Uranium mining in the Alligator Rivers Region

Introduction

Uranium Mineralisation

Uranium Mineralisation

Uranium occurs naturally in surface and ground water and in soils and rocks in concentrations of a few parts per million. The top 30 cm of soil in a typical 700 sq metre building block in Australia contains approximately 700 g of uranium. Uranium, like other minerals, may exist in localised regions of relatively high concentration in the earth's crust. Where the concentration of uranium is sufficiently high, these regions or orebodies may be mined and processed to extract and consolidate the uranium into uranium oxide concentrate. This is what is produced and exported by Australian uranium mines.

Current status of uranium mines in the ARR

There are four active mineral leases within the Alligator Rivers Region which pre-date the proclamation of Kakadu National Park. These are Ranger, Jabiluka, Koongarra and Nabarlek.

Ranger is currently the only operational uranium mine in the ARR. Jabiluka, located 20 km north of the Ranger site, is currently in Long-Term Care and Maintenance after initial stages of development were halted under an agreement between Traditional Owners and the Mining Company. Koongarra is a significant uranium deposit which is yet to be subject to the process of seeking permission to develop the mine. Nabarlek ceased mining and milling activities in the late 1980s and has now been decommissioned and substantially rehabilitated. The history of uranium mining in the Alligator Rivers Region (ARR) dates back to the 1950s and there are a number of former uranium mines in the South Alligator Valley of the ARR, which were subject to mining activity from 1954 to 1964.

Uranium extraction process

Ranger Mine in the Alligator Rivers Region and Olympic Dam in South Australia both employ essentially the same technique for extracting the uranium from the ore. The ore is crushed to a fine powder and pumped as a slurry to a thickener to remove excess water, then to leach tanks where sulphuric acid is added. The acid dissolves the uranium and other minerals forming a uranium rich solution. After the solids have been removed, kerosene is used to selectively strip the uranium from the solution. Ammonia is then added to the strip solution precipitating the uranium in the form of ammonium diuranate which is passed to a furnace (called a calciner). In the calciner, the ammonia is driven off and the uranium is converted to uranium oxide concentrate, which is predominantly U3O8. The concentrate, which is a dark green to grey powder, is packed into 205 litre drums for shipment and export.