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
30 Commonwealth Government (in which all tailings will be returned underground) because evaporation from the tailings ponds was not included in the water balance modelling presented in the PER. The submission of Wasson et al (1998) states (page 13) that a major error exists in the calculations presented in the EIS and the PER for the quantity of water that can be evaporated in the ventilation shafts. They point out that the latent energy of evaporation has to be taken from the air stream resulting in a drop in the air temperature; this, in turn, will reduce the capacity of the air to hold moisture. The basic physics underlying these statements is not disputed by the Supervising Scientist but the conclusion that a major error is present in the calculations is not supported. As stated in Appendix J of the draft EIS, the absolute humidity or water vapour density, p, may be calculated from the ideal gas law which, when the vapour pressure, Pv, is given in kPa, reduces to TPvp /167.2= (1) where p is in kg/m3 and T is in oK. Figure 3.4.1 (upper graph) shows the dependence of vapour pressure on temperature at an atmospheric pressure of 100 kPa; the data were taken from Kaye and Laby (1978, p 173). From these data the absolute humidity values have been calculated using equation (1); they are presented in figure 3.4.1 (lower graph). For T=30 oC, the values of p for 85% and 60% relative humidity are 0.0259 kg/m3 and 0.0182 kg/m3 respectively. If no external energy is provided, the latent heat of vaporisation for the difference, 0.0077 kg/m3 would need to be provided by the air stream. This would result in a drop in temperature, T, given by pCpLT /= (2) where p is the change in humidity, L is the latent heat of vaporisation, is the density of air and Cp is the specific heat of air. Using L = 2.43 106 J/kg (Kaye & Laby 1978, p 235), = 1.149 kg/m3 (Kaye & Laby 1978, p 18) and Cp = 1010 J/kg/oC (CRC 1995, p 6-1), the decrease in temperature resulting from the vaporisation of the water would be 16C. As can be seen from figure 3.4.1, the absolute humidity (ie fully saturated) at 14C is about 0.012 kg/m3, a figure considerably less than the initial vapour density. Hence, the target evaporation figure cannot be achieved. The optimum performance of the proposed system can be derived as follows. As water is added to the air stream and evaporated, the water vapour density will increase linearly with decreasing temperature until a temperature is reached at which the air stream is saturated. The gradient of this linear relationship is given by CmkgLCdTdp op /)/(1078.4// 34== (3) Hence, ))(/( 00 TTLCpp p = (4) For 60% relative humidity, p0 = 0.0182(kg/m3) at T0 = 30C. This line is shown in figure 3.4.1. It intercepts the graph of absolute humidity at about 23.6C which, as proposed by Wasson et al (1998), is the wet bulb temperature (estimated as 23.8C from the data in CRC (1995) p1522). At this temperature the absolute humidity is 0.0213 (kg/m3). Thus the maximum quantity of water that can be evaporated is
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