Imagine being able to detect a radiation source no larger than a grain of sand, determine whether it's lethal 137cesium or the harmless potassium found in a banana in an instant while cruising past at street speed in a police Blazer.
Radiation detection devices called Adaptable Radiation Area Monitors, or ARAM, developed at California's Lawrence Livermore National Laboratory (LLNL), are mounted in the cargo areas in the back of SUVs called RadTrucks to take counterterrorism to the streets.
The ARAM devices are automatic portal monitors built to detect illicit low-energy gamma rays and neutron emissions characteristic of weapons-grade plutonium and highly-enriched uranium. The units are capable of providing accurate, positive warning and identification when suspicious materials come within detection range. Or, in the case of the RadTrucks, when the units come within range of the suspicious material. The New Jersey State Police has four RadTrucks. California also has a fleet of about 20 of the $200,000 vehicles. The Secret Service is also said to have one. Prior to Sept. 11, 2001, radiation portal monitors were used primarily to keep plutonium and uranium from being smuggled out of nuclear facilities, or to prevent contaminated scrap metal from entering industrial steel mills. The principle fear was that terrorists could use the contraband nuclear material to assemble a dirty bomb — a device designed to disperse radioactive contamination without the thermonuclear blast.
Even though a dirty bomb incident would be unlikely to cause many deaths, its real purpose would be to create instant terror in the form of mass panic, with lingering psychological damage. The aftermath would be as unpleasant as it is unprecedented. If a dirty bomb device were to be detonated in a crowded sports arena or holiday shopping mall, decontamination and treatment of potentially thousands of panic-stricken victims, as well as decontamination of affected areas, would be lengthy and expensive. A dirty bomb set off in a metropolitan setting would also render the contaminated area unsafe and unusable for weeks if not months, resulting in further commercial doom.
Having a speedy, reliable way to detect radioactive material, particularly while the source is in transit, has been the nuclear holy grail of homeland security officials for years. Yet, few protections exist today that can be readily installed into the stream of commerce to prevent dirty bombs and the materials for larger nuclear weapons from entering or leaving the country.
When earlier types of radiation detectors are put on the street they tend to alarm on harmless amounts of naturally occurring isotopes of potassium, radium, thorium and uranium — elements commonly found in commercial shipments and medical practices.
To avoid the nuisance alarms associated with real but non-threatening medical and industrial radiation sources, instantaneous isotope detection and identification is therefore mandatory for mobile applications. ARAM, licensed to IST-Textron Systems, accomplishes this in near realtime in the RadTrucks. Tests have demonstrated that detection passes are successful in less than 5 seconds at speeds of up to 50 mph.
ARAM provides detection and identification in one pass. "Previous generations of detection systems needed a first pass to detect a radiation source, followed by a second pass to identify the material," notes Dave Trombino, one of the Lawrence Livermore physicists that developed ARAM.
ARAM not only makes nuclear counterterrorism mobile, it makes radiation detection portable. "The 'A' in ARAM stands for Adaptable," Trombino says. "This detection system can be used in fixed locations, in mobile SUVs, on small boats or even in backpacks."