Development of a Film Diffusion Controlled Mixed-Bed Ion Exchange Model: Applicable to Radioactive Species at Ultrapure Water Concentration

Scope and Objective of the study: The study aimed at developing a generalized model for radioactive species separation in a mixed-bed ion exchange (MBIE) column. Radioactive species isolation from process water in the nuclear power plants is critical for health and environmental purposes. Radioactive species are present at extremely low concentration in the circulating water. The concentration range of the water is in sub parts per billion (ppb) level. MBIE column is often used for targeted removal of specific radioactive ions of interest. This study focused on advancing the understanding of ion exchange column behavior for radioactive species separation. The current work adopted a similar approach based on previous research work (MBIE-SIM) done by ultrapure water (UPW) research group at Oklahoma state university. Findings and Conclusions: A novel ion exchange rate model (MBIE-SIM-RAD) for radioactive species at UPW application is developed. The model shows promising results. The inclusion of radioactive decay reaction has impact on ion exchange mechanism. Although ion exchange technology has been in the use for more than 75 years, a generalized rate model for radioisotopes did not exist until now. The MBIE-SIM-RAD model approximates the film diffusion controlled ion exchange behavior. The model uses correlations and constants to estimate system properties. A set of guidelines applicable for ion exchange mechanism in a mixed-bed column is justified.