NEPTUNIUM DISTRIBUTION IN A HIGH ACID FIRST CYCLE PUREX PROCESS

This work deals with the extraction behavior of neptunium in a high ac id Purex Process. The composition of PWR fuel type with 3.2% enrichmen t, 500 MWd/t burn-up and 100 d cooling time was considered. Two consec utive cold runs were performed in a mock-up facility at IPEN-CNEN/SP w ith simulated feed solutions containing: 3M HNO3; 1M U; 455 mug Np-237 labeled with Np-239; 15 mg Zr l-1, 12 mg Ce l-1, 7 mg Ru l-1 and 13 m Mo l-1 traced with active isotopes Zr-95, Ce-141, Ru-103 and Mo-99 as FP. A 30 vol% TBP/n-dodecane was used as solvent. Countercurrent expe riments were,carried out using two 16 stages plexiglass mixer-settlers , at 25-degrees-C, during 21 h continuous operation, with O/A ratio of 2 in the extraction section and 9 and 13 in the lst and 2nd scrubbing sections, respectively. For a 65% organic loading, ca. 77% of neptuni um remains in the waste stream, without any Np valence adjustment.