Iran and "the bomb": while Iran does appear to have the uranium-enrichment capability needed to make an atomic bomb, that is not the same as having a bomb and being able to deliver it.

Does Iran have the atomic bomb? If so, how many? Are they deliverable? If not, is Iran attempting to build them? How close to completion are they? What are plans for the reactor complex at Bushehr? And what's going on Natanz?

Just like Colonel Sanders and those 11 herbs and spices, the government of the Islamic Republic of Iran doesn't want us to know. They understand the poker players' credo: it's often not what you're holding, but what others think you're holding that counts.

What can an interested and concerned private citizen do to be as informed as possible? I would suggest understanding something about the mechanics of nuclear weapons, seeking out truthful clues as to what is going on in Iran, and applying logic to reach a conclusion.

Not a Simple Task

One of the wisest things the Creator of the universe did was to make atomic bombs difficult to construct. A description of this complexity is spelled out in magnificent detail in Richard Rhodes' The Making of the Atomic Bomb. While most of the heavy lifting was done by the United States during the forties, bomb construction remains anything but simple.

Most of us are aware that chain reactions occur in our nuclear power plants. Simply put, when an atom of uranium fissions, i.e. disintegrates, it expels on average two high-energy neutrons. If one of these is absorbed by exactly one other atom causing it also to disintegrate, the "chain reaction" is termed "critical." In U.S. power reactors, water is used to slow down the neutrons so that they can be effectively captured by the uranium nuclei and this process can proceed. If the coolant water heats up appreciably, the reaction rate slows down because the neutrons are not slowed down as much. Alternatively, if the water cools down, the reaction rate increases. In other words, the system is self-regulated. Lose the coolant water and the reaction automatically stops.

Atomic bombs reverse these principles. First, they must be constructed from "bomb grade" material. Not all uranium atoms are fissile, only those of the [U.sup.235] isotope. In nature only 0.7 percent of uranium is [U.sup.235]. For a nuclear weapon, uranium must be enriched to 90 percent of the isotope. By comparison, uranium fuel for a nuclear power plant is enriched to only 3.5 percent [U.sup.235]. Even with bomb-grade uranium, the atomic explosion will occur only if the sub-critical elements of the bomb are held together for several microseconds against the burgeoning force of the reaction.

The Hiroshima bomb, Little Boy, was a "gun-type" device built from enriched uranium. Two or more sub-critical masses were fired together like opposing projectiles to obtain the critical mass. It was deployed without ever being tested, and for good reason: that's all the enriched [U.sup.235] the United States had.

The first test bomb--deemed "the gadget" by the Los Alamos scientists--and the Nagasaki bomb were both plutonium "implosion" devices that required a great deal more sophistication to construct than a uranium bomb. First, there is no plutonium found in nature--bomb-grade plutonium must be produced in a reactor specifically designed for that purpose. Power reactors do indeed produce plutonium in the course of their operation, but while transmuting [U.sup.238] to [Pu.sup.239], the fissile plutonium isotope, about 20-25 percent of the plutonium absorbs an extra neutron, making it [Pu.sup.240], an isotope known to be a "spontaneous neutron emitter." When the plutonium [Pu.sup.239]/[Pu.sup.240] mix consists of more than 12 percent [Pu.sup.240], the [Pu.sup.240] produces too many "early" neutrons to allow the nuclear explosion to take place on the rigid timetable it must follow to become an effective bomb.

But even with a reactor designed to produce bomb-grade plutonium, there are other difficulties in producing a plutonium weapon. One of these is separating the one to two percent [Pu.sup.239] from the roughly 95 percent uranium and the zoo of highly radioactive waste products from the plutonium breeding process. Making the plutonium bomb-building process especially difficult is the problem that Rhodes cites as the most difficult task in the Manhattan Project from the scientists' perspective: taking a hollow sphere of plutonium, crushing its 30 pounds into a softball sized compacted sphere, and releasing a stream of neutrons within it on a timetable of a few microseconds.

Wrath of (A.Q.) Khan

Is Iran trying to build a plutonium bomb? To do so they would need a functional reactor, which at present they do not have. A "two-reactor complex" at Bushehr, started by the Germans in the 1970s, was subsequently abandoned. In the mid-1990s, a deal was struck with the Russians to complete one of the Bushehr reactors but since then the planned 2004 completion date has been pushed out till at least the end of this year. While this reactor could be used to breed weapons-grade plutonium by replacing the fuel every couple of months instead of on a three- or four-year cycle, this would be a long-term process requiring several years. In addition, Iran would need a sophisticated separation facility to extract the plutonium. For now we can discount a plutonium device, unless furnished to Iran by another nuclear club member.

If Iran is pursuing a uranium weapon, the biggest technological problem by far is separating and purifying the tiny percentage of the fissile [U.sup.235] isotope found in uranium ore in order to obtain bomb-grade uranium enriched to 90 percent [U.sup.235]. After WWII, Dr. Gernot Zippe, a German scientist, captured by the Russians, developed an efficient centrifuge for enriching uranium that was superior to the membrane diffusion methods used in the Manhattan Project. Known as the P-1 centrifuge, the plans were stolen by a Pakistani metallurgist, A.Q. Kahn. By 1998, Pakistan was able to test several reportedly sophisticated nuclear devices thanks to Kahn's duplicity. He appears to have or have had relationships with Iran, Iraq, and North Korea as well.

In February 2003, IAEA found a "cascade," consisting of 165 centrifuges, at Iran's Natanz facility, along with parts for another 1,000 machines. What does this mean in terms of Iran's ability to build a uranium bomb?

We know that it takes about 50 kilograms (110 pounds) of 90 percent enriched uranium to build a gun-type weapon equivalent to the Hiroshima bomb. Such a bomb would be large, weighing several tons, and Iran has no known system for delivering it. (The proverbial "suitcase bomb" would be of the plutonium implosion type that, by nature of the isotope, has a much smaller critical mass.)

The already-existing P-1 cascade would take about five years to produce sufficient [U.sup.235] once the uranium was added (at the time of the inspection, there was no uranium in the centrifuges). But the House Committee on International Relations and some non-governmental organizations have reported the construction of a pilot plant near Natanz with 1,000 centrifuges. In addition, aerial photos appear to outline a large underground facility--under construction for at least three years--with room for 50,000 centrifuges.

To enrich the uranium in a centrifuge, refined uranium ore, known as yellowcake, would need to be processed at a specially built facility. The ore must be dissolved in hydrofluoric acid with some fluorine gas added to form uranium hexafluoride--a strange compound that sublimes (goes from a solid to a gas like "dry ice") at around 150[degrees]F. It is nasty, corrosive stuff, and a facility to process it would take some time to build.

Once the component materials for a uranium bomb are gathered, making a uranium device is rather easy. While having uranium-enrichment capability is not the same as having bombs, it is quite possible that Iran is well on its way.

Ed Hiserodt is the author of Under-Exposed: What If Radiation Is Really Good for You?