This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1016/j.jnucmat.2019.07.034. This is version 6 of this Preprint.
![Effect of solution chemistry on the iodine release from iodoapatite in aqueous environments](/media/repos/1/40aab2d6-4c12-4d57-a93c-f005a57ea48c.jpg)
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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 apatite waste form.
DOI
https://doi.org/10.31223/osf.io/rc57d
Subjects
Chemistry, Earth Sciences, Geochemistry, Materials Chemistry, Physical Sciences and Mathematics
Keywords
geochemistry, mineralogy, apatite structure, aqueous environment, iodine-129, mineral dissolution, nuclear waste form
Dates
Published: 2019-05-24 15:08
Last Updated: 2020-03-01 18:58
Older Versions
- Version 5 - 2019-07-29
- Version 4 - 2019-07-28
- Version 3 - 2019-07-28
- Version 2 - 2019-07-26
- Version 1 - 2019-05-18
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