Magnetic Materials: Novel Monitors of Long-Term Evolution of Engineered Barrier Systems
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 corro...
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2016-12-01
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doaj-2930d883adcb43eabfd267ce426c99f02020-11-25T00:52:43ZengMDPI AGGeosciences2076-32632016-12-01645410.3390/geosciences6040054geosciences6040054Magnetic Materials: Novel Monitors of Long-Term Evolution of Engineered Barrier SystemsSimon L. Harley0Nicola Rigonat1Ian B. Butler2School of Geosciences, University of Edinburgh, Edinburgh EH9 3FE, UKSchool of Geosciences, University of Edinburgh, Edinburgh EH9 3FE, UKSchool of Geosciences, University of Edinburgh, Edinburgh EH9 3FE, UKMost 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.http://www.mdpi.com/2076-3263/6/4/54geological disposal facilityengineered barrier systembentonitebuffermagnetsNd-Fe-Bneo magnetsferriteAlNiCo |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Simon L. Harley Nicola Rigonat Ian B. Butler |
spellingShingle |
Simon L. Harley Nicola Rigonat Ian B. Butler Magnetic Materials: Novel Monitors of Long-Term Evolution of Engineered Barrier Systems Geosciences geological disposal facility engineered barrier system bentonite buffer magnets Nd-Fe-B neo magnets ferrite AlNiCo |
author_facet |
Simon L. Harley Nicola Rigonat Ian B. Butler |
author_sort |
Simon L. Harley |
title |
Magnetic Materials: Novel Monitors of Long-Term Evolution of Engineered Barrier Systems |
title_short |
Magnetic Materials: Novel Monitors of Long-Term Evolution of Engineered Barrier Systems |
title_full |
Magnetic Materials: Novel Monitors of Long-Term Evolution of Engineered Barrier Systems |
title_fullStr |
Magnetic Materials: Novel Monitors of Long-Term Evolution of Engineered Barrier Systems |
title_full_unstemmed |
Magnetic Materials: Novel Monitors of Long-Term Evolution of Engineered Barrier Systems |
title_sort |
magnetic materials: novel monitors of long-term evolution of engineered barrier systems |
publisher |
MDPI AG |
series |
Geosciences |
issn |
2076-3263 |
publishDate |
2016-12-01 |
description |
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. |
topic |
geological disposal facility engineered barrier system bentonite buffer magnets Nd-Fe-B neo magnets ferrite AlNiCo |
url |
http://www.mdpi.com/2076-3263/6/4/54 |
work_keys_str_mv |
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