On the Liquid Entraiment and Its Removal

The over-all decontamination factor in the evaporation of radioactive liquid in a natural circulation evaporator reported in the previous paper indicated some disagreement with that obtained by Monowitz et al. The present paper deals with the decontamination factor in an evaporator, a pipe line and a cyclone, pertaining to the pilot plant mentioned in the previous report. According to our experiment, the decontamination factor in the evaporator proves to be mostly independent of the height of vapor space (0.6m and 1.1m, respectively), as shown in Fig. 3. Theoretical calculation from the jet velocity at which a single gas bubble bursts also demonstrates the results obtained experimentally. The results of the studies made on the decontamination factor in the pipe line and the cyclone are shown in Figs. 5 and 6. In our further studies conducted on the system consisting of an evaporator, a pipe line, a cyclone, a glass-fiber-packed tower and a condenser, the over-all decontamination factor ia found to be between 107 and 108. The drag coefffiicient of the glass-fiber-packed bed proves to obey the Langmuir and Iberall's equation.The decontamination factor without downtake indicates approximately the same value as in a natural circulation type evaporator, when the mass velocity is large. However, the mass velocity at the maximum decontamination factor is larger than in the natural circulation type. Fig. 9 shows the decontamination factor without downtake.The results obtained by us with the evaporator are, as summarized in Fig. 10, in good agreement with those of the experiment by Monowitz et al, which was conducted in a large scale evaporator. However, taking into consideration the presence of demisters which are usually installed in an industrial scale equipment, the mass velocity at the optimum over-all decontamination factor may be set within the range of 2, 000kg/m2·hr to 3, 000kg/mm2·hr.