Dozens of nuclear research reactors still run on the kind of fuel that can be used to make an atomic bomb. The United States and the Soviet Union set them up during the Cold War as part of an effort to encourage the peaceful use of nuclear power and to build alliances.
Since the 1980s, there have been various initiatives to undo that work, secure the fuel and convert the reactors.
Two and half years ago, the Bush administration pledged to make these programs a priority. NPR's David Kestenbaum has a status report on the U.S. efforts to secure bomb-grade nuclear material around the world.
According the Department of Energy, since the new initiative began, almost 750 pounds of highly enriched uranium have been sent back to Russia — enough for at least several bombs. In the same time, six reactors around the world have been converted so they run off low-enriched uranium.
That still leaves 80 on the government's to-do list.
One thing the Global Threat Reduction Initiative has not managed to be successful at is to secure the used nuclear fuel from the research reactors built by the Soviet Union. These "spent-fuel" rods are still out there.
They can also used to make an atomic bomb, says Matthew Bunn, a nuclear expert at Harvard's Kennedy School of Government. He says the initiative is doing reasonably well. But he says it doesn't cover all the reactors out there, or all the bomb-grade nuclear fuel sitting around. If reactors aren't going to be converted, he says, they need to be better protected.
"People need to understand the importance of what has been done," Bunn says. "Every one of these buildings that doesn't have highly enriched uranium in it means one less opportunity for terrorists to get their hands on the essential ingredients of a nuclear bomb."