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- ItemPilot plant development of processes for the production of nuclear grade uranium dioxide(Institution of Chemical Engineers, 1972-08-17) Alfredson, PGMost types of nuclear power reactors use fuel in the form of high density uranium dioxide pellets clad in Zircaloy. Sinterable uranium dioxide powder is usually produced via the ammonium diuranate (ADU) route. This involves dissolution of uranium ore concentrates (yellow cake) in nitric acid, purification by solvent extraction using tributyl phosphate in kerosene, precipitation of ADU, filtration, drying, calcination and reduction with hydrogen to give uranium dioxide powder. The Australian Atomic Energy Commission has carried out pilot plant development of these processes to demonstrate the production of nuclear grade uranium dioxide from Australian yellow cake and to improve the processes and technology wherever possible. This paper describes the processes and equipment with particular reference to the improvements which have been made. The nitric acid requirements in the solvent extraction process have been substantially reduced and a pulsed fluidised bed reactor has been developed for the continuous calcination-reduction of ADU to uranium dioxide. The influence of the conditions for precipitation of ADU on its rate of filtration and on the fabrication behaviour of the uranium dioxide powder is also described.
- ItemThe possible transmutation of radioactive waste from nuclear reactors(Australian Institute of Physics, 1974-05-21) Harries, JRA nuclear reactor power program produces high level long lived radio-active wastes. The high level activity is associated with fusion products, but beyond 400 years the principal waste hazard is from transuranic elements produced in the reactor. Several schemes have been proposed for the transmutation of the problem isotopes into more easily handled isotopes. The neutron flux in a thermal reactor is not high enough to significantly reduce the longer lived fission product isotopes 90Sr and 132Gs, but the transuranic elements can be reduced by recycling through power reactors. The limitation on recycling of the transuranic elements is the separation process to remove trace quantities from the wast stream. In fact reactors the transuranic elements are the principal fuel and fast reactor waste contains only half as much 90Sr as thermal reactors. However, the overall waste hazard is similar to thermal reactors. A sufficiently intense neutron flux for fission product transmutation could perhaps be produced by a spallation reactor driven by a proton linear accelerator or a controlled thermonuclear reactor. However, both concepts are still some years in the future. Transmutation by accelerator sources of protons, electron or gammas tend to require more energy than neutron transmutation.
- ItemX-ray spectral measurements of a dense plasma focus(Australian Institute of Physics, 1974-05-21) Hogg, GR; Tendys, JThe tine resolved spectrum of the x-ray emission from the dense plasma focus has been measured over the energy range 1 to 5 keV using a four channel foil absorption spectrometer. The energy distribution of the electrons in the plasma can be calculated from these measurements and the electron temperature derived.
- ItemPapers presented at a topical session on Gamma rays from nuclear reactions : held during the 7th International Nuclear Data Committee Meeting at Lucas Heights, Sydney, Australia, on 9th October 1974(Australian Atomic Energy Commission, 1974-10-09) Kenny, MJThe 7th International Nuclear Conference Data Committee meeting was held at Lucas Heights, Sydney, Australia, in October 1974. During the meeting, a topical session was held entitled, "Gamma Rays from Nuclear Reactions". Papers were presented by a number of INDC delegates and by participants from the Australian Atomic Energy Commission, the Australian National University and the University of Melbourne.
- ItemDynamic membranes(Institution of Chemical Engineers, 1975-08-20) Evans, JVDynamic membranes are formed when water containing membrane-forming additives is circulated under pressure over a porous surface to deposit a thin membrane layer at the interface. In-situ procedures of this type have the potential advantage that membranes may be removed when performance becomes unsatisfactory and replaced without disassembly of equipment. Dynamic membranes are capable of a very high flux and, compared to conventional film membranes, hold promise of providing more economic processing, particularly for the high-fouling feeds often found in waste water treatment. Kraus, Johnson and co-workers at the Oak Ridge National Laboratory have investigated a range of ion exchange membranes dynamically prepared from organic polyelectrolytes including poly-acrylic acid, polyvinyl sulphonic acid, polyvinyl pyridine, and humic acid, and from inorganic polyelectrolytes formed from solutions of hydrolysable metal ions. It is also sometimes possible to form such membranes from polyelectrolytes already present in waste waters such as sewage. Because their rejection properties are based upon relatively long-range coulombic forces, ion-exchange membranes have the potential to function with a more open structure than that required of neutral membranes and hence to allow a greater flux. Conventional ion-exchange membranes, when manufactured with sufficient strength for reverse osmosis applications, are too impermeable. The dynamic technique provides a method for forming very thin ion-exchange membranes which are capable of use at high pressure and which have a very high flux. The performance of these membranes, as with other ion-exchange membranes, deteriorates with increasing feed concentration and the presence of polyvalent counter-ions. Their usefulness for single-stage seawater desalination thus appears doubtful, but they have promise for waste water treatment, where very high salt rejection is not always required. Dynamic membranes have also been formed from a range of neutral additives including hydroxyethyl cellulose, polyvinyl pyrrolidone and polyethylene oxides.4 Although often successful in removing large molecules by ultrafiltration, the salt rejection of these membranes is poor, usually less than 30 per cent. Neutral membranes are difficult to prepare by this technique because polymer additives which are soluble enough to form dynamic membranes are too hydrophilic to form membranes of low enough water content for good salt rejection. Whilst exhibiting poor salt rejection in their neutral form, dynamic ion-exchange membranes can still act as ultrafiltration membranes.
- ItemRegeneration of caustic potash solution used for the disposal of gaseous fluorides(Institution of Chemical Engineers, 1975-08-23) Royston, D; Burwell, A; Janov, J; Le Page, AH; Levins, DM; Ring, RJ; Vilkaitis, VKA system for the disposal of fluorine and gaseous hydrogen fluoride was developed as part of an experimental 1500 A fluorine cell facility used to investigate the production of fluorine. The design, operation and performance of the plant have been described in detail by Royston et al.1,2. The cell produced fluorine and hydrogen at 0.24 & s-1 with both gases containing approximately l0 vol.% hydrogen fluoride. These off—gases were disposed of continuously by scrubbing with 5-8.5 wt.% caustic potash solution which was regenerated by reaction with lime on a batch basis. This paper outlines the selection of the system and describes its operation and performance.
- ItemAustralian uranium resources, development and supply(Australian Atomic Energy Commission, 1978-09-25) Battey, GC; Warner, RKThe geologically favourable areas for the occurrence of uranium in Australia and the geology of major deposits are discussed as well as exploration programs and expenditures. Australia has no short-term requirement for nuclear power generation and its reserves of 289.000 tonnes uranium, together with the prospects for further discoveries indicate that the country is destined to become a major exporter of uranium. The Government's decisions on the development of the uranium miming and milling industry are outlined and information is given on the plans to bring new projects into operation.
- ItemThe development of safety criteria for use in the nuclear industry(Institution of Chemical Engineers in Australia and the Institution of Engineers, Australia, 1978-11-06) Higson, DJLimits to routine radiation exposure have been laid down in the health regulations of industrial nations and provide a basis for the safe operation of nuclear power stations, uranium mines and other nuclear installations. However, these limits do not take account of the possibility of accidents, which may also be a major concern in the siting and design of plants. In this paper specific limits to fatal accident frequencies are recommended. An indication of the required level of safety has been derived from the records of other industries and human activities which are already regarded as safe.
- ItemThe 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, JFResearch 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.
- ItemDisposal options for high level nuclear waste(Australian Atomic Energy Commission, 1982-01-18) Reeve, KDThe options for the management/disposal of high level nuclear waste are discussed; it is concluded that irretrievable disposal of solidified waste is a likely end step in all disposal schemes. Disposal will probably be either in mined repositories or in deep drill holes. Two solidified waste forms - borosilicate glass and SYNROC - are considered in some detail. It is concluded that SYNROC would provide a higher level of assurance of radionuclide retention in both disposal concepts. Deep drill-hole disposal using SYNROC is an attractive concept which should be given increased attention.
- ItemHigh-level radioactive waste disposal : the international scene(Australian Atomic Energy Commission, 1983-11-30) Costello, JMThe status of developments in spent fuel reprocessing, high-level wast solidification and geologic isolation is reviewed. Some generic studies on the possible range of annual radiological doses to individuals from waste repositories are discussed and compared with doses from existing nuclear power and fuel cycle operations, and with the dose received annually from the naturally occurring radiation background. The significance of neptunium-237 in dose estimation is discussed, together with technological trends in separation and disposal of long lived actinide elements.
- ItemLeaching of heavy metals and radionuclides from uranium tailings(Institution of Chemical Engineers : Institution of Engineers, Australia : Royal Australian Chemical Institute, 1985-08-25) Ring, RJ; Levins, DM; Cooper, MBThis paper presents results of accelerated column leaching tests carried out to estimate the long-term release rate of heavy metals and radionuclides from Australian uranium tailings. The effect of limestone and lime treatment before impoundment is examined. A simple model is proposed which can be used, in association with seepage data, to estimate the total quantities of contaminants released over many centuries.
- ItemCatalytic decomposition of peroxygen compounds in uranium leaching circuits(Institution of Chemical Engineers : Institution of Engineers, Australia : Royal Australian Chemical Institute, 1985-08-25) Secomb, RJ; Ring, RJ; Nugent, AJThis paper reports on the kinetics of decomposition of hydrogen peroxide and Caro's acid under conditions encountered in uranium leach circuits. The relative catalytic activity of the metal ions was measured as a function of pH and temperature. The percentage utilisation of oxidants was measured in batch and continuous flow experiments in the presence of Fe(II) where oxidant reduction and decomposition occur simultaneously. The results are used to identify conditions which can maximise the use of oxidant in large-scale leaching circuits.
- ItemManagement of wastes from the processing of rare earth minerals(Institution of Engineers Australia, 1988-08-28) Hart, KP; Levins, DMAustralia is the leading producer and exporter of the rare earth mineral, monazite, but currently does not process it beyond the physical beneficiation stage. Recent discoveries of new uses for rare earth has renewed interest in monazite processing in Australia. Two proposals of rare earth processing plants have been announced and a number of other companies are engaged in feasibility studies. Chemical processing of monazite involves digestion in caustic soda to 'crack' the phosphate matrix, dissolution of the rare earths in acid and their separation by multi-stage solvent extraction usually in mixer-settlers. The processing is complicated by the presence of 4-8 wt% thorium and 0.1-0.3 wt% uranium in the monazite. Experiments have shown that lead-210 and uranium are partially solubilized in the caustic digestion stage and radium is dissolved along with the rare earths. Over 99.5% of the radium can be precipitated as barium/radium sulphate by the addition of barium chloride and soluble sulphate. This radium-bearing solid waste can be combined with the uranium/thorium residue so that essentially all the radionuclides are contained in the one waste stream. The volume of this waste stream is not large and it is feasible to store it on-site in an engineered facility. The safe disposal of this waste would be facilitated by the establishment of a national facility for radioactive and other toxic wastes.
- ItemCrystal chemistry and phase manipulation in Synroc(Trans Tech Publications Ltd, 1991) Vance, ER; Moricca, SA; Thorogood, GJ; Lumpkin, GRSynroc is a multi-phase ceramic designed for geological immobilisation of radioactive waste produced by reprocessing nuclear fuel from power reactors . The main crystalline phases are hollandite, perovskite, zirconolite, and reduced titanium oxide. The compositions of these phases and the nuclides they can incorporate in solid solution are shown in Table 1. Table 1. Principal Phases comprising Synroc Phase Nominal Composition Waste nuclides incorporated Estimated wt%*  Hollandite Ba1.14(Al, Tr3+)2.28Ti6O16 Cs, Sr, Rb 25 Perovskite CaTio3 Sr, RE, An 20 Zirconolite CaZrTi2O7 RE, An 20 Titanium Oxide TinO2n-1 - 35 *No HLW present RE = rare earths, An = actinides. The main (Synroc-C) formulation is designed for Purex reprocessing waste and the standard composition is wt%: Al2O3(4.3); BaO(4.4); CaO(8.8); ZrO2(5.6); TiO2(57.9); waste oxides (20). The loading of high-level waste (HLW) oxides can be varied if desired, but probably cannot exceed a value of 30-35% . Several variants of this composition have been formulated at the laboratory scale, with Synroc-D, E and F being directed towards Savannah River (U.S.A.) military waste, encapsulation of high-level nuclear reprocessing waste and unreprocessed spent fuel respectively. © 1991 Trans Tech Publications Ltd.
- ItemPlans for AMS dating at Lucas Heights(Australian National University, 1991-01-29) Smith, AM; Bird, JR; Fink, D; Shying, M; Shahgholi, NA refurbished tandem accelerator has been installed at ANSTO for which a major role will be the use of Accelerator Mass Spectrometry (AMS) techniques for measurements of 14C and other radioisotopes such as 10Be, 26Al, and 41Ca. The tandem accelerator is being upgraded with recent advances om accelerator technology aimed at achieving a terminal voltage of 10 MV and other performance features needed for first-rate AMS measurements. Dual ion sources will be used, one being a high intensity source which will be suitable for difficult isotopes such as 10Be, 26Al, and 41Ca, as will as for high throughput in radiocarbon measurements. The second source will be dedicated to high precision radiocarbon measurements with minimum cross-contamination and memory effects. Computer control systems will be used to facilitate high precision measurements on standards and unknowns. In the longer term it is hoped to develop a gas ion source to permit 14C measurements on Co2 obtained directly from field samples. The facility is expected to commence a measurement services in 1992. Sample preparation facilities are being developed concurrently at Lucas Heights and at other places such as radiocarbon laboratories, with special attention to minimising the possibility of contamination of samples at the ultra-low levels which can be measured by AMS (isotope ration of the order of 10-15).
- ItemSynroc formulations for various high-level nuclear wastes(American Ceramic Society, 1991-04-28) Vance, ER; Moricca, SA; Thorogood, GJ; Smith, KLOf the chemically resistant titanate phases comprising Synroc, perovskite is the least durable and adjustments to the Synroc formulation to reduce the amount of perovskite are under study. Results are described of experiments designed to reduce the perovskite level to < 5 wt%. A simulated waste loading of 20 wt% was used. Other Synroc formulations for high Al, high (Al + U), high (Na + Al + Fe + U) and actinide-rich waste have been calculated and tested experimentally via leaching, X-ray diffraction and electron microscopy.
- ItemRemoval of water impurities by hydrous oxides(Institution of Engineers, Australia, Institution of Chemical Engineers & Royal Australian Chemical Institute, 1991-09-19) Amal, R; Raper, JA; Waite, TDIn this study, the effects of adsorbed fulvic acid, a naturally occurring organic acid, on the kinetics of hematite aggregation and on the resulting structure of hematite aggregates are investigated. A model based on colloid stability theory which also accounts for the structure of the aggregates formed is used to describe the aggregation kinetics of these adsorbed particles. The study of aggregate structure shows that the fractal dimensions of hematite aggregates which are partially acid molecules are higher than those obtained with no adsorbed fulvic acid The scattering exponents obtained from static light scattering experiments of these aggregates range from 2.83 +- to 3.42 +- 0.1.