Uranium-234

Uranium-234 is an isotope of Uranium. In natural uranium, 234U occurs as the decay product of 238U, but makes up only 0.0055% of the uranium because its halflife of 246,000 years is only about 1/18,000 as long as the halflife of 238U.

Extraction of 234U from natural uranium is not feasible. Pure U-234 can be extracted (by ion exchange) from pure plutonium-238 which has been aged to allow some of it to decay to 234U.

Enriched uranium contains more U-234 than natural uranium; this is a side effect of enrichment for U-235, which concentrates even lighter isotopes even more, and does not bring any benefit. Similarly, depleted uranium contains much less U-234 (around 0.001% ) which makes its radioactivity slightly more than half that of natural uranium, since natural uranium has an equilibrium concentration of 234U and therefore an equal number of decays of 238U and 234U.

234U has neutron absorption cross sections of 100 barns thermal, 700 resonance integral; thus in a thermal reactor, it is converted to fissile 235U at a faster rate than the much larger amount of 238U, with absorption cross section of 2.68, is converted to 239Pu; thus spent nuclear fuel should have around half or less of the 234U that was in the fresh fuel.