[en] The investigated U deposit near Poppenreuth (Hoehensteinweg) in northeast Bavaria is situated among Upper Proterozoic biotite gneisses and mica schists with ENE- to NE-striking foliation. In this paper, the element distribution is determined of the elements involved in the U-Th petrogenic cycle (Zr, Ce, Th, U, P and Na); as are the mineralogical changes of the primary U minerals. The problem of lithogene element supply is studied. The area abundant in U is compared with other U-bearing sodium enriched host rocks in order to improve the selection of exploration target areas. Content: the primary U and Th minerals; plutonic mobilizates; episyenites and sodium metasomatites; propylitic rocks; U minerals and their relation to the primary U minerals; the origin of Hoehensteinweg uranium deposits. (Auth.)

[en] Laboratory-scale aqueous-chlorine leaches were conducted on quartz-pebble conglomerates, pegmatite and vein-type ores. Optimum leach temperatures, pulp density and retention times were determined. Uranium extraction of 98 per cent was obtained from the Elliot Lake, Madawaska Mines of Bancroft and Rabbit Lake ores, 96 per cent from the Key Lake ore and 86 per cent from the Agnew Lake ore. However, tailings containing 15-20 pCi g^-1 of radium-226 were obtained only from the Elliot Lake and Agnew lake quartz-pebble conglomerates and Bancroft pegmatite-type ores by second-stage leaches with HCl. The second-stage leach results indicate that multistage (3 or 4) acid-chloride or salt-chloride leaches might be effective to obtain tailings containing 15-20 pCi ²²⁶Ra g^-1 from the high-grade vein-type ores. Comparative reagent-cost estimates show that the sulphuric-acid leach process is far less expensive than aqueous chlorine leaching. Nevertheless, only the aqueous chlorine and acid-chloride leaches in stages are effective in producing tailings containing 15-20 pCi ²²⁶Ra g^-1 from the typical Canadian uranium ores. (Auth.)

[en] Uranium extractions above 82 per cent have been realized from the ore by sulfuric acid leaching at 30⁰C without addition of any oxidant other than air. Increasing the temperature to 70⁰C resulted in a complete extraction of uranium in the presence and absence of chemical oxidants. In the temperature range of 30-50⁰C, the hydrogen peroxide resulted in yield improvements of 5 to 6 per cent relative to the effect of air. At 30⁰C the hydrogen peroxide was found to be a more efficient oxidant than sodium chlorate. An equation, similar to the Langmuir adsorption form, has been developed and its applicability in the description of uranium rate phenomena demonstrated. The process of uranium extraction resulted in two apparent activation energies, which were for the lower temperature range ΔE = 245 J/mol and for the higher temperature range ΔE = 642 J/mol. These relatively low ΔE values suggest that the extraction of uranium may be diffusion controlled and more than one reaction mechanism is associated with the process. (orig.)

[en] A total of 1386 bulk samples of manganese nodules from several areas of the North and South Pacific were analysed for uranium; variations in the U contents of nodules within individual nodules and crusts have been documented on a local scale and on a regional scale. Uranium appears to be one of those elements not associated with the biogenic cycling of elements into nodules in the equatorial high-productivity zone. The principal factor controlling these variations appears to be the clear association of U with Fe in the nodules. Uranium is therefore most probably coprecipitated with Fe from seawater in an iron-rich ferromanganese oxide phase. This explains the higher U contents of nodules containing MnO₂ compared to 10A manganite as the principal manganese oxide phase. Data for a manganese crust from the equatorial North Pacific nodule belt suggest normal seawater deposition for uranium and other metals (Mn, Fe, Ni and Cu) superimposed on possibly basalt alteration as the principal growth mechanisms for the crust. (Auth.)

[en] A sequential, selective extraction procedure was used to assess the geochemical associations of uranium, thorium-230 and radium-226 in a uranium-ore blend and the tailings derived therefrom at an acid-leach uranium mill. The data indicate that the major part of the extractable uranium is associated with a readily acid-soluble fraction in both ore and tailings. The major part of the extractable ²²⁶Ra was associated with an iron, manganese hydrous-oxide fraction in the ore and tailings. Thorium-230 was the least leachable of the radionuclides studied. The major portion of the extractable ²³⁰Th was associated with alkaline-earth sulfate precipitates, organic matter, or both. The specific effects of milling on each of the nuclides are discussed. (orig.)

[en] The uranium concentrations as a function of size fraction were determined in 246 stream sediment samples, 100 from the Estancia Valley, New Mexico, 100 from an area north of the Grants New Mexico uranium area and 46 from the Black Hawk Mining District in southwestern New Mexico. Statistical analysis of the data from the Estancia Valley and the Grants area show uranium concentrations in stream sediment size fractions larger than 0.125 mm to be nearly independent of particle size while the uranium concentrations increase with decreasing particle size for particles smaller than 0.125 mm. The correlation between uranium content and a calculated surface area for the sediment fraction for samples from the Black Hawk Mining District exceeds 0.9. In contrast, the uranium contents of sediments from the Estancia Valley and Grants area show a much lower correlation with the calculated surface area of the sediment fraction. The authors propose that the observed statistical differences are related to the fact that the stream sediments of the Black Hawk Mining District represent a mechanical disintegration of igneous and metamorphic rocks with little or no chemical weathering while the sediments of the Estancia Valley and the Grants area represent chemically mature sediments. The consequences of a surface-area-dependent elemental distribution on geochemical sampling are discussed. (Auth.)

[en] The many studies of uranium oxides have been critically reviewed, and a temperature-composition phase diagram for the entire system from U to UO₃ has been prepared. Suggested changes in the interpretation of the region around U₃Osub(8-y) have been incorporated in this diagram. (Auth.)

[en] This paper presents an overview of the solution-mining process and the health-physics monitoring programs developed over the last four years at several production facilities as a result of the radiological character of these processes. Some special monitoring considerations are presented which are required due to the manner in which radon gas is evolved in the process and the unique aspects of controlling solution flow patterns underground. An overview of the major aspects of the health physics compliance and monitoring programs that have been developed are discussed. (Auth.)

[en] A study of radon gas concentration, surface radon flux and other radiation variables has been conducted at uranium tailings sites. Meteorological data such as barometric pressure, air temperature and rainfall, and soil profile data including temperature, porosity and Ra-226 content have also been measured in order to investigate the relationship of these variables with radiation data. Radon gas measurements were conducted at several depths and at the soil/air interface. Results show that the radon gas concentration increases with depth. However, radon which escapes to the atmosphere is limited to the boundary layer, and the pore concentration of radon in this zone is significantly affected by barometric pressure changes and other meteorological variables. (Auth.)

[en] α-spectrometric determinations of U and Th contents and their isotopic ratios have been made on different grain-size fractions of six samples from the Hoehensteinweg mine near Tirschenreuth. The samples, granites and gneisses, are from two fault gouges, which differ mainly in inclination and uranium content. Uranium is found to be enriched in the smaller grain-size fractions. Disequilibria between the isotope pairs ²³⁴U/²³⁸U and ²³⁰Th/²³⁴U exist more or less in all fractions, the more so in the fractions of the samples with high U content. In contrast, no significant disequilibrium has been found in the primary black ore from the Hoehensteinweg mine. The main U mineral is brannerite, which correlates with the Ti (oxalate) values determined by leaching procedures. (orig.)