Simple radiochemical neutron-activation method for the determination of uranium in ultramafic rocks

A radiochemical neutron-activation method for the determination of trace concentrations of uranium in rocks is described. The method is based on separation of 23·5-min ²³⁹U after alkaline fusion by extraction with tri-n-butyl phosphate from moderately concentrated nitric acid, followed by measurement of the 74-keV γ-ray with a Ge(Li) detector. The limit of detection is 0·2 ng of U under the present conditions, and the precision at the 0·005 ppm level is about 10%. The method is especially useful for determination of uranium in ultramafic rocks.