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Title: Occurrence of naturally enriched {sup 235}U: Implications for plutonium behavior in natural environments

Abstract

It is generally accepted that uranium and most of the fission products, with the exception of the alkalis, alkaline earths and rare gases, remained in the irradiated uranium oxides during the nuclear reactions that took place 2.0 Ga ago in the Oklo uranium deposit (Gabon). New isotope investigations show that clay minerals from argillaceous rocks neighboring the natural fission reactor 10 at Oklo have depleted {sup 235}U with {sup 235}U/{sup 238}U ratios ranging between 0.00560 and the common natural value of 0.00725. One sample, however, is enriched in {sup 235}U with a {sup 235}U/{sup 238}U ratio of 0.007682. Leach experiments of this sample with dilute 1N HCl revealed that the {sup 235}U enrichment is actually restricted to the insoluble residue ({sup 235}U/{sup 238}U = 0.010511), whereas the leachate remains depleted in {sup 235}U. This unique discovery of very enriched uranium, together with samarium, neodymium, rubidium, and strontium isotopic analyses, indicate that a small amount of plutonium could have been more mobile than uranium in the reactor 10, and it is suggested that plutonium was incorporated in the crystallographic structure of clay minerals such as the chlorites. 28 refs., 3 figs., 1 tab.

Authors:
; ;  [1];  [2];  [3]
  1. CNRS, Strasbourg (FR)
  2. CNRS, Gif-sur-Yvette (FR)
  3. Centre d`Etudes Nucleaires, Grenoble (FR)
Publication Date:
OSTI Identifier:
138711
Resource Type:
Journal Article
Journal Name:
Geochimica et Cosmochimica Acta
Additional Journal Information:
Journal Volume: 57; Journal Issue: 6; Other Information: PBD: Mar 1993
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; PLUTONIUM; ENVIRONMENTAL TRANSPORT; URANIUM; NATURAL NUCLEAR REACTORS; FISSION PRODUCTS; URANIUM OXIDES; NUCLEAR REACTIONS; GABON; ENRICHED URANIUM; SAMARIUM; NEODYMIUM; RUBIDIUM; STRONTIUM; RADIONUCLIDE MIGRATION; PLUTONIUM 239; URANIUM 235; URANIUM 238; CHLORITE MINERALS; Yucca Mountain Project

Citation Formats

Bros, R, Gauthier-Lafaye, F, Stille, P, Turpin, L, and Holliger, Ph. Occurrence of naturally enriched {sup 235}U: Implications for plutonium behavior in natural environments. United States: N. p., 1993. Web. doi:10.1016/0016-7037(93)90072-5.
Bros, R, Gauthier-Lafaye, F, Stille, P, Turpin, L, & Holliger, Ph. Occurrence of naturally enriched {sup 235}U: Implications for plutonium behavior in natural environments. United States. https://doi.org/10.1016/0016-7037(93)90072-5
Bros, R, Gauthier-Lafaye, F, Stille, P, Turpin, L, and Holliger, Ph. 1993. "Occurrence of naturally enriched {sup 235}U: Implications for plutonium behavior in natural environments". United States. https://doi.org/10.1016/0016-7037(93)90072-5.
@article{osti_138711,
title = {Occurrence of naturally enriched {sup 235}U: Implications for plutonium behavior in natural environments},
author = {Bros, R and Gauthier-Lafaye, F and Stille, P and Turpin, L and Holliger, Ph},
abstractNote = {It is generally accepted that uranium and most of the fission products, with the exception of the alkalis, alkaline earths and rare gases, remained in the irradiated uranium oxides during the nuclear reactions that took place 2.0 Ga ago in the Oklo uranium deposit (Gabon). New isotope investigations show that clay minerals from argillaceous rocks neighboring the natural fission reactor 10 at Oklo have depleted {sup 235}U with {sup 235}U/{sup 238}U ratios ranging between 0.00560 and the common natural value of 0.00725. One sample, however, is enriched in {sup 235}U with a {sup 235}U/{sup 238}U ratio of 0.007682. Leach experiments of this sample with dilute 1N HCl revealed that the {sup 235}U enrichment is actually restricted to the insoluble residue ({sup 235}U/{sup 238}U = 0.010511), whereas the leachate remains depleted in {sup 235}U. This unique discovery of very enriched uranium, together with samarium, neodymium, rubidium, and strontium isotopic analyses, indicate that a small amount of plutonium could have been more mobile than uranium in the reactor 10, and it is suggested that plutonium was incorporated in the crystallographic structure of clay minerals such as the chlorites. 28 refs., 3 figs., 1 tab.},
doi = {10.1016/0016-7037(93)90072-5},
url = {https://www.osti.gov/biblio/138711}, journal = {Geochimica et Cosmochimica Acta},
number = 6,
volume = 57,
place = {United States},
year = {1993},
month = {3}
}