The ABCs off A-Bombmaking

By Frederic Golden

Can anyone with the money master the subject?

Suppose a small nation with limited technological skills wants to build an atomic bomb. Could it succeed? Yes, most nuclear experts think the answer is yes, especially if the country already possesses a nuclear reactor and the know-how to run it. One of the unhappy facts of the nuclear age is that the same reactors used in peaceful nuclear research and in the production of electricity can also serve as the starting points for fabricating A-bombs.

Building its own reactor would be extremely difficult for a Third World country. But buying one would not be much of a problem, particularly for a nation like Iraq, flush with petrodollars. At least 15 countries* are now offering nuclear technology on the international market. Their wares include not only a variety of reactors and fuels, along with the necessary technicians, but also reprocessing machinery that could be used for recovering the lethal ingredients for bombmaking from the spent reactor materials. A tidy set of such equipment that would be suitable for conversion to weapon construction would cost upwards of $250 million.

A nation that had signed the 1968 nonproliferation treaty, only to decide that it wanted a nuclear weapon after all, would have to conceal its operations from the International Atomic Energy Agency (IAEA), a Vienna-based affiliate of the U.N. The agency's inspectors are often on hand when nuclear fuel is loaded into a reactor. They install sealed closed-circuit TV cameras for continuous on-site monitoring, and they return periodically to check this equipment. Still, the IAEA's inspectors do not always get to see what they would like in member countries. For a time during the Iraq-Iran fighting, for example, Baghdad refused to allow IAEA officials into the area.

A bigger problem is that more and more people around the world know how to build bombs. Even U.S. college students, poring through declassified Government technical papers, have put together designs for rudimentary A-bombs. Articles have been written about the subject. The key ingredient for both the bombs and the reactors is the same: fissile material such as uranium or plutonium, whose atoms can readily split, scattering tiny, fast-moving particles called neutrons. When neutrons score bull's-eyes on the nuclei of neighboring atoms, they split them as well, unleashing still more neutrons, which in turn cause more breakups, all of which release energy.

In a nuclear reactor, such a chain reaction is kept under control by "absorbers"--usually boron or cadmium rods. These capture neutrons that might otherwise split more atoms. But if the fissile material is pure enough, and sufficiently compressed, as in a bomb, the chain reaction speeds up. Heat accumulates, and the material blows apart to produce the nuclear age's familiar mushroom cloud.

Most nuclear reactors and some nuclear weapons use a rare isotope of uranium called U-235. To explode, the U-235 must be relatively pure, preferably 90% or more. Commercial U.S. reactors, by comparison, usually run on a mix containing only 3% U-235. This hampers would-be bombsmiths, since enriching U-235 to a high level demands extremely complex separation techniques that are still beyond the capability of all but the most advanced industrial countries. Yet there are some relatively simple ways of overcoming this handicap.

One would be to buy enriched uranium from a nuclear nation as part of a deal for a reactor designed to burn such weapons-grade fuel. The reactor Iraq acquired from France would have used 93% enriched U-235. During the course of operation, some of this material might be skimmed off for nuclear weaponry, although that would be a risky proposition. The IAEA inspectors might spot the diversion, or some of the foreign technicians at the site might blow the whistle on the schemers.

But diverting enriched U-235 is not the only option for the bombmaker. A-bombs can also be fashioned out of plutonium, which is a byproduct of the modern alchemy that occurs in reactors. Even relatively small reactors can produce several pounds a month of a type of plutonium that lends itself to bombmaking. Equally important, plutonium, unlike the nearly identical isotopes of uranium, is a separate element with its own distinctive characteristics. Thus it is relatively easy to pick out by ordinary chemical means from other radioactive material.

After only a year or so of operation, enough plutonium (about 35 Ibs.) could be generated in a small reactor to build two or three bombs of the type dropped on Nagasaki. The plutonium would be formed into a hollow sphere containing a small neutron source that might be made of radium and beryllium. The plutonium itself would be wrapped in a beryllium or uranium reflector, which helps contain neutrons and prolong the chain reaction. This shield would in turn be covered by a layer of TNT charges, the most critical aspect of the design. The charges would have to be so carefully shaped that the detonation would direct their force largely inward, crushing the plutonium into a solid, compact ball. The plutonium would quickly reach what bombmakers call supercritical density. As the chain reaction went out of control the material would explode.

By today's superpower standards, a Nagasaki-type bomb would be puny--the equivalent of a mere 10,000 tons of TNT. But that might be more than enough to terrorize an enemy, or crush a nonnuclear neighbor. --By Frederic Golden

*In addition to the U.S. these include the Soviet Union and three of its allies--Czechoslovakia, East Germany and Poland--Britain France, West Germany, The Netherlands, Belgium, Sweden, Switzerland, Italy, Canada and Japan.

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