Effects of microstructure on radiolytic degradation of nuclear grade cationic resins: Gel versus macro-porous

A study was undertaken to evaluate the effect of gamma radiation on the physico-chemical and functional properties of strong cationic ion exchange resins with varying microstructures i.e., gel and macro-porous type, used in purification systems of water-cooled nuclear reactors. The effect of metal ion loading on degradation behavior was probed to simulate the in-situ irradiation scenario in used resin. The resins are expected to undergo physico-chemical and functional degradation due to different oxidizing and reducing species from water radiolysis. Nevertheless, evaluating the extent of degradation based on the morphological and structural differences was of interest. The extent of resin degradation was estimated by analyzing the change in pH, conductivity, total organic carbon (TOC), chemical oxygen demand (COD) and the extent of reactive site loss from the leached ions. Leaching of SO42− ions and the formation of lower organic acids resulted in decreased pH and increased conductivity, TOC and COD values. The change in exchange capacity and physical and structural changes in the irradiated resin's surface was probed with X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR) and Field emission scanning electron microscopy (FE-SEM). Gel resin showed more significant functional group loss, while hydrogen generation was more from macroporous resin due to its more rigid and dense structure.