science, politics, and getting it wrong

One surefire way to panic the heck out of people is to mention nuclear bombs and radical Islam in the same sentence. I dunno about you, but I kinda had a mini-freakout when I read about the amount of enriched uranium the United Nations says that Iran has at its disposal for bomb making. It was hard not to, with the alarming headlines: the LA Times said "IRAN HAS ENOUGH FUEL FOR A NUCLEAR BOMB, REPORT SAYS"; the New York Times was a little more low-key: "IRAN HAS MORE ENRICHED URANIUM THAN THOUGHT." Coupled with our mostly ignorant, media-induced fear of all things Muslim, this was a briefly heart-stopping revelation. But as is true of any story told by any human being, it's the framing that counts. Both reports, in their xenophobia, downplayed the fact that the enriched uranium Iran possesses has only been enriched by 4% (reactor grade), while bomb-worthy uranium must be at least 85% enriched. Even Mother Jones' Kevin Drum was rather alarmist about it, though he at least admits the Iranians have decided both to do less reactor-grade enrichment than they could and not to further enrich what they've got. Then there's the brilliant, anonymous, senior UN official who said ''You have enough atoms' to make a nuclear bomb," according to Drum. Atoms? Huh?

So what does that mean, exactly? How much is "enough" weapons-grade uranium? And how much more work would it be for Iran to enrich that reactor-grade uranium to bomb-making level? And how easy would it be to spot it? Cheryl Rofer over at WhirledView has a great post on most of these questions, in an entry appropriately titled "Whoo-hoo! Atoms of Fissionable Material Everywhere!"

That's right: everywhere.

As Rofer says,

Ah yes. And if you live in Boulder, Colorado, or in Connecticut, or New York City, you have enough U-235 under your house (or perhaps block) to amass a nuclear bomb! Or . . . all that sea water lapping up against the California coast has uranium in it too! I have a call in to the IAEA to inspect your homes!

 Not just random atoms, but enough U-235! Whoa!

Several radioactive isotopes of uranium exist in nature, but in very small concentrations (2-4 parts per million), and decay very slowly. Although U-235 is the only naturally fissile (fissionable by low kinetic energy neutrons) isotope, it occurs in such small concentrations that it's not dangerous. In fact, naturally occurring uranium salts (uranium dioxide), which are a vivid yellow, were frequently added in small amounts to glass to give it a characteristic and unique fluorescence sometimes called Vaseline glass. Yes, it's radioactive, but the radioactivity is approximately equivalent to what occurs naturally in the human body. Even a collector's houseful of it isn't dangerous. And it glows beautifully under black light (UV radiation).

U-238 is also fissionable, but it takes higher energy particles to set it off. It's U-235 that's most often used in weapons. There are some high concentration (up to 70% uranium oxide) ore deposits in Canada, but much of the ore that's mined is low-concentration (0.01 to 0.25%). Once the ore is crushed, leached with acid, and precipitated it becomes something called "yellowcake," which contains at least 75% uranium oxides (see picture at left). Further purification involves halides of uranium (a compound with halogen), which are reduced with alkali earths and by thermal decomposition, or through electrolysis in a molten salt solution. What you're left with at this stage is a quite pure chunk of radioactive metal. This is still not enriched uranium. That's a whole other process.

Enrichment begins with uranium hexafluoride, or "hex" as it's known to the nuke people, obtained by taking yellowcake through a multi-step process that starts with dissolving it in nitric acid and involves further steps with ammonia, reduction with hydrogen, the addition of hydrofluoric acid and finally oxidation with fluorine to produce hex. Hex is highly toxic, violently reactive with water, and corrosive to metals, so if it's going to be enriched it's often stored in glass, in a vacuum, as in the picture at right, where you can see the gray-white crystals it forms at room temperature.

From this stage the hex, at least in Iran and much of U.S., goes to a gas centrifuge, or a "cascade" of centrifuges (left). These aren't the table-top kind you see in a chem lab, though the principle is similar. Heated slightly, the crystalline form of hex, still under vacuum, evaporates and the spinning of the centrifuges separates out the heavier molecules of U-238 and the lighter ones of U-235 until you're left with a very dense heavy metal composed of at least 20% (called weapons-usable) but more often at least 85% (wepons-grade) enriched or highly enriched uranium.

The less enriched the uranium, the higher the critical mass, or gross amount, required to sustain a sufficiently powerful chain reaction. For example, you'd need, at minimum, about 110 lbs. (50-52 kg.) of highly enriched (85%) uranium to arm a nuclear weapon. (The LA Times, I'd like to point out, got this number wrong, mixing kilograms with pounds.) You'd need far more than that of 20% enriched, which would make a very (physically) large (even though the payload is small), very crude bomb unless constructed with sophisticated techniques, all of which are classified by experienced bomb-making nations, and most of all, extremely costly. (Remember, it was, in part, the cost of the nuclear arms race that toppled the U.S.S.R.)

According to the UN report, Iran has approximately 2,200 lbs. of low enriched uranium (LEU). It takes approximately 2,200-3,700 lbs. of LEU to make enough Highly Enriched Uranium (HEU) for one bomb. Although Iran now has enough LEU for the task, it does not yet have the facilities to do so, a fact the doesn't appear in either story until well down the page. It would take more high-speed centrifuge cascades than are currently online or in the works, not to mention an actual bomb-construction facility. Although Iran has barred UN inspectors from some of its facilities (claiming that none are currently ready to receive nuclear material and thus not subject to inspection), satellite imagery would surely spot any new facilities constructed for bomb-making purposes.

It's hard to say what any individual's intentions are, let alone a whole nation's. But it also doesn't help to scare monger with misleadingly constructed news reports that make it sound as if Iran has plenty of weapons-grade uranium at its disposal. It doesn't; nor does it seem to be interested in producing any. The biggest issue, in other words, is not the uranium Iran has declared, but the uranium the U.N. Security Council doesn't know about—if there is any. Sound familiar? Weapons of Mass Destruction, anyone?  We jumped to disastrous conclusions with Iraq; it would be wise not to do the same thing with Iran.

You can read the 5-page report to the Security Council here. It's worth the time to get the straight story without the media frame.

[Hat-tip to Will Shetterly for drawing my attention to this factual distortion.]

Comments

[Donncha]

When you hear "Iran has this, Iran has that" I think it's important to count on one hand the number of wars started by Iran in the last few hundred years, and on the other count the number of times we (the west) have started a war with Iran.

Then figure out where the likely problem is.

[Juan Nunez-Iglesias]

What a great post. Even the Economist, a usually excellent publication, engages in scaremongering about Iran. Is it really possible that people will forget the lessons of Iraq even before that war is over?

[CCPhysicist]

Mmmmm, Yellowcake.

There is uranium, enriched uranium, and highly enriched uranium, as you point out. People with an agenda will deliberately confuse "enriched" with "highly enriched" to feed on the ignorance you address here. I don't know the actual numbers for those two "enriched" categories, but, roughly speaking, the step from 0.7% to 3% is smaller than the step from 3% to 9x%. However, once you have the ore and the enrichment technology, the only other ingredient you need is time and money.

And after that investment you have one bomb, just enough to irritate someone who probably has a few hundred, or someone we know has a several thousand, without changing much of anything. Ask India and Pakistan how their weapons programs have helped resolve the situation in Kashmir.

If Iran wants to recreate the Persian Empire, is this likely to work?