Unc Nuclear Industries, Inc.

Warren D Wittekind

Thomas E Hall

Wayne M Lechelt

William C Boyce

Leroy C Howard

A method and apparatus are described for performing X-ray fluorescence analysis where the physical relationship between the source/detector and the object being examined is not controlled. This technique and apparatus is particularly advantageous in performing an in situ analysis of the concentration of one or more elements present in a matrix of a material such as rock. In accordance with this aspect of our invention, such a mineral assay is performed by drilling a borehole into the matrix, inserting into the borehole a probe containing a suitable XRF source/detector, irradiating the matrix, detecting the spectrum of radiation that is produced and analyzing this spectrum. Preferably, the concentration of the assayed element is determined from the following formula: ##EQU1## where S is the number of photons counted having energies in a signal range where the X-ray spectral line of the assayed element is observed, C is the number of photons counted in a range where a radiation peak is observed, B is the number of photons counted in a background range, E is the number of photons counted in a range adjacent that where said radiation peak is observed, and K.sub.1 through K.sub.6 are empirically determined constants relating to the performance of the probe.

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Richland, WA, United States of America

Warren D Wittekind