A UN IAEA scientist carries barrels at the Tuwaitha nuclear plant, near Baghdad, for inventory of nuclear material.

A UN International Atomic Energy Agency (IAEA) scientist carries barrels at the Tuwaitha nuclear plant, near Baghdad, where a team of seven is making an inventory of the nuclear material which was under its safeguard at the site before ­the war.

Ramzi Haidar/AFP/Getty Images

Ever since the bombings of Hiroshima and Nagasaki and the following nuclear arms race, the safety and security of nuclear weapons continues to intrigue us. The idea of anyone stealing dangerous weapons and unleashing them on targets has made its way into countless suspense novels, movies and television shows. The plot is familiar -- the bad guy steals the nuclear bomb, and it's the hero's job to catch the thief and defuse the bomb. More than one season of the popular television program "24" has focused on stolen nuclear material. We see it all the time in popular culture, but how easy is it in the real world for someone to steal a nuclear weapon?

When the Cold War between the United States and Russia ­ended in the early nineties, the threat of nuclear disaster appeared to fade. The events of Sept. 11, 2001, changed this -- when a group of terrorists hijacked four planes and destroyed the World Trade Center in New York City with two of them, fears increased over the possibility of stolen nuclear material being used in a future attack.

Intelligence shows that these fears aren't quite unfounded. Authorities in Russia, a country with a large arsenal of nuclear weapons and material used for building bombs, have reported hundreds of attempted smuggling incidents since September 2001. U.S. authorities and the CIA have acknowledged uncovering terrorists plots to obtain nuclear information.

How serious are these attempts to steal nuclear material? Could someone steal an entire nuke, or ­is it easier to steal different parts and assemble a bomb? What about missing weapons? Should we just be worried about bombs, or are there other kinds of weapons someone could use? In this article, we'll look at how safe the world's nuclear weapons arsenal is and see how close it is to the movies.