RICHLAND, Wash. -- The Cold War may be over, but the Hanford Nuclear Reservation continues to battle Russian invaders -- tumbling, radioactive tumbleweeds. 

Russian thistle is a dead menace here on the windswept desert of south-central Washington. Each winter, the deep tap root on the plant decays, and the spiny brown skeleton above ground breaks off and rolls away. 

"Our dream is that we have this place tumbleweed-free," says Ray Johnson, a biological control manager for radiation protection at Fluor Hanford, the contractor managing the U.S. Department of Energy site. 

But that's about as likely as a Soviet revival. 

While less than 1 percent of the tumbleweeds corralled and compacted at Hanford are radioactive, the ones that are cost a bundle to clean up. 

Hanford is the most contaminated nuclear site in the country, built in 1943 for the top-secret Manhattan Project. For 40 years, Hanford would make plutonium for the nation's nuclear arsenal, including the atomic bomb that was dropped on Nagasaki, Japan. 

Russian thistle, a non-native or invader species, is a particular problem at underground burial sites for radioactive waste, where their tap roots reach down as far as 20 feet and suck up such nasty elements as strontium and cesium. 

A stiff winter wind can send the tumbleweed as far away as four miles, and then "we've lost control of our contamination," Johnson says. But most get hung up within a few hundred yards, usually on sagebrush, fences or in stairwells at the buildings scattered across the site. 

Two years ago, uncontrolled contamination spread by fruit flies at the site made Hanford a national laughingstock, spoofed by humor columnist Dave Barry and in the syndicated comic strip, "Sylvia." 

The flies had been attracted to a soil fixative with saccharin in the base that was being sprayed on a contaminated site. They flew to a lunch room and spread the taint to nearby Dumpsters, which wound up at the Richland municipal landfill. 

Johnson can laugh -- a little bit -- about it now, recalling attempts to find the source of the contamination. As crews ran radiation detectors around the lunch room, and passed over a fruit fly, "the contamination flew away," he recalls. 

The journeys of a few thousand fruit flies cost $2.5 million to clean up. 

Riding herd on Hanford's tumbleweeds, and its flying insects, is part of an annual $4 million integrated soil, vegetation and animal control (ISVAC) program, run by DynCorp. for Fluor. 

Radiation control specialists survey the tumbleweeds on the 560-square-mile reservation, using Geiger-Mueller counters that click when radioactivity is present. If contaminated tumbleweeds are found, an ISVAC crew is called in for disposal duty. 

"The weeds are fairly low danger," says Todd Ponczoch, a radiation control technician, scanning tumbleweeds along a fence line with a Geiger counter. None was registering as radioactive on a recent trip. 

A large, three-pound radioactive tumbleweed might measure out at 150 millirads, or about 1/100th of the allowable annual dose of radiation per person at Hanford. 

Radioactive tumbleweeds are pitchforked by specially trained and clothed workers into a regulated garbage truck, compacted and disposed of at an on-site low-level waste dump. A trail of paperwork is required as well. 

The sites must be satisfactorily cleaned up and covered with six inches of good fill material. 

Nonradioactive tumbleweeds are territory for the Teamsters. 

"It's an easy job. It gets us outside," says Joe Aldridge, a Teamster from Richland, as he pitchforks a plant into the garbage truck, which can hold about 1,800 pounds of tumbleweeds. "Digging ditches is a lot worse." 

The uncontaminated tumbleweeds are dumped in an open pit. Up until five or six years ago, the "clean" tumbleweeds were burned and the ash buried. But the state Department of Health put a halt to that practice for fear that some radioactive tumbleweeds might find their way into the mix and disperse contamination into the air. 

Preventive measures are also part of the control program, and include backpack, roadside and aerial spraying with herbicide to kill the thistle. Sometimes a bio-barrier -- a costly engineered textile -- is laid down to block the formation of thistle roots. 

"What you've got to do is make sure your contaminated areas are tumbleweed-free," Johnson says. 

Clearly, this isn't Kansas, where at least two enterprising souls are raising Russian thistles, turning them into tumbleweeds and selling them for home decor. But in the vast, open and uncontaminated portions of the reservation, some areas are simply left to nature. 

Even Johnson can acknowledge their rightful place in the world: 

"If we didn't have them, the West wouldn't be the West, and we couldn't sing 'Tumblin' Tumbleweeds.' "