What is yellowcake, anyway?

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July 18 2003 5:05 PM

What Is Yellowcake, Anyway?

Milled uranium oxide, yours for $10.90 a pound.

CIA Director George Tenet testified  Wednesday before a Senate panel that's looking into why the agency initially believed a fishy report that Iraq had tried to buy 500 metric tons of uranium "yellowcake." What is yellowcake, exactly?

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Yellowcake is milled uranium oxide, known to chemists as U3O8. When uranium ore comes out of the mine, it actually contains fairly little of the precious radioactive element. Though some mines in Canada, the world's leading uranium producer, are now yielding ore that contains 20 percent uranium, lower purity levels are more typical. Ore that contains less than 1 percent uranium is not unusual.

The milling process gets rid of the useless minerals that dominate the ore. First, raw ore is passed through a series of industrial-sized crushers and grinders. The resulting "pulped" ore is then bathed in sulphuric acid, a process which leaches out the uranium. After some drying and filtering, the end product is yellowcake: a coarse, oxidized powder that is often yellow in color but can also have a red or gray tint, depending on the number and type of impurities that may remain. Ideally, a drum of yellowcake should wind up looking something like this.

Yellowcake is a first step toward enriched uranium, but it's a long way from being weapons-grade. The powder must still be converted into uranium hexafluoride before it can be enriched, the process that makes the sort of uranium used by nuclear power plants and bomb-makers alike. Because UF6 can be easily turned into a gas, it is ideal for enrichment, which must be done in a gaseous state.

Despite all the hubbub over Saddam Hussein's efforts to buy yellowcake, the stuff is by no means a rare commodity. Worldwide production is currently around 64,000 tons per year, and that's sure to rise as Central Asian nations like Kazakhstan begin to expand their uranium-mining industries. (By comparison, about 45,000 tons of tungsten, vital to the steel industry, is produced annually.) The competition has depressed yellowcake prices just a tad in recent months; a pound now costs about $10.90, down a dime from what it was trading for this spring.

Explainer thanks Matthew Bunn of HarvardUniversity.

Brendan I. Koerner is a contributing editor at Wired and a columnist for Gizmodo. His first book, Now the Hell Will Start, is out now.

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