| 摘要 |
PURPOSE:To recover Ru from radioactive waste in high efficiency, by oxidizing Ru in the waste, evaporating and absorbing produced ruthenium tetroxide, reducing the oxide and recovering in the form of ruthenium dioxide. CONSTITUTION:A high activity radioactive waste 2 containing Ru is supplied through a feed pipe 3 to a reaction vessel 1 and heated with a heating means 5 to >=50 deg.C in a state acidified with >=2.5N nitric acid and, at the same time, an oxidizing agent (e.g. O3) and a carrier gas are supplied to the reaction vessel 1 through a blasting pipe 6 and a feed pipe 7, respectively. The produced ruthenium tetroxide is evaporated and transferred together with the carrier gas through a line 8 to an adsorption column 9. The ruthenium tetroxide is subjected to gas-liquid contact with an absorbent 10 supplied through a spray tube 13 of a circulation line 12 and is absorbed to the absorbent. The absorption liquid 10 is introduced through a line 14 into a reduction tank 15, mixed and reduced with a reducing agent 17 supplied from a feeding apparatus 18 to form ruthenium dioxide or metallic Ru, which is supplied to a solid-liquid separation tank 19 and separated into Ru 22 and waste liquid 23.
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