Assessment of the Jabiluka Project : report of the Supervising Scientist to the World Heritage Committee
Johnston, A.; Prendergast, J. B.; Bridgewater, Peter
E-Publications; E-Books; PublicationNT; Supervising Scientist Report; 138
Alligator Rivers Region
Main report--Appendix 2 of the Main Report. Submission to the Mission of the World Heritage Committee by some Australian Scientists ... --Attachment A. Johnston A. and Needham S. 1999. Protection of the environment near the Ranger uranium mine--Attachment B. Bureau of Meteorology 1999. Hydrometeorological analysis relevant to Jabiluka--Attachment C. Jones, R.N., Hennessy, K.J. and Abbs, D.J. 1999. Climate change analysis relevant to Jabiluka--Attachment D. Chiew, F and Wang, Q.J. 1999. Hydrological anaysis relevant to surface water storage at Jabiluka--Attachment E. Kalf, F. and Dudgeon, C. 1999. Analysis of long term groundwater dispersal of contaminants from proposed Jabiluka mine tailings repositories--Appendix 2 of Attachment E. Simulation of leaching on non-reactive and radionuclide contaminants from proposed Jabiluka silo banks.
Uranium mill tailings - Environmental aspects - Northern Territory - Alligator Rivers Region; Environmental impact analysis - Northern Territory - Jabiluka; Uranium mines and mining - Environmental aspects - Northern Territory - Jabiluka; Jabiluka - Environmental aspects
Supervising Scientist Report; 138
1 volume (various pagings) : illustrations, maps
https://hdl.handle.net/10070/462403; https://hdl.handle.net/10070/462400; https://hdl.handle.net/10070/462405; https://hdl.handle.net/10070/462406; https://hdl.handle.net/10070/462408; https://hdl.handle.net/10070/462409; https://hdl.handle.net/10070/462411
81 equivalent of 1000 years for predictions of the movement of radium and uranium, and 200 years for other contaminants. The hybrid approach utilised by Kalf and Dudgeon (1999) enables detailed calculations to be undertaken where necessary, without hindering the development of the large number of solutions required to undertake a proper risk assessment. The prediction of solute concentrations downstream of the tailings repositories at Jabiluka is not trivial because groundwater flow and contaminant transport are complex three-dimensional processes. It is not uncommon in studies involving groundwater modelling for the precision of the outcomes to be limited by availability of data, because of the high cost of obtaining appropriate data through drilling. At Jabiluka, ERA has had additional difficulties to overcome because of restrictions on access to areas from which data are required. The Monte-Carlo simulations help overcome these limitations by assessing model outputs for a wide range of parameters. The Monte-Carlo simulation requires a probability distribution of the range for each parameter, and, in the current work, each value of a particular parameter was assigned an equal probability; this approach is conservative and ensures worst case scenarios are produced. Downstream concentrations of contaminants emanating from the tailings have been presented by Kalf and Dudgeon (1999) in dimensionless or normalised form so that they can be used for predicting the impact for a range of source concentrations. Relative or normalized concentrations are expressed in terms of fractions or percentages of the source concentrations whatever they may happen to be. The results in the modelling report can, therefore, be used to determine absolute concentrations once the source concentrations are known more precisely. For example, differing assumptions on the permeability of the tailings give rise to different effective source concentrations two metres out from the mine void or silos. The effect of permeability on concentrations of solutes far from the source can then be assessed quite rapidly using the relative concentration data from the analytical model. 6.3.3 Properties and constituents of tailings Recent developments in dewatering technologies (eg cyclones, centrifuges, belt filters etc) have enabled production of tailings pastes which have a lower water content than the parent tailings material, and superior environmental performance. Addition of binders such as Portland cement, as is proposed at Jabiluka, can then be conveniently undertaken to ensure the tailings remain environmentally benign. Cincilla et al (1997) have suggested that the tailings stream should contain at least 15% by weight of particles of less than 20 m diameter, and that under these circumstances segregation can be avoided in a tailings paste. Golder and Associates (1997) undertook measurements on the particle size distribution and rheological characteristics of tailings from Jabiluka; they found that greater that 30% of the tailings had a particle size less than 20 m, and that the tailings were well suited to the application of paste technology. Although only limited work has been completed on the properties of Jabiluka tailings because the mine is not operational, physical properties of tailings at Ranger have been studied by Richards et al (1990). Ore at Jabiluka and Ranger originates from Cahill Formation schists and will be subject to the same milling process. Hence the tailings from the two mines are expected to have similar physical and chemical properties. The tailings permeability is illustrated in figure 6.3.4 as a function of effective stress, because when tailings are in place they are subjected to overburden pressure that reduces their permeability. Richards et al (1990) fitted Equation 6.1 to the tailings permeability data, and their equation has been shown to be consistent with tailings permeability data at other minesites (B
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