This invention relates to the field of reclaiming tungsten values from tungsten alloys. In particular, this invention relates to reclaiming tungsten values from tungsten alloys containing thoria.

 

Tungsten-thoria is a tungsten alloy containing fine particulates of thorium oxide (thoria) dispersed throughout the tungsten matrix. Some of the applications for tungsten-thoria include the making of filament wire for the lighting industry and rods for the welding industry. Scrap tungsten-thoria which is produced in the manufacturing of these products may not be easily disposed of because of the radioactive properties of the thoria. Since the thoria typically comprises about 0.5 to 2 weight percent of the tungsten-thoria, it would be desirable to separate the thoria from the tungsten-thoria so that the total mass of radioactive material is substantially reduced and can be disposed of more easily.

 

One generally used method for reclaiming tungsten from tungsten scrap involves an oxidizing fusion process whereby the tungsten metal is converted into a soluble tungstate such as sodium tungstate. Tungsten scrap is combined with strong oxidizers such as nitrates, peroxides, or chlorates, and heated to initiate a highly exothermic reaction whereby the soluble tungstate is formed. For example, U.S. Pat. No. 4,603,043 describes a fusion process using a combination of sodium nitrate and sodium hydroxide to covert tungsten to sodium tungstate. However, because of the violent and potentially explosive nature of the exothermic reactions caused by these oxidizers, these methods are unsuitable for use with tungsten-thoria because of the increased potential for the release of radioactive thoria particles. Therefore, it would be advantageous to have a method for efficiently recovering tungsten values from tungsten-thoria which minimizes the risk of releasing hazardous quantities of thoria particles into the atmosphere.

 

 

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