ANSTO :: Browsing by Author "Lowson, RT"

Browsing by Author "Lowson, RT"

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234U/238U signatures associated with uranium ore bodies: part 1 Ranger 3
(Elsevier Science Ltd, 2013-04-01) Lowson, RT; Mclntyre, MG
The Ranger 3 ore body is an early Proterozoic U ore body in the Alligator Rivers U province, Northern Territory, Australia. It has surface expression with a redox front located between 30 and 50 m below the surface. The ground water U concentration and U-234/U-238 AR signature in the top 10 m of the weathered zone are reported for 357 samples collected over 4 wet seasons, at 5 depths, along a transect in-line with the hydraulic gradient and along the centre line of the ore body and its associated dispersion halo. The results show that the weathered zone displays a general U isotope feature for this type of ore body with the U-234/U-238 AR for the ground water and amorphous phase of the solid matrix being less than 1. The ground water U-234/U-238 AR is independent of the annual monsoonal climate and depth within the range surface to 10 m. In the vicinity of the U ore body the ground water U-234/U-238 AR is 0.75 and is very similar to the U-234/U-238 AR of the amorphous phase of the solid (0.76). The U-234/U-238 ARs of the amorphous phase and ground water rise and separate to values of 0.88 and 1.02 at the end of the transect. The rise and separation in U-234/U-238 AR are interpreted as evidence that the source of the U in the ground water is from the water-soluble sub-phase of the amorphous phase and that the ground water flow is too fast to allow the processes occurring across the solid water interface to reach chemical equilibrium. The data set is a robust characterisation of the coarse and fine detail of the U-234/U-238 AR signature in the weathered zone of U ore bodies. © 2013, Elsevier Ltd.
234U/238U signatures associated with uranium ore bodies: part 2 Manyingee
(Elsevier Science Ltd, 2013-04-01) Lowson, RT; Mclntyre, MG
The Manyingee ore body is a roll-front U ore body located at depth in the Cretaceous sandstone sediments of a Proterozoic palaeo valley. It is located in a confined aquifer. The aquifer is recharged 4 km upstream by the Ashburton River. Groundwater samples were collected at and up to 4.7 km downstream of the ore body. The ground water U-234/U-238 activity ratios (AR) were elevated to 1.86 in the vicinity of the ore body and then declined to 1.06 over the 4.7 km transect. The elevated U-234/U-238 ARs are attributed to selective leaching of U-234 sites by oxidising waters, with a recoil as a necessary precursor to produce activated U-234 sites. Direct ejection into another phase following a recoil is considered to be a minor contributor to U-234 U-238 disequilibrium in this environment. The profile is considered to be typical of the U-234/U-238 AR profile at and down gradient of the redox front of a U ore body. © 2013, Elsevier Ltd.
234U/238U signatures associated with uranium ore bodies: part 3 Koongarra
(Elsevier Science Ltd, 2013-04-01) Lowson, RT
The Koongarra ore body is an early Proterozoic U ore body in the Alligator Rivers U province, Northern Territory, Australia. It has surface expression with a redox front located similar to 30 m below the surface. The U-234/U-238 activity ratios (AR) for the ground water and the amorphous phase of the solid have been analysed for the ore zone and dispersion halo as a function of depth. The results display a U-234/U-238 AR signature with depth which may be common to all U ore bodies. The U-234/U-238 AR is depressed below secular equilibrium in the weathered material above the redox front; rises significantly above secular equilibrium in the vicinity of the redox front; and is followed by a gradual decrease with depth below the redox front. The amplitude of the profile is a function of local conditions. A model is proposed for the signature in which oxidising waters preferentially leach the U-234 sites at the redox front due to preconditioning of the U-234 sites by a recoil during the decay of U-238 to U-234. Mass balance requires the solid material left behind the redox front to have a U-234/U-238 AR reduced below I. Local second order effects may be superimposed on the signature. The signature may have application to calibrating scenarios for nuclear waste repositories, assisting in understanding historical climates, economic evaluation of U ore bodies and U exploration. © 2013, Elsevier Ltd.
Analysis for the radionuclides of the natural uranium and thorium decay chains with special reference to uranium mine tailings
(Australian Atomic Energy Commission, 1986-08) Lowson, RT; Short, SA
A detailed review is made of the experimental techniques that are available or are in the process of development for the determination of 238U, 235U, 234U, 231Pa, 232Th, 230Th, 228Th, 228Ra, 226Ra, 223Ra, 210Po and 210Pb. These products of the uranium and thorium decay chains are found in uranium mine tailings. Reference is also made to a procedure for the selective phase extraction of mineral phases from uranium mine tailings.
Bacterial leaching of uranium ores - a review
(Australian Atomic Energy Commission, 1975-11) Lowson, RT
The bacterial leaching of uranium ores involves the bacterially catalysed oxidation of associated pyrite to sulphuric acid and Pe3+ by autotrophic bacteria and the leaching of the uranium by the resulting acidic, oxidising solution. Industrial application has been limited to Thiobacillus thiooxidans and Thiobacillus ferrooxidans at pH 2 to 3, and examples of these are described. The bacterial catalysis can be improved with nutrients or prevented with poisons. The kinetics of leaching are controlled by the bed depth, particle size, percolation rate, mineralogy and temperature. Current work is aimed at quantitatively defining the parameters controlling the kinetics and extending the method to alkaline conditions with other autotrophic bacteria.
Corrosion of aluminium in pure water and dilute solutions
(Australian Atomic Energy Commission, 1973-07) Berzins, A; Evans, JV; Lowson, RT
An investigation into the corrosion of aluminium in flowing near-neutral water at 50 C is reported. The corrosion rate passed through a minimum as the pH was changed from pH 5.0 to 8.0. The pH at the point of minimum corrosion was sensitive to atmosphere, being highest in oxygen-saturated water. The corrosion rate was reduced and spallation of the oxide film prevented by saturating the water with oxygen.
From Rum Jungle to Wismut - Reducing the environmental impact of uranium mining and milling
(The Institution of Engineers Australia, 1994-05-01) Zuk, WM; Jeffree, RA; Levins, DM; Lowson, RT; Ritchie, AIM
Australia has a long history of uranium mining. In the early days, little attention was given to environmental matters and considerable pollution occurred. ANSTO has been involved in rehabilitation of a number of the early uranium mining sites, from Rum Jungle in Australia's Northern Territory to Wismut in Germany, and is working with current producers to minimise the environmental impact of their operations. ANSTO's expertise in amelioration of acid mine drainage, radon measurements and control, treatment of mill wastes, management of tailings, monitoring of seepage plumes, mathematical modelling of pollutant transport and biological impacts in a tropical environment are summarized.
An instrumented leach column for the study of sulphide oxidation in waste heaps
(Australian Atomic Energy Commission, 1985-05) Lowson, RT; Sarbutt, JV
The construction commissioning and first year of operation of a large scale instrumented leach column are described. The column material was sulphidic mine overburden. Monitored parameters included matrix potential temperature redox potential dissolved oxygen pore space gas water addition and drainage together with pH, Cd, Cu, Fe, Ni, Zn, Cl, F, SO42 and PO43 in the effluent.
ISO 9001 accreditation in an R&D environment - is it possible?
(International Atomic Energy Agency, 2004-10-24) Szymczak, R; Henderson-Sellers, A; Lowson, RT; Chisari, R
The Australian Nuclear Science and Technology Organisation (ANSTO) is Australia's national nuclear organisation and its centre of Australian nuclear expertise. ANSTO is in the process of replacing its 1950’s, 15 MW, high flux (up to 1015 n cm-2 s-1) reactor with a new reactor which will allow it to continue its cutting edge nuclear science and radiopharmaceutical production well into the 21st century. A ministerial requirement for licensing the facility is ISO 9001 accreditation of its quality management system. The accreditation process has been staggered at ANSTO. Individual divisions are attaining ISO 9001 accreditation separately, leading up to site-wide accreditation of an overarching ANSTO Business Management System. ANSTO Environment is the largest multidisciplinary environmental research group in Australia and the largest R & D unit at ANSTO, comprising around 150 biologists, chemists, engineers, geophysicists, meteorologists, microbiologists, oceanographers, physicists, and technicians (Fig. 1). ANSTO Environment operates and maintains a wide range of advanced nuclear and analytical facilities including three particle accelerators, a 10 MV Tandem accelerator, a 3 MV Van de Graaff accelerator and a newly acquired 2MV HVEE tandetron; a high current 50 kV Metal Vapour Vacuum Arc Ion Implantation (MEVVA) Facility; a Secondary Ion Mass Spectrometer (SIMS); and many other laboratory and field-based facilities. The objective of ANSTO Environment is to carry out a problem-focused, balanced program of strategic and applied research and development, using its nuclear science-based core expertise and closely-related techniques, to: assist the Commonwealth Government to further its national and international initiatives, and to protect and conserve the natural environment through sustainable development; · assist industry in advancing Australia's competitive position in the world economy; · ensure that environmental monitoring of nuclear facilities is effective in assuring operational adherence to sound environmental protection principles. “Make everything as simple as possible, but not simpler” Albert Einstein In February 2000 ANSTO Environment successfully acquired ISO 9001:2000 accreditation of its quality management system and was amongst the first organisations to adopt the new 2000 revision of the international ISO 9001 standard. The new standard allows a much more flexible and less prescriptive format for quality management systems however, in the absence of examples of accreditation in the R & D area, presented a challenge in concept, definition of process, buy-in by staff and subsequent maintenance of the successful certification. The ANSTO Environment Manual of Good Management Practice [1] outlines our identity, our vision, our core values, our responsibilities, our operational processes and our commitment to continual improvement via internal and external review. This paper is a description and discussion of the elements, concepts and process for achieving staff buy-in in the face of initial opposition. This included identifying those necessary elements of a good management system, rejection of pejorative dogma associated with ‘Quality’ and ownership of the process by all the staff.
ISO 9001 accreditation in an R&D environment - is it possible?
(International Atomic Energy Agency, 2006) Szymczak, R; Henderson-Sellers, A; Lowson, RT; Chisari, R
The Australian Nuclear Science and Technology Organisation (ANSTO) is Australia's national nuclear organisation and its centre of Australian nuclear expertise. ANSTO is in the process of replacing its 1950’s, 15 MW, high flux (up to 1015 n cm-2 s-1) reactor with a new reactor which will allow it to continue its cutting edge nuclear science and radiopharmaceutical production well into the 21st century. A ministerial requirement for licensing the facility is ISO 9001 accreditation of its quality management system. The accreditation process has been staggered at ANSTO. Individual divisions are attaining ISO 9001 accreditation separately, leading up to site-wide accreditation of an overarching ANSTO Business Management System. ANSTO Environment is the largest multidisciplinary environmental research group in Australia and the largest R & D unit at ANSTO, comprising around 150 biologists, chemists, engineers, geophysicists, meteorologists, microbiologists, oceanographers, physicists, and technicians (Fig. 1). ANSTO Environment operates and maintains a wide range of advanced nuclear and analytical facilities including three particle accelerators, a 10 MV Tandem accelerator, a 3 MV Van de Graaff accelerator and a newly acquired 2MV HVEE tandetron; a high current 50 kV Metal Vapour Vacuum Arc Ion Implantation (MEVVA) Facility; a Secondary Ion Mass Spectrometer (SIMS); and many other laboratory and field-based facilities. The objective of ANSTO Environment is to carry out a problem-focused, balanced program of strategic and applied research and development, using its nuclear science-based core expertise and closely-related techniques, to: · assist the Commonwealth Government to further its national and international initiatives, and to protect and conserve the natural environment through sustainable development; · assist industry in advancing Australia's competitive position in the world economy; · ensure that environmental monitoring of nuclear facilities is effective in assuring operational adherence to sound environmental protection principles. “Make everything as simple as possible, but not simpler” Albert Einstein In February 2000 ANSTO Environment successfully acquired ISO 9001:2000 accreditation of its quality management system and was amongst the first organisations to adopt the new 2000 revision of the international ISO 9001 standard. The new standard allows a much more flexible and less prescriptive format for quality management systems however, in the absence of examples of accreditation in the R & D area, presented a challenge in concept, definition of process, buy-in by staff and subsequent maintenance of the successful certification. The ANSTO Environment Manual of Good Management Practice [1] outlines our identity, our vision, our core values, our responsibilities, our operational processes and our commitment to continual improvement via internal and external review. This paper is a description and discussion of the elements, concepts and process for achieving staff buy-in in the face of initial opposition. This included identifying those necessary elements of a good management system, rejection of pejorative dogma associated with ‘Quality’ and ownership of the process by all the staff.
The kinetics of chlorite dissolution
(Elsevier, 2007-03-15) Lowson, RT; Brown, PL; Comarmond, MJ; Rajaratnam, G
A model for the dissolution of chlorite has been developed based on fast ligand assisted proton attack of the alumina tetrahedra within the alumina-silica lattice followed by slower dissolution of the remnant silica lattice. While the rate determining step is within the silica dissolution regime, the rate is a function of the H+ and Al3+ concentrations and the dominant aqueous Al species. Individual rates may be described by a generic rate equation applicable across the spectrum of Al species: where rn is the rate subscripted for the nth Al species, k is the rate constant of the rate controlling step, K is the surface exchange constant, β is the solution stability constant subscripted for the Al species, a is the species activity subscripted for species and raised to the power of the stoichiometry, p and q are stoichiometric coefficients, z is the ligand charge and τ is the fractional coefficient for the precursor of the rate defining step. The observed rate is the sum of the individual rates. When the observed rate is in a domain of dominance for a single aluminium species and in the absence of strong complexing agents such as oxalate, the observed rate is proportional to (a3H+/aAl3+)τn. The model is supported by experimental data for the dissolution of chlorite over a pH range of 3–10 and temperature range 25–95°C. The results have hydrometallurgical application. © 2007, Elsevier Ltd.
Potential - pH diagrams at temperatures above 298.16 degrees K, Part 2 - potential - pH diagrams of water for the temperature range 298.16 - 573.16 degrees K
(Australian Atomic Energy Commission, 1972-03) Lowson, RT
The Potential — pH diagrams are presented for water over the temperature range 298.16-573.16º K. The diagrams are discussed with reference to variation of the thermodynamic stability of species H20(l) , H +, 0H-, H-, H202, H0-2, H1, H2, 02, 0S and H20(g) with temperature. The diagrams demonstrate the variation of Kw and the neutral point of water with temperature. The maximum for Kw was —11.86 at 473.16º K (200ºC) with a corresponding minimum pH value of 5.93.
Radium and heavy metal transport beneath an abandoned uranium tailings dam
(Australian Nuclear Science and Technology Organisation, 1988-09) Jeffery, JJ; Sinclair, G; Lowson, RT
An abandoned uranium tailings dam at Moline in the Northern Territory of Australia was the site of a study to assess the movement of potentially toxic elements from tailings into subsoil. The tailings at Moline were first laid down in 1959 and have since been leached by prevailing rainfall. Sixteen sampling sites were selected to give a good representation of the dam. At each site a trench was excavated through the tailings and into the subsoil then samples of subsoil were taken at 10 cm intervals down to a depth of 50 cm. A sample of the tailings overlying the tailings-subsoil interface was also taken. Samples were analysed for radium uranium copper zinc and lead. At most sites there was only minor accumulation of these elements in the 0-10 cm subsoil layer immediately below the interface with concentrations typically one or two orders of magnitude less than the concentrations in overlying tailings. Below 10 cm the concentrations were typically at or close to background concentrations.
The rum Jungle tailings dam - chemical profile of the subsoil
(Australian Nuclear Science and Technology Organisation, 1987-09) Lowson, RT; Evans, JV; Sarbutt, JV; Sinclair, G; Folk, E
In a survey of soils below the Rum Jungle uranium mine tailings dam parameters measured were pH moisture content particle distribution total Cu water-extractable Cu, Ca and SO4 and acid-extractable Ra. The cation profile had a marked discontinuity at the soil/tailings interface. This was attributed to a complex hydrogeology and to the presence of a reduction zone in the soil immediately below the tailings. The tailings acted as an aquaclude to a water table which fluctuated with the monsoonal season. The reduction zone acted as a cation trap preventing cation transport. The radium concentration dropped to levels acceptable to public health within a few centimetres of the soil/tailings interface.
Uranium and other contaminant migration in groundwater at a tropical Australian Uranium Mine
(Elsevier, 1998-12-15) Brown, PL; Guerin, M; Hankin, SI; Lowson, RT
Hydrogeochemical modelling (utilising the modelling tools MODFLOW, MT3D and HARPHRQ) has been used in conjunction with laboratory-based experiments and a field monitoring program to investigate the fate of uranium and other contaminants in excess water sprayed on a 33 ha region of the Ranger Uranium Mine (RUM), northern Australia. The results indicate that uranium is retained in the surficial layer of the lateritic soils of the area. Conservative contaminants are not retained by the soils and are transported into the groundwater. Subsequently, they migrate relative to the groundwater flow rate towards the river system down hydraulic gradient of the irrigation area. © 1998 Elsevier Science B.V.

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