ROCKY FLATS, Colo. - At the peak of the Cold War, 8,000 workers labored around the clock in top-secret buildings west of Denver to build the deadliest devices ever invented - thermonuclear bombs.

Now, with Russia and the United States cutting their nuclear arsenals, the Rocky Flats site - once one of the world's most dangerous bomb plants - will shut down by 2006. Its grounds will become a wildlife refuge.

First, though, the government must level hundreds of buildings and remove huge volumes of highly radioactive material left from decades of making hydrogen bombs.

Crews are sending tons of this waste to disposal, storage and recycling sites around the country.

However, the most dangerous material - more than six tons of heavily guarded plutonium suitable for use in H-bombs - is destined for the U.S. Department of Energy's Savannah River Site, near Aiken. There, if all goes according to plan, it would be recycled into fuel for electric generating reactors.

Plutonium shipments to SRS could begin anytime after May 15.

But getting the substance across the South Carolina border is becoming a political and public relations headache.

Gov. Jim Hodges vows to use state troopers - even lie down in the road himself if necessary - to turn away plutonium-hauling trucks, unless he is convinced the feds won't leave the plutonium in his state permanently.

At the U.S. Justice Department, lawyers are looking at whether to send federal marshals along with the shipments to South Carolina, and studying the law about whether Hodges can block the shipments.

So far, the Energy Department's promises have left Hodges unconvinced. "The federal government is asking us to take them at their word," Hodges said. "Given their track record, that's not good enough."

On Wednesday, the governor sued the Energy Department, asking a federal court to block the plutonium shipments until Washington studies the impact on public health and the environment.

Hodges' stance has thrown the Energy Department, and some people in Colorado, into a tizzy.

If the plutonium does not begin moving out of Colorado soon, the department will miss its 2006 deadline for closing Rocky Flats, the agency says.

Energy Secretary Spencer Abraham says he fears the Russians might lose interest in cutting weapons if the United States cannot show it is making progress in getting rid of its nuclear material.

In Colorado, Denver's newspapers have called Hodges "silly" and likened him to a Confederate rebel. U.S. Sen. Wayne Allard, R-Colo., who introduced the bill to make Rocky Flats a wildlife refuge, says Hodges will be to blame if plans fall apart.

His press secretary has referred to Hodges, a Democrat, as an "Elmer Fudd."

Allard and Hodges are running for re-election, raising the possibility that their battles have as much to do with politics as protecting their states from nuclear hazards.

STATES CHALLENGE FEDS

The plutonium from Rocky Flats is just the first part of more than 34 tons of the radioactive metal - enough to make thousands of H-bombs - that will be shipped to SRS from Energy Department sites over the next several years. Much of the plutonium is from dismantled bombs. Russia has agreed to dispose of a similar amount of the material.

The plutonium shipped to SRS would be reprocessed into a fuel for commercial nuclear reactors. When that fuel is spent, it would be disposed at a planned repository at Yucca Mountain, Nev.

To reprocess the plutonium, the Energy Department plans to spend $3.8 billion to build and operate two massive structures at SRS. Hodges' fear is that the structures won't be built, and the plutonium will sit indefinitely.

RAIDED BY THE FBI

The cleanup and closure of the 6,500-acre Rocky Flats facility, once one of the world's filthiest bomb factories, will set the tone for other such projects to come, nuclear experts say.

At a cost of more than $7 billion, the Rocky Flats effort is one of the biggest public works projects in the nation's history and the first of its kind - the complete dismantling of a major nuclear weapons plant - in the world.

The U.S. Atomic Energy Commission began building Rocky Flats in 1951. The facility took plutonium, produced by reactors at SRS and the government's Hanford plant in Washington state, and turned it into plutonium "pits," or triggers for nuclear bombs.

A hollow sphere that varies in size from a grapefruit to a soccer ball, a plutonium pit explodes with the power of the bomb that obliterated Hiroshima during World War II. But in thermonuclear weapons, the pit serves mainly as a starter - the pit is a compact atomic bomb that detonates the larger hydrogen bomb. Pits made at Rocky Flats can trigger weapons 600 times more powerful than the bomb dropped on Hiroshima.

Declassified reports reveal that Rocky Flats made about 70,000 pits in 36 years. Manufacturing at the site halted in 1989, when the FBI raided the factory for alleged environmental crimes. An Energy Department contractor paid more than $18 million in fines.

Because of the numerous environmental and safety deficiencies, Rocky Flats never resumed operations. In 2000, the Energy Department signed a contract with Kaiser-Hill, an environmental restoration company, to clean up the site, tear down its hundreds of structures, and close it down by the end of 2006.

Energy Department officials say they are now about a third of the way through the cleanup. Grassy areas and piles of rubble now mark the spots where some of the plant's support buildings and laboratories once stood.

Nearly every day, tractor-trailer rigs loaded with radioactive waste in huge shipping casks depart for the various storage sites around the country.

"We have more than 700 buildings here, large and small, and every one of them will be decontaminated and torn down," said Pat Etchart, a Rocky Flats spokesman as he drove a visitor through the complex recently.

Some of those buildings cover the equivalent of three football fields and have walls more than 5 feet thick. Tearing down such massive structures would be a major feat under even ordinary circumstances.

But the dismantling job becomes immensely more complex when workers must dress out in bright yellow moon suits and follow precise, detailed safety steps to protect themselves from nuclear materials and radiation.

Most of the demolition wastes are assumed to be contaminated, and must be carefully packaged and hauled off to secure sites.

NOTORIOUS BUILDING

During the peak of Rocky Flats' bomb-making activity, several of its structures were described as some of America's "most dangerous buildings." Perhaps the most notorious is Building 771, a windowless, two-story concrete edifice built into a hillside in 1951. It is where almost every nuclear weapon ever made by the United States started.

Building 771 shaped plutonium into gray ingots the size of a hockey puck. Purifying the plutonium required vast amounts of nitric acid, hydrochloric acid, hydrogen fluoride and other caustic liquids. The workers' greatest fear was leaks from valves and pipes.

The more than six tons of plutonium - the exact amount is classified - now awaiting shipment to SRS is stored in heavily guarded Building 371, the only structure at Rocky Flats that still contains the material. At one time, seven buildings held the substance.

Energy Department officials say they could speed the cleanup if they could get rid of the plutonium. Providing security for the material costs hundreds of thousands of dollars a day, funds that could be applied to the cleanup effort if the plutonium were gone, they say.