The Uranium 234 Content of Natural Uranium and the Specific Alpha-Activities of the Isotopes

The uranium 234 content of natural uranium was determined, by a combination of alpha-counting and mass spectrometer techniques, to be 0.005481\ifmmode\pm\else\textpm\fi{}0.000012 weight percent, the precision being expressed on the basis of 95 percent probability. This corresponds to a half-life of (2.522\ifmmode\pm\else\textpm\fi{}0.008) \ifmmode\times\else\texttimes\fi{} ${10}^{5}$ years. Considering possibilities of bias, these figures are believed to lie within one percent of the true values. In conjunction with this determination, the half-lives of the other natural uranium isotopes were also measured.