Method for locating and evaluating subsurface uranium deposits having an apparent grade of up to approximately 5% contained U3O8

摘要

This invention relates to a novel method for both locating and evaluating subsurface uranium-bearing formations containing an apparent grade of up to approximately 5% of contained U3O8 which comprises the steps of taking readings of the natural gamma count from an unknown radioactive formation on both the shielded and unshielded detectors with the external gamma source shielded, uncovering the external gamma source and reading the count-rate on both the shielded and unshielded detectors, comparing the ratio of the natural gamma count recorded by the unshielded and shielded detectors with a similar ratio recorded by the same detectors in a uranium-bearing matrix of known concentration no greater than approximately 5% in a state of equilibrium to ascertain first if a state of disequilibrium exists and, secondly, if a state of disequilibrium is found to exist then to determine if this state of apparent disequilibrium is being influenced by the presence of either thorium or potassium or, alternatively, is primarily the result of a disequilibrium between uranium and its daughter products. The natural radiation seen by the shielded probe provides the data for a determinatin of the apparent grade of U3O8 used in later calculations. Finally, if the disequilibrium is found to exist between uranium and its daughter products, then determining the direction and approximate order of magnitude of the disequilibrium by analyzing the ratio of the count rates detected by the shielded and unsheilded detectors ascertained from a suspected uranium-bearing formation, the former seeing only the natural radiation while the latter looks at essentially all the radiation including that induced by the external source, and comparing it with a comparable ratio taken by the same detectors from a known uranium-bearing formation containing not more than approximately 5% U3O8 at equilibrium to see whether the back-scattered radiation was substantially attenuated or not within the formation or, alternatively, increased due to induced X-ray fluorescence.