Running on natural uranium, they start-up with the U235 in it, but during the cycle between fwo refuelling, they do turn a lot of the u238 in p239 (that's called having a "high breeding ratio", all reactors have a breeding ratio, they're not call breeders unless it's >1, self-sustained cycles if ~1, and vanilla if <1. In a PWR, something like 25% of the energy at the end of the life of the rods is from p239=from the original u238. The future EPR will have a breeding ratio of 0.7, so it will be even higher than that.)

Candu reactors have high breeding ratios with uranium and thorium, unfortunately the uranium side makes them proliferation friendly (I have a canadian science paper on this I should deconstruct one day).

Pierre

True.

guaranteed to evoke a violent reaction from police is to challenge their right to "define the situation." --- David Graeber citing Marc Cooper