Shit’s heating up with Iran. There’s an intended pun here, since the news of the day is the IAEA (the ‘nuclear watchdog’ arm of the UN) claims it can confirm that Iran is enriching uranium at up to 20% at a heavily guarded underground bunker. According to the IAEA’s own report from last November (pdf here), this was all according to plan and was reported to the IAEA in June of 2011. So the fuss appears to be that it is actually happening, and predictably the fuss is a loud one from typical hypocritical whiners like the US about how “this means Iran’s building a bomb which will destabilize the region and oh mercy won’t somebody think of the children.”
(To make my point, it’s time for an aside for those unfamiliar or curious, as I was, about uranium enrichment and its role in making deadly weapons. If you are already an expert on these subjects, then please skip to the close parenthesis.
Recall from high school chemistry that all matter is composed of atoms, each of which in turn contains a nucleus at its center made up of electrically neutral neutrons and positively charged protons. These nuclei are stable against the incredibly repulsive force of those protons through a medium called the strong nuclear force [clever!], but for very heavy nuclei — those containing lots of protons and neutrons — the strong nuclear force could be subverted by the weak nuclear force [yay!] if only there were a little energy to get those protons ‘over the hump’ as it were. This would cause the nucleus to split into two [sometimes three] pieces, thereby releasing all that energy the strong force was keeping pent up, in a process called fission.
The famous Manhattan Project was commissioned during the second world war in order to kill unsuspecting Japanese civilians by finding a way to unleash this explosive force on command. The idea was to get a lot of these heavy nuclei together and hit them with something. More precisely, certain nuclei are unstable enough that if you hit them with a neutron, they will split apart into two smaller nuclei, some extra free neutrons, and a fair amount of energy. Those neutrons hit other unstable nuclei, and before you know it, you have an explosive chain reaction.
It turns out a good choice for the heavy nuclei are a particular isotope of uranium, U-235. You hit one with a neutron, it becomes U-236 just long enough to break apart in a shower of smaller nuclei, neutrons, heat, and light. The problem is that the vast majority of uranium on earth is a much less radioactive (and hence less unstable) isotope, U-238. Wikipedia says U-238 is about 140 times more abundant, and that’s saying something since there isn’t much of that lying around either. While radioactive, you just can’t get the chain reaction with this heavier stuff. To make matters worse, it’s pretty much all mixed together: there aren’t chunks of pure U-235 conveniently scattered about the New Mexico desert. So what did those clever Manhattan Project scientists do? Basically, they devised elaborate techniques to ‘enrich’ the uranium, or in other words to toss the U-238 and keep the U-235.)
But now let’s consider the hype. The same wiki article linked above and quoted below indicates that commercial nuclear reactors often use uranium enriched to between 3 and 5% U-235, while noting that ‘research reactors’ — so called for their use in producing radioisotopes for medical research and treatment, among other things — can use enrichments as high as 19.75%. Indeed, the 20% number bandied about so hysterically is a threshold between Low Enriched Uranium (LEU) and High Enriched Uranium (HEU). Apparently a ‘crude weapon’ could be fashioned with the best LEU, but ‘usually’ weapons-grade uranium is 85% HEU or better; Little Boy of Hiroshima fame was 80%, and that bomb was crude compared to today’s standards. The nuclear cores of atomic submarines usually contain ‘at least 50%.’ Perhaps most tellingly, modern US nuclear weapons are comprised of two stages: the first is a different nuclear fuel, Plutonium-239, to create an initial nuclear explosion, which then sets off a chain reaction in a 40-80% HEU core. Even with bottomless pockets funding a half century of research and development to create a two-staged nuclear explosive, we still need to enrich that stuff so that the concentration of U-235 is at least 50 times higher than in nature. The best Iran is talking about now is only half that concentration.
Could Iran use this uranium they are enriching to create a nuclear bomb? Probably, but only a very crude one. But could uranium enriched to that purity also have legitimate non-WMD purposes, like what Iran has been saying all along? I believe so, based on a cursory investigation into the nature and uses of enrichment. And all this is a totally separate question to whether Iran would dare use a nuclear bomb even if they could make one. There is a lot more to say about the present situation with Iran, and I plan to say at least some of it soon, but the fuss about enrichment activities is clearly less about safety or stability and more about regional control and possibly even warmongering jingoism. Look out below?