Decontamination of Radioactive Contaminants from Iron Pipes using Reactive Microemulsion of Organic Acid in Supercritical Carbon Dioxide

概要

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The ferrite fixed on the iron pipes was decontaminated by a reactive microemulsion in supercritical carbon dioxide (SC-CO2). The specimens were prepared by treating the iron pipes with steam at 1,273 K for 2 min. The specimen was not dissolved in 3 mol·dm−3 HNO3 because its surface was covered with ferrite, while the original iron pipe was easily dissolved. This difference was used for determination of the fraction of ferrite. The fraction of ferrite covering the iron pipes was 1.5±0.3 wt%. A microemulsion containing organic acid was prepared using a fluorinated reagent, pentadecafluorooctanoic acid (PFOA), and a non-fluorinated surfactant, polyoxyethylene (2) nonylphenyl ether (NP-2) and citric acid. In the former system, PFOA acted as a surfactant as well as an acid. By observation of the phase equilibrium, the microemulsion was found to be stabilized when the molecular ratio of water to surfactant, the w value, was 5.0 for the PFOA+H2O+SC-CO2 system, and 8.7 for the NP-2+citric acid+SC-CO2 system at 25 MPa, and 323 or 353 K. Although the removal fractions of the ferrite were 0 and 1% for the PFOA and NP-2 system, respectively, at 25 MPa, 323 K, they increased to 92 and 56% at 25 MPa, 353 K.
社団法人日本原子力学会の論文
2006-06-25