A policeman from the Port Authority of New York and New Jersey uses a radiation detector to check a tractor trailer. The radiation detector will respond to a shipment of batteries, medical X-ray supplies, gases and toxic materials.

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Preventing Nuclear Terrorism

When dealing with national nuclear weapons programs, the key players are generally intelligence organizations, politicians and the International Atomic Energy Agency (IAEA). And while nations and their leaders can prove difficult to negotiate with at times, other potential nuclear threats are far more elusive. How do you impose sanctions against a terrorist organization? Who inspects the warehouses of an illegal smuggling cartel?

­When it comes to the trafficking of radioactive materials, it's easy to underestimate the problem. After all, the plots of most TV shows, movies and video games revolve around the actions of a single smuggling or terrorism operation. How many black-market dealers could there be in the world, right?

The answer to that question may terrify you. According to the IAEA Illicit Trafficking Database, there were a reported 252 incidents of unauthorized acquisition, provision, possession, use, transfer or disposal of nuclear or radioactive materials -- and that's just the total for 2006. Between 1993 and 2006, a total of 1,080 incidents were reported [source: IAEA]. The materials ranged from radioactive medical materials to quantities of enriched uranium. To learn more about these alarming crimes, read How easy is it to steal a nuclear bomb?

Various military, law enforcement and intelligence agencies work together to intercept these items, using everything from high-tech radiation detection equipment to old-fashioned detective work. Confiscating the materials is just the first step. Traditional investigation practices might allow authorities to track down the intended recipient -- and even trace the materials back to their source. Nuclear forensics, however, allows detectives to follow clues inside the materials themselves.

For instance, if investigators examine the isotopes and impurities in a sample of uranium, they can actually tell where it was mined and how it was processed. There's a finite number of places in the world either could have taken place. Plutonium, on the other hand, has to undergo enrichment in a particle reactor, and careful analysis at a nuclear laboratory can pinpoint exactly what kind of reactor was used. Once detectives know where the materials originated, they can focus their investigation on how they were leaked or stolen to begin with.

­But what happens if preemptive efforts fail? How can nuclear forensics help in the wake of an actual nuclear attack?