U-235 Enrichment
Rate U-235/238= (352/349)0.5= 1.004
The enrichment after n diffusion barriers is (1.004)n
Minimum amount of U-235 needed in LWR is 2.1% (3x more concentrated than in natural form)
(1.004)263=3 or 263 diffusion stages needed
Enrichment is an expensive process
Large amount of energy is needed to push the UF6 through so many barriers