Modeling and Comparison of Continuous and Semi-Continuous Processes for Simulating Decontamination of Liquid Nuclear Wastes by the Coprecipitation of Strontium Ions with Barium Sulphate

Abstract

In the nuclear industry, large volumes of liquid wastes with a low radioactivity have to be treated. The method which is commonly applied to remove contaminants consists of the use of an insoluble finely divided solid material formed in situ by precipitation in the waste stream. In this study, a new mathematical approach of the adsorption of radioactive strontium on growing barium sulphate precipitate is established and used for the decontamination process modeling in both continuous and semi-continuous stirred tank reactors. The comparison of the two types of reactors is carried out under the same operating conditions by studying the influence of the stirring speed and, respectively, the mean residence time (for continuous stirred tank reactor) and/or process time (for semi-batch stirred tank reactor) on the efficiency of the decontamination process. Simulations have shown that the mean residence time is the critical parameter in controlling decontamination in the continuous reactor, while the stirring speed plays a minor role. Comparison of results indicates that the best configuration to carry out the decontamination process is the semi-batch stirred tank reactor.