New nuclear deterrents

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The failed attempt by a bunch of medical doctors who tried to detonate Mercedes Benz automobiles parked on London's busy streets and packed with the kind of propane cylinders Americans use to fuel backyard barbecues sent antiterror alert levels in the United Kingdom to their highest possible level.

Without minimizing the danger posed by the doctors' plot, it is worth noting that the men were incompetent and the explosives no larger than is commonplace in Iraq today. Suppose a group of terrorists were less incompetent, were nuclear physicists, and the explosive made from uranium?

In 1977, the standard answer to the question, "can terrorists make their own atomic bomb?" was likely "no, it takes another Manhattan Project." Today, the answer is more likely a clear "yes, if somebody gives them uranium or plutonium." Indeed, some of America's deepest strategic thinkers, including former Defense Secretary William Perry and hydrogen bomb designer Richard Garwin, think the probability of a terrorist nuclear explosion is around 20 percent per year. If that is so, it is only a matter of time, and perhaps not very much time.

We ask, "What do we do in the days and years before an attack to discourage terrorists from trying and to deter potential donor states which might provide either the nuclear explosive material or even a complete device?"

During the Cold War, the United States and the Soviet Union understood certain rules of the game, at least after the Cuban Missile Crisis of 1962. A nuclear attack by either country against the other would result in a second strike certain to inflict "unacceptable damage." Deterrence was stable over a wide range of possible scenarios.

In contrast, the kinds of well-funded religious or millennialist terror groups capable of assembling nuclear devices, given the uranium or plutonium, have neither infrastructure nor population that can be threatened by a second strike. The tool of mutual deterrence has been lost. But something remains. Few believe even a group such as al Qaeda or Aum Shinrikyo (which actually tried to create its own Manhattan Project in Australia) will be able to produce its own nuclear explosive material. That material must come from a small, but potentially growing, number of states.

If the donor of the fissile material, or even a complete weapon, could be identified with certainty, a process involving nuclear forensics, appropriate retaliation could be contemplated. And if potential donors knew they would be caught, they might well be deterred from furnishing material to terrorists in the first place. Both uranium-235 and plutonium, as used in nuclear weapons, do contain fingerprints and signatures that can lead back to their origin with fairly high certainty, if not as good as DNA analysis.

Most signatures rely on the fact no sample of material is ever "pure." There are always impurities associated with the mine of origin, the refining, processing and enrichment (or reprocessing of plutonium), and the chemical separation of the fissile metal. These can all be traced and identified, the combination is unique, or nearly so, to the source.

The United States needs to beef up its current program for nuclear attribution and forensics. The national laboratories at Livermore, Calif., and Los Alamos, N.M., need improved facilities, and more people to make major progress. One of the core groups at Lawrence Livermore National Laboratory lacks the funding to keep even its top scientists engaged full-time on forensics. Other groups at both labs are also thin. Without new investment in people and laboratory equipment, the nation will likely lose its ability to attribute nuclear blasts.

It is likely to be necessary to gather the radioactive fallout from a nuclear explosion very quickly and return it to a laboratory within hours before the rarest isotopes decay away. To do so, the United States will need a domestic sampling program using aircraft with sniffers and filters to gather the dust. Probably half a dozen C-130 class planes will do, each prefitted with attachment points, and with roll-on/bolt-on sampling machines that need only be used on a real mission or in training so the aircraft need not be dedicated to the role. It would be appropriate for the Air National Guard to supply both planes and crew.

But all this requires a library of samples from every state that enriches uranium or reprocesses plutonium, regardless of whether they have nuclear weapons or intend to acquire them. This "nuclear type culture collection" should include material from every uranium mine, from every enrichment plant, and from every reprocessing facility. Ideally, samples should be routinely collected after every batch of material passes through the various stages from ore to finished product.

As soon as the samples are collected, they must be characterized in several appropriate labs in a number of states; after an incident is not when to begin sifting through hundreds or thousands of flasks of radioactive material for the first time. The results must be held confidential, because some nuclear weapons information could be contained within a small minority of them. Analyses done both before and after any event will have to be done in a double-blind manner so the labs do not know the origin of the samples, nor even which samples are used as calibration standards, and which are real.

The whole will need to be coordinated by an international body such as the International Atomic Energy Agency (IAEA) or a purpose-built organization. Mohamed ElBaradei, IAEA director general, recently confirmed to us his agency would be willing to coordinate such a project and establish the sample gathering and cataloging system. We believe national laboratories as well as the IAEA's own laboratory in Austria must be involved in the lab work to give any results full credibility.

All this will require an international agreement, a "Prove Innocence Treaty," or PIT, which establishes a nuclear sample library and the organization to run it. We believe virtually all nations will sign up to such a treaty and faithfully adhere to it. After all, in a terrorist nuclear strike, the country that refused to cooperate in advance will be the first suspect.

If a state that supplies nuclear material to terrorists can be identified with reasonable certainty, and if the United States makes clear that state will suffer consequences appropriate to its culpability, we believe some deterrence will be restored to what is now an uncontrolled situation. The nature of the American response must be thought through and be appropriate; it need not be nuclear but can fall anywhere on a broad spectrum.

A country that knowingly and deliberately supplied the material might rate a military response; one that had massive stockpiles of uranium and plutonium, previously under loose controls, might get off more lightly if it could show it sought to recover missing material. There is no reason the United States or other potential victim countries need make public their contemplated reactions in advance, and every reason the potential victims should have well-thought-through contingency plans.

There is another benefit to a PIT. Providing samples to the PIT laboratory system could be written into safeguards agreements that cover states such as Iran that declare they wish to enrich or reprocess nuclear material purely for peaceful purposes.

We have focused on nuclear explosives because they present the greatest threat. But "dirty bombs" are likelier to be used. A broad program of nuclear forensics combined with an appropriate PIT library of samples will help track the perpetrators of a radiological attack.

We believe the risk of a nuclear strike by terrorists is real and think a good system to identify the culprit is the first, essential step toward reducing the prospects of such a catastrophe.

Peter D. Zimmerman, a nuclear physicist is professor of science and security in the War Studies Department of King's College, London, and is the former chief scientist of the Senate Foreign Relations Committee. Hans Binnendijk is the Theodore Roosevelt Chair and founding director of the Center for Technology and National Security Policy at the National Defense University. The opinions expressed are the authors' own and not necessarily those of the United States government or any organizations with which they are affiliated.