By Doug Tsuruoka
Homeland security officials are rushing defense labs to make sensors that can detect small nuclear weapons that some authorities fear terrorists might use to devastate a U.S. city.
A March 22 Australian TV report highlighted the need. The story claimed the al-Qaida terror group has bought nuclear "briefcase bombs" on the black market in Central Asia.
Use of the word 'briefcase' sent a shudder through security authorities everywhere. It would mark a huge threat if nuclear bombs that small were developed, let alone in dangerous hands. Almost all experts doubt briefcase bombs exist.
But suitcase bombs do exist. The Soviets developed such trunk-sized nuclear bombs during the Cold War. Moscow has always maintained that no suitcase bombs have escaped its close watch, but reports pop up from time to time that rogue Soviet scientists have helped develop suitcase - and now briefcase - nuclear bombs for the black market.
Such a threat is almost unimaginable. But experts are forced to use the word "almost."
So Far, No 'Breakthroughs'
A big problem is most nuclear experts say the government is far from developing sensors that reliably detect such weapons despite the urgency sparked by 9-11.
"The detection problem is a hard nut to crack," said Richard Lanza, a senior scientist and nuclear engineer at the Massachusetts Institute of Technology. "I don't think there have been any breakthroughs."
Pinpointing bomb-grade nuclear material is difficult, says Kyle Olson, a former Senate terrorism prober. Many items give off as much radiation as a nuclear bomb, which itself actually emits little radiation.
"Any detector compact and sensitive enough to pick up trace levels of radiation from (suitcase bombs) is also readily spooked by natural environmental or industrial radiation," said Olson.
There are promising products, though. One is called an active detector, says Tom Cochrane, director of the nuclear program for the Natural Resources Defense Council, an environmental policy group.
It's being developed at the Lawrence Livermore National Laboratory in California, says Cochrane, a nuclear physicist and former arms control monitor.
The device shines a stream of photons or neutrons through an object that might carry a small nuclear weapon, like a shipping container or suitcase. It would produce gamma rays if it hit any nuclear material, which would show up on the device's display screen.
Ivan Oelrich, a nuclear physicist at the Federation of American Scientists, a policy group in Washington, D.C., has another approach.
"You can shoot neutrons through a shipping container. If the pattern of neutrons coming out the other side is different, it would suggest there's a bomb inside," said Oelrich, who directs the federation's strategic security project.
The methods mentioned by Cochrane and Oelrich take an active approach to sensing nukes by creating tiny atomic reactions that can be detected. But neither device has been built, and many glitches could still surface, Cochrane concedes. One big glitch could be the cost, which could reach the hundreds of millions of dollars.
Homeland Security officials, meanwhile, have put stop-gap detectors in place.
In October 2001, President Bush ordered that hundreds of nuclear sensor devices be installed at major U.S. ports, border posts and key public buildings. He did this after officials got a report that terrorists planned to smuggle a 10-kiloton nuclear weapon into New York City. (The A-bomb dropped on Hiroshima carried 15 kilotons.)
The report proved false. But some estimated such a bomb, detonated in an area like Manhattan, could kill 100,000 to 500,000 people.
These stop-gap sensors, called gamma ray and neutron flux devices, sense radioactive materials or generate images of bombs inside luggage, crates or vehicles.
But the devices aren't that reliable, says Cochrane.
He says both types of detectors can be beaten by breaking a suitcase bomb into small parts and rearranging them to avoid detection.
He says the gamma-ray devices can't detect radiation emissions from some bomb materials, including uranium.
The government also is using older products such as Geiger counters, which can pick up radiation.
But such radiation sensors can be foiled by lead shielding. And suitcase bombs that use highly refined plutonium emit little radiation, making them harder to detect.
"If it's a well-designed, military-style weapon, the radiation signatures are tiny," said Oelrich of the science policy group.
Death Deepened Mystery
Besides being reliable, an effective sensor must work fast at ports, airports and other checkpoints. As a practical matter, screenings must be selective, Cochrane says.
Said Oelrich, "The process can't take more than a minute or so because the U.S. moves millions of shipping containers a year."
There's another big challenge, says MIT's Lanza. Terrorists might find ways to booby-trap nukes to explode if detected. "We're not dealing with stupid people," he said.
This is scary stuff. Most experts don't know if terrorist groups have anything close to an atomic bomb. One bright spot is there might be no briefcase-sized nukes.
"It still isn't possible for the U.S. or the Russians or anyone to build a nuclear device as small as a briefcase," Oelrich said. As for Russia's suitcase bombs, "We don't have any evidence that any are missing."
Still the only major reference to missing suitcase bombs remains a 1997 U.S. TV interview with former Russian National Security Adviser Alexander Lebed.
He said Russia's military had lost track of over 100 suitcase-sized nuclear bombs.
He later recanted. His assertion was never proved, and Lebed, a rival to Russia's current leadership, died in a helicopter crash in April 2002 that some authorities considered suspicious.