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Abstract

The removal of oil films from the inner surface of a stainless steel tube cell using aqueous cleaning solutions was studied. The two oils used in the cleaning experiments, Sunquench 1042 and heavy mineral oil, contained P32 labeled tributyl phosphate (TBP) as a radioactive tracer. The β- particles emitted from the radioactive TBP were detected by a CaF2 scintillator and used as a measure of the amount of oil remaining in the tube cell. Cleaning experiments performed at different flow rates, surface treatment, and surfactant concentrations indicated that initially the oil films were removed rapidly. At the end of the experiments, the oil removal rate reduced significantly, eventually becoming negligible. The stainless steel morphology affected oil removal significantly, and the rougher tube tended to retard the oil removal. The rate and extent of the decontamination were significantly increased in the presence of sodium dodecyl sulfate, a nonionic surfactant. Experimental data were compared to a hydrodynamic model based on the removal of a liquid contaminant from a solid surface by an immiscible fluid. The model deviated from the experimental data due to the presence of instabilities at the oil-water interface.