YAKIMA – Workers at the nation’s most contaminated nuclear site are conducting a sting operation to dig up radioactive wasp nests that could number in the thousands.
Mud dauber wasps built the nests, which are largely inactive now, at the Hanford Nuclear Reservation in 2003. That’s when workers finished covering cleaned-up waste sites with fresh topsoil, native plants and straw to help the plants grow – creating perfect ground cover for the insects to build their nests.
Fortunately for the wasps, nearby cleanup work also provided a steady supply of mud. Today, the nests are “fairly highly contaminated” with radioactive isotopes, such as cesium and cobalt, but don’t pose a significant threat to workers digging them up.
The wasps, not radioactive, are long gone. They don’t reuse their nests when they colonize each spring.
“This is just an example of the issues we deal with in digging up burial grounds,” said Todd Nelson, spokesman for Washington Closure Hanford, the contractor hired to clean up the area under the oversight of the U.S. Department of Energy. “You don’t know what you’re going to run into, and this is probably one of the more unusual situations.”
The federal government created Hanford in the 1940s as part of the top-secret Manhattan Project to build the atomic bomb. The site produced plutonium for the first atomic blast and for the bomb that was dropped on Nagasaki, Japan, at the end of World War II, and plutonium production continued through the Cold War.
The work left a mess of radioactive and hazardous waste to be cleaned up next to the region’s largest waterway, the Columbia River. The effort is expected to last decades and cost more than $50 billion.
Part of the cleanup involves tearing down the outer shells and ancillary buildings of nine nuclear reactors to “cocoon” them safely for 75 years, and digging up solid reactor waste that was buried in trenches decades ago.
The black wasps collect small pieces of mud to build nests for their eggs. In this case, they built their nests in a 75-acre area around H reactor, pulling the mud from the bottom of a storage basin that once held irradiated nuclear fuel.
The reactor operated from October 1949 to April 1965.
The steady cleanup work in the area also provided a steady supply of mud for the wasps, said Scott Parnell, Washington Closure’s project manager for work near H Reactor. In one 6-acre area, the nests are so congested that workers can barely walk without stepping on one. They could number in the thousands.
“You can’t separate one from the other very well,” he said. “So in that area, we’re going in and just digging up that entire area up to a foot deep.”
Workers started using excavators three weeks ago to dig up the area, including vegetation that had already been replanted. Because they are in enclosed cabs on the excavators, no protective clothing is required.
The material is then placed in a container and taken to the onsite landfill for slightly radioactive wastes, said Dave Martin, the company’s radiological engineer. He said the work should be completed by the end of June.
Nelson said workers will eventually replant vegetation in the area, at a cost of about $25,000.
John Price, project manager for environmental restoration for the Washington Department of Ecology, called the nest removal a “loose end” for cleanup in the H Reactor area.
It also shows the workers do a good job of controlling radiation, because technicians discovered the radiation during their monitoring, he said.
“They said, ‘Oh, we have some radiation where it doesn’t belong,’ and they told us about it,” he said. “Now, they’ll just keep digging up the stuff until all the radioactivity is gone.”