Nuclear Terrorism FAQ

From the Nuclear Threat Initiative and The Project on Managing the Atom at Harvard's Belfer Center
Wednesday, September 26, 2007; 12:00 AM

Is it really plausible that terrorists could get and use a nuclear bomb?

Yes. Unfortunately, terrorist use of a nuclear bomb is a very real danger. During the 2004 presidential campaign, President George W. Bush and Senator John Kerry (D-Mass.) agreed that nuclear terrorism was the single greatest threat to U.S. national security. Published estimates of the chance that terrorists will detonate a nuclear bomb in a U.S. city over the next ten years range from 1 percent to 50 percent. In a 2005 poll of international security experts taken by Senator Richard Lugar (R-Ind.), the median estimate of the chance of a nuclear attack in the next ten years was 29 percent -- and a strong majority believed that it was more likely that terrorists would launch a nuclear attack than that a state would. Given the horrifying consequences of such an attack, even a 1 percent chance would be enough to call for rapid action to reduce the risk.

What materials could terrorists use to make a nuclear bomb?

To make a nuclear bomb requires either highly enriched uranium (HEU) or plutonium. Neither of these materials occurs in nature, and producing either of them requires expensive facilities using complex technologies, almost certainly beyond the capability of terrorist groups. Hence, if all of the world's stockpiles of nuclear weapons, HEU and plutonium can be effectively protected and kept out of terrorist hands, nuclear terrorism can be prevented: no nuclear material, no bomb, no nuclear terrorism.

How difficult would it be for terrorists to get the materials needed to make a nuclear bomb?

Highly enriched uranium and plutonium are hard to make, but may not be so hard to steal. These raw materials of nuclear terrorism are housed in hundreds of facilities in dozens of countries -- some with excellent security, and some secured by nothing more than an underpaid guard and a chain link fence. There are no binding global standards setting out how well nuclear weapons and the materials needed to make them should be secured.

Theft of the essential ingredients of nuclear weapons is not just a hypothetical worry, it is an ongoing reality. The International Atomic Energy Agency (IAEA) has documented 15 cases of theft of HEU or plutonium confirmed by the countries concerned (and there are additional well-documented cases that the countries involved have not yet been willing to confirm). In many of these cases, the thieves and smugglers were attempting to sell the material to anyone who would buy it -- and terrorist groups have been seeking to buy it.

How much expertise is needed to make a nuclear bomb? Would a large operation be required?

Unfortunately, government studies have concluded that once a terrorist organization had the needed nuclear material, a handful of skilled individuals might be able to make a crude nuclear bomb using commercially available tools and equipment, without any large fixed facilities that might draw attention, and without access to classified nuclear weapons information. Getting nuclear material and making a crude nuclear bomb would be the most complex operation terrorists have ever carried out ¿ but the risk that a sophisticated group could pull it off is very real. Roughly 90 percent of the effort in the Manhattan Project was focused on making nuclear bomb material; getting stolen nuclear material would allow terrorists to skip the hardest part of making a nuclear bomb.

The simplest type of nuclear bomb, known as a "gun-type" bomb, slams two pieces of nuclear material together at high speed. The bomb that destroyed Hiroshima, for example, was a cannon that fired a shell of HEU into rings of HEU. Plutonium cannot be used to make a gun-type bomb with a substantial explosive yield, because the neutrons that all plutonium emits cause the bomb to blow itself apart before the nuclear reactions proceeds very far. To make a bomb from plutonium would require a more complex "implosion-type" bomb, which would be more difficult for terrorists to build -- but government studies have repeatedly concluded that this possibility also cannot be ruled out.

How much nuclear material would terrorists need to make a bomb?

The amount of nuclear material needed to make a bomb depends on the material and the skill of the bomb-maker. A simple gun-type nuclear bomb would require approximately 50 kilograms of HEU -- an amount that would fit in a suitcase. Implosion-type bombs are more efficient, requiring less nuclear material. Unclassified estimates suggest that basic first-generation implosion-type bombs like the Nagasaki bomb can be made with 6 kilograms of plutonium or 15 kilograms of HEU. With these relatively small amounts, a terrorist group could potentially build a bomb with the power of thousands of tons of high explosive. Sophisticated nuclear weapon states can potentially make nuclear bombs with smaller amounts of nuclear material.

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