BASIC STUDY ON EFFICIENT DEGRADATIVE TREATMENT PROCESS OF RADIOACTIVE PERFLUORO OIL BY USING SUBCRITICAL WATER REACTION

抄録

Various types of machine oil are used for analysis and utility equipment, and these organic liquid wastes are stored in the nuclear facilities and laboratories due to lack of appropriate treatment processes. Treatment of organic liquid waste is one of principal tasks, since radiolysis of organic material generates various hazardous products. Perfluoro oil, generally used in vacuum pumps, is difficult to be decomposed because of chemical stability. Calcination of fluorine compounds is possible to generate toxic and corrosive gas products. In order to achieve complete mineralization of the organic liquid wastes, application of subcritical water reaction was examined. In this study, effect of introducing a functional group into a perfluoro compound on its decomposition performance was experimentally evaluated. First, we carried out the transformation of perfluorohexane to perfluorohexyl iodide or perfluoroheptanoic acid based on reported procedures. Next, laboratory scale batch-wise decomposition tests with subcritical water on perfluorohexyl iodide and on perfluoro heptanoic acid were carried out. Analyses on degraded organic products remaining in the H₂O phase by atmospheric pressure ionization mass spectrometry and liquid chromatograph mass spectrometry were carried out. The decomposition products of each fluorine compound were identified, confirming that subcritical treatment is a promising treatment method.