It has now been confirmed that Iraq has indeed received massive shipments of uranium, as alleged by the United States, and as previously only supported by forged documents. According to reports, up to 2,000 tons have been delivered, and this number does not even include the at least 230 tons delivered as early as 1991.
This revelation is all the more interesting when you consider the unlikely source for these huge shipments, none other than the United States military itself. Delivery has taken place using millions of depleted uranium shells that were used against Iraqi targets.
Depleted uranium, or simply "DU," is a by-product of the uranium enrichment process, where uranium is prepared for usage in nuclear reactors or atomic bombs. In depleted uranium, the amount of the fissile isotope, U-235, is reduced in comparison to natural uranium. There is no difference in chemical properties between natural uranium, enriched uranium and depleted uranium. All are mildly radioactive.
Depleted uranium has three properties that make it very attractive for military use. First, uranium has a high density of 19.07 grams per cubic centimeter, twice the density of lead. This means that a uranium projectile of the same mass is only half as large as a lead projetile, concentrating the kinetic energy upon impact on a smaller area, allowing uranium shells to better penetrate the enemy's armor. The second property is its flammability. Like very fine iron dust, uranium can spontaneously ignite and then burn at high temperatures of above 6,000 degrees celsius. And the third welcome property is that DU is dirt cheap, as it is essentially a waste material from the production of enriched uranium with little civilian use other than counterweights.
Natural uranium is a mix of three major isotopes, U-238 (99.2%), U-235 (0.7%) and U-234 (0.05%). For use reactors or bombs, uranium has to be enriched, meaning the concentration of the fissible U-235 isotope. Nuclear reactors require a concentration of at least 3% U-235, while the isotope must be as pure as possible for use in an atomic bomb. During the enrichment process, uranium is separated into amounts with higher and lesser U-235 content. The result is enriched uranium on one side and depleted uranium on the other. Depleted uranium contains about 99.8% of U-238, 0.2% of U-235 and 0.01% of U-234. All isotopes are radioactive, but U-234, despite its small quantity, is the most worrying because of its short half life.
Usage of DU munition is highly controversial because of its potential health hazards. When a projectile hits armor, it evaporates and incinerates. The resulting uranium oxide dust can travel for miles and miles, spread by the wind, where it is inhaled not only by soldiers on the battlefield but also by civilians. Within the body, alpha radiation can affect the human body directly - a hazard that does not exist in storage, where alpha radiation cannot penetrate the shell's case.
Opponents go as far as calling DU illegal, and its usage in Iraq a war crime. There are reports of increased cancer rates and birth defects in Iraq, and some consider the exposure to uranium dust a factor in the still-mysterious balkan syndrome and gulf war syndrome (US troops also used DU munition in the Kosovo conflict and in the 1991 gulf war). Some case studies are consistent with high radiation exposure. So far, the United States military flatly refused to consider DU as a factor, presenting reports that quote the harmlessnes of (non-vaporized) depleted uranium and the general lack of scientific research. For the same reasons, the United States refuses considering decontamination.
But even without radiological and toxicological concerns, there is a possible frightening twist to the story.
In its war against terrorism, the United States constantly scares the public with images of terrorists detonating an atomic bomb within an american city. In order to protect against that scenario, New York City goes as far as installing radiation detectors in its subways, with sometimes not-so-funny side effects.
Terrorists face three problems in building an atomic bomb: acquiring uranium or plutonium, enriching it, and then building a bomb.
The last step turns out to be easiest, as the principles of nuclear weapon design are well-known. In the "gun design" that worked so well on Hiroshima, one sub-critical piece of U-235 is simply fired with into another sub-critical piece of U-235 at high velocity, combining to a critical mass. Anybody with a solid background in physics (such as a Ph.D. from a western university) and access to a good scientific library can figure this out and even take steps in optimizing the design.
The second step of bomb building, enriching uranium into as-pure-as-possible fissible U-235, is more difficult. In addition to the prerequisites already mentioned (a Ph.D. and some books), this requires sophisticated equipment. The process of enriching uranium is is well-documented and simple in theory: the fact that U-235 is lighter than the U-238 isotope can be used to separate the two isotopes. In gaseous form (by reacting with fluor to uranium hexafluoride), separation can be achieved using diffusion or centrifugal force. Repeat that step often enough, and U-235 starts to accumulate.
But in practice, the enrichment process is difficult, tedious, and time consuming, as the difference in molecular weight between U235F6 and U238F6 is minimal. It's a high-technology process that requires advanced laboratory equipment.
Gas centrifuges are on export control lists. So it is not easy for a potential terrorist to shop around, but with the asserted background in physics, accessible litereature, engineering expertise, it would be possible to create the required equipment from scratch. It's not a school lab project, but it would be achievable with a small number of dedicated people, given time and unlimited funding.
However, potential terrorists face a problem starting with the first step, the acquisition of uranium. Assuming that there is some sanity left in the world, they will not be able to actually purchase uranium. However, purchase is not the only option. Uranium is actually a very common element, about 50 times more common than gold. It is present in soil all over the world, at an average concentration of 3 grams per ton. Terrorists can start mining uranium by digging up their back yard. A higher concentration of uranium is found in uranium ore mines, but terrorists don't have access to mines and would be very lucky indeed to find a higher-than average uranium concentration in their back yard. In any case, it is not that easy to extract uranium. They would also require enormous amounts of crude soil, an industrial-size mine and processing plant. That would hardly go unnoticed for the years it would take to mine and extract sufficient quantities. Even in remote areas, mine and plant would be spotted easily enough by satellites.
So in the past, access to uranium was too difficult for terrorists to contemplate.
But after the two gulf wars, all they have to do is to walk around battlefields in Iraq with a Geiger counter, and pick it off the ground. Munition that actually hit a target will be impossible to retrieve, but it is a good assumption that most shells missed their targets and were left in the sand. Hundreds of pristine shells will we within easy distance of each killed Iraqi tank.
Do the math: if the US expended 2000 tons of depleted uranium, that makes, at a concentration of 0.2%, 4,000 kilograms of pure U-235. The bomb that was dropped on Hiroshima contained about 25 kilograms U-235. Experts estimate that modern atomic weapons can be built with as little as one kilogram, using sophisticated conventional detonators to compress a uranium core into a critical mass. These advanced weapons require knowledge and research that is out of reach for terrorist organizations, so 25 kilograms can be considered the least amount these terrorists would need. But even after considering that it is impossible to pick up all 2000 tons of expended munition or even a sizable fraction of it, and also considering that it is impossible to extract all U-235 from depleted uranium, there is a wide margin to produce enough material for a single warhead.
By taking the first factor, the acquisition of uranium, out of the equasion, production of an atomic bomb has become much more feasible. The mining of uranium from natural sources is basically an impossibility for any terrorist organization. Enrichment, however, is just a matter of application of science. It would take time, money, knowledge, effort and experimentation, but it is certainly not impossible.
But yet all of the above considers the worst case, of terrorists spending years of lab work and hundreds of thousands of dollars on equipment in order to develop an atomic bomb.
The low-tech "mass-disruptive" way would be much easier indeed, requiring some effort but zilch expertise and no knowledge at all. (In fact, it's beneficial to have no knowledge of the radiation risks.) All terrorists have to do is to pick up as little as 10 kilograms of depleted uranium shells. They do not need to enrich it, only to grind it into fine dust. Combined with a conventional detonator, depleted uranium dust would make a "terrific" dirty bomb if detonated in any major city, requiring at least temporary evacuation and costly cleanups.
Thanks to the United States, the world is a much safer place indeed. Or is it?
First published on April 19, 2003. This essay represents nothing but my personal opinion. Please feel free to distribute the text, or to link to it.
Frank Pilhofer <fp -AT- fpx.de> Back to the Homepage Last modified: Tue Apr 29 19:18:26 2003