Uranium mining method far from `benign'

The mining technique of in situ leaching (ISL), often referred to as solution mining, is becoming an increasingly favoured method for the extraction of uranium across the world. This is primarily due to its low capital and operating costs compared to conventional mining. Little is known about the environmental impact of this method, and mining companies have been able to exploit this to promote the method as “environmentally benign”.

The ISL process involves drilling ground water bores or wells into a uranium deposit, injecting corrosive chemicals to dissolve the uranium within the ore zone, then pumping back the uranium-laden solution.

The method can be applied only to uranium deposits located within a ground water system or confined aquifer, commonly in palaeochannel deposits (old buried river beds).

Although ISL is presented in simplified diagrams by the nuclear industry, the reality is that geological systems are inherently complex and not predictable.

There are a range of options for the chemistry of the mining solutions. Either acidic or alkaline chemical agents can be used in conjunction with an oxidising agent to dissolve the uranium.

Typical oxidising agents include oxygen or hydrogen peroxide, while alkaline agents include ammonia or sodium-bicarbonate or carbon dioxide. The most common acidic chemical used is sulphuric acid, although nitric acid has been tried at select sites and in laboratory tests.

The chemicals can have potentially serious environmental impacts and cause long-term changes to ground water quality.

The use of acidic solutions mobilises high levels of heavy metals, such as cadmium, strontium, lead and chromium.

Alkaline solutions tend to mobilise only a few heavy metals such as selenium and molybdenum. The ability to restore the ground water to its pre-mining quality is, arguably, easier at sites that have used alkaline solution chemistry.

A review of the available literature on ISL mines across the world can easily counter the myths promulgated about ISL uranium mining. Whether one examines the USA, Germany, Russia and associated states, Bulgaria, the Czech Republic, Australia or new ISL projects across Asia, the truth remains the same -- the ISL technique merely treats ground water as a sacrifice zone and the problem remains “out of sight, out of mind”.

ISL uranium mining is not controllable, is inherently unsafe and is unlikely to meet “strict environmental controls”. It is not an environmentally benign method of uranium mining.

The use of sulphuric acid solutions at ISL mines across Eastern Europe, as well as a callous disregard for sensible environmental management, has led to many seriously contaminated sites.

Perhaps the most severe example is Straz pod Ralskem in the Czech Republic, where up to 200 billion litres of ground water is contaminated. Restoration of the site is expected to take several decades or even centuries.

Solution escapes and difficult restorations have been documented at ISL sites in Texas and Wyoming.

Australia has encountered the same difficulties, especially at the controversial Honeymoon deposit in South Australia during pilot studies in the early 1980s and at Manyingee in Western Australia until 1985.

The Honeymoon pilot project used sulphuric acid in conjunction with ferric sulphate as the oxidising agent. The wells and aquifer experienced significant blockages due to the minerals jarosite and gypsum precipitating, lowering the efficiency of the leaching process and leading to increased excursions. The aquifers in the vicinity of Honeymoon are known to be connected to aquifers used by local pastoralists to water stock.

The Howard Coalition government allowed the resurrection of the Honeymoon project in 1997 by Canadian Southern Cross Resources, while the new owner of the nearby Beverley uranium deposit, Heathgate Resources (a subsidiary of US nuclear multinational General Atomics) is keen to establish an operating uranium mine before possible election of a Labor federal government.

By 1998, new pilot trials were established at Honeymoon and, for the first time, at Beverley. Heathgate has finally released its environmental impact statement for the proposed Beverley project.

[Gavin Mudd is an environmental hydrogeologist commissioned by Friends of Earth and the Australian Conservation Foundation to study the performance and environmental impacts of ISL mines worldwide. Mudd's 154-page report is now available. It documents in greater detail information in this article, with extensive use of graphics and diagrams as well as clear and concise text. The report is available in hard copy or electronic Acrobat format (for a small fee). Visit <http://home.vicnet.net.au/~seaus/> and follow the links.]

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