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Uranium in Fertilizers

(last updated 13 Sep 2011)

Contents:


Introduction


There are two sources for uranium in fertilizers: elevated natural uranium concentrations in phosphate rock that have not been removed during the fertilizer production process, or uranium in waste solutions from the nuclear fuel industry that are used as fertilizers.

Uranium in Phosphate

Phosphate rock has an average uranium content of 50 to 200 ppm.

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)

 

Uranium in Nuclear Fuel Industry Waste Solutions

Several steps in the uranium fuel industry produce waste solutions that are used as fertilizers. During the wet conversion process of uranium ore concentrate to uranium hexafluoride (UF6), an ammonium nitrate (NH4NO3) waste solution is produced. During the reconversion of UF6 to UO2, an ammonium hydroxide ((NH4)OH) solution is produced.
These solutions contain trace amounts of uranium and other toxic constituents.

 


IMPACTS


Rough estimates for the uranium uptake and related radiation hazard from consumption of food grown on soil containing elevated concentrations of uranium can be obtained with the Uranium in Soil and Building Material Individual Dose Calculator. For more sophisticated assessments, see Dose calculation software.

 


ISSUES


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

 


LITERATURE


The Recovery of Uranium from Phosphoric Acid , IAEA-TECDOC-533, International Atomic Energy Agency, Vienna, 1989, 104 p.

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)

Presentations - 3rd Seminar on protecting water bodies from negative impacts of agriculture - Loads and fate of fertiliser derived from uranium, 4 - 5 June 2007, Braunschweig, Germany

Loads and Fate of Fertilizer-Derived Uranium, Edited by Luit J. De Kok and Ewald Schnug, Leiden 2008

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