Estimation of natural thorium in low level effluents from processing plants

This is a report of simple estimations of natural thorium in low level effluents generated during the reprocessing of irradiated Th/ThO2 rods for the recovery of 233U. The method involved co-precipitation of thorium with ceric iodate at pH 1.29±0.01 and subsequent photometric determination. Conditions were optimised to eliminate the interferences of other ions present in the effluent. Approximately 15 mg each of phosphate, fluoride and sulphate, 10 mg of iron, and 300 μg zirconium did not interfere in the estimation of 2-5 μg Th/100 ml of the effluent. Average thorium recovery was around 101.9%±2.6% when nearly 10 μg of thorium were spiked. (author) 3 refs.; 3 figs.; 2 tabs