Recovery of U and Pu from Nitric Acid using N,N-di(2-ethylhexyl)butanamide (DEHBA) in Mixer-Settler Extractors

Abstract

The recovery of U and Pu from nitric acid using N,N-di(2-ethylhexyl)butanamide (DEHBA) in mixer-settler extractors was calculated by a simulation code, and a continuous counter-current experiment using mixer-settler extractors was performed. The flow rate, stage number, and nitric acid concentration were chosen as the parameters for the calculation, and the simulation code provided appropriate experimental conditions for separating U from Pu. The continuous counter-current experiment was carried out with three mixer-settler extractors consisted of the following 5 steps: U–Pu extraction (6 stages), Scrub (10 stages), U recovery (6 stages), Pu back-extraction (10 stages), and U back-extraction (16 stages). The results of the continuous counter-current experiment showed that the percentages of U and Pu extracted using 1.5 mol/dm³ (M) DEHBA from 4 M nitric acid were > 99.9% and 97.84%, respectively. Extracted Pu was back-extracted to the aqueous phase via contact with 0.15 M nitric acid, while most of the U content remained in the organic phase. Uranium in the organic phase was then back-extracted via contact with 0.01 M nitric acid, and the percent of U in the U fraction stream was 96.06%. The percentages of U and Pu in the Pu fraction stream were 3.94 % and 97.48%, respectively.

Keywords:

• N,N-dialkylamide
• monoamide
• U
• Pu
• counter-current extraction
• mixer-settler
• reprocessing

ACKNOWLEDGMENT

This study was the result of research entitled “Development of decontamination technology of recovered uranium from nuclear fuel reprocessing for fast reactors,” which was entrusted to the Japan Atomic Energy Agency (JAEA) by the Ministry of Economy, Trade, and Industry (METI). We would like to thank Mr. Yagi, Mr. Sekita, Mr. Saito, Mr. Shiga, Mr. Kanazawa, and other members of the Research Group for Aqueous Separation Process Chemistry for their cooperation with the experiment.