Reactive Transport Modelling of the Long-Term Interaction between Carbon Steel and MX-80 Bentonite at 25 °C

The geological disposal in deep bedrock repositories is the preferred option for the management of high-level radioactive waste (HLW). In some of these concepts, carbon steel is considered as a potential canister material and bentonites are planned as backfill material to protect metallic waste cont...

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Autores principales:	M. Carme Chaparro, Nicolas Finck, Volker Metz, Horst Geckeis
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	radioactive waste disposal iron–bentonite interaction reactive transport numerical model Mineralogy QE351-399.2
Acceso en línea:	https://doaj.org/article/77c4bbfeec1e454e9adb1c65c4e52bdf
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spelling	oai:doaj.org-article:77c4bbfeec1e454e9adb1c65c4e52bdf2021-11-25T18:26:45ZReactive Transport Modelling of the Long-Term Interaction between Carbon Steel and MX-80 Bentonite at 25 °C10.3390/min111112722075-163Xhttps://doaj.org/article/77c4bbfeec1e454e9adb1c65c4e52bdf2021-11-01T00:00:00Zhttps://www.mdpi.com/2075-163X/11/11/1272https://doaj.org/toc/2075-163XThe geological disposal in deep bedrock repositories is the preferred option for the management of high-level radioactive waste (HLW). In some of these concepts, carbon steel is considered as a potential canister material and bentonites are planned as backfill material to protect metallic waste containers. Therefore, a 1D radial reactive transport model has been developed in order to better understand the processes occurring during the long-term iron-bentonite interaction. The numerical model accounts for diffusion, aqueous complexation reactions, mineral dissolution/precipitation and cation exchange at a constant temperature of 25<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo> </mo><mo>°</mo><mi mathvariant="normal">C</mi></mrow></semantics></math></inline-formula> under anoxic conditions. Our results suggest that Fe is sorbed at the montmorillonite surface via cation exchange in the short-term, and it is consumed by formation of the secondary phases in the long-term. The numerical model predicts precipitation of nontronite, magnetite and greenalite as corrosion products. Calcite precipitates due to cation exchange in the short-term and due to montmorillonite dissolution in the long-term. Results further reveal a significant increase in pH in the long-term, while dissolution/precipitation reactions result in limited variations of the porosity. A sensitivity analysis has also been performed to test the effect of selected parameters, such as corrosion rate, diffusion coefficient and composition of the bentonite porewater, on the corrosion processes. Overall, outcomes suggest that the predicted main corrosion products in the long-term are Fe-silicate minerals, such phases thus should deserve further attention as a chemical barrier in the diffusion of radionuclides to the repository far field.M. Carme ChaparroNicolas FinckVolker MetzHorst GeckeisMDPI AGarticleradioactive waste disposaliron–bentonite interactionreactive transportnumerical modelMineralogyQE351-399.2ENMinerals, Vol 11, Iss 1272, p 1272 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	radioactive waste disposal iron–bentonite interaction reactive transport numerical model Mineralogy QE351-399.2
spellingShingle	radioactive waste disposal iron–bentonite interaction reactive transport numerical model Mineralogy QE351-399.2 M. Carme Chaparro Nicolas Finck Volker Metz Horst Geckeis Reactive Transport Modelling of the Long-Term Interaction between Carbon Steel and MX-80 Bentonite at 25 °C
description	The geological disposal in deep bedrock repositories is the preferred option for the management of high-level radioactive waste (HLW). In some of these concepts, carbon steel is considered as a potential canister material and bentonites are planned as backfill material to protect metallic waste containers. Therefore, a 1D radial reactive transport model has been developed in order to better understand the processes occurring during the long-term iron-bentonite interaction. The numerical model accounts for diffusion, aqueous complexation reactions, mineral dissolution/precipitation and cation exchange at a constant temperature of 25<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo> </mo><mo>°</mo><mi mathvariant="normal">C</mi></mrow></semantics></math></inline-formula> under anoxic conditions. Our results suggest that Fe is sorbed at the montmorillonite surface via cation exchange in the short-term, and it is consumed by formation of the secondary phases in the long-term. The numerical model predicts precipitation of nontronite, magnetite and greenalite as corrosion products. Calcite precipitates due to cation exchange in the short-term and due to montmorillonite dissolution in the long-term. Results further reveal a significant increase in pH in the long-term, while dissolution/precipitation reactions result in limited variations of the porosity. A sensitivity analysis has also been performed to test the effect of selected parameters, such as corrosion rate, diffusion coefficient and composition of the bentonite porewater, on the corrosion processes. Overall, outcomes suggest that the predicted main corrosion products in the long-term are Fe-silicate minerals, such phases thus should deserve further attention as a chemical barrier in the diffusion of radionuclides to the repository far field.
format	article
author	M. Carme Chaparro Nicolas Finck Volker Metz Horst Geckeis
author_facet	M. Carme Chaparro Nicolas Finck Volker Metz Horst Geckeis
author_sort	M. Carme Chaparro
title	Reactive Transport Modelling of the Long-Term Interaction between Carbon Steel and MX-80 Bentonite at 25 °C
title_short	Reactive Transport Modelling of the Long-Term Interaction between Carbon Steel and MX-80 Bentonite at 25 °C
title_full	Reactive Transport Modelling of the Long-Term Interaction between Carbon Steel and MX-80 Bentonite at 25 °C
title_fullStr	Reactive Transport Modelling of the Long-Term Interaction between Carbon Steel and MX-80 Bentonite at 25 °C
title_full_unstemmed	Reactive Transport Modelling of the Long-Term Interaction between Carbon Steel and MX-80 Bentonite at 25 °C
title_sort	reactive transport modelling of the long-term interaction between carbon steel and mx-80 bentonite at 25 °c
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/77c4bbfeec1e454e9adb1c65c4e52bdf
work_keys_str_mv	AT mcarmechaparro reactivetransportmodellingofthelongterminteractionbetweencarbonsteelandmx80bentoniteat25c AT nicolasfinck reactivetransportmodellingofthelongterminteractionbetweencarbonsteelandmx80bentoniteat25c AT volkermetz reactivetransportmodellingofthelongterminteractionbetweencarbonsteelandmx80bentoniteat25c AT horstgeckeis reactivetransportmodellingofthelongterminteractionbetweencarbonsteelandmx80bentoniteat25c
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Reactive Transport Modelling of the Long-Term Interaction between Carbon Steel and MX-80 Bentonite at 25 °C

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