Development of processes for pilot plant production of purified uranyl nitrate solutions

Abstract

Nuclear purity uranyl nitrate solutions were produced from Rum Jungle yellow cake by dissolution in nitric acid and purification by solvent extraction with 20 vol.% tributyl phosphate in kerosene using pump -mix mixer-settler contactors. The design of the equipment, experimental studies and operating experience are described. Dissolution of yellow cake and recycled uranium oxide materials was readily carried out in a 100 ℓ dissolver to give solutions containing 300 gU ℓ -1 and 0.5 to 4 П nitric acid. Filtration of silica from this solution prior to solvent extraction was not necessary in this work for yellow cake containing 0.25 per cent silica. A low acid flowsheet for uranium purification was developed in which the nitric acid consumption was reduced by 76 per cent and the throughput of the mixer-settler units was increased by 67 per cent compared with the initial design flowsheet. Nine extraction and seven scrubbing stages were used with a feed solution containing 300 gU ℓ -1 and 1.0 П nitric acid and with a portion of the product recycled as scrub solution. The loaded organic phase was stripped in 16 stages with 0.05 П nitric acid heated to 60º C to give a 120 gU ℓ -1 product. The uranium concentration in the raffinate was < 0.04 g ℓ-1, corresponding to ~ 0.01 per cent of the feed.