Abstract:
The recovery plant of the department of conversion and pelletisation of the AEC recovers uranium from different types of scrap. If an accident should occur in the conversion plant, for example if the filters do not shut off effectively, the HF-scrubbers can be contaminated with uranium. The contaminated K2C03 solution will be pumped as scrap to the recovery plant for the uranium to be recovered effectively from the contaminated solution. A suitable recovery method had to be developed. Two possible methods were investigated namely i) precipitation and reduction and ii) anion exchange. As possible reduction agents, acid and tartaric acid were investigated at different pHs, temperatures and in different excess amounts. U6 is reduced with difficulty and the solutions are very consentrated, therefore unknown salts were coprecipitated with the insoluble LJ 4 double salt with K and F-. The reduction of U6 by ultraviolet light in the presence of oxalic acid was also investigated. Promising results were found, but unpractical changes have to made to be the plant to implement the method. Because of the slight amount of success and the problems involving the necessary changes to the plant to implement the reduction and precipitation process, a second method of anion exchange was investigated. The results with the Duolite A162 anion exchanger in the CQ3 2 – form showed that the 15% K2C03 solution is too concentrated and that the mother solution must be diluted. The F- ion has no mentionable influence on the extraction. The uranyl carbonate complex was successfully leached from the resin by means of NH4NQ3 and HN03. The distribution coefficients (D) were determined for the resin in the C03 2 - form and for the resin in the 0H- form. According to the 0-values, more successful extractions were obtained for the resin in the 0H-form. With the resin in the 0H- form the diluting factor for the mother solution is smaller, the operating pH is smaller, the resin has a greater capacity for the uranyl carbonate complex and less problems were experienced with gas formation during leaching. Implementing the process in the existing plant involves relatively few disturbances. The second method investigated, namely anion exchange, is recommended for the recovery plant as a suitable method of recovery.
