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±0.000012 weight percent, the precision being expressed on the basis of 95 percent probability. This corresponds to a half-life of (2.522±0.008) × ${10}^5$ 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.