2Why Separate? Must Separate Lighter U235 from U238 Only U235 is fissionableNecessary to produce reactor fuel which is 3.6% U235Weapons grade is 90% U235Lead container supposedly containing stolen weapons grade UraniumBillet of highly enriched U235
3Uranium Enrichment Centrifuges Uses UF6 gas (Uranium Hexafluoride)Solid UF6 in vial
4How Gas Centrifuge Works Originally developed in Russia by Austrian scientist
5Gas Centrifuge Details The centrifugal forces push the heavier uranium 238 (U-238) closer to the wall of the rotor than the lighter U-235.The gas closer to the wall becomes depleted in U-235 whereas the gas nearer the rotor axis is enriched in U-235.The arrows in the first illustration depict the gas flowing within the rotor.The gas flow can be produced by a temperature gradient over the length of the centrifuge. UF6 depleted in U-235 flows upwards adjacent to the rotor wall, while UF6 enriched in U-235 flows downwards close to the axis. The two gas streams are removed through small scooped pipes, called "scoops."
6Spin 50,000 to 70,000 RPMOn magnetic bearingsRun ten years without attentionLow power useGive 1,000,000 g’s10 to 20 stage cascade needed to get 3.6% U235 from 0.7% natural occurring
8Gaseous Diffusion Process Passes UF6 gas repeatedly through porous barriers with very tiny holes barely big enough for a molecule to squeeze throughLighter U235 squeezes through more easilyPaducah, Kentucky Gaseous Diffusion Plant
11More On Gaseous Diffusion Original process used in WWII at Oak Ridge, Tenn. facilityMuch more expensive to operate than centrifugesNeeds up to 1400 stages to get reactor grade fuelOak Ridge K25 plant begun in 1943