Sample records for brannerite

  1. Heavy ion irradiation effects of brannerite-type ceramics (United States)

    Lian, J.; Wang, L. M.; Lumpkin, G. R.; Ewing, R. C.


    Brannerite, UTi 2O 6, occurs in polyphase Ti-based, crystalline ceramics that are under development for plutonium immobilization. In order to investigate radiation effects caused by α-decay events of Pu, a 1 MeV Kr + irradiation on UTi 2O 6, ThTi 2O 6, CeTi 2O 6 and a more complex material, composed of Ca-containing brannerite and pyrochlore, was performed over a temperature range of 25-1020 K. The ion irradiation-induced crystalline-to-amorphous transformation was observed in all brannerite samples. The critical amorphization temperatures of the different brannerite compositions are: 970 K, UTi 2O 6; 990 K, ThTi 2O 6; 1020 K, CeTi 2O 6. The systematic increase in radiation resistance from Ce-, Th- to U-brannerite is related to the difference of mean atomic mass of A-site cation in the structure. As compared with the pyrochlore structure-type, brannerite phases are more susceptible to ion irradiation-induced amorphization. The effects of structure and chemical compositions on radiation resistance of brannerite-type and pyrochlore-type ceramics are discussed.

  2. A scheme for the complete elemental characterisation of brannerite mineral using ICP-AES

    International Nuclear Information System (INIS)

    Brannerite occurs along with other refractory minerals in pegmatite veins. Literature survey indicates lack of systematic and detailed chemical analysis procedure for brannerites. This paper report suitable sample decomposition procedures, yielding stable sample solution, suitable for the ICP-AES determination of major, minor and certain trace elements normally associated with brannerite mineral. Three different simple decomposition procedures such as (i) acid digestion (ii) fusion with lithium metaborate (iii) fusion with mixture of tetra sodium pyrophosphate and monosodium dihydrogen phosphate are used to obtain the sample solution for elemental analysis. In presence of higher concentrations of uranium and titanium, the major elements in brannerite mineral, a detailed study of the influence of uranium and titanium on ICP-AES determination of other elements, three commonly used emission lines of each element was carried out. The REEs, Y, Sc and Th have been determined after the removal of major matrix elements using oxalate precipitation. The accuracy of the proposed procedures is established by analyzing synthetic brannerite samples prepared by mixing high purity oxides or chlorides in a proportion similar to natural brannerite samples. The results indicate the method is accurate. The reproducibility studies carried out on one sample shows the % RSD varied from 2 to 5%. (author)

  3. Chemical durability studies of synthetic brannerite for immobilization of actinide-rich radioactive waste

    International Nuclear Information System (INIS)

    This report summarises the work being carried out at ANSTO since 2000 under research agreement No. AUL-10644. It covers the dissolution of synthetic brannerite in acidic and alkaline fluids, the effects of solution pH and U valence state on the dissolution of U-substituted thorutite, and kinetic modelling of the oxidative dissolution of brannerite. The dissolution of synthetic brannerite in aqueous media at 40 deg C and 90 deg C under atmospheric redox conditions has been studied. At 40 deg C, the presence of phthalate as a buffer component in the pH range of 2 to 6 has little effect on uranium release from brannerite. Bicarbonate increases uranium release and enhances the dissolution of brannerite. Compared to UO2, brannerite is more resistant to dissolution in bicarbonate solutions. In under-saturated conditions at 90 deg C, the dissolution of brannerite is incongruent (preferential release of uranium) at pH 2 and nearly congruent at pH 11. TEM examinations reveal a polymorph of TiO2 (pH 2 specimen) and a fibrous Ti-rich material (pH 11 specimen) as secondary phases. XPS analyses indicate the existence of U(V) and U(VI) species on the surfaces of specimens both before and after leaching, and U(VI) was the dominant component on the specimen leached in the pH 11 solution. The dissolution of the thorium analogue of brannerite (ThTi2O6-I) and U(IV)/U(V) doped Th-brannerite (Th0.97U0.03Ti2O6-II and Th0.955U0.03Ca0.015Ti2O6-III) in aqueous media under atmospheric condition has been studied to elucidate the effects of pH and uranium valence state on the dissolution rate. The dissolution of I is nearly stoichiometric but slightly preferential release of U occurs for II and preferential release of Ca and U occurs for III. The V-shape pH dependence previously observed for U-brannerite only occurs for U (not other matrix elements) for II, indicating that the pH dependence is related to the U oxidation state upon dissolution. The normalised U dissolution rates of III are

  4. A crystal-structure refinement of synthetic brannerite, UTi2O6, and its bearing on rate of alkaline-carbonate leaching of brannerite in ore

    International Nuclear Information System (INIS)

    The crystal structure of synthetic, stoichiometric brannerite, UTi2O6, has been refined to R=2.23% from MoKα radiation. Monoclinic, with space group C2/m, a 9.8123(15), b 3.7697(6), c 6.9253(9) A, β 118.957(6)0, brannerite is isostructural with thoruitite, ThTi2O6 (Ruh β Wadsley 1966). The co-ordination of U by O is distorted octahedral, the bond distances being 2 x 2.252(2), 4 x 2.296(1) A. There is an additional pair of short nonbonded U-O contacts, 2 x 2.824(2) A. The co-ordination around Ti is also distorted octahedral, with the Ti-O distance between 1.854(3) and 2.104(3) A. The depth of penetration of an alkaline-carbonate leaching solution into natural brannerite from Eldorado, Saskatchewan, has been found to vary nonuniformly with both time and crystallographic direction of leaching attack. The rate of dissolution for a free crystal is 1.33 cubic micrometers per second or, using the density calculated from the cell data, 8.5 x 10-12 g/s

  5. Use of emanation thermal analysis to characterize thermal reactivity of brannerite mineral

    Czech Academy of Sciences Publication Activity Database

    Balek, V.; Vance, E.R.; Zeleňák, V.; Málek, Z.; Šubrt, Jan


    Roč. 88, č. 1 (2007), s. 93-98. ISSN 1388-6150 Grant ostatní: GA MŠk(CZ) LA 292; GA MŠk(CZ) ME 879 Institutional research plan: CEZ:AV0Z40320502 Keywords : brannerite * emanation thermal analysis Subject RIV: CA - Inorganic Chemistry Impact factor: 1.483, year: 2007

  6. Mineralogy and geochemistry of phosphate minerals and brannerite from the Proterozoic Carbon Leader Reef gold and uranium placer deposit, Witwatersrand, South Africa

    International Nuclear Information System (INIS)

    Yttrium-phosphate, the most common phosphate phase, is closely associated with detrital uraninite. It is assumed having formed by the reaction of mobile phosphate with Y and HREE liberated from the lattice of detrital uraninite, during diagenesis and/or metamorphism of the sediments. Authigenic brannerite (UTi2-3O6-8) is well-defined microscopically and geochemically. Textural relationships indicate that both titanium migrated to uraninite, forming brannerite, and mobile uranium caused the 'branneritization' of rutile/leucoxene. Microprobe analyses demonstrate that brannerite from the Carbon Leader Reef displays a distinct and small variation of UO2/TiO2 ratios, which lie close to the theoretical value of 1.117 for UTi3O8, in contrast to uraniferous leucoxene/brannerite from other Witwatersrand-type deposits, the latter showing a wide scatter of UO2/TiO2 ratios. (orig./HP)

  7. Enthalpies of formation of U-, Th-, Ce-brannerite: implications for plutonium immobilization (United States)

    Helean, K. B.; Navrotsky, A.; Lumpkin, G. R.; Colella, M.; Lian, J.; Ewing, R. C.; Ebbinghaus, B.; Catalano, J. G.


    Brannerite, ideally MTi 2O 6, (M=actinides, lanthanides and Ca) occurs in titanate-based ceramics proposed for the immobilization of plutonium. Standard enthalpies of formation, Δ H0f at 298 K, for three brannerite compositions (kJ/mol): CeTi 2O 6 (-2948.8 ± 4.3), U 0.97Ti 2.03O 6 (-2977.9 ± 3.5) and ThTi 2O 6 (-3096.5 ± 4.3) were determined by high temperature oxide melt drop solution calorimetry at 975 K using 3Na 2O · 4MoO 3 solvent. The enthalpies of formation were also calculated from an oxide phase assemblage (Δ H0f-ox at 298 K): MO 2 + 2TiO 2=MTi 2O 6. Only UTi 2O 6 is energetically stable with respect to an oxide assemblage: U 0.97Ti 2.03O 6 (Δ H0f-ox=-7.7±2.8 kJ/mol). Both CeTi 2O 6 and ThTi 2O 6 are higher in enthalpy with respect to their oxide assemblages with (Δ H0f-ox=+29.4±3.6 kJ/mol) and (Δ H0f-ox=+19.4±1.6 kJ/mol) respectively. Thus, Ce- and Th-brannerite are entropy stabilized and are thermodynamically stable only at high temperature.

  8. Enthalpies of formation of U-, Th-, Ce-brannerite: implications for plutonium immobilization

    International Nuclear Information System (INIS)

    Brannerite, ideally MTi2O6, (M=actinides, lanthanides and Ca) occurs in titanate-based ceramics proposed for the immobilization of plutonium. Standard enthalpies of formation, ΔH0f at 298 K, for three brannerite compositions (kJ/mol): CeTi2O6 (-2948.8 ± 4.3), U0.97Ti2.03O6 (-2977.9 ± 3.5) and ThTi2O6 (-3096.5 ± 4.3) were determined by high temperature oxide melt drop solution calorimetry at 975 K using 3Na2O · 4MoO3 solvent. The enthalpies of formation were also calculated from an oxide phase assemblage (ΔH0f-ox at 298 K): MO2 + 2TiO2=MTi2O6. Only UTi2O6 is energetically stable with respect to an oxide assemblage: U0.97Ti2.03O6 (ΔH0f-ox=-7.7±2.8 kJ/mol). Both CeTi2O6 and ThTi2O6 are higher in enthalpy with respect to their oxide assemblages with (ΔH0f-ox=+29.4±3.6 kJ/mol) and (ΔH0f-ox=+19.4±1.6 kJ/mol) respectively. Thus, Ce- and Th-brannerite are entropy stabilized and are thermodynamically stable only at high temperature

  9. Radiometric dating of brannerite and biotite minerals from Ladi-ka-bas, Sikar District, Rajasthan

    International Nuclear Information System (INIS)

    In this paper results of radiometric dating on brannerite and biotite minerals from Ladi-ka-bas area are reported. The area falls in the North Delhi Fold Belt of Rajasthan where occurrences of uranium mineralized rocks have been reported from a number of places. In Ladi-ka-bas area hydrothermal uranium mineralization is hosted within quartz-biotite schist, albitite, impure quartzite and carbonate rocks of the Mesoproterozoic Ajabgarh Group of Delhi Supergroup. The Branerite is the main uranium bearing phase in these mineralized rocks. The age data obtained in this study will be useful in understanding the uranium mineralization events in this very important region.

  10. Mineralogical and process controls on the oxidative acid-leaching of radioactive phases in Elliot Lake, Ontario, uranium ores: II - Brannerite and allied titaniferous assemblages

    International Nuclear Information System (INIS)

    In representative run-of-mine samples from the Panel and New Quirke mines of the Elliot Lake uranium district, Ontario, brannerite, a metamict uranous titanate, occurs in microscopic grain-aggregates which display wide variations, both in textural habit and in the relative proportions of brannerite, titania polymorphs and/or 'uraniferous titania'. As is widely documented, much of the brannerite occurs as trellis-like arrays of laths and needles pseudomorphing rutile or anatase. In some cases, the laths and needles are cemented by coffinite. Brannerite, with an average composition of (U0.629 Th0.039 Ca0.020) (Ti2.199 Fe0.13)O69 contains ≤3 wt% Th and is distinctly Ti-rich relative to the ideal composition, UTi2O6. Much of the Si reporting consistently in electron microprobe analyses (between 1 wt% and 5 wt%) is tentatively attributed to contamination by the quartz-sericite matrix, and a minor proportion is attributed to the presence of coffinite intergrowths. 'Uraniferous titania' (average partial composition by weight: 10.8% U, 0.3% Th, 32.9% Ti) is considered to represent an intermediate stage in the conversion of titania to brannerite. The leaching behaviour of brannerite in its different modes of occurence was studied qualitatively by the rotating-disc (polished section). (author). 23 refs., 4 tabs., 11 figs

  11. Thermochemical investigations of zirconolite, pyrochlore and brannerite: Three materials relevant to issues of plutonium immobilization (United States)

    Helean, Katheryn Bridget

    For the purpose of immobilizing plutonium, a crystalline ceramic waste form is being developed that can be described as a pseudo-quaternary system consisting of CaHfTi2O7- CaPuTi2O7- CaUTi2O7- GdTi2O7. High-temperature oxide melt solution calorimetry offers an effective methodology for the determination of enthalpies of formation of rare earth-bearing and other refractory oxides relevant to the proposed waste form. Calorimetric investigations of the waste form end-member phases (using Ce as a Pu analogue) plus brannerite, the major waste form impurity, were conducted using 3Na2O•4MoO3 solvent at 975 K. Standard enthalpies of formation, DeltaH°f (kJ/mol), were derived for three pyrochlore phases: Ca0.93Ce1.00Ti 2.035O7.00 (-3656.0 +/- 5.6), Ca1.46U 4+0.23U6+0.46Ti1.85O 7.00 (-3610.6 +/- 4.1) and Gd2Ti2O 7 (-3822.5 +/- 4.9). Enthalpies of formation with respect to an oxide phase assemblage, DeltaH°f-ox: CaO+MO2+2TiO2=CaMTi2O7 or Gd 2O3+2TiO2=Gd2Ti2O7 , and an oxide/perovskite phase assemblage, DeltaH° f-pv+ox: CaTiO3+MO2+TiO2=CaMTi 2O7, M = Ce, U were also calculated. DeltaH° f-ox (kJ/mol): Gd2Ti2O7 (-113.4 +/- 2.8); Ca1.46U4+0.23U 6+0.46Ti1.85O7.00 (-123.1 +/- 3.4); Ca0.93Ce1.00Ti2.035O7.00 (-54.1 +/- 5.2). DeltaH°f-pv+ox (kJ/mol): Ca1.46U4+0.23U6+ 0.46Ti1.85O7.00 (-5.1 +/- 4.0); Ca 0.93Ce1.00Ti2.035O7.00 (+21.0 +/- 5.5). A significant metastability field was defined with respect to an oxide/perovskite phase assemblage. DeltaH°f (kJ/mol) were derived for two zirconolite phases: CaZr1.03Ti1.97O7 (-3719.4 +/- 3.9) and CaHf1.02Ti1.98O 7 (-3720.5 +/- 3.9). DeltaH° f-ox (kJ/mol): CaZr1.03Ti1.97O7 (-89.6 +/- 2.8); CaHf1.02Ti1.98O7 (-74.8 +/- 3.1). CaZr1.03Ti1.97O7 was stable with respect to a perovskite plus oxides assemblage (DeltaH° f-pv+ox = -8.8 +/- 3.3 kJ/mol). CaHf1.02Ti 1.98O7 was marginally metastable in enthalpy (Delta H°f-pv+ox = +6.0 +/- 3.5 kJ/mol). DeltaH°f (kJ/mol) were derived for three brannerites: CeTi2O6 (-2948.8 +/- 4.3); U0.97Ti2.03O6

  12. The impact of brannerite on the release of plutonium and gadolinium during the corrosion of zirconolite-rich titanate ceramics

    International Nuclear Information System (INIS)

    Titanate ceramics have been selected as the preferred waste form for the immobilization of excess plutonium. Corrosion tests are underway to try to understand the long-term behavior of this material. In this paper, results from PCT-B static dissolution tests are used to provide an explanation of the observed corrosion behavior of a zirconolite-based ceramic. Two important observations are made. First, Ca is released at a constant rate [7 x 10-5 g/(m2 day)] in PCT-B tests for up to two years. Second, the release rates for Pu and Gd increase with time (up to two years) in PCT-B tests. The first observation suggests that the ceramics continue to corrode at a low rate for at least two years in PCT-B tests. The second observation suggests that the release rates of Pu and Gd are controlled by some process or processes that do not affect the release rate of other elements. Evidence indicates that this is due to the preferential dissolution of brannerite from the ceramic

  13. Interim report task 2: performance testing - task 2.4: natural mineral analog studies physical and chemical characteristics of brannerite in natural systems to Lawrence Livermore National Laboratory under contract B345772

    Energy Technology Data Exchange (ETDEWEB)

    Lumpkin, G R; Colella, M; Leung, S H F


    To investigate the long-term alteration behavior of brannerite, we have undertaken a study of 13 natural samples from various geological environments, including granites, granitic pegmatites, quartz veins, and placer deposits. Literature data and U-Th-Pb chemical dating carried out in this work indicate that the samples range in age from approximately 20 Ma to 1580 Ma. Where independent age data or estimates are available for comparison, the U-Th-Pb chemical ages are in reasonable agreement for the younger samples, but the older samples tend to show evidence for Pb loss (up to about 80%), a common feature of metamict Nb, Ta, and Ti oxide minerals. Our results show that many of the samples exhibit only minor alteration, usually within small patches, microfractures, or around the rims of the brannerite crystals. Other samples consist of variable amounts of unaltered and altered brannerite. Heavily altered samples may contain anatase and thorite as fine-grained alteration products. Certain samples exhibited fracturing of the associated rock matrix or mineral phase in the immediate vicinity of the brannerite grains. These fractures contain U bearing material and indicate that some U migrated locally from the source brannerite.

  14. Electrochemical behavior of [(Mn(Bpy))(VO3)2]≈(H2O)1.24 and [(Mn(Bpy)0.5)(VO3)2]≈(H2O)0.62 inorganic–organic Brannerites in lithium and sodium cells

    International Nuclear Information System (INIS)

    The performance of MnV2O6 (MnV) and its [(Mn(Bpy))(VO3)2]≈(H2O)1.16 (MnBpy) and [(Mn(Bpy)0.5)(VO3)2]≈(H2O)0.62(MnBpy0.5) hybrid derivative compounds was investigated against sodium and lithium counter electrodes. For MnV2O6 stable capacities of 850 mAh/g were achieved in lithium cells, the best value reported so far. The whole capacity is ascribed to a conversion reaction in which the amorphization of the compounds takes place. No significant differences in the capacities for the inorganic compound and the hybrid ones were observed. Interestingly, the potential hysteresis decreases in the hybrid compounds. The difference between Li and Na cell capacity most probably comes from the difference of standard potential of the two redox couples Li+/Li and Na+/Na of about ca. 0.3 V leading to an incomplete conversion reaction and thus lowers capacity in the case of Na cells. The Raman and IR ex-situ experiments after cycling indicate that the bipyridine organic ligands are completely decomposed during the electrochemical testing. The IR studies in MnV inorganic and MnBpy and MnBpy0.5 hybrid electrodes after the electrochemical cycling, suggest that the SEI formation and bipyridine degradation give rise to different aliphatic compounds. - Graphical abstract: The electrochemical performance of [(Mn(Bpy))(VO3)2]≈(H2O)1.16 and [(Mn(Bpy)0.5)(VO3)2]≈(H2O)0.62 against sodium and lithium counter electrodes give rise to the structural collapse of the initial compounds. The IR and Raman studies show that the Bpy organic ligand is completely decomposed during the during the electrochemical testing. However, after the amorphization stable capacities as high as 850 mAh/g for lithium cells were achieved. - Highlights: • We test the lithium and sodium insertion in hybrid brannerites. • Capacities as large as 850 mAh/g were obtained for the Li cells. • The capacity and good cycling is ascribed to a conversion reaction of the electrodes. • The Bpy molecule of the hybrid

  15. The mineralogical zoning and ores types of the Elkon ore field (Saha-Yakut Republic, Russian Federation)

    International Nuclear Information System (INIS)

    The mineralogical zoning and ore types of the Elkon ore field, one of the largest in the world, are described. The brannerite mineralization with finely dispersed brannerite is located in the central zone of the ore field. At the periphery of the central zone, dispersed brannerite is replaced by crystalline brannerite. Zone of uraninite is distributed along the northwest flank of the ore field, and the molybdenite-brannerite zone with nasturan occurs at its southeast flank. Regional distribution of various uranium minerals and various paragenetic associations determine ore types with regards to content of useful components, the form of their occurrence, composition and structural features of ores. Several types of ores have been distinguished according to above characteristics. (author)

  16. The Bondons uranium deposit: a typical example of a polyphase metallogenesis

    International Nuclear Information System (INIS)

    Four metallogenic stages have been uncovered in the Bondons deposit: 1. metamorphic ante-to syn-S 2 (brannerites); 2. hydrothermal (a) breakdown of brannerites in pitchblende I and anatase; (b) vein paragenesis (pitchblende II, adularia, carbonates); 3, supergene redistribution of previous ores. Thus the deposit fits in a complex polygenetic model, rather than in a simple supergene model at the level of a weathering paleosurface

  17. Uranium-bearing and associated minerals in their geochemical and sedimentological context, Elliot Lake, Ontario

    International Nuclear Information System (INIS)

    The depositional energy environment of the Rio Algom-Denison ore reef was investigated on a regional scale using several parameters including pebble size. Regional trends of decreasing pebble size coincide with the regional direction of sediment transport. Pebble size was also used to characterize the depositional energy environment at the sample level. Quartz-pebble size and pyrite-grain size as determined from the same samples have a correlation coefficient of 0.93 which indicates that the coarse granular pyrite is detrital. Bulk chemical analyses of selected elements (U, Th, Pb, Ti, Ce, La, Y and Zr) which were chosen to reflect specific minerals (uraninite, brannerite, monazite and zircon), showed strong correlation with quartz-pebble size of the respective samples. Electron microprobe analyses of uraninite and brannerite are reported. The uraninites have typical pegmatitic compositions. Several types of brannerite are described; the conclusion reached is that although some brannerite may be detrital, most of it formed by adsorption of uranium onto titania collectors. Redistribution of some of the uranium has not changed the placer nature of the ore reef. Genesis of individual minerals (pyrite, uraninite, brannerite, zircon and monazite) is discussed. It is concluded that the mineralogy and its geochemical expression have been controlled by processes of fluvial deposition. As a result of the regional patterns in depositional environment, the ore reef shows a broad mineralogical zoning. Fluctuations in depositional energy have also produced lithologically related mineral zoning on a smaller scale. (author)

  18. The effect of mineral content on the degree of deviation from radioactive equilibrium in the ancient uranium ores of the Ukraine

    International Nuclear Information System (INIS)

    The degree of radioactive nonequilibrium of ores was found to increase in the following order in accordance with the varying mineral content: relatively coarse-grained uraninite (UO2) - coffinite (USiO4), brannerite (UTi2O6) - secondary fine grained coffinite, brannerite-secondary minerals of thin veins, boltwoodite ((Ca,Na,K)(UO2)[SiO3OH]·1.5H2O), and membranous uraninite (UO2.25). This is ascribed to a different loss of radioactive recoil atoms by crystals because of real crystals dimensions and defects and features of ideal atomic structure of minerals

  19. Processing of Sierra Albarrana uranium ores; Tratamiento de los minerales de uranio de Sierra Albarrana

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez Jodra, L.; Perez Luina, A.; Perarnau, M.


    Uranium recovery by hydrometallurgy from brannerite, found in Hornachuelos (Cordoba) is described. It has been studied the acid and alkaline leaching and salt roasting, proving as more satisfactory the acid leaching. Besides the uranium solubilization by acid leaching, is described the further process to obtain pure uranyl nitrate. (Author)

  20. Processing of Sierra Albarrana uranium ores

    International Nuclear Information System (INIS)

    Uranium recovery by hydrometallurgy from brannerite, found in Hornachuelos (Cordoba) is described. It has been studied the acid and alkaline leaching and salt roasting, proving as more satisfactory the acid leaching. Besides the uranium solubilization by acid leaching, is described the further process to obtain pure uranyl nitrate. (Author)

  1. U4+ minerals of different ages and different origins

    International Nuclear Information System (INIS)

    The geological history and some occurences of the three main minerals of U4+ are discussed: uraninite = pitchblende UO2, coffinite USiO4 and brannerite approx. UTiO6. In the first 21/2 aerons uraninite from granites was able to form enormous placer deposits. With increasing of atmospherical oxygen, coffinite and 'pitchblende' formed from U6+ solutions by reduction became more abundant. But it must be mentioned that coffinite can be formed very early as a pegmatite mineral and, on the other hand, uraninite, as a magmatic one until recent time. Brannerite forms magmatic or high hydrothermal deposits, reducing conditions supposed obviously at all times. It is very quickly isotropized and besides that partly decomposed to from anatase with increasing U → Pb. A determination of its content could be roughly used for age determination especially in very old occurences. The photographs are an essential part of the paper. (orig.)

  2. Uranium deposits of the Asian sector of Pacific ocean ore belt

    International Nuclear Information System (INIS)

    Brief description of three basic types of uranium ore deposits in the Asian sector of the Pacific Ocean ore belt, namely uranium-molybdenum vein deposits in the continental volcanic depressions, proper uranium-molybdenum vein deposits in the mesozoic granites and gold-brannerite deposits of the rejuvenated early-proterosoic fractures is given. Schemes of various deposits are presented, petrological and isotope data (K-Ar method) are considered and petro- and oregenesis are analyzed. refs., 9 figs

  3. Extraction of uranium from its ores

    International Nuclear Information System (INIS)

    The ore is ground and mixed with sulphuric acid to give a moist ore containing a sulphuric acid concentration of less than 4N without forming a continuous liquid phase. The moist ore is cured at from 500 to 1000 while passing an oxidising gas through it. Using this method it is possible to achieve uranium extractions of % or better in 24 hours or less. This invention provides an improved method for acid leaching of uranium from its ores and especially from those ores which contain uranium as a finely-diaseminated refractory material, such as brannerite or uraninite. (LL)

  4. Preconcentration of low-grade uranium ores with environmentally acceptable tailings, part I

    International Nuclear Information System (INIS)

    The low-grade ore sample used for this investigation originated from Agnew Lake Mines Limited, Espanola, Ontario. It contained about 1% pyrite and 0.057% uranium, mainly as uranothorite with a small amount of brannerite. Both of these minerals occur in the quartz-sericite matrix of a conglomerate. A preconcentration process has been developed to give a high uranium recovery, reject pyrite, radium and thorium from the ore and produce environmentally acceptable tailings. This process applies flotation in combination with high intensity magnetic separation and gravity concentration

  5. Les minéralisations Cu_(Ni_Bi_U_Au_Ag) d'Ifri (district du Haut Seksaoua, Maroc) : apport de l'étude texturale au débat syngenèse versus épigenèseThe Cu_(Ni_Bi_U_Au_Ag) mineralization of Ifri ('Haut Seksaoua' district, Morocco): contribution of a textural study to the discussion syngenetic versus epigenetic (United States)

    Barbanson, Luc; Chauvet, Alain; Gaouzi, Aziz; Badra, Lakhifi; Mechiche, Mohamed; Touray, Jean Claude; Oukarou, Saı̈d


    The Cu ore of Ifri is a chalcopyrite stockwork hosted by Cambrian formations and was until now interpreted as a syngenetic massive sulphide deposit. Textural studies highlight two generations of pyrite early (Py I) and late (Py II) with respect to the regional deformation. The chalcopyrite stockwork overprinted Py II, outlining the epigenetic nature of the Cu mineralization. Regarding the origin of Cu-depositing fluids, the presence in the stockwork paragenesis of an U, W, Sn association and preliminary Pb/Pb dating of a brannerite belonging to this association suggest a contribution of the Tichka granite. To cite this article: L. Barbanson et al., C. R. Geoscience 335 (2003).

  6. Durability testing of heavy ion irradiated crystalline ceramics

    International Nuclear Information System (INIS)

    The purpose of this report is to assess the effects of heavy-ion irradiation on the durability of pyrochlore-rich baseline ceramics and single-phase pyrochlore, zirconolite and brannerite ceramics. Development of a titanate-based crystalline ceramic form to immobilize surplus weapons-useable plutonium for disposition is the mission of the Plutonium Immobilization Project (PIP). A major development and testing activity for this program is performance testing and qualification of the wasteform for a repository. As part of the performance testing, the leaching behavior of the ceramic form must be evaluated to determine the anticipated repository behavior. To study the impact of radiation damage on the performance of the ceramic, the damage must be accelerated using techniques such as 238Pu doping and ion irradiation. The purpose of this report is to assess the effects of heavy-ion irradiation on the durability of pyrochlore-rich baseline ceramics and single-phase pyrochlore, zirconolite and brannerite ceramics. Ion irradiation of ceramic pellet surfaces will transform the outermost several tenths of microns of the surface into a metamict (i.e., noncrystalline) state. Short-term monolithic leach tests on unirradiated and irradiated samples should elucidate any significant differences in the durability of the undamaged crystalline surface versus the damaged metamict surface. Data developed under this task will support a preliminary integrated data report to be supplied to the Office of Civilian Radioactive Waste Management (RW) for use in the license application for the candidate Yucca Mountain repository

  7. Characterization of phase assemblage and distribution in titanate ceramics with SEM/EDS and X-ray mapping

    International Nuclear Information System (INIS)

    Titanate ceramics have been selected for the immobilization of excess plutonium. The baseline ceramic formulation leads to a multi-phase assemblage, which consists of a majority pyrochlore phase plus secondary phases. The phase distribution depends on processing conditions and impurity loading. In this paper, we report on the characterization of the phase assemblage and distribution in titanate ceramics using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), and x-ray dot mapping. Two titanate ceramics were studied a baseline ceramic and a ceramic with impurities. In the baseline ceramic, the secondary phases that were observed include zirconolite, brannerite, and rutile. Additional phases, such as perovskite, an Al-Ti-Ca phase, and a silicate phase, formed in the impurity ceramic. The distribution of these phases was characterized with backscattered electron (BSE) imaging, except for zirconolite. While the zirconolite exhibited weak contrasts in BSE images and could not be easily distinguished from the pyrochlore matrix, its distribution was effectively characterized with x-ray mapping. Quantitative analyses of BSE images and x-ray maps reveal that the impurity ceramic contains less brannerite, rutile, and pores than the baseline ceramic

  8. Nature of uranium mineralisation in the Kerpura - Tiwari-ka-bas Area, Sikar District, Rajasthan

    International Nuclear Information System (INIS)

    Mineralisation of uraninite and brannerite occurs in the albitised metasedimentary and intrusive igneous rocks of Kerpura-Tiwari-ka-bas area in Sikar District, Rajasthan. Samples collected from well dumps contain 0.016 to 1.52% U3O8 with very low ThO2. The host rocks show wide variation in chemical composition due to varying degree of alkali metasomatism, associated alteration and composition of protoliths. The spatial distribution of uranium in groundwater as well as rock samples from well dumps indicates localisation of the uranium mineralisation along NNE-SSW and NW-SE directions in Kerpura block. Petrographic and lithogeochemical studies point towards close genetic relationship between alkali metasomatism and uranium mineralisation. The mineralisation seems to be due to mobilisation of uranium and other LILEs by metasomatising fluids and their deposition along shear zones at a later stage, which may not be spatially related to zones of intense albitisation. (author)

  9. Investigations on the Nature and Physical Concentration of Spanish Uraniferous Quartzites

    International Nuclear Information System (INIS)

    A study was made of a sample of radioactive material from Santa Elena (Jaen) containing 130 ppm U3O8, 600 ppm ThO2, 4.96% ZrO2 and 14.29% TiO2. Over 150 million tons of material were examined. In the light of the studies carried out the material can be defined as a rutilo-zirconiferous quartzite with a double radioactivity source due to the uranium enclosed in the zircon lattice structure and to the presence of monazite. The possibility of brannerite or davidite being present can be discarded. There is likewise no conclusive evidence of the presence of sphene, rutile being the most abundant titanium mineral- The author determined the features of the ore with a view to its physical concentration and applied magnetic and gravimetric separation and the flotation process. The use of oleic acid as collector has permitted good zircon recovery. (author)

  10. Investigations on the nature and physical concentration of Spanish uraniferous quartzites

    International Nuclear Information System (INIS)

    A study was made of a sample of radioactive material from Santa Elena (Jaen) containing 130 ppm U3O8, 300 ppm ThO2, 4.96% ZrO2 and 14.29% TiO2. Over 150 million tons of material were examined. In the light of the studies carried out the material can be defined as a rutilo-zirconiferous quartzite with a double radioactivity source due to the uranium enclosed in the zircon lattice structure and to the presence of monazite. The possibility of brannerite or davidite being present can be discarded. There is likewise no conclusive evidence of the presence of sphene, rutile being the most abundant titanium mineral. The author determined the features of the ore with a view to its physical concentration and applied magnetic and gravimetric separation and the flotation process. The use of oleic acid as collector has permitted good zircon recovery. (author)

  11. Mineralogical test as a preliminary step for metallurgical proses of Kalan ores

    International Nuclear Information System (INIS)

    Mineralogical tests as a preliminary step for hydrometallurgy of Kalan ores, including Eko Remaja and Rirang have been carried out to identify the elements and minerals content which affect the metallurgical process, especially the leaching and purification of uranium. Mineralogical tests have been done by means of radioactive and radioluxugraph tests to identify radioactive minerals; thin specimen analysis, Scanning Electron Microscopy (SEM) to identify elements and morphology, EPMA to analyse qualitatively the elements, X-ray Diffractometer (XRD) to identify of minerals content; and X-ray Fluorescence (XRF) and chemical analyses to determine total elements qualitatively and quantitatively. The experimental results show that the Eko Remaja ores contain uraninite and brannerite, iron and titan oxides, sulfides, phosphates and silicates minerals, while the Rirang ores contain uraninite, monazite and molybdenite

  12. Crystal structure, spectroscopy and thermodynamic properties of MIVWO6(MI - Li, Na)

    International Nuclear Information System (INIS)

    In the present work lithium (sodium) vanadium tungsten oxides with brannerite structure is refined by the Rietveld method (space group C2/m, Z=2). IR and Raman spectroscopy was used to assign vibrational bands and determine structural particularities. The diffuse reflectance spectra allow to calculate bandgap for MIVWO6(MI - Li, Na). The temperature dependences of heat capacity have been measured first in the range from 7 to 350 K for these compounds and then between 330 and 640 K, respectively, by precision adiabatic vacuum and dynamic calorimetry. The experimental data were used to calculate standard thermodynamic functions, namely the heat capacity Cpo(T), enthalpy Ho(T)-Ho(0), entropy So(T)-So(0) and Gibbs function Go(T)-Ho(0), for the range from T→0 to 640 K. The differential scanning calorimetry was applied to measure decomposition temperature of compounds under study. - Graphical abstract: Fragment of the structure of Li(Na)VWO6.


    Directory of Open Access Journals (Sweden)

    Gh. Rogobete


    Full Text Available The underground exploitation of the ores established many waste dumps. The mineralization with pechblenda, the main uranium ore, exists in lenticular layers of small thickness. The rocks with uranium mineralization recover in the waste dumps, increasing the level to the ionizing radiation exposition. In Tincota the radiation levels found where between 50 and 600 c/s, with maximum levels 600-1200 c/s in the waste dump. The road DJ 680 Caraşova-Voislova are the levels 800-1200 c/s, that is 2-3 times more than the dose accepted in the Norms. The magnetite are from Boul Peak is associated with a radioactive ore (brannerit and the road Ruschiţa-Voislova was contaminated, the levels at the flotation base near the road reached times more than normally.

  14. Effect of microstructure changes on the mobility of radionuclides in simulated HLW ceramics

    International Nuclear Information System (INIS)

    Ceramic matrices for immobilization of HLW (e.g. perovskite, zirconolite, brannerite, zircon mineral based ceramics), prepared at ANSTO and C.I.A.E., respectively were characterized at the NRI Rez from the viewpoint of their microstructure and transport property changes caused by leaching. Scanning electron microscopy (SEM) and diffusion structural analysis (DSA) techniques were used. The thermal behavior of 'as leached' and 'as prepared' samples were compared. The DSA was used for the evaluation of atomic transport properties of the ceramic matrices. The effect of leaching on the thermal stability of the ceramics microstructure was characterized. The behaviour of the ceramic HLW matrices in simulated repository conditions was predicted by using the results of the mathematical modeling. (author)

  15. The 'pitchblende-nodule-assemblage' of Mitterberg (Salzburg, Austria)

    International Nuclear Information System (INIS)

    Radiometric investigations of the presently closed copper mine of Mitterberg, Salzburg, led to the discovery of uranium mineralizations. Samples with pitchblende nodules up to two inches in size were found in old mining dumps. Altaite, bournonite, brannerite, calvaverite, cinnabar, coloradoite, galena, native gold, hessite, metacinnabar, molybdenite, pyrite, pyrrhotite, sphalerite and thus far unknown mineral 'X', an alteration product of rammelsbergite, were identified by the author. U and Mo of the 'Nodule-Assemblage' are explained as mobilization products of weak, strata-bound uranium mineralizations in quartzites of the 'Violet Series', a Permo-Carboniferous sedimentary sequence cut by the main copper vein. The later uranium mineralization of presently unassessed economic potential will be discussed in another paper. Age determinations (KOEPPEL, in PETRASCHECK 1975) of the reniform pitchblende indicate a crystallization age of 90 million years. This implies that the copper mineralization of the main copper vein can be related to Upper-Cretaccous remobilization processes. (orig./HK) 891 HK

  16. Geology and genesis of uranium deposits in the early proterozoic: Blind River - Elliot Lake Basin, Ontario, Canada

    International Nuclear Information System (INIS)

    Large stratiform uranium deposits in the Blind River - Elliot Lake basin, Ontario, Canada, occur in early Proterozoic siliciclastic beds and lenses deposited in paleo-depressions and marginal portions of a pericratonic basin at the southern margin of the Canadian Shield. They are heavy mineral concentrations deposited syngenetically with quartz pebble conglomerate. The beds form the basal part of the Huronian Supergroup deposited between 2.6 and 2.25 Ga ago. Uranium mineralogy shows evidence of later modification by epigenetic processes. A conceptual genetic model for formation of the deposits is as follows: (a) derivation of uranium-bearing detritus from granitic source rocks, which were emplaced during the Kenoran Orogeny; (b) fluvial transportation of this detritus under oxygen-deficient conditions (between 10-2 and 10-6 Pal (Present Atmospheric Level)) and deposition of the well-sorted material as placer concentrations; and (c) diagenetic modification of the deposits associated with formation of authigenic minerals such as 'brannerite' (a U-Ti-Si phase) and coffinite. The uraniferous conglomerate consists of quartz pebbles embedded in an arkosic matrix with abundant pyrite, uraninite, 'brannerite', monazite, zircon and other heavy minerals. Locally hydrocarbon seams, veins and nodules are found in the conglomerate and they contain elevated amounts of uranium and gold. Several uranium-bearing conglomerate beds (reefs), indicate cyclic sedimentation related to epeirogenetic movements of the source area and/or the depositional sites. The main reefs form large sheet-like bodies containing from 10,000 to more than 100,000 tonnes of uranium metal. The younger members occur in the Elliot Lake segment, i.e. in the Quirke syncline. The Huronian Supergroup is intruded by gabbroic dykes and locally contains intercalated gabbroic sills. The mines in the Blind River - Elliot Lake basin have, from 1955 until the end of 1984, produced 108,847 tonnes of uranium metal from ores

  17. The origin of the Avram Iancu U-Ni-Co-Bi-As mineralization, Băiţa (Bihor) metallogenic district, Bihor Mts., Romania (United States)

    Zajzon, Norbert; Szentpéteri, Krisztián; Szakáll, Sándor; Kristály, Ferenc


    The Băiţa metallogenic district in the Bihor Mountains is a historically important mining area in Romania. Uranium mining took place between 1952 and 1998 from various deposits, but very little is known about the geology and mineralogy of these deposits. In this paper, we describe geology and mineralogy of uranium mineralization of the Avram Iancu uranium mine from waste dump samples collected before complete remediation of the site. Texturally and mineralogically complex assemblages of nickeline, cobaltite-gersdorffite solid solution, native Bi, Bi-sulfosalts, molybdenite, and pyrite-chalcopyrite-sphalerite occur with uraninite, "pitchblende," and brannerite in most of the ore samples. The association of nickel, cobalt, and arsenic with uranium is reminiscent of five-element association of vein type U-Ni-Co-Bi-As deposits; however, the Avram Iancu ores appear to be more replacement-type stratiform/stratabound. Avram Iancu ore samples contain multistage complex, skarn, uranium sulfide, arsenide assemblages that can be interpreted to have been formed in the retrograde cooling stages of the skarn hydrothermal system. This mineralizing system may have built-up along Upper Cretaceous-Paleogene "Banatite" intrusions of diorite-to-granite composition. The intrusions crosscut the underlying uraniferous Permian formations in the stacked NW-verging Biharia Nappe System. The mineralization forms stacked, multilayer replacement horizons, along carbonate-rich lithologies within the metavolcanic (tuffaceous) Muncel Series. Mineral paragenesis and some mineral chemistry suggest moderate-to-high solid solutions associated with minute but abundant uranium minerals. Within the later arsenide-sulfarsenide mineral assemblage, there is great variation in Ni, Co, and S content with generally increasing arsenic content. Uranium minerals in this late-stage assemblage include very fine euhedral uraninite and brannerite inclusions in arsenide-sulfarsenide minerals. Native bismuth and Bi

  18. Elkon - A new world class Russian uranium mine

    International Nuclear Information System (INIS)

    Full text: The uranium deposits of Elkon district are located in the south of Republic of Sakha Yakutia. Deposits contain about 6% of the world known uranium resources: 342 409 tonnes of in situ or 288 768 tonnes of recoverable RAR + Inferred resources. Most significant uranium resources of Elkon district (261 768 tonnes) were identified within five deposits of Yuzhnaya zone. The uranium grade averages 0.15%. Gold, silver and molybdenum are by-products. Principal resources are proposed to be mined by conventional underground method. Location, shape and dimensions of uranium ore bodies are primarily controlled by NW-SE oriented and steeply SW dipping faults of Mesozoic age and surrounding pyrite-carbonate-potassium feldspar alteration zones. Country rocks are Archean gneisses. Deposits are of metasomatic geological type. Principal mineralization is represented by brannerite. The Yuzhnaya zone is about 20 km long. It was explored by underground workings and drill holes. Upper limit of ore bodies is at a depth of between 200 m and 500 m. Depth persistence exceeds 2 000 m. Uranium mining enterprise Elkon was established in November 2007. It is a 100% Atomredmetzoloto subsidiary. The planned producing capacity is 5 000 m tU/year. It will perform the entire works related to uranium mining, milling, ore sorting, processing and uranium dioxide production. Technology of ore processing assumes primary radiometric sorting, thickening, sulphide flotation for gold concentrate extraction, subsequent autoclave sulphuric-acid uranium leaching from flotation tails and uranium adsorption onto resin, roasting and heap leaching for uranium from low grade ores, cyanide leaching of gold. Due to a considerable abundance of brannerite ore is classified as refractory. Elkon development include 4 main stages: feasibility study and infrastructure development (2008- 2010), mine and mill construction (2010-2015), pilot production (2013-2015), mine development and achieving full capacity

  19. Genesis of sandstone-type uranium deposits in the Sierra Pintada district, Mendoza, Argentina: a Moessbauer study

    International Nuclear Information System (INIS)

    The genesis of sandstone-type uranium deposits in the Cochico Group (Permo-Triassic) of the Sierra Pintada district, San Rafael, Mendoza, has been studied. This is the most important uranium district in Argentina. Uranium sources, uranium transport and precipitation are discussed. Uraninite and brannerite, the main uranium minerals, occur within the matrix of sandstone. Several phenomena can be deduced regarding the depositional environment. Where oxygen was available, precipitation of hydrated ferric oxides occurred; γFe2O3.nH2O varieties (identified by Moessbauer spectroscopy) precipitated in the upper levels of the aquifer, where CO2 partial pressure was lower, giving reddish or reddish-brown beds. The CO2 partial pressure also determines the distribution of biogenic agents such as bacteria. Bacteria thus find a more favourable environment for their development and action in upper levels of an aquifer. In the corresponding horizons local reduction occurred where UO2 precipitated; therefore the highest uranium concentrations correspond to sandstone levels with reddish or reddish-brown pigment. These pigments have been identified by Moessbauer spectroscopy. (Auth.)

  20. Cerium as a Surrogate in the Plutonium Immobilized Form

    International Nuclear Information System (INIS)

    The Department of Energy (DOE) plans to immobilize a portion of the excess weapons useable plutonium in a ceramic form for final geologic disposal. The proposed immobilization form is a titanate based ceramic consisting primarily of a pyrochlore phase with lesser amounts of brannerite, rutile, zirconolite, vitreous phases and/or other minor phases depending on the impurities present in the feed. The ceramic formulation is cold-pressed and then densified via a reactive sintering process. Cerium has been used as a surrogate for plutonium to facilitate formulation development and process testing. The use of cerium vs. plutonium results in differences in behavior during sintering of the ceramic form. The phase development progression and final phase assemblage is different when cerium is substituted for the actinides in the form. However, the physical behavior of cerium oxide powder and the formation of a pyrochlore-rich ceramic of similar density to the actinide-bearing material make cerium an adequate surrogate for formulation and process development studies

  1. Heavy mineral distribution and geochemistry related to sedimentary facies variation within the uraniferous intermediate reefs placers, Witwatersrand Supergroup, South Africa

    International Nuclear Information System (INIS)

    The Intermediate Reefs placers of the Precambrian Central Rand Group, Welkom goldfield, comprise interbedded quartz arenites, quartz wackes, and pyritic U-Au bearing quartz pebble conglomerates which currently are of subeconomic potential. On lithological grounds the Intermediate Reefs are subdivided into two members. The present investigations showed that the lower member is developed as a mature placer which accumulated in a perennial braided stream environment, and the upper one as immature sedimentary deposits which were accumulated under ephemeral conditions. Geochemical and mineragraphic studies reveal that for the Intermediate Reefs zone, brannerite is the principal uranium carrier and that the gold/uranium ratio is low when compared to other reefs of the Welkom goldfield. The studies, furthermore, show that the two members of the Intermediate Reefs differ in the relative abundance of their detrital minerals. It is suggested that these differences are caused by differing lithologies in the respective provenance terranes rather than by variations of the prevailing sedimentary processes. The subeconomic ore grade of the Intermediate Reefs is attributed to: (i) lack of economic minerals in their sedimentary source, (ii) absence of reworkable well mineralized placers in their footwall, and (iii) inadequate hydraulic conditions preventing the efficient accumulation of uraninite and gold. (author). 28 refs, 9 figs, 3 tabs

  2. Metasomatic uranium mineralisation of the Mount Isa North Block

    International Nuclear Information System (INIS)

    Proterozoic uranium deposits of the Mt Isa North Block are centred 40 km north of Mt Isa, NW Queensland. Regionally, the deposits occur within the Leichhardt River Fault Trough of the Mt Isa Inlier. Uranium mineralisation is likely related to the 1 600-1 500 Ma Isan Orogeny. Structurally-controlled uranium mineralisation is preferentially hosted in greenschist facies basalts and interbedded clastic sediments of the Eastern Creek Volcanics (ECV). Uranium deposits of the Mt Isa North Block are defined by the following general characteristics: • Pervasive sodium and calcium metasomatism, expressed as red albitite with finely disseminated hematite and calcite, with distal zones of chlorite and magnetite. • Uraniferous albitite deposits typically comprise en echelon lenses and shoots. • Mineralisation is developed along N- to NE-striking shear zones with associated brittle deformation of the host lithologies. • Host rocks are mostly basalt flows with flow-top breccias and interbedded sandstones and siltstones of the ECV; quartzites are also locally mineralised. • Uranium mineralogy of albitites comprises brannerite, coffinite, uraninite and uraniferous zircon. The Mt Isa North Blocks includes 11 tenements being explored for uranium by Summit Resources. Summit’s five uranium resources total 95.7 Mlb U3O8. Summit is in a 50/50 Joint Venture with Paladin on the Valhalla and Skal deposits. Paladin also has a direct ownership of 81.99% of the issued shares of Summit Resources. (author)

  3. Uranium mineralization along the northeastern margin of proterozoic Chhattisgarh Basin around Chitakhol, Central India: a petromineralogical study

    International Nuclear Information System (INIS)

    Uranium mineralization occurs along the unconformity contact between the basement granites and the overlying Chandrapur sediments of the Chhattisgarh Supergroup along the northeastern margin of the Chhattisgarh Basin around Chitakhol area, Korba and Janjgir - Champa districts, Chhattisgarh. A number of uranium occurrences, spread over an area of 20 km2, have been delineated with surface samples analyzing up to 0.39% U3O8 in sediments, 2.72% U3O8 in basement granites and up to 0.21% U3O8 in basic dykes. The uranium mineralization is confined to the basement granites and the overlying sediments proximal to the unconformity contact. The basic dykes traversing the basement granites are also mineralized. Uranium mineralization at the depth is associated with carbonaceous black shale and is represented by coffinite and pitchblende. Uraninite, brannerite with 'U-Fe-Ti' complex, meta-autunite and uranophane also contribute to the mineralization. However, in surface and near surface samples uranium occurs in adsorbed state on to goethite and also as filling the criss-cross fractures. Fracture filled, epigenetic, hydrothermal type of uranium mineralization related to the Proterozoic unconformity is manifested

  4. Petrographic and mineragraphic investigations of the archaean gold placer at Mount Robert in the Pietersburg greenstone belt, Northern Transvaal

    International Nuclear Information System (INIS)

    The fossil gold placer on Mount Robert near Potgietersrus, northern Transvaal, occurs in the Uitkyk Formation. This formation consists of arenaceous rocks with interlayered conglomerates and shales, and occurs at the top of the Archaean Pietersburg Sequence which forms the Pietersburg greenstone belt. The host rock of the occurrence consists of conglomerates. Its fragments indicate that the provenance area consisted of acid porphyritic lava, chert, banded iron-formation, quartzite, basic lava, vein quartz, and shale. It is suggested that the Uitkyk sediments were transported over short distances and originated from the erosion of a greenstone terrane. The mineralogy of the ore is relatively simply and resembles that of the much younger Witwatersrand banket. Rounded allogenic and, to a lesser extent, idiomorphic to hypidiomorphic authigenic pyrite form the main constituents. Less abundant but genetically interesting ore minerals that have been found so far are leucoxene-rutile, chromite, molybdenite, zircon, carbonaceous matter, and brannerite. The Mount Robert occurrence can be regarded as a primitive forerunner of the Witwatersrand goldfield. Ineffective sedimentary enrichment processes and an environment unfavourable for life-forms that could have acted as biogenic gold and uranium concentrators are regarded as possible reasons for the low gold content and scarcity of uranium-bearing minerals in the investigated Uitkyk conglomerates

  5. Atomic mineral speciation in Cuddapah Basin and its environs (India): genetic implications for uranium mineralisation

    International Nuclear Information System (INIS)

    The X-ray diffraction (XRD) studies reveal that in syngenetically-mineralised (widespread) Neoarchaean to Palaeoproterozoic basement granitoids, the primary uranium minerals (PUMs) are uranium oxide (uraninite), uranium-silicate (coffinite), and uranium titanium oxide (brannerite), whereas, the (remobilised) secondary uranium minerals (SUMs) have only three species: (i) hydrous oxide hydrate (ianthinite and masuyite), (ii) silicate (uranophane, beta-uranophane, and kasolite), and (iii) phosphate (hydrogen-autunite, metaautunite, and meta-uranocircite), besides a solitary occurrence of arsenate hydrate (metazeunerite) in a fracture zone. Interestingly, thorium and rare-earth element (REE) mineral occurrences are also widespread though with limited speciations. Syngenetic thorium and REE mineral species are phosphate (monazite and xenotime) and silicate (thorite and chevkinite). Furthermore, niobium-tantalum mineral phases, with occasional occurrences in pegmatitic phases within the basement granitoids, are exemplified by columbite-tantalite, samarskite, microlite, and euxenite. In the Nellore schist belt, restricted species of uranium minerals have been noted: oxide (uraninite) and silicate (uranophane and beta-uranophane), whereas, the REE phase is chevkinite. Considerable speciations of rare-metal, rare-earth, and thorium minerals are noted in the younger granite

  6. Preconcentration of a low-grade uranium ore yielding tailings of greatly reduced environmental concerns. Part V

    International Nuclear Information System (INIS)

    The low-grade ore sample used for this investigation contained 0.057 percent uranium with uranothorite as the major uranium-bearing mineral and a small amount of brannerite, occurring in the quartz-sericite matrix of a conglomerate. The preconcentration procedures, consisting of pyrite flotation with or without flotation of radioactive minerals, followed by high intensity wet magnetic treatment of the sized flotation tailings, produced pyrite and radioactive concentrates of acceptable uranium grades ranging from 0.1 to 0.135 percent uranium. The combined concentrates comprised 37 to 49 percent of the ore by weight with the following combined recoveries: 95.6 to 97.9 percent of the uranium; 94.7 to 96.3 percent of the radium; 97.8 to 99.3 percent of the thorium over 98 percent of the pyrite. The preconcentration tailings produced comprised between 51 and 63 percent of the ore by weight and contained from: 0.0022 to 0.0037 percent U; 12 to 17 pCi/g Ra; 0.002 to 0.004 percent Th less than 0.03 percent S. Because these tailings are practically pyrite-free, they should not generate acidic conditions. Due to their low radium content, their radionuclide hazards are greatly reduced. These preconcentration tailings therefore, could be suitable for surface disposal, mine backfill, revegetation or other uses

  7. Geology and uranium mineralisation around Ampulli Area, Papum-Pare District, Arunachal Pradesh, North-East India

    International Nuclear Information System (INIS)

    Uranium mineralisation associated with Middle Proterozoic Bomdila Group (Daling equivalent) metasediments have been located intermittently over a strike length of 310 m with 0.11 to 2.0 m thickness around Ampulli area of Papum-Pare district, Arunachal Pradesh. The metasediments trend NE-SW and dip 20°- 85° due either side. The grab and trench samples assayed 0.012 - 0.36% eU3O8, 0.006 - 0.19% U3O8 (beta/gamma), 0.009 - 0.235% U3O8 (Chem.) and less than 0.010% ThO2. The host rocks have been identified as tourmaline bearing biotite-quartz schist, garnet bearing muscovite-biotite-quartz schist and muscovite-biotite schist. Uraninite, brannerite and U-Ti complex are observed with uranocircite and meta-uranocircite, the secondary uranium minerals. Replacement of uraninite by molybdenite and pyrite suggested earlier oxide and later sulphide phase. Partial chemical analysis indicated aluminous nature of the host rock and their high K2O/Na2O (3.3-10.73) ratios are suggestive of predominance of potash feldspar over sodic and effects of potash metasomatism. Both syngenetic as well as epigenetic hydrothermal origin of uranium mineralisation has been suggested. (author)

  8. Mineralogical changes in Witwatersrand placer uranium during Proterozoic weathering, Welkom Goldfield, South Africa

    International Nuclear Information System (INIS)

    The Eldorado paleosurface marks the last major period of erosion in the Witwatersrand succession in the Welkom goldfield. Fluvial and debris-flow pediments on this surface contain placer concentrates that were ultimately derived by the repeated erosion of subcropping placers, which occur within a sequence of onlapping formations, separated by unconformities, near the southern margin of the basin. Autoradiographs of core drilled through the pediment indicate that uranium mineralization is associated with detrital pyrite accumulations on the Eldorado paleosurface. This mineralization occurs as fluvial bedload concentrates that were deposited in shallow paleochannels, and with conglomeratic diamictites. Comparison of heavy mineral assemblages in crushed concentrates of the subcropping placers with those from the Eldorado pediment, indicates that: the suite of heavy minerals is the same; all three varieties of pyrite show detrital rounding, including secondary pyrite that originally formed in situ in the older placers; kerogen particles appear to be rounded allogenic grains of broken columnar kerogen derived from erosion of older placers; uraninite is very sparse and occurs as rare inclusions in the rounded kerogen grains and even more rarely as free allogenic grains; there is extensive evidence of alteration because the uranium occurs predominantly as brannerite and uraniferous leucoxene. The rarity of uraninite indicates that most of the grains of that mineral were destroyed during reworking and exposure to the elements on a fan pediment. The destruction could have been due to the oxidation of tetravalent uranium to hexavalent uranium by a weakly oxidising atmosphere. (author). 15 refs, 8 figs, 3 tabs

  9. Determination of Quality, Quantity, and Geometry of Uranium Deposit at North Tanah Merah, Kalan, West Kalimantan

    International Nuclear Information System (INIS)

    The research based on 1997/1998 the systematic prospect ion result which was discovered a uranium mineralization zones indication with in the area of 11,733 m2 at Tanah Merah. That mineralization were found with in favourable, rock of quartzite that intruded by granitic rock. Uranium minerals are uraninite and brannerite, fill in spots and incontinously WNW-ESE fractures. The aim of this research was to find information about sub surfaces uranium geology characteristic, geometric, and U resources available at North Tanah Merah using shallow geological exploration drilling. The result of drilling at 3 locations arising 60 m depth each, have found some uranium mineralization indications that was identified as in uranium ore lensis. The geometri of the lensis is 5 cm-3 m lenght, 15 cm maximum wide and 5-150 thick. The result of U reserve estimation around 3 drill holes with in 5.064 m2 area and at 66 m depth, is contain 31.348 tons U with in inferred category. (author)

  10. Expected radiation effects in plutonium immobilization ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Van Konynenburg, R.A., LLNL


    The current formulation of the candidate ceramic for plutonium immobilization consists primarily of pyrochlore, with smaller amounts of hafnium-zirconolite, rutile, and brannerite or perovskite. At a plutonium loading of 10.5 weight %, this ceramic would be made metamict (amorphous) by radiation damage resulting from alpha decay in a time much less than 10,000 years, the actual time depending on the repository temperature as a function of time. Based on previous experimental radiation damage work by others, it seems clear that this process would also result in a bulk volume increase (swelling) of about 6% for ceramic that was mechanically unconfined. For the candidate ceramic, which is made by cold pressing and sintering and has porosity amounting to somewhat more than this amount, it seems likely that this swelling would be accommodated by filling in the porosity, if the material were tightly confined mechanically by the waste package. Some ceramics have been observed to undergo microcracking as a result of radiation-induced anisotropic or differential swelling. It is unlikely that the candidate ceramic will microcrack extensively, for three reasons: (1) its phase composition is dominated by a single matrix mineral phase, pyrochlore, which has a cubic crystal structure and is thus not subject to anisotropic swelling; (2) the proportion of minor phases is small, minimizing potential cracking due to differential swelling; and (3) there is some flexibility in sintering process parameters that will allow limitation of the grain size, which can further limit stresses resulting from either cause.

  11. Blind River uranium deposits: the ores and their setting

    International Nuclear Information System (INIS)

    In the Blind River area, Proterozoic clastic sedimentary and minor volcanic rocks (Huronian Supergroup) unconformably overlie and transgress northward over dominantly granitic Archean terrane (2500 million years) and are intruded by Nipissing Diabase (2150 million years). Later deformations and metamorphic events are recognized. The Matinenda Formation (basal Huronian) comprises northward-derived arkose, quartzite, and pyritic, uraniferous oligomictic conglomerates, which contain 75 percent of Canada's uranium reserves. Historic grades approximate 2 pounds U3O8/ton (1 kilogram/metric ton), but lower grade material can be mined with increasing price. Some thorium and rare earths have been marketed. The conglomerate beds lie in southeasterly striking zones controlled by basement topography down-sedimentation from radioactive Archean granite. Distribution of monazite relative to uraninite and brannerite and the presence of uranium values in overlying polymictic conglomerates, which truncate the ore beds, indicate that the mineralization is syngenetic, probably placer. The role of penecontemporaneous mafic volcanics is problematical, but these could have been a source for sulphur in the pyrite. Drab-coloured rocks, uranium and sulphide mineralization, and a post-Archean regolith formed under reducing conditions all suggest a reducing environment. Sedimentary features indicate deposition in fast-flowing shallow water and possibly a cold climate. In the upper Huronian (Lorrain Formation), a monazite and iron oxide assemblage associated with red beds suggests a change to oxidizing conditions

  12. Tectono-metamorphic evolution of the internal zone of the Pan-African Lufilian orogenic belt (Zambia): Implications for crustal reworking and syn-orogenic uranium mineralizations (United States)

    Eglinger, Aurélien; Vanderhaeghe, Olivier; André-Mayer, Anne-Sylvie; Goncalves, Philippe; Zeh, Armin; Durand, Cyril; Deloule, Etienne


    The internal zone of the Pan-African Lufilian orogenic belt (Zambia) hosts a dozen uranium occurrences mostly located within kyanite micaschists in a shear zone marking the contact between metasedimentary rocks attributed to the Katanga Neoproterozoic sedimentary sequence and migmatites coring domes developed dominantly at the expense of the pre-Neoproterozoic basement. The P-T-t-d paths reconstructed for these rocks combining field observations, microstructural analysis, metamorphic petrology and thermobarometry and geochronology indicate that they have recorded burial and exhumation during the Pan-African orogeny. Both units of the Katanga metasedimentary sequence and pre-Katanga migmatitic basement have underwent minimum peak P-T conditions of ~ 9-11 kbar and ~ 640-660 °C, dated at ca. 530 Ma by garnet-whole rock Lu-Hf isochrons. This suggests that this entire continental segment has been buried up to a depth of 40-50 km with geothermal gradients of 15-20 ° 1 during the Pan-African orogeny and the formation of the West Gondwana supercontinent. Syn-orogenic exhumation of the partially molten root of the Lufilian belt is attested by isothermal decompression under P-T conditions of ~ 6-8 kbar at ca. 530-500 Ma, witnessing an increase of the geothermal gradients to 25-30 °C·km- 1. Uranium mineralizations that consist of uraninite and brannerite took place at temperatures ranging from ~ 600 to 700 °C, and have been dated at ca. 540-530 Ma by U-Pb ages on uraninite. The main uranium deposition thus occurred at the transition from the syn-orogenic burial to the syn-orogenic exhumation stages and has been then partially transposed and locally remobilized during the post-orogenic exhumation accommodated by activation of low-angle extensional detachment.

  13. Fluid inclusion study of the uranium mineralised granite cataclasite/mylonite and quartz reef in the Mulapalle area, Cuddapah district, Andhra Pradesh

    International Nuclear Information System (INIS)

    Granite cataclasite and mylonite in the basement fracture zones around Mulapalle in the southwestern environs of the Cuddapah basin are uraniferous with the presence of brannerite, U-Ti complex and uraninite. The ENE-WSW trending fracture zone is cut by NW-SE trending quartz reef. Fluid inclusion study carried out on quartz from the mineralized cataclasite and as well as from the quartz reef shows the presence of both primary [8-20 microns] and abundant secondary up to [6 microns] inclusions. Most of the inclusions are bi-phase (L+V) liquid rich having a degree of fill around 0.90 with constant liquid to vapour ratio. Few inclusions are liquid monophase and multiphase [S+L+V]. They behave as H2O-NaCl system and homogenize into liquid phase at low temperature range [125 to 200 degC] except some bi-phase inclusions in the barren quartz reef, which are found to behave as an impure H2O-NaCl system admixed with other salts. Wide variation of salinity in the range of 3-25 wt%e NaCl is recorded by the inclusions in both the mineralized cataclasite and the barren quartz reef. The trapping pressure [PT] of the inclusions of barren quartz reef spreads between 200 to 600 bars while those of mineralized cataclasite restricts to upper end of that range. Some inclusions in mineralized cataclasite that homogenize at high temperatures [200 to 250 degC] show PT between 800 to 1000 bars. The presence of more than one population without any change in fluid composition indicate their origin at different stages of deformation modifying the primary inclusions of the granite and from fluids migrated through fractures at later stages. In the barren quartz reef, the distribution of inclusions of contrasting salinity implies the environment of mixing of connectively driven hydrothermal fluid of metamorphic origin and meteoric water. (author)

  14. Interim report on task 1.2: near equilibrium processing requirements - attrition milling part 1 of 2 to Lawrence Livermore National for contract b345772

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, M W A; Vance, E R; Day, R A; Eddowes, T; Moricca, S


    The objective of Task 1.2 has only partly been achieved as the work on Pu/U-formulations and to a significant degree on Th/U-formulations has been performed under grinding/blending conditions that did not replicate plant-like fabrication processes, particularly in the case with the small glovebox attritor. Nevertheless the results do show that actinide-rich particles, not present in specimens made via the alkoxide-route (equilibrium conditions), occur when the grinding process is not efficient enough to ensure that high-fired PuO{sub 2}, ThO{sub 2} and UO{sub 2} particles are below a critical size. Our current perception is that the critical size for specimens sintered at 1350 C for 4 hours is about 5 {micro}m in diameter. The critical size is difficult to estimate, as it is equal to the starting diameter of actinide oxides just visible within brannerite regions. Our larger scale attritor experiments as well as experience with wet and dry ball milling suggests that acceptable mineralogy and microstructure can be obtained by dry milling via attritor and ball mills. This is provided that appropriate attention is paid to the size and density of the grinding media, grinding additives that reduce caking of the powder, and in the case of attritors the grinding speed and pot setup. The ideal products for sintering are free flowing granules of {approx} 100 {micro}m containing constituents ground to about 1 {micro}m to ensure homogeneity and equilibrium mineralogy.

  15. Fundamental thermodynamics of actinide-bearing mineral waste forms

    International Nuclear Information System (INIS)

    In September 2000, the US and Russia reached an agreement to jointly disposition roughly 68 metric tons of weapons usable plutonium. (Agreement 2000) In Russia, 34 metric tonnes of weapons-grade plutonium will be dispositioned by burning the plutonium as mixed oxide (MOX) fuel. In the US, 25 metric tons of plutonium recovered from pits and clean metal will likewise be dispositioned by burning as mixed oxide (MOX) fuel and about 9 metric tonnes of plutonium stored throughout the DOE complex will be dispositioned by immobilization in a ceramic which will then be encapsulated in high-level waste (HLW) glass. In all cases, the plutonium will be made equal to or less attractive for reuse in nuclear weapons than the much larger and growing inventory of plutonium in spent nuclear fuel. This threshold of unattractiveness is commonly referred to as the ''spent fuel standard.'' In the US, the final products from plutonium disposition, irradiated fuel and ceramic encapsulated HLW, will be emplaced in the Federal Waste Repository, which is assumed to be Yucca Mountain. The ceramic form selected for the disposition of plutonium is composed of a series of titanate-based phases which are generally referred to as SYNROC (short for Synthetic Rock). The particular formulation that was selected is composed of about 80 vol % pyrochlore, about 15 vol % brannerite, and about 5 vol % rutile. If impurities are present in the PuO2 feed material, about a half a dozen other phases can also form. The most common of these are zirconolite and a silicate glass. A screening process conducted in 1995, resulted in the selection of borosilicate glasses and titanate-based ceramics (e.g. SYNROCs) as the best available options for immobilization of plutonium. In 1998, a pyrochlore-rich ceramic form was selected in preference to a boro-silicate glass form. More information about the development and selection of the ceramic formulation can be found in the Plutonium Immobilization Program's Baseline

  16. The mobility of radioactive elements in a Uranium exploitation zone

    International Nuclear Information System (INIS)

    One of the purposes of this study is to gain knowledge on the possibilities of accumulations of the radioelements (238U, 232Th, 226Ra) in a given ecosystem, and, particularly, the knowledge of the mechanisms implied in the transfer of these radioelements around the abandoned mining exploitations. The final purpose is the evaluation of the quantity of the radioelements susceptible to reach the man. The research is directed towards a quantitative evaluation of the transport rate of the contaminating element in the soil. There have been studied the surroundings of ore mines in the Boul Massif in Poiana Rusca Mountains in Romania. These exploitations had been closed and abandoned in 1990. From a geological point of view, the region is formed from crystalline schists, banat eruptive and sedimentary rocks. The iron deposit is totally situated in crystalline rocks in Poiana Rusca Mountains. The concentration of magnetite in the deposit is 25% with a relatively uniform dissemination in the ore. Brannerite (UCaThY)(TiFe)2O6, was also found in the same place. It is an ore should contain UO3 in proportion of up to about 33%. In 1963 there were stood out areas with radioactive minerals with gamma doses in the range of 500-9100 nGy/hour. In the same time, there were also identified a few points in which the concentration of thorium and uranium were significant. The areas with radioactive mineralizations were generally limited and strictly located in the limit of the iron ores deposit. By closing the mining activities huge quantities of waste rock stored in unprotected dump remained abandoned. As a result of the process of ore extraction, the waste rock and a very low percentage of metallic minerals were stored in tailing ponds, with a clay liner necessary to isolate the tailing from the reast of the aquifer

  17. Metasomatic uranium mineralization of the Mount Isa North Block

    International Nuclear Information System (INIS)

    Full text: Proterozoic uranium deposits of the Mt Isa North Project are centred 40 km north of Mt Isa, NW Queensland. Regionally, the deposits occur within the Leichhardt River Fault Trough of the Mt Isa Inlier. Uranium mineralisation is likely related to the 1 600-1 500 Ma Isan Orogeny. Structurally controlled uranium mineralisation is preferentially hosted in greenschist facies basalts and interbedded clastic sediments of the Eastern Creek Volcanics (ECV). Uranium deposits of the Mt Isa North Project are defined by the following general characteristics: - Pervasive sodium and calcium metasomatism, expressed as red albitite with finely disseminated hematite and calcite, with distal zones of chlorite and magnetite. - Uraniferous albitite deposits typically comprise en echelon lenses and shoots. - Mineralisation is developed along N- to NE-striking shear zones with associated brittle deformation of the host lithologies. - Host rocks are mostly basalt flows with flow-top breccias and interbedded sandstones and siltstones of the ECV; quartzites are also locally mineralised. - Geochemically the deposits are characterized by enrichment of U, Na, Ca, Sr, Zr, Th, Hf and P, and depletion of K, Ba, Rb and Cs. Uranium mineralogy of albitites comprises several phases of refractory uranium minerals (e.g. brannerite, coffinite). The Mt Isa North Project includes 11 tenements being explored for uranium by Summit Resources. Summit's five uranium resources total 95.7 Mlb U3O8. Scoping studies focused on geologic assessment, environmental baseline monitoring and metallurgical test work of the Valhalla deposit are in progress. Summit is in a 50/50 Joint Venture with Paladin on the Valhalla and Skal deposits. Paladin also has a direct ownership of 81.99% of the issued shares of Summit Resources. (author)

  18. Chapter 2. Geological setting of uranium mineralization

    International Nuclear Information System (INIS)

    Uranium mineralization in the Western Carpathians is mainly bound to the Permian sequences. The most important stratiform uranium mineralization is related either to the Permian acid volcanism of Gemericum and Tatricum, or to sandstones with abundant organic matter in Hronicum of the Kozie Chrbty Mts. Less important uranium mineralization occurs in veins and stock-works cutting the Paleozoic sequences of Gemericum and the Neogene volcanic rocks of Central Slovakia. The most important stratiform uranium-molybdenum mineralization occurs in the Permian volcanoclastic and volcanic rocks near Novoveska Huta. The important stratiform uranium mineralization occurs near Kalnica in the Permian Selec formation of Tatricum in the Povazsky Inovec Mts. The Permian acid volcanism was the important factor of primary uranium mineralization. The Permian Maluzina Formation of Hronicum contains uranium and copper mineralization in the Kozie Chrbty, Nizke Tatry and Male Karpaty Mts. The most important is the uranium mineralization in the Kozie Chrbty Mts in Vikartovce, Kravany, Svabovce and Spissky Stiavnik deposits. The Maluzina Formation is of similar character as the Kozie Chrbty Mts that continues on the northern slopes of the Nizke Tatry Mts. The stratiform uranium mineralization occurs in the lower ore-bearing horizon underlying the Kravany Beds in valleys Benkovsky Potok, Ipoltica and Nizny Chmelenec. Quartz and quartz-apatite veins with uranium mineralization occur in the eastern part of the Slovenske Rudohorie Mts. The common feature of this vein mineralization is cutting of the Early Paleozoic rocks of Gemericum in a proximity of the Gemeric granites. Quartz veins with uranium mineralization represented by uranite and brannerite are accompanied by gold in Peklisko and Zimna Voda. The oldest manifestation of uranium mineralization in the Western Carpathians is occurrence of pegmatite with uraninite in antimony deposit Dubrava in the Nizke Tatry Mts. It is related to the

  19. The South Greenland regional uranium exploration programme

    International Nuclear Information System (INIS)

    This report describes the work and results of the last two field seasons (1080 and 1982) of the Syduran Project. The field work was concentrated in the Motzfeldt Centre and the Granite zone with a short reconnaissance of five uranium anomalies in the Migmatite Complex. The results from the Motzfeldt Centre show that it is composed of at least 6 syenite units which can be divided into two major phases of igneous activity. The radioactive mineralisation has been mapped by gamma-spectrometer and has proved to be very extensive. Uranium mineral occurrences found in the Granite Zone occur in the many faults and fractures, which dissect the area. A study of the fractures and fault movements in the zone makes it possible to suggest an overall structural framework in which to place the uranium occurrences in the zone. Field work on the Igaliko peninsula was confined to a small area known as Puissagtag where four pitchblende veins have been discovered. Numerous uraniferous showings, associated with fractures, have been located in the Vatnaverfi peninsula south of the Igaliko Fjord. Mineralogical studies have shown that 12 of these showings contain pitchblende, that 7 of them contain coffinite and that most of them contain brannerite. The most interesting find during the 1982 field season was in the Migmatite Complex. Five anomalously high uranium areas in the complex were explored briefly with the helicopter-borne scintillometer. Near a place called Igdlorssuit, where a particlarly high gamma-spectrometer anomaly was found during the reconnaissance gamma-spectrometer survey, a large raft of meta-sediments in rapakivi granite was found, in which radioactive mineralisation occurred. This proved to be due to fine disseminated uraninite which occurs over some 150 m of strike length with a width of 1-2 m. The results confirm that there is a good possibility of finding exploitable uranium mineral occurrences in South Greenland. (author)

  20. Cerium as a surrogate in the plutonium immobilization waste form (United States)

    Marra, James Christopher

    In the aftermath of the Cold War, approximately 50 tonnes (MT) of weapons useable plutonium (Pu) has been identified as excess. The U.S. Department of Energy (DOE) has decided that at least a portion of this material will be immobilized in a titanate-based ceramic for final disposal in a geologic repository. The baseline formulation was designed to produce a ceramic consisting primarily of a highly substituted pyrochlore with minor amounts of brannerite and hafnia-substituted rutile. Since development studies with actual actinide materials is difficult, surrogates have been used to facilitate testing. Cerium has routinely been used as an actinide surrogate in actinide chemistry and processing studies. Although cerium appeared as an adequate physical surrogate for powder handling and general processing studies, cerium was found to act significantly different from a chemical perspective in the Pu ceramic form. The reduction of cerium at elevated temperatures caused different reaction paths toward densification of the respective forms resulting in different phase assemblages and microstructural features. Single-phase fabrication studies and cerium oxidation state analyses were performed to further quantify these behavioral differences. These studies indicated that the major phases in the final phase assemblages contained point defects likely leading to their stability. Additionally, thermochemical arguments predicted that the predominant pyrochlore phase in the ceramic was metastable. The apparent metastabilty associated with primary phase in the Pu ceramic form indicated that additional studies must be performed to evaluate the thermodynamic properties of these compounds. Moreover, the metastability of this predominant phase must be considered in assessment of long-term behavior (e.g. radiation stability) of this ceramic.

  1. Current Situation In The IRT-T Based Neutron-Activation Analysis Application In Scientific Research Institute Of Nuclear Physics At Tomsk Polytechnic University

    International Nuclear Information System (INIS)

    Full text: The works on the neutron-activation analysis application were started from the first days of actual IRT-T launch. E.M. Lobanov (Tashkent), I.P. Alimarin, G.N. Flerov (Moscow) set up the basis for future specialists training and creation of the laboratory in SRI of Nuclear Physics. They considered that Tomsk reactor should be used primarily for works encouraging further development of productive forces of Siberia and Far East. Analytical assistance was provided to industrial, scientific and scientific-industrial organizations to: - gain new materials with the given properties; - research and explore mining resources, oil and gas, develop new ore deposits; - control the level of environmental pollution and rehabilitation; - evaluate influence of nuclear energy industries and fuel-energy complexes of Siberian region on environmental condition and dynamics of environmental pollution, taking into account difficulties of natural resources rehabilitation in Siberia. We don't stop on technical equipping and capabilities of IRT-T in solving set problems. Here are some examples: - during the last years researches directed to prediction and research of new oil and gas-fields were carried out; - he neutron-activation analysis of non-traditional resources of rare-earth and noble metals (metallic slate traces) were developed; - the research of new fields containing uranium (mainly brannerite and uraninite). The difficulties of these minerals decomposition are known. Thus the neutron-activation analysis is suitable and must be used in this field. The report will contain the detailed information with exact examples and results of application of the neutron-activation analysis on the basis of IRT-T in Scientific Research Institute of Nuclear Power at Tomsk Polytechnic University. (authors)

  2. Geochemistry and mineralogy of the radioactive minerals associated with some pegmatite veins of the Ukma-Nawahatu Hursi sector, Purulia district, W.B., in the Precambrian Chhotanagpur Gneissic complex

    International Nuclear Information System (INIS)

    Some barite-bearing pegmatites in the Ukma-Nawahatu-Hursi sector (23° 25 min - 26 sec N, 86° 02 min - 04 sec E) in Purulia dist., West Bengal, have association of radioactive minerals in the form of coarse-grained pitchblack lumps and irregular patches. The present author and his associates first reported the occurrence of this radioactive belt along a ENE-WSW shearzone during their fieldwork in November, 1978. Groundborne radiometric survey and isorad mapping has established a radioactive high zone of about 15 km length running through Ukma, Nawahatu and Hursi areas. Mineralogical studies of the radioactive minerals have revealed the occurrence of Chevkinite, Aeschynite, Brannerite, Allanite, Uraninite, Tyuyamunite, Davidite, Euxenite, Samarskite, Thorutite, Autunite, Cerianite, in association with quartz, barite, microcline as the principal minerals and various minor minerals like biotite, vermiculite, hornblende, augite, orthoclase, celsian, muscovite, calcite, epidote, zoisite, ilmenite, sphene, rutile, hematite, magnetite, anatase, galena and sodic plagioclase. The barite-bearing pegmatites occur as lenses or lenticular veins hosted by garnetiferous sillimanite-biotite-quartz-schist or occasionally by migmatite. Near Nawahatu the radioactive barite-pegmatite vein occurs at or near the junction between the footwall amphibolite and hangingwall garnetiferous schist. The pegmatite veins have followed mainly schistosity of the host rock and dip at 70°-80° towards south. Chemical analyses of individual radioactive minerals by SEM-EDX and also of the bulk radioactive lumps by ICP-MS have shown significant concentration of U, Tb and Rare earths. Minor and trace element analyses also record notable contents of Zr, Ga, Sc, Pb, Zn, Nb, Cu, Ni, V, Cr, As, W, Pd, Ag and TI. Details of chemical analytical data are presented here. Chemically active fluids generated during metamorphism, metasomatism and granitic activity appear to have played a significant role in the

  3. Elemental imaging of organic matter and metal associations in ore deposits using micro-PIXE and micro-EBS

    Energy Technology Data Exchange (ETDEWEB)

    Fuchs, S., E-mail: [Earth and Planetary Science, McGill University, Montreal, (Canada); Przybylowicz, W.J., E-mail: [Materials Research Department, iThemba LABS, National Research Foundation (South Africa)


    phases and the formation of new minerals (sericite, brannerite, pyrophyllite). The results give strong evidence that Au and U were transported by circulating aqueous and/or insoluble organic phases and precipitated in solidified bitumen seams and nodules. (author)

  4. Elemental imaging of organic matter and metal associations in ore deposits using micro-PIXE and micro-EBS

    International Nuclear Information System (INIS)

    phases and the formation of new minerals (sericite, brannerite, pyrophyllite). The results give strong evidence that Au and U were transported by circulating aqueous and/or insoluble organic phases and precipitated in solidified bitumen seams and nodules. (author)

  5. Dispersion of impurities in pyrochlore/zirconolite-based ceramics

    International Nuclear Information System (INIS)

    Pyrochlore-rich and zirconolite-rich ceramics have been developed for the immobilization of excess weapons Pu. The ceramics are composed of a mixture of pyrochlore, zirconolite, brannerite and rutile. Impurity ions are present in most Pu-waste streams. Most of these impurities can be incorporated into the phases present in the ceramic; however some, such as B and Si, can promote the formation of additional phases. In this work, the impurity ions were classed into sets with supposedly the same valency (2+, 3+, 4+, 5+ and 6+). One set containing Np and Th and another set containing the glass formers (Al, Si, B, Na and K) were also made. These sets of elements were then added to a 'baseline' ceramics of nominal sintered composition, 95 wt.% pyrochlore (Ca0.89Gd0.22(Pu or Ce)0.22U0.44Hf0.23Ti2O7) and 5 wt.% HF-doped rutile, (Ti0.9Hf0.1O2). A sufficient amount of each of these sets of impurity ions was added so that the primary phases of the baseline ceramic were saturated with them and secondary phases formed. Both Pu/U-doped Ce/U-doped samples were made. The impurity elements were added as nitrates to an alkoxide-route precursor, which was calcined and then ball milled. Pellets were pressed from the powder and sintered in Ar, air or 3.7% H2 in Ar at about 1350 degrees Celsius for 4 hours. The obtained results are summarized in this work. As a matter of fact, most of the ions can be accommodated in the ceramic, but the partitioning across the different phases in the ceramic is not even. The groups will preferentially move to certain phases or, if sufficient amounts are present, result in the formation of new phases. The conclusion is that all ions of similar size and valency behave in a similar manner unless there are volatility problems

  6. Main geological settings of uranium mineralization in the Baltic shield

    International Nuclear Information System (INIS)

    dislocations, widespread permeable zones of cracks, breccia, schistosity, uraniumspecialized rocks with abundant movable varieties, massive uranium-specialized granitoid, greizenized granite and host gneiss. Uranium mineralization is in the axial parts of the FFD zones close to the contact of the Yatulian dolomite with the Ludicovian aleurolite and shungite-bearing aleurolite. It is seen on either an east-west steeply dipped or overturned anticline limb, or in the core of the nearhinge synclines. The mineralization is controlled by an area of hydrothermal-metasomatic albite-carbonate- micaceous alteration. Uranium mineralization in the FFD zones is mainly concentrated in sulfide-carbonate-pitchblende veins. Ore-bearing areas containing complex deposits are 2 - 2.5 km long and 500 - 600 m wide. There are several ore deposits lying at the depth of 100 -180m in each area. The deposits are of a complicated shoestring or cigar shape ranging in length from 1100 to 1800 m, being 15 - 50m thick. The uranium mineralization is represented with brannerite, coffinite, pitchblende. The mineralization potential of this type is determined by the discovery of five uranium-associated deposits within the Onega depression FFD zones (Srednyaya Padma, Kosmozero and others). The Early Proterozoic Kuusamo -Pana - Kuolajarvi and Imandra - Varzuga troughs characterized with widely spread uraniumspecialized black schists are highly prospective for ore deposits of this type

  7. Mineral chemistry of tantalate species new in the Borborema Pegmatitic Province, Northeast Brazil

    Directory of Open Access Journals (Sweden)

    Hartmut Beurlen


    Full Text Available Tantalate samples, supposedly of the columbite group, were collected in the Borborema Pegmatitic Province, aiming to test the Mn/(Mn+Fe and Ta/(Ta+Nb ratios as geochemical indicators of pegmatite fractionation. Surprisingly, preliminary microprobe data allowed recognizing some species, so far unknown in the Province, namely titanian ixiolite, fersmite, brannerite, strüverite, natrobistantite, plumbo- and stibiomicrolite, plumboand uranpyrochlore. The identification of these exotic tantalates with unusual composition, in addition to its distribution in several pegmatites, far from the classical Alto do Giz and Seridozinho pegmatites, indicate that the elevated degree of fractionation is not restricted to these two occurrences but may be reached in other pegmatite areas of the Province. It indicates also that this degree of fractionation may be very variable between pegmatites in small areas. The zoning patterns observed in the titanian ixiolite, with Ti and Nb enrichment at the borders at expense of Ta enriched in the core, are also quite unusual and reverse in comparison with the normal trend of progressive Ta and Mn enrichment in tantalates with the degree of fractionation. A similar "reverse" trend was observed in titanian wodginite of petalite/pollucite bearing pegmatites of the Separation Rapids Province in Ontario, Canada.Amostras de tantalatos, supostamente do grupo das columbitas foram coletadas na Província Pegmatítica da Borborema na perspectiva de testar as razões Mn/(Mn+Fe e Ta/(Ta+Nb como indicadores do grau de fracionamento dos pegmatitos. Resultados preliminares de microssonda permitiram, surpreendentemente, reconhecer espécies incomuns de tantalatos desconhecidos na província, como titano-ixiolita, brannerita, fersmita strüverita, natrobistantita, plumbo- e stibiomicrolita, plumbo- e uranopirocloro. A identificação destes tantalatos exóticos e com composições inusitadas, somados à sua ocorrência em vários pegmatitos

  8. Mise en solution et précipitation de l'uranium et du thorium dans les conditions de moyenne et haute température (résumé Solution and Precipitation of Uranium and Thorium under Average and High-Temperature (Summary

    Directory of Open Access Journals (Sweden)

    Moreau M.


    (France and different uranium deposits or anomalies (Quebec, Rössing, Madagascar, etc. . U and Th are precipitated in the katazone in the form of solid uranothorianite solids in silica-deficient media, and in the form of uranothorite in granites and syenites. Non-thoriferous uraninite precipitation in French leucogranites can be explained first of all by the low thorium concentration of aqueous solutions during the deuteric phase. During progressive metamorphism, a delay can be observed in uranium mobilization under relatively oxidïzing conditions when U is associated with Ti and OH. In the mesozonal realm, brannerite stabilizes uranium in the presence of titanium all the way to analexis. Beyond that it becomes dissociated by giving off non-thoriferous uraninite and rutile.

  9. Investigations on uranium sorption on bentonite and montmorillonite, respectively, and uranium in environmental samples

    International Nuclear Information System (INIS)

    uranium(VI) speciation in water samples is controlled by pH as well as bicarbonate and calcium concentrations and is dominated by the very stable aquatic complexes Ca2UO2(CO3)3, (UO2)2CO3(OH)3- and UO2(CO3)34-. Influences of humic substances or phosphate ligands on uranium(VI) complexation were not detected. Uranium association with aquatic colloids in the studied samples as found to be negligible. With the help of a combination of the AREM-EDX method and batch experiments, uraninite (UO2) and brannerite (UTi2O6) could be identified with an occurrence frequency of about 67 % and 33 %, respectively. This combination allowed the conclusion that uranium release from tailing materials is controlled by the dissolution of uraninite, which itself is governed by the dissolution of calcite. Furthermore, a mobilisation of uraninite colloids smaller than 200 nm from tailing material into the used model solutions was observed.

  10. Investigations on uranium sorption on bentonite and montmorillonite, respectively, and uranium in environmental samples; Untersuchungen zur Uransorption an Bentonit bzw. Montmorillonit sowie von Uran in Umweltproben

    Energy Technology Data Exchange (ETDEWEB)

    Azeroual, Mohamed


    uranium releases from tailings into the aquatic system. The results showed that uranium(VI) speciation in water samples is controlled by pH as well as bicarbonate and calcium concentrations and is dominated by the very stable aquatic complexes Ca{sub 2}UO{sub 2}(CO{sub 3}){sub 3}, (UO{sub 2}){sub 2}CO{sub 3}(OH){sub 3}{sup -} and UO{sub 2}(CO{sub 3}){sub 3}{sup 4-}. Influences of humic substances or phosphate ligands on uranium(VI) complexation were not detected. Uranium association with aquatic colloids in the studied samples as found to be negligible. With the help of a combination of the AREM-EDX method and batch experiments, uraninite (UO{sub 2}) and brannerite (UTi{sub 2}O{sub 6}) could be identified with an occurrence frequency of about 67 % and 33 %, respectively. This combination allowed the conclusion that uranium release from tailing materials is controlled by the dissolution of uraninite, which itself is governed by the dissolution of calcite. Furthermore, a mobilisation of uraninite colloids smaller than 200 nm from tailing material into the used model solutions was observed.