Forbes Global, 12.24.01
A terrorist sidles into a crowded train station with a radioactive bomb
tucked into his suitcase. Do we have the technology to spot it?Dirty nukes--suitcase-size bombs made of explosives studded
with scavenged chunks of radioactive material--could become the next tool of
terrorism, far more devastating than hijackings and anthrax. Can they be
"If a nuclear attack comes, it
won't be from an ICBM but more likely in the hold of a container ship," says
Paul Leventhal, president of the Nuclear Control Institute in Washington, D.C.
"The threat is very real. It's hard to grasp because it's so unthinkable. Denial
is a key factor in our weak state of security."
New technology is the key to strengthening security. Until
recently the only equipment for spotting a suitcase bomb was an unwieldy machine
the size of a refrigerator that used liquid nitrogen to cool crystal detectors
down to 184 degrees Celsius below zero and took hours to produce a reading. U.S.
federal agencies are deploying new detectors that put the Geiger counter's
90-year-old technology to shame. They are fast enough to scan trucks and cars as
they pass through toll booths, portable enough to be used almost anywhere and
sensitive enough to distinguish between a weapons-grade isotope and the less
dangerous form in an X-ray machine.
Berkeley Nucleonics, a privately held company in San Rafael,
California, sells an $8,000 handheld detector, called SAM 935, that uses sodium
iodide crystals and powerful software that can identify 90 isotopes in one
second. Berkeley's chief rival, SAIC in San Diego, has sold hundreds of its
cesium iodide handheld screeners to the FBI and other agencies.
SAIC also makes larger "portal" detectors
that look like the metal detectors at airports. Packed into two suitcases, these
$10,000 snoopers also use sodium iodide crystals to spot radiation on people,
but they can't distinguish between isotopes. That requires a scan with a more
precise handheld device. "This time next year there will be hundreds of these
used at critical points across the U.S.," says James Winso, a director of
Signs of the growing risk occurred
long before Sept. 11. Since 1993 nearly 400 cases of illegal trafficking in
nuclear and radioactive materials have been tracked by the International Atomic
Energy Agency in Vienna. In 18 instances small amounts of bomb-grade uranium or
plutonium were involved. In July four men were arrested in Georgia, the former
Soviet republic, on a charge of plotting to sell 2 kilograms of enriched uranium
235; it takes 25 kilos of it to build a bomb.
Customs agents carry devices like basic Geiger counters in
their shirt pockets to measure radiation exposure. But though the Geiger counter
spots radiation easily, it can't determine which isotope is present and
therefore is unable to tell whether danger is at hand. Geiger counters use an
electrically charged wire inside a metal tube filled with methane and argon gas.
A window at one end lets in ionizing radiation from a decaying isotope. The
radiation ionizes an atom in the gas mixture, setting off a cascade of electrons
that hit the wire and register as an electric pulse counted by a meter or
amplified into the familiar "click-click."
The newer detectors forgo wires and gas in favor of highly
engineered crystals made from sodium iodide or cesium iodide. These crystals,
the size of ice cubes, are grown slowly in ovens heated as high as 980 degrees
Celsius, increasing by just one centimeter a day. They are so dense that they
can absorb radiation entirely. When exposed to an isotope, the crystals flash
for 50 billionths of a second. Since every isotope that spews gamma or X rays or
charged particles does so in a unique way--an atomic fingerprint, of sorts--the
color and intensity of the flash tells the detector which isotope is present and
in what quantity.
SAM 935, introduced in
1995 and upgraded annually, looks like a big can of shaving cream and has a
crystal positioned inside the opening at one end. Once an isotope causes the
crystal to flash, a photosensitive cathode releases electrons into a vacuum tube
where a chain reaction produces a cascade, as in the Geiger counter. Resulting
electrical pulses are analyzed by software that can determine which isotopes are
Founded in 1960, Berkeley
Nucleonics, which peddles measurement devices to the nuclear and chemical
industries, has annual sales of less than $50 million. It has sold hundreds of
the new detector units to the military, the Environmental Protection Agency, the
Department of Energy and emergency response teams.
Terrorists could find a way around some of these scanners--for
example, by lining a suitcase with lead. SAIC and Berkeley Nucleonics can
respond with additional detectors that pick up neutrons. In the end nuclear
security comes down to a battle of brainpower.
As Winso says, "A lot of these terrorists have fine German or
American engineering educations. They're smart."
Let us hope our guys are smarter.