Numerical modeling and experimental validation of heat transfer in a research nuclear reactor evaporator by considering the precipitate formation

Abstract

One of the wastewater treatment units in the Tehran Research Nuclear Reactor (TRNR) is an evaporator unit, which consists of a semi-batch single-stage kettle-type evaporator with heating coils and auxiliary equipment. The concentrate of this unit is immobilized in cement. So, the precipitate specie, concentrate composition, and its amount are important parameters for further waste treatment steps. In this research, a new bulk mathematical model is developed based on the total mass balance, the partial mass balance of ions in the concentrate and precipitates, as well as the energy balance to investigate the performance of the Tehran Research Nuclear Reactor evaporator. The resulting ordinary differential equations are solved numerically with a proposed algorithm. In this simulation, Pitzer equations are used to calculate the activity coefficient of water and ions, density, and solubility of salts. The temperature and pressure dependence of the developed model parameters are also considered. Moreover, the effect of precipitate formation on the overall heat transfer coefficient with time dependence correlation is also taken into account. Results show a good agreement between the experimental data and the developed model, and the relative error of different parameters is reported between 2% and 13%.