STUDIES ON THE TREND AND RECOVERY-PURIFICATION OF Np IN HIGH-ACID PUREX PROCESS

Coextraction of Np with Pu and U in 1A extraction eontactor and the stripping of Np from 1AP organic phase in 1N contactor in high-acid purex process by using cascade counter-current extraction method are investigated. In the extraction conditions of 1A contactor, the valence of U, Np in 1AF is adjusted with NH_4VO_3. The recovery of Np, Pu and U is 99. 5%～99.9%, 99.96% and 99. 998%. respectively. The influence of the flow rate of 1AX and concentration of HNO_3 on the recovery of Np is studied. In 1N contactor, the experimental results show that, by using NaNO_2 as stripping agent, the stripping yield of Np is 99.6% and the separation factor (SF_(Pu/Np)) is 1.27×10~3～1.37×10~3, while by using NH_2OH·HNO_3 and N_2H_5NO_3 as stripping agent, the stripping yield of Np is 99. 2% and 93% and SF_(Pu/Np)is 4. 3×10~2 and 26. However, all the SF_(Pu/Np) are the same, i. e., 5×10~3 for the three different stripping agents mentioned above.