In the last forty years, Uranium has become one of the worlds most important energy minerals. Primarily, Uranium produced in Australia has used for the sole production of electricity. However a small proportion of the Uranium mined is for important medical isotopes. It is for this reason that Uranium mining is an ever-important and pressing point of discussion. Mining itself has been criticized for the massive effect it on the environment around it. Uranium mining is no different, and more often then not, the after effects of Uranium mining are more detrimental to the environment.
Unlike other mining, Uranium mining has also caused a major stir in the actual use of the Uranium after it has been mined. The environmental problems of Uranium mining go further then the actual mining and by products. The uses of Uranium have been seen as risky and dangerous. Using Uranium as a source of energy has already shown the disastrous effects. The melt down at Chernobyl is still causing health problems in citizens after 30 years. On the upside, Uranium mining creates employment and boosts the Australian Economy.
It is for these reasons that Uranium Mining is a process that needs to be looked at carefully before any judgements are made on it’s future in Australia. Chemistry Of Uranium and Uranium Mining In the Earth’s crust, mineral Uranium averages about two parts per million. Traces of Uranium occur just about everywhere on earth. In Australia, the existence of uranium has been noted since the 1890’s. In 1930, ores were mined at Radium Hill in South Australia for minute deposits of Radium. The Radium was used for medical purposes.
As a result of the Radium mining, a couple of hundred kilograms of uranium was obtained and used exclusively to produce colours in glass and ceramics. In 1954 the Government started up a major uranium producer in Run Jungle, known as Rum Jungle Mine. Because of this Australia began to emerge as a potential source of uranium for the world’s nuclear electricity production. 1970’s large amounts of Uranium deposits were found dotted around Australia. This signaled the start of mines in the Northern Territory such as Ranger and Jabiluka, and also in South Australia with Olympic Dam.
Uranium is found rocks of the earth’s crust, at 4 parts per million. The extraction (removal) or mining process varies from where the uranium ore deposits are found. Surface cut techniques are used where the uranium ore if found close to the surface. Surface cut mines involved the uranium being found close to the surface, so the uranium is removed from a shallow pit. Fig 1. 0 Ranger Mine found in the Northern Territory. The uranium ore is removed via the open cut mining method. Underground mining is used when the ore is found deep underground. In this process, the ore is removed in a similar fashion to copper; the mine is built in the ground.
Olympic Damn Mine in South Australia, relies on the underground mining process. Another way to remove ore is called In-Situ Leaching. It is a popular way to mine Uranium, as it doesn’t affect the landscape as much as open cut or underground mining. It is used to remove Uranium filled sand that is found in water in a porous rock, which itself confined in a non-porous rock. In situ leaching involves a leaching liquid (ammonium-carbonate or sulfuric acid) pumped through drill- holes into underground uranium deposits, with the uranium bearing liquid is pumped out from below.
Ore mined in open pit or underground mines, unlike in situ leaching, has to be crushed and leached in a uranium mill. A Uranium mill is a chemical plant designed to extract uranium from ore. It is usually located near the mines to limit transportation. In the most cases, sulfuric acid is used as the leaching agent, but alkaline leaching can also used. As the leaching agent not only extracts uranium from the ore, but also several other constituents like molybdenum, vanadium, selenium, iron, lead and arsenic, the uranium must be separated out of the leaching solution.
The final product produced from the mill, commonly referred to as “yellow cake” (U3O8 with impurities), is packed and shipped in casks. The reaction between the uranium ore and sulfuric acid. The UO2 is then oxidised. In some cases uranium has been removed from low-grade ore by a process called heap leaching. This may be done if the uranium contents are too low for the ore to be economically processed in a uranium mill. Heaping leaching is performed by using a leaching liquid (often sulfuric acid) being introduced to the top of the pile of ore.
The acid or leaching liquid, percolates down until it reaches a liner below the pile or ore, where it is caught and pumped to a processing plant. This liquid contains the uranium. During leaching, the piles of ore present a hazard because of the risk of release of dust, radon gas and leaching liquid. (referenced from Hardy, C J, 1978, The Chemistry of Uranium Milling, Radiochimica Acta 25, 121-134) Nuclear Mining and Milling has a serious social relevance. The tailings from the Uranium mining have serious health risks and environmental hazards. There are many serious environmental arguments over the mining of Uranium.
The mining process itself in Australia has strict guidelines, yet the waste products from the mining process still have an extremely detrimental effect on the environment. Uranium mill tailings (or waste products from the crushing and leaching of the ore) are normally dumped as sludge in special ponds or piles (heaps). These piles/ponds are then abandoned. The amount of sludge produced is roughly equal to that of the ore milled. Long-living decay products such as the radioactive elements Thorium-230 and Radium-226 are not removed from the sludge. This means that the sludge contains over half of the initial radioactivity of the ore.
As well as this, unfortunately, due to mainly technical limitations not all of the Uranium present in the ore can be removed in the milling process. Therefore, the sludge (which is the waste product) still contains at least 5% of the uranium present in the ore to start off with. The sludge also contains a variety of heavy metals and other contaminants. These include arsenic, as well as the highly corrosive chemical reagents used during the milling process (such as the sulfuric acid used in leaching). The mining and milling process fundamentally removes the hazardous constitutes in the ore from their relatively safe underground location.
Mined Uranium itself does not emit hazardous radiation. Radium-226 found in the tailings continuously decays to the radioactive gas Radon-222. Radon-222 has a decay product that has been thought to cause lung cancer. Radon releases are a major hazard that continues even after uranium mines are shut down. The Radon can escape from the interior of the tailing piles or sludge. Since radon spreads quickly with the wind, many people receive small additional radiation doses. However, in Australia the majority of mines are based away from residential or populated areas.
It is a concern for workers though, but with safety apparatus, the risk factor is non-existent. Tailing deposits are also subject to many different kinds of erosion. During and after a heavy rainfall, erosion gullies can form where the tailing deposits are left. Floods can destroy the whole deposit, leaving it dispersed everywhere. Interestingly enough, plants and burrowing animals can penetrate into the deposit and disperse the material, which subsequently enhances the radon emanation and make the deposit more susceptible to erosion. When the surface of the pile dries out, the fine sands are blown by the wind over adjacent areas.
Erosion leaves the tailing deposits at a risk of dispersion. Seepage from tailing piles is another major hazard. Seepage poses a risk of contamination to ground and surface water. This water can be transferred to fish that swim in the water, then to whoever consumes the fish. Tailings dams are more often then not, not of stable construction. In most cases, they were made from sedimentation of the tailing sludge. Some are even built on geologic faults. This means that they are at greater risk of an earthquake. Strong rain or snowstorms can also cause dam failures. It is of no surprise that time after time dam failures have occurred.
It was thought that bringing the tailings back to where the ore was mined would be an acceptable solution for the tailing disposal. Even though most of the Uranium was removed from the material, it did not mean the material was less hazardous. Most of the contaminants are still present. It is because of the processes the materials have to go through to extract the uranium which leaves the material in a condition where the contaminants are much more mobile (sludge and sand), therefore the material susceptible to migration into the environment. In most cases, tailings have to be dumped on the surface for lack of other options.
Here, the protection requirements can more easily be controlled by appropriate methods, but additional measures have to be performed to assure protection from erosion. Uranium mining has also caused some concerns because of where the ore deposits are located. Jabiluka mine is in the heart of Kakadu, a National Park, and also in the mines in the Arnhem region. Aboriginal communities are against the mine sites as they are on their cultural land and heritage. It can be argued however, that with strict regulations in the mining and milling of Uranium, the environmental effects and cultural disturbances can be minimal.
The mine-tailing dam should for one not be built on a geological fault. This itself is an obvious way of minimizing the risk of contaminants being released. The site should not be located anywhere near or in the flood plain of rivers, and the level of the dam should be deep. If there is any seepage from the tailing dam, it shouldn’t pose a risk to the ground water. During investigation of the site, ground water flow has to be monitored, to allow development of computer based three- dimensional ground water models. These models can be used for prediction of effects of supposed or real contaminant releases.
This in itself can show the health and risk factor in the mine tailing. With this technology, we can work towards finding out ways in which to minimize the risks involved with the tailings. The deposits of the clay appropriate for lining and covering the deposit should not be located too far away, and the site should be remote from residential areas. It’s these basic guidelines, that when followed, make Uranium mining and milling quite safe and not hazardous to the environment or people (taken from OECD NEA 1993, The Safety of the Nuclear Fuel Cycle, ch 2)
To increase the safety of a tailing deposit area, be it a damn or a pile, certain management are applied to reduce the risk of hazardous contaminants being released into the environment. Dewatering of the sludge, smoothing of the slopes, and installation of erosion protection. On top of the pile, an appropriate cover should be installed for protection against release of gamma radiation and radon gas, beginning of precipitation, intrusion of the plants and animals, and erosion. This cover in most cases consists of several different layers to meet all requirements.
Moreover, the catchement collection and treatment of seepage water is necessary to release purified waters to the surface water only. In the long term however, water treatment should no longer be necessary. Uranium mining, despite the outcry against the environmental problems it can cause, is quite a positive and good thing for the Australian society. Through the mining and milling process, jobs are created and new skills gained. Unemployment is a big issue in Australia, and by boosting the employment rate, essentially boosting the economy.
Uranium mining also brings Australia money through exports. In 1997-98 Australian Uranium accounted for 15 per cent of world production, worth about $288 million to Australia. (Lambert et al, 1996, Australia’s Uranium Resources, BRS (expenditure, early resource) Fig 1. 1 Showing the amount of money Uranium export brings Australia Taken from: ‘Australia’s Uranium and who owns It’ Briefing Paper (Found at http://www. uic. com. au/nip01. htm) Advancements in mining technology will mean that hazardous contaminants in the Uranium tailings can be removed before the sludge is dumped in dams or piles.
By doing so, the sludge piles/dams would be of no hazard to the environment and could be used to fill back up the mining sites. At the moment there are strict laws that govern Australian these laws and mine sites, are in place to minimize the risk of hazardous radiation being released from the waste piles (tailing dams, sludge piles etc). Only the future can tell what Uranium holds for us. Uranium mining at the present moment has a lot of controversy surrounding it, and the effects on the environment and cultural groups.
It has to be realised that the laws governing Uranium Mining in Australia are strict and dictate how Uranium mining is undertaken. This means that there is little to no risk of the tailings being deposited on ‘risky’ sites, and the risk of hazardous contaminants being released into the environment are small. By being sensitive to the views and culture of the Indigenous people, and involving them in decisions surrounding the mine, it won’t be long until mining companies and these people come to an understanding or agreement.
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