Results 1 - 1 of 1
Results 1 - 1 of 1. Search took: 0.016 seconds
[en] Highlights: • First study on the effect of aqueous ions on the degradation of waste form for I-129. • First summary on probable iodine release pathways in various aqueous environments. • Enhanced iodine release by elevated ion exchange, basic pH, and ionic strength. • Discovered secondary phases vanadinite Pb5(VO4)3Cl and hydroxylvanadinite Pb5(VO4)3OH. • Low ionic content and neutral pH are vital to the disposal safety of nuclear waste. - Abstract: To ensure the safe disposal of nuclear waste, understanding the release process of radionuclides retained in the nuclear waste forms is of vital importance. Iodoapatite Pb9.85(VO4)6I1.7, a potential waste form for iodine-129, was selected as a model system for ceramic waste forms in this study to understand the effect of aqueous species on iodine release. Semi-dynamic leaching tests were conducted on bulk samples in cap-sealed Teflon vessels with 0.1 mol/L NaCl, Na2CO3, Na3PO4, and Na2SO4 solutions under 90 °C, fixed sample surface area to solution volume ratio of 5/m, and periodic replacement of leaching solutions. The reacted solutions were then analyzed by Inductively Coupled Plasma-Mass Spectrometry and Inductively Coupled Plasma-Optical Emission Spectrometry; the leached surfaces were characterized by X-ray diffraction, scanning electron microscopy, and infrared spectroscopy. The result shows that, compared to deionized water, the ion-rich solutions enhanced the iodine release as a result of the increased ionic strength, reduced activity coefficient of dissolved species, and increased solution pH. Surface reactions can lead to the formations of secondary phases by ion-exchange and precipitation. These findings suggest that an ion-rich environment in the geological repository can be detrimental to the disposal safety of the nuclear waste form.