The Hanford nuclear reservation, in the windswept desert of south-central Washington State, is being menaced by radioactive tumbleweeds. Russian thistle has tap roots that reach down as far as 20 feet into the ground. Every winter, the roots decay and the spiny brown skeletons break off and roll away, a common occurrence in desert areas all over the U.S.

The problem is, about one percent of these tumbleweeds are radioactive because their deep roots have sucked up nuclear waste like strontium and cesium. The cost of cleaning up the pesky weeds can run into millions of dollars. ?Our dream is that we have this place tumbleweed-free,? says Ray Johnson, a biological control manager at Fluor Hanford, the company that manages the U.S. Department of Energy site. Most of the weeds get hung up on fences or on sagebrush, or end up in the stairwells of buildings, but a stiff winter wind can blow the weeds as far away as four miles and then ?we?ve lost control of our contamination,? says Johnson.

Hanford is the most contaminated nuclear site in the country. It was built in 1943 for the top secret Manhattan Project. For 40 years, Hanford made plutonium for the U.S. nuclear arsenal, including the atomic bomb that was dropped on Nagasaki, Japan. The last reactor was shut down in 1986.

Radiation control specialists survey the tumbleweeds on the 560-square-mile reservation, using Geiger counters that click when radioactivity is present. Radioactive tumbleweeds are picked up with pitchforks by specially trained and clothed workers, who place them in a regulated garbage truck. They are then compacted and disposed of in an on-site low-level waste dump. The number of radioactive weeds must be documented and the waste sites are eventually cleaned up and covered with six inches of clean soil or gravel.

Uncontaminated tumbleweeds are dumped into an open pit. They used to be burned, but the state Department of Health was worried that some radioactive ones might find their way into the pit by mistake and contaminate the air.

Two years ago Hanford had a fruit fly emergency. The flies were attracted to a soil fixative with saccharin in it that was being sprayed on a contaminated site. They flew to a lunch room, then spread the contamination to nearby trash bins, which wound up in the local municipal landfill. That mess cost 2.5 million dollars to clean up.

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