Thwart Terrorists' Dream of American Hiroshima

"Al-Qaida has tried to acquire or make nuclear weapons for at least 10 years ... and continues to pursue its strategic goal of obtaining a nuclear capability."

— 9/11 Commission Report

CAMBRIDGE, Mass. — Sixty years ago, the Americans ended World War II by dropping Little Boy and Fat Man from B-29 bombers onto Hiroshima and Nagasaki. This was the explosive climax to the military's most expensive weapons program — the Manhattan Project to design and build a nuclear bomb.

Located on the beautiful and isolated Pajarito Plateau at the foot of the Jemez Mountains, but only 90 miles from Albuquerque, the highly classified project brought together nearly 6,000 of the world's most brilliant physicists and technicians. The U.S. Congress gave the project a blank check, agreeing that regular briefings on the project's cost "would not be necessary." In the end, inventing and building a working bomb cost the U.S. government $1.9 billion dollars — equivalent to $20 billion in today's dollars.

The chilling reality is that a terrorist group today would not need to assemble such a talented team, or spend that amount of money, to get its bomb. It no longer takes the mind of an Oppenheimer or a Fermi to invent a nuclear weapon. Standing on the shoulders of these giants, with documents like the Los Alamos Primer easily accessible in the public domain, a Princeton undergraduate in the 1970s constructed what could be a perfect terrorist weapon: a bomb the size of a beach ball with a 10-kiloton yield. Members of the physics department at Princeton who had worked on the Manhattan Project believed that the young man's bomb would work. All that the design lacked, and the only true obstacle standing between terrorists and a similar bomb, was the 26 pounds of highly enriched uranium (HEU) or 9 pounds of plutonium. Even 60 years ago, the same Manhattan Project physicists deemed the "gun-type" Little Boy bomb design so reliable that they never bothered testing it before detonating it over Hiroshima.

The only thing keeping al-Qaida from building a nuclear weapon is the fissile material needed to produce a self-sustaining chain reaction for a nuclear explosion. The strategic narrows of preventing nuclear terrorism is preventing jihadists from acquiring such fissile material. Here, physics is on our side: no fissile material, no nuclear explosion, no nuclear terrorism.

Fortunately, producing highly enriched uranium or plutonium — the key ingredients of a nuclear bomb — is beyond the capability of nonstate terrorists — a multibillion-dollar, multiyear undertaking. To make one bombs-worth of HEU would require five tons of uranium ore and 6,500 centrifuges working in a cascade for a year. Al-Qaida could not produce the fissile core of a nuclear bomb. But they could buy it from a state that had — or from thieves with stolen material in a nuclear state. As the 9/11 Commission noted, Osama bin Laden is planning an American "Hiroshima." Locking down all highly enriched uranium and plutonium must therefore become the nation's No. 1 priority. Fortunately, there is a finite amount of highly enriched uranium and plutonium in the world, and it is within our power to secure it from theft.

A serious campaign to prevent terrorists from acquiring nuclear weapons will require substantially greater political will from the United States and our allies as well as a new strategic approach, organized under a Doctrine of Three No's:

The first strand of the strategy — No Loose Nukes — requires securing all nuclear weapons and weapons-usable material, on the fastest possible timetable, to a new gold standard.

No New Nascent Nukes means no new national capabilities to enrich uranium or reprocess plutonium.

The third No — No New Nuclear Weapons States — draws a bright line under the current eight nuclear powers and says unambiguously, no more.

If we think about the reality that New York could end up like Hiroshima, or Albuquerque like Nagasaki, we would demand a Manhattan Project-like effort to prevent it. Then, we were racing against Germany to get the bomb. Now we are in a race against terrorists and thieves to lock down all fissile material that could fuel a bomb that would destroy an American city.

Graham Allison, director of the Belfer Center for Science and International Affairs at Harvard University's Kennedy School of Government, is author of "Nuclear Terrorism: The Ultimate Preventable Catastrophe."