Minor Actinides Separation by N,N,N’,N’,N’’,N’’-Hexaoctyl Nitrilotriacetamide (HONTA) Using Mixer-settler Extractors in a Hot Cell

ABSTRACT

A continuous counter-current test to separate minor actinides (MAs: Am and Cm) by N,N,N’,N’,N’’,N’’-hexaoctyl nitrilotriacetamide (HONTA) as an extractant was performed using mixer-settler extractors installed in a hot cell. Nitric acid of 0.08 M (mol/dm³) containing MAs and rare earths (REs) recovered from high-level liquid waste was used as the feed, and the experiment was conducted for 14 h. MAs were extracted by 0.05 M HONTA dissolved in n-dodecane, with Am and Cm being recovered at 94.9% and 78.9%, respectively. HONTA hardly extracted Y, La, and Eu from the feed (99.9% for Y, 99.9% for La, and 96.7% for Eu), most of which were distributed to the RE fraction. A portion of Nd was extracted by HONTA, and consequently the ratio of Nd in the RE fraction was 83.5%. HONTA could separate MAs and REs by adjusting the nitric acid concentration without using complexants. In addition, the concentrations of MAs and some REs in each stage were calculated using a simulation code, and the results are consistent with the experimental values. This code indicates that the ratios of MAs in the MA fraction and REs in the RE fraction could be ≥99% by optimizing separation conditions.

KEYWORDS:

• Solvent extraction
• mixer-settler
• americium
• curium
• HONTA
• hot cell

Acknowledgments

We would like to thank Dr. Yasuji Morita for the valuable comments on this manuscript, and we also thank Mr. Kawasaki, Mr. Sagawa, Mr. Yagi, Mr. Tayama, Mr. Kurosawa, Mr. Shibata, and other members of the Research Group for Partitioning for their cooperation with our experiments.