[CraigD]

Originally Posted by freeztar

So what about the U-235 Craig brought up?

Uranium is found in nature in various forms, mostly as and . 99.2742% of the uranium is the isotope U-238, 0.7204% U-235. To get a useful fuel for a conventional fission reactor, these two isotopes are partially separated, usually by spinning them in powerful centrifuges to an ‘enriched” concentration as low as 1% U-235, typically 3 to 5%, or in the case of weapons and high-performance reactors, as high as 90%. The by product is depleted uranium, which typically has less than 0.2% U-235.

Originally Posted by freeztar

In the wiki article I linked to in my last post, it says that the U-238 is converted into Plutonium-239. Is that a typo?

Here’s the neutron capture and decay chain by which U-238 in a breeder reactor is transmuted into Pu-239:
U-238(92p +146n) +1n -> U-239(92p +137n) -> Np-239(93p +136n) -> Pu-239(94p +135n)

The half lives of U-239 and Np-239 are about 2.355 and 2.117 days, respectively, so this is a fairly fast chain. The difference in mass is about .0021299 AMU, so it’s about 84 times less energetic than U-235 +1n fission.

All of this is common information, available from wikipedia and many other sources, though it takes a bit of digging to put it all together. I’ve been putting together my own enhanced periodic table database tool for the past year, which helps in digging up the data without having to click, copy and paste across a gaggle of webpages.