted about noon.
Workers outside the 200 East Area of central Hanford were being allowed to leave buildings then, but about 3,000 workers in the 200 East Area continued to shelter in place. They included about 1,000 workers at the vitrification plant under construction.
No one was being allowed to enter the site beyond the security barricades and flights over the reservation were restricted.
Earlier in the morning workers near Purex noticed a 4-foot-by-4-foot depression that was 2 to 4 feet deep over the tunnel.
About six workers were in Purex and were evacuated and the initial order to take shelter was issued when the depression was noticed.
The Hanford emergency center was activated at 8:26 a.m. and the Hanford Fire Department was on scene in central Hanford.
Franklin and Benton counties each activated their emergency operations centers, but said the public did not need to take any protective actions.
The Richland School District told parents and others who were concerned that there was no danger that any radioactive contamination could reach its schools and that they were not affected in any way by the incident. Washington State University Tri-Cities also assured students and alumni there was no danger at its Richland campus.
Work continued at the commercial nuclear power plant on leased land at Hanford outside the security barricades.
Workers at the plant, the Columbia Generating Station, were not told to shelter indoors. The plant is about 12 miles from Purex, according to Energy Northwest, which operates the plant.
Private pilots in the area have been told to avoid flying over Hanford. The Hanford Patrol is working with the Federal Aviation Administration to put a formal air restriction in place until the FAA can confirm there is no danger.
Although workers in the 200 East Area were still sheltering indoors early Tuesday afternoon, ventilation systems had been turned on and a prohibition against eating and drinking had been lifted. When ventilation systems were turned off as part of the emergency response, some equipment that generates heat also was powered down.
Historically at Purex, railcars full of highly contaminated materials and equipment from the plant were backed into waste disposal tunnels at the plant and left there as a disposal method. The material was so radioactive that several empty cars were placed between the railcar holding waste and the locomotive to protect the driver from radiation.
The massive plant, formally called the Plutonium Uranium Extraction Plant, was used to chemically process irradiated fuel rods to remove plutonium for the nation’s nuclear weapons program.
The last radioactive material was placed in the tunnels in the early 1990s.
The tunnels are more than 100 feet long.
Last year a new legal deadline was set requiring the DOE to start some work toward assessing the the waste disposal tunnels by September of this year.
The plant was built in the 1950s and operated from 1956 to 1972 and again from 1983 to 1988.
PUREX processed about 70,000 tons of uranium fuel rods to produce about 75 percent of Hanford’s production.
Plans call for eventually decontaminating and demolishing PUREX. The option of grouting the rail cars in place — encasing them in concrete — has been considered.
Removal of the cars would entail extreme worker safety hazards, DOE has said.
Hanford, a 580-square-mile site in Eastern Washington, near Richland, produced plutonium from World War II through the Cold War. Parts of the site remain heavily contaminated with radioactive and hazardous chemical waste.
Washington Gov. Jay Inslee said DOE had notified him of the emergency, which was followed by a call from the White House to alert him to the emergency, as well.
“This is a serious situation, and ensuring the safety of the workers and the community is the top priority,” he said. “We will continue to monitor this situation and assist the federal government in its response.”
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