Abstract
Most safety cases for the deep geological disposal of radioactive waste are reliant on the swelling of bentonite in the engineered barrier system as it saturates with groundwater. Assurance of safety therefore requires effective monitoring of bentonite saturation. The time- and fluid-dependent corrosion of synthetic magnets embedded in bentonite is demonstrated here to provide a novel and passive means of monitoring saturation. Experiments have been conducted at 70 °C in which neo magnets, AlNiCo magnets, and ferrite magnets have been reacted with saline (NaCl, KCl, CaCl2) solutions and alkaline fluids (NaOH, KOH, Ca(OH)2 solutions; pH = 12) in the presence of bentonite. Nd-Fe-B magnets undergo extensive corrosion that results in a dramatic change from ferromagnetic to superparamagnetic behaviour concomitant with bentonite saturation. AlNiCo magnets in saline solutions show corrosion but only limited decreases in their magnetic intensities, and ferrite magnets are essentially unreactive on the experimental timescales, retaining their initial magnetic properties. For all magnets the impact of their corrosion on bentonite swelling is negligible; alteration of bentonite is essentially governed by the applied fluid composition. In principle, synthetic magnet arrays can, with further development, be designed and embedded in bentonite to monitor its fluid saturation without compromising the integrity of the engineered barrier system itself.
Highlights
One of the essential features of Geological Disposal Facility (GDF) concepts for the disposal of high-level radioactive waste in the deep sub-surface is the protection of radioactive waste canisters from corrosion in order to avoid, or at least minimize, the release of radionuclides into the near-field environment and beyond
Neo magnets and AlNiCo magnets are corroded by saline and/or alkaline fluids in the presence of bentonite
Over time this leads to measurable degradation in their magnetic properties, such as their intrinsic magnetic field, that can serve as a proxy for saturation of the surrounding bentonite
Summary
One of the essential features of Geological Disposal Facility (GDF) concepts for the disposal of high-level radioactive waste in the deep sub-surface is the protection of radioactive waste canisters from corrosion in order to avoid, or at least minimize, the release of radionuclides into the near-field environment and beyond. To achieve this most Waste Management Organisations (WMOs) have developed safety cases based on the cumulative properties of multi-barrier systems. Good sorption properties are favoured, so that if any radioactive material is released into the near-field its dispersion is limited by the negligible hydraulic
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
