The Lowest-Tech Atom Bomb

Continued from page 1

By Richard A. Muller

October 11, 2002

True, the Turkish police did intercept the HEU. But experience with drug smuggling shows that we catch only a small fraction of what is smuggled. This suggests that Saddam might even now have many kilograms.

Suppose he has a significant quantity of HEU-what could Saddam do? Uranium bombs, unlike the more complex plutonium bombs, don't require the tricky implosion method, but can employ the simple, reliable gun method. This is all explained in detail by one of the original designers of the Hiroshima bomb, Robert Serber, in his book, The Los Alamos Primer. Serber says that the critical mass for a uranium-tampered bomb is 15 kilograms; the Hiroshima bomb, which used three critical masses, was finished two years and four months after the Los Alamos laboratory opened. It was considered so reliable that it was never tested before it was used.

Fortunately for Saddam, Serber's book gives equations and tricks (such as the use of neutron-reflecting tampers, or casings) that apparently eluded even Heisenberg, the leader of Nazi  uranium project. What's more, Saddam's designers have been at work for over a decade, while waiting for their supreme ruler to obtain the HEU.

But Saddam has no missiles that could reach the United States. What could he do with a few small bombs?

Unlike weapons-grade plutonium, (which is typically contaminated with Pu-240, a spontaneous neutron emitter), U-235 is difficult to detect without active probing, as with a thermal neutron source). It emits alpha particles and some energetic gamma rays, but these can be shielded with lead. This makes HEU relatively easy to smuggle. The easiest way to get a bomb into the US is probably in a shipping container. We wouldn't detect it unless we were tipped off about where to look.

Let's imagine a bad case. Saddam sets off a bomb in Washington D.C. Unlike the designers of the Hiroshima and Nagasaki bombs, he derives great pleasure from mass death. Unlike bin Laden, he takes credit immediately for his terrorism. He announces that he has additional weapons, and that if the U.S. retaliates, he will start setting them off in major U.S. cities.

Last month, British Prime Minister Tony Blair announced that Saddam has been seeking to buy uranium from African countries (which produce 20 percent of the world supply). This is, of course, illegal, since he has no reactors, and no legitimate use for large amounts of uranium. But why would he do this, if he already had HEU? Doesn't his interest prove that he is, at worst, rebuilding calutrons?

No. If I were Saddam, I would import uranium in order to give that impression, to lull the U.S. into a false sense of security, into believing that there is plenty of time. Let's not make that same mistake twice-of assuming that Saddam is doing it in the obvious way.

What hope have we? Well, maybe the Kazakhstan case was a fluke, and there is not a significant quantity of HEU available. Maybe most of the reported smuggling cases were actually fraud, or CIA sting operations designed to find out who is buying, and there is no real HEU to purchase. (A widely-reported seizure on September 28 in Turkey, 250 km from the Iraqi border, contained no real uranium.) Maybe Saddam has already made a bomb, but hasn't yet figured out how to sneak it into the U.S. Maybe Serber deliberately put plausible but misleading information into his book that would foil and delay a terrorist, and make an untested bomb into a dud.

We can hope.