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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.
- 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 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.
- 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.
- 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.
- ItemNew research reactor for Australia(Technicatome, 1992-05-18) Miller, RHIFAR, Australia's major research reactor, was commissioned in 1958 to test materials for an envisaged indigenous nuclear power industry. HIFAR is a Dido type reactor which is operated at 10 MW. With the decision in the early 1970's not to proceed to nuclear power, HIFAR was adapted to other uses and has served Australia well as a base for national nuclear competence; as a national facility for neutron scattering/beam research; as a source of radioisotopes for medical diagnosis and treatment; and as a source of export revenue from the neutron transmutation doping of silicon for the semiconductor industry. However, all of HIFAR's capabilities are becoming less than optimum by world and regional standards. Neutron beam facilities have been overtaken on the world scene by research reactors with increased neutron fluxes, cold sources, and improved beams and neutron guides. Radioisotope production capabilities, while adequate to meet Australia's needs, cannot be easily expanded to tap the growing world market in radiopharmaceuticals. Similarly, neutron transmutation doped silicon production, and export income from it, is limited at a time when the world market for this material is expanding. ANSTO has therefore embarked on a program to replace HIFAR with a new multi-purpose national facility for nuclear research and technology in the form of a reactor: a) for neutron beam research, - with a peak thermal flux of the order of three times higher than that from HIFAR, - with a cold neutron source, guides and beam hall, b) that has radioisotope production facilities that are as good as, or better than, those in HIFAR, c) that maximizes the potential for commercial irradiations to offset facility operating costs, d) that maximizes flexibility to accommodate variations in user requirements during the life of the facility. ANSTO's case for the new research reactor received significant support earlier this month with the tabling in Parliament of a report by the Australian Science and Technology Council on recommended priorities for government expenditure on major national research facilities over the next ten years. A new research reactor was one of seven proposals recommended by the Council for priority during that period. As basis for ANSTO's normal activities is nuclear science and technology rather than reactor development, it will be necessary to purchase much of the nuclear specific technology and hardware with the emphasis being on modern but proven technology. In January 1992 ANSTO commenced a two year preliminary engineering and financial study that will define the user requirements, assess the availability of reactor designs compatible with those requirements, complete preliminary design and provide a detailed costing and schedule for the provision of the facility. The report of this study will form the basis of a submission to Government for funding for detailed design and construction. Initial operation of the reactor is scheduled for 2003. The overall project schedule is shown.
- Item59Ni production rates in mesosiderites measured with AMS(Wiley, 1993-07-01) Fink, D; Tuniz, C; Herzog, G; Albrecht, A; Fifield, LK; Allen, GL; Paul, MThe cosmogenic radionuclide 59 Ni(t1/2=76ka) has great potential as a monitor of thermal neutrons in metal-rich extraterrestrial materials. In deep samples from larger meteoroids (which can support a big neutron flux) containing >1% or so of nickel, thermal neturon capture on 58Ni (delta th=4.6b) is the dominate production mechanism. Near the surface of millimeter-sized bodies production occurs via primary proton, fast neutron, and a reaction channels on Fe, Co, and Ni. We have applied AMS to the measurement of 59Ni activities (see  for details) in four samples from the metal phase to f the mesosiderites Estherville (fall,1879) and Budulan(find). The activities range from 1.5 to 3.5 dmp/g-Ni. Related work is described in [2,3]. To discuss neutron fluxes in Budulan, we must correct the measured 59Ni activities for terrestrial age. By using measured 41Ca activities (13-19 dpm/kg-Fe ) and a maximum production rate PFe(41Ca), in stony irons of 21dpm/kg-Fe  we deduce a maximum terrestrial age of 35 ka. After correction for this terrestrial age and normalization of L-chondrite composition , the production rates of 59Ni,PFe(59Ni), range from 5-13 dpm/g-Ni; these values are 2-3x greater than those reported in  for large irons and ~10x those for chondrites. Albrecht et al.  and Fink et al.  present 41Ca data in the silicate and metal phases from the same Estherville and Budulan samples. If thermal neutron production were solely responsible for PFe(59Ni) and PS2(41Ca) (the latter corrected for spalliation of oxidized iron in pyroxene), the thermal neutron fluxes, o, inferred from each nuclide in a sample should be the same. We deduce ratios of o(59Ni)/o(41Ca) that range from 0.75 to 1.65. Differences in epithermal yields can account for only a minor fraction of this variation as the ratio of the total resonant neutron absorption intergrals for 40Ca and 58Ni is within 10% of the ratio of the thermal neutron cross sections alone. A twofold change in Budulan's terrestrial age alters the flux ratio by 10% at most. Like 41Ca[9,10], PFe(59Ni) can be used to estimate shielding depths and lower limits on the preatmospheric radius. Calculations by  give a maximum value for PFe(59Ni) of 22 atoms/min/g-Ni at the center of an L chondrite with a radius of 300 g/cm2. The 10Be and 26A1 activities in Estherville  and respective semi-empirical production rate formulas  set a maximum meteoroid radius of 300 g/cm2. Our measured value for 59Ni implies a lower radius limit of 150 g/cm2 and shielding depths of 60-150g/cm2. Similarly, we suggest a radius of 200< R < 400 g/cm2 and shielding depths from 40-200 g/cm2 for Budalan. We infer that the above samples originated at relatively large depths (except for perhaps Budulan 2428) in meteoroids with preatmospheric radii >30cm, assuming a mesosiderite density of 5.5 g/cm3. Interestingly, those samples (Budulan2357 and Estherville 3311) having 41Ca production rates that indicate a higher degree of shielding have flux rations equal to or less than 1; the other two samples have 41Ca contents typical of near-surface exposure and have ratios o(59Ni)/o(41Ca) larger than unity. This correlation indicates that P59 from fast neutron reactions on 60,61Ni enhances 59Ni production at near-surface regions.
- ItemTwo dimensional antiferromagnetic ordering in MnPS3(Australian and New Zealand Institutes of Physics, 1994-02-09) Wildes, AR; Kennedy, SJ; Hicks, TJMnPS3 with space group C— has a layered monoclinic structure. Within the layers the manganese atoms form a hexagonal net with each manganese atom having three manganese neighbours within the layer. Below 80K the magnetic structure is three dimensional with the antiferromagnetic ordering within the layers coupled ferromagnetically between the layers and the moment direction perpendicular to the layers. We report the discovery of a truly two dimensional antiferromagnetic ordering in the temperature range 80-130K. This order is not immediately obvious from a neutron powder diffraction pattern as the antiferromagnetic intensity appears as rods rather than spots in reciprocal space and is therefore smeared out in a powder pattern. Preliminary analysis indicates that the moment in the two dimensional structure lies in the layer plane. If this is so it would have to result from a unidirectional rather than planar anisotropy so that the system is described within the Ising model, the only model which will sustain long range magnetic order in two dimensions. The neutron diffraction data at various temperatures will be presented along with supporting single crystal susceptibility measurements.
- ItemProcess optimization and characterization of Ni-Ge-Au ohmic contacts to n+ GaAs heterostructures(Australian and New Zealand Institutes of Physics, 1994-02-09) Lumpkin, NE; Lumpkin, GR; Butcher, KSAA process for the formation of low resistance Ni-Ge-Au ohmic contacts to n+ GaAs heterostructures was optimized using multivariable screening and response surface experiments [1,2]. Of seven variables screened by a fractional factorial experiment, the strongest effects were: total Ge+Au evaporative thickness, Ge:Au ratio and post-alloy cooling time. A response surface experiment run on these three variables enabled the development of an empirical model of ohmic contact resistance (Rc), with a predicted optimum value of 0.07 ± 0.03 Ωmm. Twenty confirmation runs yielded an average Rc of 0.07± 0.04 mΩm, a reduction of 50% on the standard average process value of 0.14 ±0.1Ω mm. A non-optimized (Rc = 0.17 Ωmm) and an optimized (Rc = 0.04 Ωmm) sample were characterized using SEM-EDS, cross-sectional AEM, and XPS techniques. The non-optimized sample has prominent surface dendrites and a heterogeneous microstructure consisting of blocks of Ni0.5Ge0.4As0.1 in a matrix of Au0.7Ga0.2As0.1 and Ge-rich phases. Some of the Ge-rich crystals extend downward 50 nm into the substrate and are epitaxial to the n+ GaAs. The optimized sample has faint surface dendrites and a homogeneous fine-grained microstructure consisting of islands of Ni0.5Ge0.25As0.25 in a matrix of Au0.8Ga0.15As0.05. XPS depth profiles are in qualitative agreement with these results - the non-optimized sample shows a higher Ge content in the metal layer and less Ge in the GaAs substrate relative to the optimized sample. This work shows that 1) multivariable experimental methods can be used to optimize Ni- Ge-Au ohmic contacts to n+ GaAs, 2) the critical parameters for this process are Ge+Au layer thickness. Ge:Au ratio, and post alloy cooling time, and 3) lower Rc values are realized by effective diffusion of Ge from the metal layer into the GaAs substrate .
- ItemThe micro pore structure of concrete determined by small angle neutron scattering(Australian and New Zealand Institutes of Physics, 1994-02-10) Sabine, TM; Bertram, WK; Aldridge, LPSmall angle neutron scattering (SANS) is a complementary technique to electron microscopy for the elucidation of the shape and size of inhomogenities in the nanometric size range. SANS has the advantage that a large volume ( - 0.5 cm3 ) of the specimen is illuminated by the beam, and experiments can be earned out at atmospheric pressure on water saturated samples. It has the disadvantage mat, except for very simple systems, interpretation of the experimental data is not unambiguous. We have collected SANS data on a range of samples of concrete containing different water/cement ratios. The data was collected on the LOQ instrument at the ISIS spallation neutron source. We discuss interpretation of the data in terms of microscopic inhomogenities in the structure of concrete.
- ItemCharge compensation mechanisms for aliovalent impurities in perovskite and zirconolite(Australian and New Zealand Institutes of Physics, 1994-02-10) Vance, ER; Day, RA; Begg, BD; Blackford, MGAs part of the chemical design of Synroc-type ceramics for the immobilisation of different high-level radioactive wastes from nuclear fuel reprocessing, it is necessary to understand the various possible charge compensation mechanisms which occur when up to tens of atomic percent of rare earths and actinides are incorporated in solid solution in perovskite (CaTiO3) and zirconolite (CaZrTi2O7). In particular the solid solution of Gd in the Ca site of perovskite and the incorporation of Nd, Ce, U, Np and Pu in the Ca and Zr sites of zirconolite have been studied by XRD, SEM, TEM, and XANES. The essential conclusions are that in formulations where charge compensating ions are made available, then this is the preferred mechanism for incorporation of these cations in Ca and Zr sites. However in formulations where such compensators are not made available, it is possible for charge compensation to take place via significant abundances of cation vacancies, or by the appearance of unexpected valence states stabilised by crystal-chemical forces. An example of the latter is the probable stabilisation of Ti3+ in Ti sites, and of trivalent Ce and actinides in Ca and Zr sites, even under quite oxidising conditions. A complication in these studies is the effect of prevailing or inherited redox conditions. Redox conditions influence phase abundances and compositions as they control the valencies of cations capable of more than one oxidation state. There is also an indication that reducing conditions can promote oxygen site deficiencies in some formulations. Other complicating factors relate to sample fabrication, arising from the need to make extremely chemically uniform phases having the desired composition. This requires prolonged heating at high temperatures to achieve complete solid-state reaction that may result in selective losses due to volatilisation. Incipient melting due to localised eutectic formation and the apparently straightforward task of efficient stoichiometric mixing on a 1 to 10 um scale are other problems which have had to be overcome in sample fabrication.
- ItemA study of transition metal implanted single crystal YBa2 Cu3 O7-δ(Australian and New Zealand Institutes of Physics, 1994-02-10) Martin, JW; Russell, GJ; Cohen, DD; Evans, PJ; Hartmann, AThe modification of materials by ion-implantation is a method by which the structure and properties of a material can be altered in a controlled fashion and the study of these modified structures can lead to a better understanding of the parent material. The application to the Held of high temperature superconductors has been present ever since the discovery of the new oxides. In this study, high quality single crystal YBa2 Cu3 O7-δ was implanted separately with several different transition metal ions. The implantation was carried out using a metal vacuum vapour arc (MEVVA) ion source operated at 30kV with an approximate dose of ixlO17 ions/cm2 being applied. The resulting crystals were subsequently annealed in two separate anneal cycles in an oxygen atmosphere at 55O°C for a total of 108 hours. The sample analysis techniques involved the use of Rutherford backscattering spectroscopy (RBS), at both 2 and 3.07MeV, a.c. susceptibility measurements, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) for compositional, superconductivity, crystal structure and bonding analysis respectively. This paper will report on the results of this study which have shown that the implantation of nickel increased the rate of oxygenation in the near surface region, obtaining a transition temperature of 92°K after only 108 hours anneal time, whereas the implantation of iron was deleterious with a transition temperature of only 78°K reached after the same anneal cycles.
- ItemModelling the microstructure of cement(Australian and New Zealand Institutes of Physics, 1994-02-10) Bertram, WK; Sabine, TM; Aldridge, LPTo gain a better understanding of the factors that influence the strength and durability of concrete the microporosity of hydrated cement paste has been investigated, by small angle neutron scattering (SANS). The great advantage that SANS has over the more conventional methods of microporosity analysis such as mercury or gas intrusion, is that for SANS measurements it is not necessary to dehydrate the samples and the process is non-intrusive. However the results from SANS are often open to several different interpretations and it is necessary to obtain additional information where possible .One method of obtaining such additional information is through computer modelling of the process of cement hydration. In this poster we present the results of a 3- dimensional computer model that simulates the growth of a layer of calcium-silicate-hydrate (CSH) on a surface. The model used is similar to that for random aggregates (TA Witten and LM. Sanders, Phys. Rev. Lett. 19,1400 (1981)). The model calculates the porosity and the pore size distributions, which can men be compared with those obtained from SANS measurements.