Milling uranium purification

Concentrates are shipped from the uranium mill to a uranium refinery or conversion plant. Here chemical impurities are removed and the purified uranium is converted into the chemical form needed for the next step in the fuel cycle. Figure 1.14 shows concentrates being converted into uranium hexafluoride (UF ), the form used as process gas in the gaseous diffusion process for enriching U. Other possible products of a uranium refinery used in other fuel cycles are uranium metal, uranium dioxide, or uranium carbide. Uranium purification and conversion processes are also described in Chap. 5. 

Extraction.3 — The method used in extracting vanadium from its ores varies widely with the nature and richness of the ore and the value of the by-products. The difficulties encountered are mainly in connection with the purification of vanadium from uranium, aluminium, iron, and silica. It is probable that no two mills use exactly the same process. In general the methods 4 use (1) an acid method, producing soluble vanadyl compounds or (2) an alkali method, producing soluble alkali vamwlates. The following outline methods illustrate the general principles employed —... 

I rt 1 of Table 5.19 lists mills using carbonate leaching. There is no standard process for recovery of uranium from carbonate leach liquors. The trend is away from precipitation with NaOH as crude NajUj07 toward further purification as by UO4 precipitation at Rio Algom or by ion exchange followed by precipitation as (NH4)3U207 at George West. 

Virtually all of the Canadian mills have used a variant of the acid-leaching process developed by the Mines Branch to extract uranium fiiom the ore, and all but Port Radium have followed this by ion-exchange purification of the leach solution with strong-base resins. The uranium usually is precipitated with ammonia to produce ammonium diuranate (yellow cake). 

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