Uranium was considered a highly strategic material by socialist Czechoslovakia and thanks to the country's rich reserves mining was quite extensive. It has had a serious impact on the environment which will take decades to clean up. Czech scientists have come up with a solution tailored for one particular mining area - using the by-products of uranium mining to produce - commercial fertiliser.
When uranium mining was finally abandoned in North Bohemia in 1996 after almost 30 years, some 5 million tonnes of sulphuric acid used to extract uranium had been injected into the ground. An underground lake of highly acidic solutions and other chemicals still threatens to contaminate reservoirs of subterranean water in a large area.
"From today's point of view this mining method was absolutely inappropriate for this particular area with drinking water reservoirs and unstable bedrock. It was unfortunate and it was a mistake."
Tomas Rychtarik of the state company Diamo, a successor of the Czechoslovak uranium industry, which now specialises in environmental clean-up projects. In cooperation with the Czech Academy of Sciences a unique method was devised to remove the noxious chemicals from underground and ideally turn them into something useful. The contaminated solutions are first condensed using heat, producing crystalline alum stone, precisely ammonium aluminium alum. But as the acidic lake recedes a mountain of alum stone grows underground.
Jana Bludska, the director of the Institute of Inorganic Chemistry.
The final product is a fertiliser rich in nitrogen and sulphur. It has passed a series of trials which ruled out possible radioactivity and proved it was as efficient as other types of commercial fertilisers. The reserves of alum stone in the North Bohemian uranium mines will last for 30-40 years of production of the fertiliser which has a national patent and is now in commercial production.
The whole clean-up of the former uranium mines in North Bohemia is expected to last until 2040 and the costs are estimated to exceed 40 billion crowns (almost 2 billion US dollars).
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