The Department of Energy's National Nuclear Security Administration ships Cold War-era uranium overseas, where the containers -- sought by terrorists for dirty bombs -- are secretively trucked to government-owned nuclear research reactors in the Netherlands, Belgium, Czech Republic and Poland. (South Africa and Australia also use American uranium to produce moly-99 in research reactors.)
Private companies rent time in the reactors to irradiate enriched uranium targets, producing an atomic alphabet soup. Nearby processing facilities fish out the moly-99, and the radioactive material is loaded onto commercial airline flights bound for the United States in protective containers.
Three companies dominate the American market for moly-99 -- Lantheus, Curium and GE Healthcare. They distribute the material to specialized pharmacies around the country, where technicians process it into a diagnostic imaging agent called technetium-99. The companies work against a ticking clock: Because of its short half-life, just 66 hours for moly-99 and six hours for the imaging agent, the material must be quickly delivered to hospitals and administered to patients.
"The whole industry is like a duck going on a fast-flowing river," said Kevin Charlton, an analyst at the Organization for Economic Cooperation and Development's Nuclear Energy Agency in Paris. "On the surface, it looks like things are going very smoothly, but under the water, their legs are going really fast."
Countless things can go wrong, starting with the first step.
The worldwide supply of moly-99 relies on a fleet of government-subsidized nuclear research reactors built mostly during the Khrushchev-Eisenhower era.
Regular maintenance and major repairs can shutter the reactors, sometimes for months, and so-called scrams -- caused by anything from a hiccup in a reactor's cooling system to an errant lightning strike -- frequently halt production. "It's a nuclear reactor," Charlton said. "The only thing you can do is shut it off."
Even the Mayo Clinic in Rochester, Minn., a prestigious cancer treatment center, can be left waiting for shipments of the generators that contain the imaging agent. "We've had days when no generator comes in at all, or it's been cut in half," said Andrew Paulsen, supervisor of the clinic's radiopharmaceutical laboratory.
And the ephemeral nature of moly-99 always looms. On a recent afternoon, inside a locked laboratory at Stanford Hospital's nuclear medicine department in Palo Alto, Calif., a technician held a lead-lined, plastic cylinder containing a syringe of fragile atoms that had traveled around the globe.
Once the imaging agent is injected into a patient's body, it emits gamma rays that can be detected by gamma cameras that look like X-ray machines. The radioactive tracer lights up on a computer monitor wherever the heart's blood vessels are blocked or bones are riddled with potentially cancerous tumors. The imaging agent was first used in medical applications in the 1960s because its short half-life meant that patients were getting less exposure to radioactivity than from other diagnostic tracers.