A Primer On Nuclear Enrichment

All Things Considered:

Most uranium is useless for nuclear fuel or weapons. Less than 1 percent of it is the light, radioactive isotope uranium-235 that's used for power plants and bombs.
But if you gasify uranium with fluorine and put it in a rapidly spinning centrifuge, you can separate the nuclear wheat from the chaff. As the centrifuge spins, the heavier, nonradioactive U-238 moves to the centrifuge wall, while the U-235 moves toward the center, explains Houston Wood, a University of Virginia engineering professor who worked on gas centrifuges at the U.S. Department of Energy.
Ultimately, two streams are removed: one of enriched U-235, the second depleted in U-235. And when you take the material that has more 235 and conduct the process over and over again, you eventually get uranium that is 90 percent U-235: weapons-grade uranium.
Getting that weapons-grade product takes thousands of centrifuges, spinning as quickly as possible and arranged in what's called a cascade.
How fast they can go depends on what they're made of. An aluminum centrifuge can only spin at about 350 meters per second before it bursts, explains Wood. Another material, maraging steel, can spin at 450 meters per second.
Even more appealing is carbon fiber, used to make products like golf club shafts and bicycle frames. Centrifuges made of carbon fiber can reach speeds of 1,000 meters per second.
That's where the game of nuclear "keep away" comes in. Much of the global effort is aimed at blocking Iran from getting the highly specialized materials needed to make those fast-spinning centrifuges.

I had never heard of maranging steel.  Pretty cool stuff.