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Extracting Uranium From Ore

Most metals are fairly easy to extract from ore. First of all a concentrate is prepared by manual sorting, seiving, flotation, or electrostatics and then smelting is used to bring out the fairly pure metal. These techniques do not work with uranium however and the concentrate has to be prepared by chemical means which usually entail roasting the ore to dehydrate it, drive off any carbon and oxidise any materials that are present; there are then various methods employed to leach out the uranium, dependant upon local practice and the chemical constitution of the ore. This work is carried out close to the extraction area and the resultant concentrate, usually known as 'yellow cake', then contains between about 70% to 95% pure uranium compounds. This is then shipped off to a specialised centre for purification into uranium metal.

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The first stage of this process is to dissolve the yellow cake in nitric acid; solvent extraction using tributyl phosphate in a hydrocaron solution extracts the uranium from the various impurities and then the extract is washed with dilute nitric acid to produce uranyl nitrate in a very pure form. This is then heated to a high temperature to produce uranium trioxide; hydrogen is introduced to reduce this to the dioxide, the extra oxygen molecule being taken by the hydrogen to form water; and then this UO2 is treated with hydrogen fluoride at a high temperature to create uranium tetrafluoride and water. This is then heated yet again, this time with magnesium to form molten metallic magnesium together with magnesium fluoride slag. Phew! Are you still with me so far?