Overview
Owned and operated by Energy Resources of Australia Ltd. (ERA), a 68.4 per cent owned subsidiary of Rio Tinto Australia, the Ranger Mine is located approximately 250 kilometers east of Darwin, in Australia's Northern Territory.
ERA is one of the largest uranium producers in the world, producing around 10 per cent of the world's mined uranium production. Since 1980, the Company has mined ore and produced drummed uranium oxide at its Ranger mine.
Mining at the Ranger operation is expected to continue until at least 2008, with milling operations to produce uranium oxide continuing until at least 2011. The laterite processing plant will contribute approximately 400 tonnes per annum of uranium oxide to ERA’s production over seven years from 2008 through to 2014.
Location
ERA corporate offices are located in Darwin, Northern Territory, and mining operations are located in Jabiru, 260 kilometres east of Darwin. ERA mines uranium ore and produces drummed uranium oxide at the Ranger mine in Jabiru, and holds title to the nearby Jabiluka deposit.
Geology
The Ranger ore bodies were discovered by an airborne radiometric survey in October 1969 and were confirmed by drilling in the mid 1970s. There are about 14 kilometres of favourable rocks through the Project Area. The southern-most six kilometres contain Ranger #1 and #3. These ore bodies are about 1,200 metres apart and are in many ways very similar. They occur in exactly the same stratigraphic position and the host rocks and their mineralogy are identical.
Mining & Operations
Mining at the Ranger operation is expected to continue until at least 2008, with milling operations to produce uranium oxide continuing until at least 2011. The laterite processing plant will contribute approximately 400 tonnes per annum of uranium oxide to ERA’s production over seven years from 2008 through to 2014.
ERA is one of the largest uranium producers in the world, producing around 10 per cent of the world's mined uranium production. Since 1980, the Company has mined ore and produced drummed uranium oxide at its Ranger mine, 260 kilometres east of Darwin in Australia's Northern Territory.
ERA also holds title to the Jabiluka deposit, 22 kilometres north of Ranger. This world-class deposit is under long term care and maintenance and will not be developed by ERA without the consent of the Mirarr Traditional Owners.
The process for extracting uranium ore from the mine to producing drums of uranium oxide involves a number of complex operations, including exploration, extraction, sorting, crushing, and production.
Processing
The plant has a production capacity about 5,000 tonnes+ of U3O8 per year.
Each operating area contains a control room from which an operator can remotely start and stop all equipment in that area, determine the status of equipment and control all key process variables. All control systems are micro-processor based. Generally, each area is controlled by one person who is responsible for all aspects of operation.
Uranium ore is crushed to a size finer than 19 millimetres in a three stage crushing and screening circuit. The fine ore is then mixed with water and ground to a size finer than 0.22 millimetres in a grinding circuit that includes one rod and two ball mills.
The ore slurry is thickened before being pumped to leaching vessels where, over a period of about 24 hours, more than 90% of the uranium in the ore is dissolved using sulfuric acid.
The uranium in solution is then separated from the depleted ore in a seven-stage washing (Counter Current Decantation - CCD) circuit. After separation, the acidity of the depleted ore (tailings) is neutralised with lime before being pumped to the tailings repository, while the uranium solution is passed through a clarifier and set of sand filters. This filtering removes any fine solid particles before the uranium solution enters the solvent extraction circuit.
At this stage the uranium solution is carrying many other dissolved elements in addition to uranium. The solvent extraction process uses an amine carried in a special grade kerosene to purify and concentrate the uranium solution. Ammonia is also used in this process. The resultant pure, but quite weak uranium solution is then pumped to precipitation tanks.
A uranium compound (ammonium diuranate) is precipitated from the clean uranium solution with the further addition of ammonia. This substance is bright yellow and commonly called yellowcake.
In the final stage of the process the yellowcake is heated to 800 degrees Celsius in an oil-fired, multi-hearth calciner. This 'cooking' process produces the final product, a dark green powder which is more than 98% pure U3O8. The product is then packed into 200 litre steel drums which are sealed and loaded into shipping containers ready for transportation.
