Simulation study on the use of strippable coatings for radiocesium decontamination of concrete

The contamination and decontamination of concrete by a soluble contaminant (radiocesium) was modeled using the finite element method. The decontamination process relied on the application of a hyper-accumulating strippable polymer (HASP) to sequester contaminant that was transported to the concrete surface. The model accounted for the transport of cesium by diffusion, capillary pressure-driven convection, and equilibrium adsorption of cesium within the concrete substrate and HASP coating. The influence of HASP properties (porosity, thickness, and cesium distribution coefficient), and a wide range of operation variables (HASP contact time, delay time until HASP decontamination begins, influence of evaporative boundary conditions) on final decontamination efficacy were explored. Transient saturation (moisture content) and cesium concentration profiles were used to understand key factors in the decontamination process, and water wicking experiments were performed to validate the capillary convection model. The results showed that prompt HASP application after the initial contamination event is critical for high decontamination efficacies. A 30-day HASP treatment removed about 90% of the contaminant when HASP was applied within 30 min of the initial contamination event, whereas the decontamination process removed less than half as much cesium if months were allowed to elapse months prior to decontamination. Multiple applications of fresh HASP were also shown to improve decontamination performance under certain circumstances.