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, rado