Uranium-234
alpha emission 4.8 | | |
| Isotopes of uranium Complete table of nuclides | ||
Uranium-234 (234U or U-234) is an
thorium-234. Next, with a short half-life, 234Th nuclei emit a beta particle to become protactinium-234 (234Pa), or more likely a nuclear isomer
denoted 234mPa. Finally, 234Pa or 234mPa nuclei emit another beta particle to become 234U nuclei.
Uranium-234 nuclei decay by
alpha emission to thorium-230, except for the tiny fraction (parts per billion) of nuclei that undergo spontaneous fission
.
Extraction of rather small amounts of 234U from natural uranium would be feasible using
alpha emission
.
fissile, it tends to absorb slow neutrons in a nuclear reactor breeding 235U. This is much more efficient than the series of steps 238U + n → 239Np → 239Pu
in replacing fissile isotope consumption.
Uranium-234 has a
neptunium-239) because 238U has a much smaller neutron-capture cross section of just 2.7 barns. In the reaction 234U + n → 235U reaction, the 234U content of 4.5% enriched fuel drops steadily over the irradiation period falling from 450g/ton HM to 205g/ton HM in fuel with an irradiation of 60GWd/ton HM.[2]
Additionally, (n, 2n) reactions with fast neutrons also convert small amounts of 235U to 234U. This is countered by the rapid conversion of available 234U into 235U through
parts per million, a higher fraction than in natural uranium's 55 parts per million. Depleted uranium separated during the enrichment process contains much less 234U (around 0.001%[3]
), which makes the radioactivity of depleted uranium about half of that of natural uranium. Natural uranium has an "equilibrium" concentration of 234U—the point at which an equal number of decays of 238U and 234U will occur.
U234 as well as U232 are common byproducts in reactors breeding Thorium 232 into U233, with Protactinium 233 as an intermediate step.
See also
References
- ^ "Management of Reprocessed Uranium" (PDF). Retrieved 2024-01-24.
- ^ "U234 Irridiation Graph" (PNG).
- ^ WHO | Depleted uranium Archived August 15, 2012, at the Wayback Machine