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Radioactive Waste Minimization by Electrolytic Extraction and Destruction in a Purex-Truex Actinide Separation System
Volume 130 · Number 2 · May 2000 · Pages 196-205
Technical Paper · Radioactive Waste Management and Disposal
Masaki Ozawa, Yuichi Sano, Chisako Ohara, Takamichi Kishi
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Electrolytic extraction of noble metals from nitric acid media was investigated. The largest deposition yield was obtained for Pd, supported by its large rate constants. Rate constants of RuNO3+ and ReO4- were, however, smaller than that of Pd2+; their yield can be improved under high cathode current supply in lower nitric acid concentration. Rather high apparent activation energy was observed for the deposition of RuNO3+. Peculiar masking or synergistic effects in their electrodeposition behaviors might be due to mutual interaction of RuNO3+, Pd2+ with ReO4- in nitric acid solution. Sufficiently different redissolution potentials for deposited metals indicate their fractional recovery by anode processing.
Mediatory electrochemical oxidation (MEO) was investigated for the mineralization of waste O D[iB]CMPO (hereafter CMPO) by burning its bulky hydrocarbon moiety under the existence of various kinds of metal ions. Only Ag2+/+ offered high-current efficiency up to 75%, fairly exceeding that by direct electrooxidation. Redox coupling characterized by a simple electron transfer, Mm+ + ne- <=> M(m-n)+ provided high E0, will act exactly as an active mediator. As for the destruction paths for CMPO by MEO, cleavage between carbonyl C and N of amide moiety was of principal importance. The coupling of Co3+/2+ is also recommended because of hydraulic advantages.
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