George W. Bush & Co., the United Nations, and the world’s nuclear powers all have their underwear in knots about Iran’s nuclear enrichment plans. It’s a serious problem, enough that BushCo is implying it will take military action against Iran if Iran does not immediately cease and desist.
For the physics-challenged, let’s set aside political sabre-rattling for a moment and gloss on the term “uranium enrichment,” to get an idea what all this brouhaha is about.
First, some elementary (ha, ha) details about uranium, number 92 on the periodic table of the elements.
The 92 refers to the number of protons in the uranium nucleus; that is its atomic number. Protons have positive electrical charge, so without some “glue” to keep them confined in the nucleus, they would just fly apart. (Y’know, “opposites attract, and likes repel.”)
Joining the protons in the nucleus are a whole lot of neutrons, which help exert an opposing, attractive force, whimsically called the “strong nuclear force.” The strong force keeps all atomic nuclei (and in fact protons and neutrons individually) in one piece.
But the strong force, like Superman, has a weakness. The strong force only works within a range of about 10-15 meters, which is not coincidentally the approximate size of the typical atomic nucleus.
Uranium’s nucleus, with 92 protons and anywhere from 142 to 146 neutrons churning around in that tiny volume, is just a little too big for the strong force to hold things together. The electrical repulsion of the protons overwhelms the strong force, and the uranium nucleus breaks apart, or decays.
Like all other elements, uranium comes in “flavors” called isotopes. Different isotopes have different numbers of neutrons, but the same number of protons and electrons. Isotopes of a single element have identical chemical behaviors, but different nuclear behaviors.
The two most important isotopes of uranium are U-235 and U-238. Both are radioactive, but of the two, U-235 is more dangerous. It is also quite rare compared to its heavier sibling.
Radioactivity is also called nuclear decay. When U-238 decays, it releases alpha particles. It will continue to decay in this way until there are no U-238 nuclei left, which can take billions of years. It’s a fairly tame process.
U-235, on the other hand, tends to split (fission) into two lighter nuclei and in the process release two neutrons. Since U-235 nuclei have fewer neutrons to strong-arm things together, getting hit by a wandering neutron tends to split the U-235 nucleus apart rather abruptly. That split releases two more neutrons, which then split up two more U-235 nuclei. These two release four neutrons, which split four nuclei, releasing eight neutrons, which split eight nuclei, and so on.
That, friends, is called a chain reaction. If you can reduce the number of neutrons flying around, you can keep the reaction under control. Nuclear scientists call this process “moderating the reaction.”
Uncontrolled chain reactions lead to one of two scenarios: reactor meltdown (the “China syndrome“) or a whopping big explosion. The key ingredient is the percentage of U-235 involved.
Mixtures of about 2% to 3% U-235 and the remainder being U-238 make for relatively safe nuclear power plants. The heat from the fission reactions is used to boil water, to turn turbines that drive electric generators.
Pure U-235, on the other hand, is the devil’s own playtoy. With a sufficient amount (the “critical mass“), about 50 kilograms, you can make a pretty nifty atomic bomb. One A-bomb is enough to wipe out in a few seconds an entire city. The Japanese so far are the only people to have had this experience, in 1945.
If you can make an atomic bomb, with the right know-how and materials, you can also make an exponentially more powerful hydrogen bomb. H-bomb make A-bombs look like firecrackers.
So what does all this radioactive detail have to do with uranium enrichment? Well, U-235 is but the merest fraction of all available uranium. To accumulate U-235, you have to separate the U-235 from the other uranium isotopes in — you guessed it — enrichment facilities.
Now, Iran says that it just wants to build enrichment facilities for its nuclear power program. Perhaps its leaders realize that oil cannot last forever, and golly, it sure would be nice to have some other source of electricity to fall back on when the oil runs out.
The US and the other nuclear powers (which include Israel, btw) are not willing to give Iran the benefit of the doubt, however. The existing nuclear powers suspect Iran may just decide to use its supply of U-235 for bombs, as well as for electricity. Or maybe just for bombs. After all, they did.
[Bombarding U-238 with neutrons, incidentally, creates another bomb-grade material, the artificial element plutonium (Pu-239).]
As the US and the former USSR have demonstrated, once a nation has the capability to make bombs, it’s just a short step to develop the capability of shooting or dropping those bombs wherever they damn well please. For those of us old enough to have lived through the Cold War, the spectre of those bombs falling was enough to scare you shitless, if you dwelled on the issue too long, like longer than five minutes.
Radioactive fallout from A-bomb and H-bomb blasts has this nasty tendency to hang around a long, long time. It gets in the water supply and in vegetation. Fish swim in radioactive water, and concentrate the radioactive isotopes in their bodies. Cattle and other livestock eat the vegetation, and concentrate the radioactive isotopes in their bodies. People eat the fish, the beef, the cheese — well, you get the idea. The results are increased rates of leukemia, cancers and birth defects. For a long, long time.
And those are among the survivors of a bomb blast.
BushCo may be using the Iranian’s uranium plan as a political football, to boost his sagging ratings at home, but the administration has a legitimate worry. As with certain prescription drugs, uranium enrichment can lead to unwanted side effects among some users, including the tendency to make bombs. Results may vary. Consult your doctor.