Effect of entrainment and overflow occurrence on concentration profile in uranium-strip bank of PUREX flowsheet

An occurrence of entrainment and overflow (a leakage flow through the overflow-passageway) should be considered in the operation of the solvent extraction process and design of an extractor because they affect the concentration profile. A computer code permitting the calculation of the concentration profile under an occurrence of such abnormal flows has been developed for the PUREX flowsheet. The concentration profile is calculated by solving overall mass balance equations considering those from abnormal flows. The effect of internal abnormal flows on the concentration profile was studied for the uranium-strip bank. The results showed that the internal abnormal flows disturbed the uranium stripping i.e. increased the uranium concentration in the solvent outflow, but the increase was far smaller than that caused by the deviation of feed flowrate into the bank due to its usual control precision which is considered in an industrial flowsheet. An occurrence of entrainment and overflow has been restricted severely because there has been no quantitative study about its effect on the concentration profile, however, the results suggested the possibility of relaxing that restriction, which provides a more flexible operation of process for disturbance and a smaller design load of a solvent extractor for the uranium-strip bank. (author)