The variability of the natural abundance of U |
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Authors: | George A Cowan Hans H Adler |
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Institution: | University of California, Los Alamos Scientific Laboratory, Los Alamos, New Mexico 87545, U.S.A. Division of Nuclear Fuel Cycle and Production, Energy Research and Development Administration, Washington D.C.20545, U.S.A. |
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Abstract: | The possibility that the atomic ratio 235u/238U may be slightly variable due to natural nuclear chain reactions such as have been identified in Gabon, West Africa, has prompted a re-examination of very precise gas mass spectrometric isotopic ratio data from a number of laboratories. Two modal values of the isotopic ratio exist in the data. Their relative difference, 0.03%, is statistically significant. The lower mode is due principally to ores from the Colorado Plateau. This difference was recognized in 1963 by the U.S. Atomic Energy Commission but the substantiating data have not been openly published. Insufficient data presently exist to attribute this difference to chemical differentiation of the uranium isotopes, presumably in the ‘sandstone’ type deposits of the Colorado Plateau, or to dilution with Precambrian ore deposits, depleted in 235U by nuclear reactions. |
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