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(last updated 13 Sep 2011)
The widely used sulphuric acid process concentrates most of the uranium and other toxic constituents in the product stream (fertilizers, detergents, etc.), while most of the radioactive decay products of the uranium series, such as Radium-226, end up in the waste gypsum.
Typical concentrations in phosphate fertilizer are 4 Bq (= 0.32 mg) Uranium-238 and 1 Bq Radium-226 per g P2O5.
The average radionuclide concentrations in phosphogypsum waste in the U.S. are 3 Bq/g for Radium-226, and 0.5 Bq/g for Uranium-238, among others. These radionuclide concentrations are lower than in most uranium mill tailings, but they have to be taken into account for the phosphogypsum waste management, see Management of Phosphate Tailings.
Various technologies exist to recover the uranium from the product stream, thus removing this unwanted constituent from the products and lowering the needs for uranium ore. Worldwide, there are approximately 400 wet-process phosphoric acid plants in operation.
Eight plants for the recovery of uranium from phosphoric acid have been built and operated in the United States since 1976 (Florida: 6, Louisiana: 2). Plants have also been built in Canada, Spain, Belgium, Israel, and Taiwan, see Facilities for Uranium Recovery from Phosphate.
Historical operating costs for the uranium recovery from phosphoric acid range from 22 to 54 US$/lb U3O8. These operating costs are by far higher than past uranium market prices, and most uranium recovery plants have been closed, therefore. In view of the recent increase of the uranium market price, the situation may change, again. (see also: Uranium Recovery from Phosphates)
Wide range of uranium and cadmium identified in fertilizer products sold for gardening: An analysis of five fertilizer brands sold in German garden centers revealed concentrations in the extraordinary wide range of 4 - 401 milligrams uranium and 3 - 40 milligrams cadmium per kilogram phosphate. These concentrations are not declared by the manufacturers, as there exists no such legal requirement nor any related concentration standard in Germany. (NDR Sep. 12, 2011)
By-product uranium production from phosphate in Louisiana to cease
Uranium waste solution from Port Hope fuel facility used as fertilizer (Ontario)
Use of Siemens' Richland, Washington, nuclear fuel plant waste solutions as fertilizer
Sequoyah Fuels Gore, Oklahoma, Uranium processing plant sprays radioactive waste as fertilizer
Radiological Considerations of Phosphogypsum Utilization in Agriculture
by C.L.Lindeken, U.S. DOE, UCRL-84927, 1980, 22 p. (780k PDF - LLNL)
Handling of radium and uranium contaminated waste piles and
other wastes from phosphate ore processing
by G.Schmidt, C.Küppers; annex by P.Robinson
Nuclear Science and Technology, Report EUR 15448 EN. 121 p. ISBN
92-827-4076-5, published by the European Commission, Luxembourg
1995.
Rock phosphates and P fertilizers as sources of U contamination in agricultural soils , by S. Kratz, E. Schnug, in: Merkel B J, Hasche-Berger A (eds): Uranium in the environment. Springer, Berlin Heidelberg 2006, pp. 57-68. (446k PDF - FAL)
Loads and Fate of Fertilizer-Derived Uranium, Edited by Luit J. De Kok and Ewald Schnug, Leiden 2008
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