Air Namibia, Flamingo, April 2012 Text and Photos Tim Osborne
Thirty Two Metres Per Litre
And you think the fuel consumption of your vehicle is bad. That is what the 275 ton haulage trucks operating at the Rossing Uranium mine average when they are hauling rocks out of the mine pit. Their trucks go through about 3000 litres of diesel per day. Multiply that times x number of trucks and one can see that mining uranium is a rather expensive operation. And that is just the resources to get the ore out of the pit not the costs of refining the ore into uranium oxide (U308) the finished product.
Namibia is enjoying a uranium boom, with relatively high prices for the product, and out of 14 ore sites identified in the Erongo region three are currently in production. Rossing’s mine is the oldest of the mines with production starting in 1976. Its open pit is massive and is 3 km by 1.5 km and 265 m deep. To reduce costs of getting the material from the bottom of the pit to the first stage crushing plant they use Komatsu trucks which are dual powered. Each wheel is turned by an electric motor. The truck has a massive diesel generator which supplies power to the electric motors. The truck also has a device which can be raised to rub against an over-head power line thus supplying electric power direct to the wheel motors. An overhead power supply runs on the road from the pit bottom to the upper lip of the pit. Once the trucks leave the pit area they change over to diesel power.
One of the most unique methods that uranium mines employ is the instant assay of the ore material. As the loaded trucks emerge from the pit they park under a radiometer which reads the amount of radiation the ore emits. The device is able to detect radiation as deep as 70 cm in the load. If the radiation is almost nil the material is most likely overburden waste and the driver of the truck is instructed to drive to the waste rock dump. If it is low grade ore then it is taken directly to the crushing plant where it is broken up into smaller rocks and carried via a conveyor belt to the next stage crushing plant. If the ore is high grade then it is taken to a special dump site.
Since the majority of ore at Rossing is very low grade the process of extraction is specific to the ore grade. They use a 12 hour sulphuric acid leaching process. The refinement of high grade ore uses a different process and Rossing would have to build another expensive separate leaching plant for the two grades. The easiest way to handle the high grade ore is to slowly mix it in with the low grade ore and process them together.
Although the mine was slated for closure in 2009 because of low uranium prices and unfavourable exchange rates in the 1990s, Rio Tinto the parent owner has extended the mine life to at least 2021. The renewed interest in nuclear power to help combat green house gases has caused the prices of uranium to rise. The mine currently supplies 7% of the worlds production.