Uranium Mining and Milling

INTRODUCTION | NUCLEAR FUEL CHAIN | CONVERSION AND ENRICHMENT >>

Traditionally, uranium has been extracted from open-pits and underground mines. In the past decade, alternative techniques such as in-situ leach mining, in which solutions are injected into underground deposits to dissolve uranium, have become more widely used.

The milling (refining) process extracts uranium oxide (U₃O₈) from ore to form yellowcake, a yellow or brown powder that contains about 90 percent uranium oxide. This is then exported to enrichment facilities.

The Problem with Uranium Mining
A succinct summary of why this has to stop.

In-Situ Leach (ISL) Mining
The only thing worse than conventional uranium mining is In-Situ Leach, or Solution mining. Find out why, and where it's going on.

Uranium Tailings Waste
Conventional mining techniques generate a substantial quantity of radioactive tailings waste during the milling phase, because the uranium is generally less than one percent of the ore.

The Environmental Approvals Process
Uranium mines need to pass an environmental approvals process before they are accepted by government. Unfortunately, the system is heavily stacked.

Occupational Health Hazards
Uranium mine workers are exposed to the highest radiation doses of any workers in the nuclear industry. Find out more...

Uranium Mining Flowsheet

The following diagram describes the approximate stages of a 'conventional' uranium mine, from exploration to export.

	1. Exploration Before mining can begin, uranium ore must be located, normally by overflying prospective areas scanning for elevated levels of radiation. Identified sites are then drilled and the core samples analysed by geologists.
Mining
	2. Excavation Uranium-bearing ore is dug from the ground. Traditional mining techniques of drilling and blasting are used, in either open pits or underground mines. Because uranium is found in such low concentrations, huge amounts of rock must be mined. For example, Olympic Dam has an ore grade of 0.05%. That means for every tonne mined, 5kg of uranium is retrieved. Huge volumes of waste rock are therefore generated. 'Waste' rock such as overlying or surrounding strata are stored in waste stockpiles, and often used after mining has finished to cover more dangerous wastes buried in the original pits.
Milling
	3. Crushing Before it can be treated, the ore must be crushed into finer fragments. After primary crushing, the ore is passed into a rotating ball mill, which grinds the rock into a fine powder. Now it's ready for treatment, but it is also readily available for uptake into the environment, as the fine particle sizes make it impossible to completely isolate from workers and the surroundings. Having increased the surface area of the rock by several orders of magnitude, the release of uranium's decay products into the biosphere is accellerated.
	4. Concentration The following stages depend largely on the kinds of ore being processed. Generally, huge amounts of water, sulphuric acid and thickener are added to the pulverised ore. The uranium bonds with the acid, and through a series of stages about 90% of the uranium is separated from the host rock.
	6. Precipitation and Drying A last phase of drying, centrifuging and chemical precipitation leaves us with yellowcake, or uranium oxide. With a chemical symbol U3O8, this is the form we are exporting our uranium in at present.
	7. Tailings Waste With most of the uranium removed, the waste is pumped into vast tailings dams, essentially man-made lakes where the poisoned material is exposed to the biosphere. In addition to the radioactive hazards, tailings may contain chemically hazardous substances including cyanide, arsenic, lead and mercury, which are now able to get into the environment by seepage, leaching and blown dust.
Export
	8. Storage and Shipping The yellowcake is stored on site for short periods and then trucked or railed to ports. At present, uranium is exported from Darwin (NT) and Port Augusta (SA).
	The uranium is taken for further treatment at enrichment plants, primarily in the USA.