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Alligator Rivers analogue project final report volume 1 summary of findings
(Australian Nuclear Science and Technology Organisation, 1992) Duerden, P; Lever, DA; Sverjensky, DA; Townley, LR
This summary report, which highlights the work and findings of the Alligator Rivers Analogue Project (ARAP) is one of a series of 16 volumes, listed below. Detailed descriptions and results are provided in Volumes 2 to 16. Full acknowledgment to individual contributions is provided in the individual reports, and in Appendix I of this report. The findings from the technical studies are discussed in the context of assessments of the long-term performance of geological repositories for radioactive wastes, which are being undertaken in many countries. They are also considered in an integrated 'Scenario Development' approach, aimed to understand the formation of the ore deposit. Despite their inherent uncertainties, the findings provide a basis for assessing the way in which radionuclides will migrate in environments with a variety of geologic settings and over a range of different geologic timescales. Thus, section 2 of this report discusses the concept of using uranium deposits as natural analogues and refers to a number of such studies, including those at the Koongarra deposit in the Alligator Rivers Region of the Northern Territory of Australia. Section 3 reviews early scientific work in the Alligator Rivers Region and summarises the results of the analogue studies undertaken between 1981 and 1987 that were funded by the US Nuclear Regulatory Commission (USNRC) and the UK Department of the Environment (UKDoE). Section 4 describes the objectives of ARAP and the manner in which the study was conducted and provides a general outline of the project and a summary of the findings. A general description of the Koongarra ore deposit, the focus of ARAP, is provided in Section 5, with Sections 6-13 providing summaries of the work carried out to characterise the site in detail and provide data for modelling. Sections 14-18 discuss how this data was used in modelling and how the results may be applied for performance assessment studies. Finally, Section 19 considers the implications of the work for performance assessment modelling.
Alligator Rivers analogue project final report volume 7 groundwater chemistry
(Australian Nuclear Science and Technology Organisation, 1992) Payne, TE; Edis, R; Herczeg, AL; Sekine, K; Seo, T; Waite, TD; Yanase, N
The objective of this volume is to provide an account of the groundwater sampling and analysis program undertaken at Koongarra, as part of the Alligator Rivers Analogue Project. Chemical parameters were investigated in groundwaters at various locations and depths in the vicinity of the Koongarra orebody. Measurements of the pH, redox state, conductivity, and bicarbonate alkalinity provided a starting point for interpreting water chemistry. Groundwater samples were obtained using submersible pumps, or, in a few cases, bailers. The concentrations of major cations and anions, such as magnesium and phosphate, were determined using a variety of standard techniques. Numerous elements were routinely analysed using quantitative or semi-quantitative ICPMS. Uranium series radionuclides and environmental isotopes were measured using radiochemical techniques and mass spectrometry. The distributions of isotopes such as deuterium, tritium, 210Pb, 13C and 14C enabled groundwater mixing and flow-paths to be studied. The occurrence and distributions of major species at Koongarra are presented in this volume, using both cross-sections and contour plans. Chemical and isotopic data for groundwater analyses carried out during the project are included in the Appendices. 47 refs., 16 tabs., 58 figs
Alligator Rivers analogue project. Uranium sorption. Final report - volume 13
(Australian Nuclear Science and Technology Organisation, 1992) Waite, TD; Payne, TE; Davis, JA; Sekine, K
In this volume, the results of studies of uranium sorption (adsorption and desorption) to both single, well-defined mineral phases, and to selected natural (Koongarra) substrates are reported. The single phases included the amorphous iron oxide ferrihydrite, crystalline silica and two naturally occurring kaolinites, KGa-1 and Nichika. The surface properties of these materials were rigorously defined, and adsorption studies were conducted over a range of solution pH, ionic strength, carbonate content, adsorbent and adsorbate concentrations, and in the presence of uranium complexants and (potentially) competing adsorbates (such as phosphate and fluoride). The results of these studies were modelled using the 'surface complexation' approach, with a diffuse layer description of the electrical double layer. The impacts of mineral phase transformations (specifically the aging of amorphous ferrihydrite to more crystalline forms) on the uptake and desorption of uranium are also reported. The amount of data obtained in this study, with a number of experimental parameters being varied over a wide range, has enabled more confidence to be placed in the modelling results. The derived model for ferrihydrite adequately accounts for the effect on U sorption of a number of parameters, most notably pH, pCO2 and total U present. Few (if any) of the models previously proposed are adequate in this respect. While the modelling of the data for the natural substrates is not as advanced, the U sorption data on the natural substrates show similar features to the U sorption on the model substrates. This suggests that the insights obtained in the modelling of the data for ferrihydrite will be valuable in deriving a model for the more complex natural substrates
Alligator Rivers analogue project final report volume 8 chemistry and mineralogy of rocks and soils
(Australian Nuclear Science and Technology Organisation, 1992) Edis, R; Cao, L; Cashion, JD; Klessa, D; Koppi, AJ; Murakami, T; Nightingale, T; Payne, TE; Snelling, A; Yanase, N
This volume contains a description of the distribution of minerals and elements at Koongarra, including the distribution of radionuclides. The Koongarra orebody is situated 225 km east of Darwin in the Northern Territory of Australia. The zone of primary uranium mineralisation has been intersected by weathering conditions, and this has resulted in the formation of a secondary ore zone and dispersion fan in the weathered zone. The uranium distribution over the site was investigated to determine the extent and direction of uranium migration from the primary uranium mineralisation. The depth patterns of uranium concentration were also investigated to elucidate depths. The distribution of elements, rock and minerals, and how they may affect uranium mobility, or indicate interactions between uranium and solid phases, were considered. Multi-elemental analyses were carried out on many samples to provide basic concentration data about various geochemically significant elements, and to elucidate how the elements interact with one another, the solid substrate and the groundwater. This included the analysis of bulk rock samples, visually distinct sub-samples, different particle sizes and chemically defined phases. Similarly, mineralogical data supplied information on the substrate reacting with the groundwater. Extensive studies were undertaken to elucidate the form of uranium in the weathered zones. These involved optical and electron microscopy studies and auto-radiography. Spatial trends of uranium series disequilibria in bulk rock, secondary uranium minerals and different chemically defined phases were analysed. These give information about uranium deposition and leaching, the evolution of the dispersion fan, the roles and relative importance of different mineralogical phases and processes involved in the retardation of radionuclides.
Alligator Rivers analogue project final report volume 9 weathering and its effects on uranium redistribution
(Australian Nuclear Science and Technology Organisation, 1992) Murakami, T; Isobe, H; Ohnuki, T; Yanase, N; Sato, T; Kimura, H; Sekine, K; Edis, R; Koppi, AJ; Klessa, DA; Connoley, C; Nagano, T; Nakashima, S; Ering, RC
In the vicinity of the uranium ore deposit at Koongarra, quartz-chlorite schist, the ore host rock, has been subjected to weathering. Although quartz is resistant to weathering, chlorite has been altered to clays and iron minerals. The chlorite weathering and the uranium association with the weathered minerals are the main topics of this study. In order to clarify the weathering of chlorite and its effects on the redistribution of uranium, the processes, mechanisms, and kinetics of the chlorite weathering, and the uranium concentrations in minerals were examined by various methods: X-ray diffraction analysis, scanning electron microscopy, electron microprobe analysis, transmission electron microscopy, autoradiography, visible spectroscopy, alpha and gamma spectrometry. The observed results were compared to those calculated, based on two different models developed for the present study. Water-rock interactions have resulted in the weathering of chlorite and precipitation and sorption of uranyl from the groundwaters with the weathering products. It is concluded that the chlorite weathering affects the uranium retardation factor, and thus uranium redistribution at Koongarra.

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