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Title: Uranium in clays of crystalline rocks

Uraniferous clay aggregates in several granites have been examined in detail with a scanning electron microscope (SEM) equipped with a high resolution backscattered electron detector (BSE) and an energy dispersive x-ray system (EDS). The same polished sections used for the microscope observations were irradiated with thermal neutrons and the etched lexan detectors were then used to determine the location of uranium with a spatial resolution of a few microns. A set of 100 samples of the following granites were used for this study: Carnmenellis granite of southwestern England, Conway and Mount Osceola granites of central New Hampshire, Sherman granite of Wyoming and Colorado, Granite Mountains granite of Wyoming, several granites from central Maine, and the Graniteville granite of Missouri. These samples contain clay rich regions as large as a few millimeters that appear to consist entirely of clay when examined with the petrographic microscope. The clays are smectite, nontronite, or vermiculite. The fission track detectors show uranium to be present within the regions. Close examination with the BSE and EDS, however, shows in every instance that the host for the uranium is not clay but clay-sized grains of the following minerals: bastnesite group, hematite, siderite, secondary monazite, secondary thorite, andmore » several different Y-bearing niobates. This finding may have severe implications for the long-term retention of uranium and transuranic elements adsorbed on clay. Perhaps the presence of clay is not significant for the long-term retention of radioisotopes. 22 refs., 7 figs.« less
Authors:
;
Publication Date:
OSTI Identifier:
5117605
Report Number(s):
DOE/ER/04972-T2
ON: DE86000878
DOE Contract Number:
AC02-78ER04972
Resource Type:
Technical Report
Research Org:
Massachusetts Inst. of Tech., Cambridge (USA). Dept. of Earth, Atmospheric and Planetary Sciences
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; 54 ENVIRONMENTAL SCIENCES; GRANITES; RADIONUCLIDE MIGRATION; SCANNING ELECTRON MICROSCOPY; URANIUM; ENVIRONMENTAL TRANSPORT; CLAYS; COLORADO; DIFFUSION; EXPERIMENTAL DATA; FISSION TRACKS; MAINE; MINERALS; MISSOURI; NEW HAMPSHIRE; RESEARCH PROGRAMS; UNITED KINGDOM; WYOMING; ACTINIDES; DATA; ELECTRON MICROSCOPY; ELEMENTS; EUROPE; FEDERAL REGION I; FEDERAL REGION VII; FEDERAL REGION VIII; IGNEOUS ROCKS; INFORMATION; MASS TRANSFER; METALS; MICROSCOPY; NORTH AMERICA; NUMERICAL DATA; PARTICLE TRACKS; PLUTONIC ROCKS; ROCKS; USA; WESTERN EUROPE 580400* -- Geochemistry-- (-1989); 050100 -- Nuclear Fuels-- Reserves, Exploration, & Mining; 510301 -- Environment, Terrestrial-- Radioactive Materials Monitoring & Transport-- Soil-- (-1987)