 Very small pure samples of 234U can be extracted via the chemical ion-exchange process - from samples of plutonium-238 that have been aged somewhat to allow some decay to 234U via alpha emission.Enriched uranium contains more 234U than natural uranium as a byproduct of the uranium enrichment process aimed at obtaining uranium-235, which concentrates lighter isotopes even more strongly than it does 235U.IAEA research paper TECDOC-1529 concludes the 234U content of enriched fuel is directly proportional to the degree of 235U—enrichment with 2% 235U resulting in 150 g 234U/tonHM, and the most common 4.5% 235U enrichment resulting in 400 g 234U/tonHM.