http://worldcat.org/entity/work/id/348524684

Component analysis of small uranium samples

In a previous report (A-158) we have given a summary of a method for the component analysis of small amounts of uranium. We have now considerably improved the technique for such analyses, and it is the purpose of the present report to give a detailed account of our present procedures. Natural uranium contains three components of mass 238, 235, and 234, with relative abundances 1.000, 1/139, 1/16,700 (in numbers of nuclei). In order to analyze a mixture of these three components, three independent measurements are obviously needed. It has proved practical to measure the mass, the alpha activity, and the slow neutron produced fission of the sample. In the interpretation of the experimental data, we assume that all fissions produced in the sample by slow neutrons are due to U(236). It has already been well established, and it is further confirmed in this work that slow neutron irradiation does not produce fission of U(238). The only basic assumption employed which has not been tested by direct experiment is the assumption that the slow neutron cross section of U(234) is sufficiently small so that the slow neutron produced fissions of this component are negligible for the very small U(234) concentrations present in these samples. There is every reason to believe that this condition has been amply satisfied in every sample measured us to the present time.

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