About every three days, unknown to most Americans, an elite team of federal scientists hits the streets in the fight against nuclear terrorism.
The deployments are part of an effort since 2001 to ratchet up the nation's defenses. More than two dozen specialized teams have been positioned across the nation to respond to threats of nuclear terrorism, and as many 2,000 scientists and bomb experts participate in the effort. Spending on the program has more than doubled since it was launched.
And an evolving national policy aims to create a system of nuclear forensics, in which scientific analysis could quickly identify the source of a nuclear attack or attempted attack. A key report on nuclear forensics is due next month.
The counter-terrorism efforts are becoming routine. Scientists in specially equipped helicopters and airplanes use radiation detectors to scan cities for signs of weapons. They blend into crowds at major sporting events, wearing backpacks containing instruments that can identify plutonium or highly enriched uranium.
So far, they have not encountered a terrorist. Near the Las Vegas Strip, they investigated a homeless person who somehow had picked up a piece of radioactive material. On the streets of Manhattan, a hot-dog vendor fresh from a medical test triggered a policeman's radioactivity sensor.
But the teams have not become complacent. If the many layers of federal defense against nuclear smuggling break down, these unarmed weapons designers and physicists, along with experts from the FBI, could be the last hope of staving off a catastrophic attack.
They are supposed to rush up to a ticking nuclear explosive (or a "dirty" bomb, which would disperse radioactive material) and defuse it before it's too late -- a situation often depicted by Hollywood that seems less fictional every year.
"After everything else fails, we come in," said Deborah A. Wilber, the scientist who directs the Office of Emergency Response at the Energy Department's National Nuclear Security Administration. "I don't believe it is a question of if it will happen. It is a question of when."
Since the attacks of 2001, the office has created 26 rapid-response units around the nation.
If a device were located, two other specialized teams would rush to the scene, one from a base in Albuquerque, where a fueled jetliner is on 24-hour alert. Another FBI team would depart from rural Virginia.
