Thorium oxide fluorides

Thorium oxide fluoride (Th2OF5) (277) has been prepared from ThF4 and ThOF, and the reaction of uranium oxides with UF4 at 400-500°C is said to produce U205F as one of the products (278). 

The metals themselves are very electropositive, and are accordingly difficult to prepare. Electrolytic reduction of a fused oxide-fluoride mixture may be used. An alloy containing about 70% cerium and smaller amounts of other rare-earth metals and iron is highly pyrophoric that is, it gives sparks when scratched. This alloy, called Mischmetal, is widely used for cigarette lighters and gas lighters. The use of a mixture of cerium dioxide and thorium dioxide in gas mantles has been mentioned under thorium. 

Thorium oxide would not be expected to react with molten alkali metal nitrates. Brambilla claims, however, that a soluble thorium species is produced in the molten phase when nitric acid vapor is combined with fluoride ion in molten nitrates (10). 

CONVERSION OF THORIUM NITRATE TO OXIDE, FLUORIDE, CHLORIDE, OR METAL... 

Purified thorium is usually produced in the form of an aqueous solution of thorium nitrate or crystals of hydrated thorium nitrate. The principal forms in which thorium is used in nuclear systems are the oxide Th02, the carbide ThC2, the fluoride Thp4, the chloride ThCl4, or the metal. Conversion to oxide, fluoride, chloride, and metal are discussed in this section production of thorium carbide was discussed in Sec. 5.3. 

Reduction with reactive metals. As with uranium, processes for producing thorium by reduction with reactive metals have been developed starting with thorium oxide, chloride, or fluoride. To show which combinations of thorium compound and reactive metal are thermodynamically... 

The chemical properties of thorium resemble those of the rare earth elements. Thorium oxides are insoluble in water and alkalis, but dissolve in acids. Th forms stable complexes with fluoride and carboxy groups. In body fluids, complexes with citrate, glutamate and transferring are formed. 

Thorium oxide is converted to fluoride by the action of hydrogen fluoride in the U.S. process carried out at the National Lead Company of Ohio, i.e. 

In the feed preparation step, uranyl sulfate solution from the reactor core and thorium oxide from the blanket system, freed of D2O and suspended in ordinary water, are fed into the dissolver tank. The di.s.solvent is 13 N nitric acid to which has been added catalytic amounts (0.04 N) of sodium fluoride. When short-cooled thorium is being processed, potassium iodide is added continuously to the dissolver to provide for isotopic dilution of the large amount of fission-produced which is present. The dissolver solution is continuously sparged with air, and the volatilized iodine is removed from the off-gases in a caustic scrubber. 

This do( s not mean that other type s of blankets are not being studied. Work is concurrently under way on thorium oxide-bismuth slurries. Also, thorium carbide, thorium fluoride, and thorium sulphide. slurrie.s arc under consideration. 

Calcium metal is an excellent reducing agent for production of the less common metals because of the large free energy of formation of its oxides and hahdes. The following metals have been prepared by the reduction of their oxides or fluorides with calcium hafnium (22), plutonium (23), scandium (24), thorium (25), tungsten (26), uranium (27,28), vanadium (29), yttrium (30), zirconium (22,31), and most of the rare-earth metals (32). 

On the basis of these facts, it was speculated that plutonium in its highest oxidation state is similar to uranium (VI) and in a lower state is similar to thorium (IV) and uranium (IV). It was reasoned that if plutonium existed normally as a stable plutonium (IV) ion, it would probably form insoluble compounds or stable complex ions analogous to those of similar ions, and that it would be desirable (as soon as sufficient plutonium became available) to determine the solubilities of such compounds as the fluoride, oxalate, phosphate, iodate, and peroxide. Such data were needed to confirm deductions based on the tracer experiments. 

Calcium metal is used in the reduction of zirconium fluorides, thorium and uranium oxides to obtain the metals. 

Calcium serves as a reductant for such reactive metals as zirconium, thorium, vanadium, and uranium. In zirconium reduction, zirconium fluoride is reacted with culcium metal. The high heat of the reaction melts the zirconium. The zirconium ingot resulting is remelted undet vacuum for purilicatinn. Thorium and uranium oxides are reduced with an excess of calcium in reactors or trays under an atmosphere of argon. The resulting tnetals are leached with acetic acid tu remove the lime. 

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