Isotopic+Ratio+of+Natural+Uranium

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Natural uranium consists of three isotopes: 238 U (99,275 %), 235 U (0,720 %) and 234 U (0,0055 %). Isotopes 238 U and 235 U are the starting nuclides of two natural decay series, the uranium and actinium series, respectively. 234 U in turn belongs to the uranium series as 238 U decays through 234 Th and 234 Pa to 234 U. All uranium isotopes are alpha emitters and their activities and isotope ratios can be measured by alpha spectrometry and also by mass spectrometry. The mass fraction of 238 U in uranium is highest (99.3%) and lowest for 234 U (0.006%). The 235 U to 238 U ratio in natural samples is almost always constant while the 234 U to 238 U ratio varies due to fractionation as a consequence of the recoil energy that 234 U receives in radioactive decay. Thus, the 234 U/ 238 U activity ratio in ground waters is often higher than one though the ratio in rock is one due isotopic equilibrium.


 * Isotope || Half-Life (y) || Alpha Energy (MeV) || Mass-% ||
 * 238 U || 4.47 •10 9 || 4.20 || 99.275 ||
 * 234 U || 2.47 • 10 5 || 4.78 || 0.0055 ||
 * 235 U || 7.04 • 10 8 || 4.40 || 0.270 ||
 * 232 U || 68.9 || 5.32 ||  ||