Uranium Mineralogy Research Articles

Crystallization of U 3O 8 and hydrated UO 3 on UO 2 fuel in aerated water near 200°C

Three processes have been identified in the oxidation of fresh UO 2 fuel in aerated water at 200–225°C. These are (i) solid-state oxidation to U 3O 7 (similar to dry oxidation), (ii) oxidative dissolution and precipitation of U(VI) as UO 3· xH 2O ( x − 0.8) and (iii) back-reduction of dissolved U(VI) on the UO 2/U 3O 7 surface to form U 3O 8 and, in one case, ianthinite (UO 2·5UO 3·10.5H 2O) or a related phase. Formation of U 3O 8 from aqueous solutions is rarely reported, so this instance is documented in detail. The reaction is discussed in relation to U-O-H thermodynamics, storage and disposai of used UO 2 fuel and uranium mineralogy.

Pedologic and climatic controls on RN‐222 concentrations in soil gas, Denver, Colorado

Soil‐gas radon concentrations are controlled seasonally by factors of climate and pedology. In a swelling soil of the semiarid Western United States, soil‐gas radon concentrations at 100 cm depth increase in winter and spring due to increased emanation with higher soil moisture and the capping effect of surface water or ice. Increased soil moisture results from a combination of higher winter and spring precipitation and decreased insolation in fall and winter, lowering soil temperatures so that water infiltrates deeper and evaporates more slowly. Radon concentrations in soil drop markedly through the summer and fall. The increased insolation of spring and summer warms and dries the soil, limiting the amount of water that reaches 100 cm. As the soil dries, radon emanation decreases, and deep soil cracks develop. These cracks aid convective transport of soil gas, increase radon's flux into the atmosphere, and lower its concentration in soil gas. Probable controls on the distribution of uranium within the soil column include its downward leaching, its precipitation or adsorption onto B‐horizon clays, concretions, or cement, and the uranium content and mineralogy of the soil's granitic and gneissic precursors.

The mineralogy and geochemistry of uranium, thorium, and rare-earth elements in two radioactive granites of the Vosges, France

AbstractTwo contrasting types of Hercynian U-rich granites can be distinguished by their accessory minerals: (1) subalkaline potassic granites (amphibole-biotite±pyroxene) characterized by apatite-zircon-thorite-sphene-allanite and rare ThO2-rich uraninite, in order of appearance in the magma, and (2) leucocratic granites (biotite and muscovite) which contain monazite-zircon-apatite-xenotime-ThO2-poor uraninite and Ti oxides. Intermediate accessory mineral associations may also exist.The mineralogy, crystallization history, and geochemistry of two high K-U-Th granites from the Vosges, France, is described. Their assemblage of U- and Th-bearing accessory minerals is listed, in order of appearance in the magma, in Group 1 (above). Trace elements (U, Th, Zr, Hf) and preliminary data on REE are discussed. In a layered sequence of the Crêtes granite, thorite, with up to 15% UO2, is shown to be important during differentiation. There is a decrease of the Th/U ratio corresponding to a slight decrease of the Th content whereas there is an increase of the U content at the end of differentiation. The Crêtes and Ballons granites have REE patterns characterized by LREE enrichment with a La/Yb ratio of about 28 (Crêtes granite) and a slight negative Eu anomaly. These relationships are typical of subalkaline potassic granites of the Hercynian. The trace element associations are similar to those of the shoshonite association with high U, Th, LREE and Ba, Rb, and Sr contents. A hypothetical model for uranium mineralization associated with such granites is discussed in the light of these data.

The mineralogy and genesis of uranium in rhyolitic ignimbrites of precambrian age from Duobblon, Sweden

AbstractThe Duobblon rhyolitic ignimbrites, of middle Precambrian age are 60 m thick. They consist of at least three flows with varying degrees of welding and have undergone devitrification, producing lithophysal and spherulitic textures. They are overlain by thick fluviatile red-bed-type conglomerates and sandstones, which in turn are capped by terrestrial acid volcanics.Uranium enrichments of up to 3000 ppm U occur within two or three peneconcordant tabular horizons which are mostly lithophysae-bearing. Fission-track investigations of the ignimbrites and overlying conglomerates and sandstones, which supplement earlier mineralogical studies, show that U occurs as fine pitchblende disseminations; as complex uranotitanates associated with Fe-Ti-Mn oxides; and as coatings associated with matrix sericite. Small amounts of O are present in such primary accessory minerals as sphene, apatite, and zircon.It is suggested that oxidizing U-bearing solutions, generated partly during devitrification of the ignimbrites and partly from the overlying volcano-sedimentary pile, produced the U enrichments with later sulphide deposition, along the more permeable lithophysal horizons in the ignimbrites.

Typomorphism of uranium minerals and its practical significance

Typomorphism refers to a series of minerals, each of which is typically developed only in a narrow range of temperature and pressure. Because uranium's mineralogy is extremely sensitive to physicochemical changes in the environment, trypmorphism of uranium minerals can be used in the exploration of uranium deposits. In this paper, the authors discuss the typomorphic features of non-uranium oxide minerals, typomorphic isotope ratios, and how typomorphism may be used in exploration. (JMT)

Uranium Mineralogy and the Geochemistry of Radioelements in Crystalfine Rocks: Preface

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Nachträge zu der topographischen Mineralogie des Urans aus alter Zeit

Nachträge zu der topographischen Mineralogie des Urans aus alter Zeit

Künstliche Verwitterung von Uran-Nickel-Erz von Key Lake, Sask., Canada - ein Beitrag der Uranmineralogie zum Umweltschutz

Künstliche Verwitterung von Uran-Nickel-Erz von Key Lake, Sask., Canada - ein Beitrag der Uranmineralogie zum Umweltschutz

Characteristic features of the mineralogy of uranium

The following characteristic features of the mineralogy of uraniun are discussed in the article: 1) all known uranium and uranium-bearing minerals contain oxygen; 2) uranium in minerals is present only in the tetra- and hexavalent states; 3) the bulk of the uranium in the earth's crust is concentrated in nonuranium minerals in the form of isomorphous replacement of other elements (thorium, zirconium, rare-earth elements, etc.); 4) the conditions under which uranium and uranium-bearing minerals are formed differ; 5) radioactivity is one of the most characteristic properties of uranium minerals.