Browsing by Author "Woolfrey, JL"

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    The development and testing of Synroc C as a high level nuclear waste form
    (Cambridge University Press, 2011-02-15) Reeve, KD; Levins, DM; Ramm, EJ; Woolfrey, JL; Buykx, WJ
    The current status of SYNROC C research and development by the Australian Atomic Energy Commission is reviewed. A non-radioactive fabrication demonstration line designed to produce 10 cm o.d., 90 cm long, cylinders of SYNROC canned in stainless steel by the method of in-can hot pressing is being commissioned. Leach tests are proving the excellent leach resistance of SYNROC. Accelerated radiation damage testing using fast neutrons has simulated storage times of up to 6.7×105 years. Thermophysical properties of SYNROC have been measured over the temperature range 20–650°C. © Materials Research Society 1982
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    The development and testing of SYNROC for high level radioactive waste fixation
    (Australian Atomic Energy Commission, 1981-02-23) Reeve, KD; Levins, DM; Ramm, RJ; Woolfrey, JL; Buykx, WJ; Ryan, RK; Champan, JF
    Research and development on the SYNROC concept for high level radioactive waste fixation commenced at the Australian Atomic Energy Commission Research Establishment, Lucas Heights, in March 1979, in collaboration with a complementary program at The Australian National University (ANU). The present paper reports progress in the project's second year and reviews its current status. An inactive 30 kg-scale SYNROC fabrication line incorporating in-can hot pressing as the fabrication step has been built for operation in mid-1981. Atmospheric pressure and hydrothermal leach tests are demonstrating the excellent leach resistance of SYNROC. Accelerated radiation damage tests using fast neutrons are simulating damage in SYNROC for periods of close to 10/sup 6/ years. In supporting research, mineral phase development, impact friability and thermophysical properties of SYNROC are being studied.
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    The effect of pH on the properties of ammonium uranate precipitated with gaseous ammonia
    (Australian Atomic Energy Commission, 1976-11) Woolfrey, JL
    Ammonium uranate (AU) powders were precipitated from a uranyl nitrate solution using gaseous ammonia to determine the effect of pH of precipitation on their composition and morphology. Increasing pH of precipitation increased the ammonia and nitrate contents and the specific surface area but decreased the crystallite size of the AU powders. The specific surface area was also increased by increasing the ammonia content of the powder. The composition and morphology of the powders were similar to those reported in the literature for AU precipitated with NH4OH.
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    Feasibility of dispersed phase grain refinement in ceramics.
    (Australian Atomic Energy Commission, 1967-02) Woolfrey, JL
    The feasibility of dispersed phase grain refinement in ceramics is assessed. Conditions for grain size stabilisation of normal grain growth are derived using a Zener type analysis for random dispersions and for the case in which all particles are located at specific sites upon a grain boundary. The calculations predict the relative stabilising effects of particles located at grain boundaries, triple—grain edges and four—grain corners. Other factors reviewed include the effects of particle size instability, nucleation of discontinuous grain growth, and possible methods for its prevention. It is concluded that dispersed phase grain refinement in ceramics is feasible. The general predictions are applied to the case of a BeO moderator and used to predict the most promising additives for further investigation.
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    Low temperature bonding of ceramics by sol-gel processing
    (Springer Nature, 2001-12) Barbé , CJ; Cassidy, DJ; Triani, G; Latella, BA; Mitchell, DRG; Finnie, KS; Bartlett, JR; Woolfrey, JL; Collins, GA
    Sol-gel bonds were produced between smooth, clean silicon or polycrystalline alumina substrates by spin-coating solutions containing partially hydrolysed silicon alkoxides onto both substrates. The two coated substrates were assembled and the resulting sandwich was fired at temperatures ranging from 300 to 600°C. The influence of the sol-gel chemistry on the film microstructure and interfacial fracture energy was investigated using a wide range of techniques, including ellipsometry, FTIR, TG-DTA, rheology, TEM and micro-indentation. For silicon wafers, an optimum water-alkoxide molar ratio of 10 and hydrolysis water pH of 2 were found. Such conditions led to relatively dense films (>90%), resulting in bonds with significantly higher fracture energy (3.5 J/m2) than those obtained using classical water bonding (typically 1.5 J/m2). Aging of the coating solution was found to decrease the bond strength. Poly-crystalline alumina substrates were similarly bonded at 600°C; the optimised silica sol-gel chemistry yielded interfaces with fracture energy of 4 J/m2. © 2000 Kluwer Academic Publishers.
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    The preparation and calcination of ammonium uranates: a literature survey
    (Australian Atomic Energy Commission, 1968-09) Woolfrey, JL
    The preparation and calcination of ammonium uranates is reviewed. Topics covered include the preparation of ammonium uranates by precipitation or soild state reaction; the effects of preparation conditions upon the composition, structure, morphology, surface area, and filtration of ammonium uranates; the thermal decomposition and reduction of ammonium uranates; and the effect of calcination conditions on the physical properties of the resultant powder.
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    Surface area changes during the calcination of ammonium uranate
    (Australian Atomic Energy Commission, 1974-09) Woolfrey, JL
    The changes in specific surface area observed during the calcination of ammonium uranate in various atmospheres have been studied using constant rate of heating, isothermal and isochronal experiments. X-ray diffraction, thermogravimetric analysis (TGA) and differential thermal analysis (DTA) results have been used to correlate these changes with the stages of reaction which occur during the calcination. During dehydration (20 to 200ºC) AU 'Type II' remains the major phase. Thermal decomposition (200 to 350ºC) produces amorphous U03 and 3-U03 which retain ammonia in their structure. These are subsequently converted to U308 by a self-reduction process (350 to 450ºC). Reduction in a hydrogen atmosphere takes place between 450 and 510ºC to produce U02. In an inert gas or air atmosphere 3-UO and UO persist to much higher temperatures, and the presence of an oxidising atmosphere may completely eliminate the self-reduction reaction. The observed specific surface area increases during dehydration and decomposition and reaches a maximum between 400 and 450ºC. The major increase in the surface area is attributed to the opening up of internal porosity, formed during decomposition, by stress-induced cracking of the particles. The internal stresses are generated by the nucleation and growth of phases which have different specific volumes from that of the parent solid. The maximum surface area was observed if self-reduction occurred. The observed decrease in specific surface area at higher temperatures is due to sintering.