Uranium-234

Infobox isotope


background = #fc6
text_color =
isotope_name = Uranium-234
isotope_filename =
alternate_names =
mass_number =234
symbol =U
num_neutrons =142
num_protons =92
abundance =0.0055%
halflife =246,000 years
error_halflife =
decay_product = Thorium-230
decay_mass =230
decay_symbol =Th
parent = Plutonium-238
parent_mass =238
parent_symbol =Pu
parent_decay = a
parent2 = Protactinium-234
parent2_mass = 234
parent2_symbol = Pa
parent2_decay = b-
parent3 = Neptunium-234
parent3_mass = 234
parent3_symbol = Np
parent3_decay = b+
mass =
spin =
excess_energy =
error1 =
binding_energy =
error2 =
decay_mode1 =Alpha decay
decay_energy1 =
decay_mode2 =
decay_energy2 =
decay_mode3 =
decay_energy3 =
decay_mode4 =
decay_energy4 = Uranium-234 is an isotope of Uranium. In natural uranium and uranium ore, ²³⁴U occurs as an indirect decay product of ²³⁸U, but it makes up only 0.0055% of the raw uranium because its half-life of just 246,000 years is only about 1/18,000 as long as the half-life of ²³⁸U.

Large-scale extraction of ²³⁴U from natural uranium would only be feasible by isotope separation similar to that used for uranium enrichment, and there is no industrial demand for isolating U-234. Pure samples of 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 as a side-effect of enrichment for U-235, which concentrates lighter isotopes even more. The increased level of U-234 in enriched natural uranium is acceptable in current nuclear reactors but re-enriched reprocessed uranium may contain higher levels which are undesirable.

²³⁴U has a neutron absorption cross section of 100 barns for thermal neutrons, and 700 barns for resonance integral, an average over neutrons of various intermediate energies. Hence, in a thermal reactor, it is converted to fissile ²³⁵U at a faster rate than the much larger amount of ²³⁸U (with an absorption cross section of 2.7) is converted to ²³⁹Pu. Thus spent nuclear fuel should contain only some of the ²³⁴U that was in the fresh fuel.

Depleted uranium contains much less U-234 (around 0.001% [ [http://www.who.int/mediacentre/factsheets/fs257/en/ WHO | Depleted uranium] ] ) which makes the radioactivity of depleted uranium about one-half of that of natural uranium, since natural uranium has an "equilibrium" concentration of ²³⁴U, and therefore an equal number of decays of ²³⁸U and ²³⁴U will occur. Depleted uranium also contains less U-235, but in spite of its half-life which is shorter than U-238's, the concentration of U-235 in natural uranium is low enough so that the U-235 depletion does not result in a significant reduction in radioactivity.

Isotope|element=Uranium
lighter=Uranium-233
heavier=Uranium-235
before=Plutonium-238 (α)
Protactinium-234 (β-)
Neptunium-234 "'(β+)
after=Thorium-230 "'(α)

ee also

*Uranium-uranium dating

References