BOISE, Idaho - In the summer of 2000, wildfires raged across nuclear compounds in the West, destroying buildings, forcing the evacuation of highly secure labs and creating a health panic over harmful radioactive contaminants being dispersed by smoke.

After five quiet fire seasons, U.S. Department of Energy fire officials say they are better prepared as the potential for a fiery summer sequel increases.

"Our training has improved, we're more focused on restricting potential human sources and we've completed the evaluation of our areas of soil contamination, so we have a better understanding what the potential effects would be if a fire burns through one of those," said Eric Gosswiller, fire marshal for the 890-square-mile Idaho National Laboratory, a DOE nuclear research compound in Idaho's high southeastern desert.

Three huge wildfires roared across INL in July 2000, scorching nearly 100 square miles inside the secure federal site, coming close to a test reactor and forcing emergency evacuations.

That same season, an out-of-control wildfire burned 40 percent of the 586-square-mile Hanford nuclear reservation in the sagebrush of south-central Washington state and briefly threatened a nuclear waste warehouse, while the Cerro Grande fire burned 7,500 acres of the Los Alamos National Laboratory site in New Mexico, prompting an 11-day evacuation.

A subsequent federal investigation found the Energy Department was unprepared for large-scale firefighting and the unique hazards that fires on nuclear sites present.

"We learned a lot of lessons complex-wide," Gosswiller said Wednesday during a gathering of DOE fire and environmental monitoring officials at INL.

Armed with mobile water cannons and off-road fire trucks that shoot streams of foam, INL crews now have detailed site maps showing areas where the soil has higher-than-background levels of radiation, where volatile or hazardous waste was dumped or spilled, and the locations of large amounts of unexploded World War II ordnance left over from the period when the Navy used INL as a gunnery test range.

Recent Western fire seasons haven't matched the scorching summer of 2000. But the potential this season is high. Two consecutive years of wet winters and springs have spurred growth of fast-burning grass and brush on normally barren rangelands.

Arjun Makhijani, a physicist and president of the Maryland-based watchdog group the Institute for Energy and Environmental Research, said DOE has not fully investigated the health and environmental risk of wind-driven fires dispersing radioactive particles that litter the ground of many federal nuclear research reservations.

"Very often DOE issues assurances before they've done their homework," said Makhijani. "If you have heavy winds and significant contamination of soil, you can get re-suspension of radioactive material. The question is, how much?"

Besides operating routine air monitoring networks, DOE crews downwind of wildfires collect samples of smoke for quick analysis of airborne contaminants. At INL, the state of Idaho also operates its own air quality monitors and posts real-time results on a Web site to alert the public during wildfires.

Scott Lee, environmental monitoring program leader at INL, said air samples taken during previous blazes show INL firefighters' exposure to radiation is about one-twentieth of the acceptable limit.

"It's insignificant and that's for someone within 100 yards of the fire, sitting there for an hour," said Lee.

Samples of radioactive particles collected during and after wildfires have also shown most of the radionuclides came from global fallout of Cold War nuclear weapons tests, Lee said. Detection of airborne radioactive particles at INL usually increases after a wildfire, when desert winds blow dirt exposed by the loss of vegetation. The dust contains radioactive particles.

Richard Wells, a senior scientist for CWI Idaho, the contractor hired to clean up radioactive and hazardous waste from approximately 500 locations at INL, said the largest potential sources of surface contamination that could become airborne during a fire have been removed or capped.

"We've largely reduced that footprint," he said. "Now, these folks in the fire department know where those zones of contamination are so they can fight fires to protect their staff as well as preventing release of that contamination."