Neptunium distribution in a high acid first cycle Purex Process

The extraction behavior of neptunium in a high acid Purex Process has been described. The composition of PWR fuel type with 3.2% enrichment, 500 MWd/t burn-up and 100 d cooling time was considered. Two consecutive cold runs were performed in a mock-up facility at IPEN-CNEN/SP with simulated feed solutions containing: 3M HNO3; 1M U; 455 μg 237Np labeled with 239Np; 15 mg Zr l-1, 12 mg Ce l-1, 7 mg Ru l-1 and 13 mg Mo l-1 traced with active isotopes 95Zr, 141Ce, 103Ru and99Mo as FP. A 30 vol% TBP/n-dodecane was used as solvent. Counter-current experiments were carried out using two 16 stages plexiglass mixer-settlers, at 25 deg C, during 21 h continuous operation, with O/A ratio of 2 in the extraction section and 9 and 13 in the 1st and 2nd scrubbing sections, respectively. For a 65 % organic loading, ca. 77 % of neptunium remains in the waste stream, without any Np valence adjustment. (author) 10 refs.; 4 figs.; 2 tabs