Enhanced Recovery of Technetium(VII) by Primary Amine Extraction from Aqueous Fluoride Solutions and Aqueous Alkaline So
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ENHANCED RECOVERY OF TECHNETIUM(VII) BY PRIMARY AMINE EXTRACTION FROM AQUEOUS FLUORIDE SOLUTIONS AND AQUEOUS ALKALINE SOLUTIONS K.ITO, Institute for Advanced Materials Processing, Tohoku University, Katahira, Sendai, Miyagi, Japan, 980-77 ABSTRACT The extraction behavior of technetium from aqueous hydrofluoric acid solution has been investigated. The recovery of Tc using two techniques, primary amine extraction in mixed heptane and 1-octanol solution and stripping with a mixed aqueous ammonium hydroxide - ammonium carbonate solution has been studied. The determination of distribution ratios and percentages of technetium in both extraction and stripping cycles was established as were the volume ratios between organic and aqueous phases. The stripping mechanism in the aqueous solution has also been investigated by the slope analysis method. INTRODUCTION Technetium-99 is one of the fission products produced in a nuclear reactor and has a very long half-life(210,000 y) and a long fl-activity decay chain. In the disposal of high level radioactive liquid waste, radioactive Tc is a serious problem for long term safety, because it remains radioactive far into the future. Recently, the CURE (Clean Use of Reactor Energy) concept0) has been proposed to enhance nuclear energy. According to the CURE concept, technetium should be transformed to stable materials such as '°°Ru, ' 01Ru and 'MRu (1). Innovative techniques for solvent extraction of technetium, in line with the CURE concept, can be introduced to various parts of the nuclear fuel cycle, including the conversion process. Primary amine extraction is favorable for the separation of technetium from uranium in a nitric acid solutiontl 2 ) and in a hydrofluoric acid solution(3 ). Amine, when used as an extractant, produces a reverse micelle (microemulsion)t4,5) in the organic phase of the extraction stages. The present study attempted to achieve a higher recovery of technetium(VII) in the solvent extraction process by applying a microemulsion with primary amine (Primene JMT) in the mixed solvent and to achieve a greater efficiency in each extraction and stripping cycle by optimizing the experimental variables. EXPERIMENTAL Technetium-95m(tl/ 2 = 61d) was produced by
95
95Mo(d,2n)
mTc
reaction, using a
Mat. Res. Soc. Symp. Proc. Vol. 353 01995 Materials Research Society
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cyclotron at the Cyclotron and Radioisotope Center, Tohoku University. The molybdenum target was dissolved in a hydrogen peroxide solution and its solution alkalified by adding ammonium hydroxide. Carrier-free 95mTc pertechnetate was extracted using tetraphenylarsonium chloride-chloroform solution. The 95 mTc0 4- was stripped into 8M(moldm-3 ) HNO 3, and from the resulting solution, HNO 3 was eliminated by evaporation(2 ). The radioactivity of 95mTc was determined by a Capintec CRC-12 radioisotope calibrator. The Primene JMT (primary amine, Rohm & Haas Co.) in a heptane solution was shaken for 1 h at 251C with an equal volume of aqueous solution containing mechanically 95 mTc04-. After equilibrati
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