Reactive transport modeling of ion exchange resins used in pressurized water reactors

In nuclear power plants, the water contained in different circuits is purified by passing through ion exchange resins. Prediction of the performance of these resins is an important help to the plant operators. To this end, the method of reactive transport modeling are well suited and is the basis of the OPTIPUR code that was designed to model the resins. The work presented in this manuscript covers three main aspects. The first one is the integration of a limitation to mass transfer in a ion exchange deep bed, taking into account a specific mobility for each chemical species, in the context of separated calculations for chemistry and transport. This model was shown to reproduce experimental data, without adjustable parameters. The second part of this work deals with the numerical aspects of reactive transport modelling. A method developed by Anderson was used to accelerate the convergence of the chemistry transport coupling in an iterative scheme. Using the information from previous iterations, and without major changes in the code, calculation times were largely decreased, as well as the number of calculations failures. The third topic is ion exchange equilibrium. The basis of a model that takes into account the change in the water content of the resin and its elasticity are described. The interactions between the functional groups, the counterions and water are considered as chemical reactions. The corresponding equilibrium constants are fitted to measurements of the water content of the resin at different relative humidity. Finally, the selectivity coefficients can be calculated and compared to literature values. (author)