Selective extraction of niobium from Zr-Nb alloy: A way towards isolating long-lived 94Nb from discharged pressure tubes of Indian PHWRs

The generation of long-lived 94Nb radioisotope in Zr-2.5Nb pressure tubes has become a major concern. Isolating 94Nb from discharged pressure tubes could potentially reduce the volume of radioactive waste, while the recovered Zr could be reused in fabricating pressure tubes. A robust solvent extraction method was developed for the selective extraction of Nb from a mixture of Zr and Nb. Nb was extracted from an aqueous HCl solution using alpha-benzoin oxime as a ligand dissolved in chloroform. The optimal concentration range of HCl in the aqueous phase for the extraction was found to be 4 to 7 M. About 0.4 % of alpha-benzoin oxime in the organic phase was found to be the optimal ligand concentration to achieve maximum extraction. About 5 min of equilibration time and four separation cycles are adequate for achieving quantitative extraction. The metal concentration in the feed solution exhibits negligible interference with the extraction of Nb into the organic phase. The method effectively separates long-lived 94Nb from discharged pressure tubes, demonstrating its practical applicability.