Skip to main content
U.S. Department of Energy
Office of Scientific and Technical Information

Prediction of Long-Term Geochemical Change in Bentonite Based on the Interpretative THMC Model of the FEBEX In Situ Test

Journal Article · · Minerals
DOI:https://doi.org/10.3390/min13121522· OSTI ID:2228534

Since nuclear energy is crucial in the decarbonization of the energy supply, one hurdle to remove is the handling of high-level radioactive waste (HLW). Disposal of HLW in a deep geological repository has long been deemed a viable permanent option. In the design of a deep geological repository, compacted bentonite is the most commonly proposed buffer material. Predicting the long-term chemical evolution in bentonite, which is important for the safety assessment of a repository, has been challenging because of the complex coupled processes. Models for large-scale tests and predictions based on such models have been some of the best practices for such purposes. An 18-year-long in situ test with two dismantling events provided a unique set of chemical data that allowed for studying chemical changes in bentonite. In this paper, we first developed coupled thermal, hydrological, mechanical, and chemical (THMC) models to interpret the geochemical data collected in the in situ test and then extended the THMC model to 200 years to make long-term prediction of the geochemical evolution of bentonite. The interpretive coupled THMC model shows that the geochemical profiles were strongly affected by THM processes such as evaporation/condensation, porosity change caused by swelling, permeability change, and the shape of concentration profiles for major cations were largely controlled by transport processes, but concentration levels were regulated by chemical reactions, and the profiles of some species such as pH, bicarbonate, and sulfate were dominated by these reactions. The long-term THMC model showed that heating prolongs the time that bentonite becomes fully saturated in the area close to the heater/canister; however, once the bentonite becomes fully saturated, high concentrations of ions in bentonite near the heater, which was observed in the field test, will disappear; illitization continues for 50 years but will not proceed further.

Sponsoring Organization:
USDOE
Grant/Contract Number:
AC02-05CH11231
OSTI ID:
2228534
Journal Information:
Minerals, Journal Name: Minerals Journal Issue: 12 Vol. 13; ISSN MBSIBI; ISSN 2075-163X
Publisher:
MDPI AGCopyright Statement
Country of Publication:
Switzerland
Language:
English

References (30)

Corrosion of carbon steel in clay environments relevant to radioactive waste geological disposals, Mont Terri rock laboratory (Switzerland) journal February 2017
Benchmarks for multicomponent reactive transport across a cement/clay interface journal January 2015
Modeling diffusion processes in the presence of a diffuse layer at charged mineral surfaces: a benchmark exercise journal September 2019
Hydrothermal Interaction of Wyoming Bentonite and Opalinus clay journal April 2020
Hydrothermal alteration of “La Serrata” bentonite (Almeria, Spain) by alkaline solutions journal August 2002
Coupled thermo-hydro-chemical models of compacted bentonite after FEBEX in situ test journal May 2008
Implementation of the Barcelona Basic Model into TOUGH–FLAC for simulations of the geomechanical behavior of unsaturated soils journal June 2011
Iron–clay interactions under hydrothermal conditions: Impact of specific surface area of metallic iron on reaction pathway journal August 2014
A new view on iron-claystone interactions under hydrothermal conditions (90 °C) by monitoring in situ pH evolution and H2 generation journal September 2017
A revisited thermal, hydrodynamic, chemical and mechanical model of compacted bentonite for the entire duration of the FEBEX in situ test journal August 2018
The hydration of bentonite buffer material revealed by modeling analysis of a long-term in situ test journal February 2020
Reactive transport models of the geochemical interactions at the iron/bentonite interface in laboratory corrosion tests journal August 2023
On the impact of temperatures up to 200 °C in clay repositories with bentonite engineer barrier systems: A study with coupled thermal, hydrological, chemical, and mechanical modeling journal October 2015
Modelling the sorption of Mn(II), Co(II), Ni(II), Zn(II), Cd(II), Eu(III), Am(III), Sn(IV), Th(IV), Np(V) and U(VI) on montmorillonite: Linear free energy relationships and estimates of surface binding constants for some selected heavy metals and actinides journal February 2005
Thermo-hydro-mechanical analysis of the complete lifetime of the bentonite barrier in the FEBEX in-situ test journal June 2023
A coupled THC model of the FEBEX in situ test with bentonite swelling and chemical and thermal osmosis journal September 2011
Long-term non-isothermal reactive transport model of compacted bentonite, concrete and corrosion products in a HLW repository in clay journal February 2017
A coupled THMC model of a heating and hydration laboratory experiment in unsaturated compacted FEBEX bentonite journal May 2010
Fe-saponite growth on low-carbon and stainless steel in hydrothermal-bentonite experiments journal December 2018
Analysis of the porewater chemical composition of a Spanish compacted bentonite used in an engineered barrier journal January 2004
Inverse hydrochemical models of aqueous extracts tests journal January 2008
Interaction processes at the concrete-bentonite interface after 13 years of FEBEX-Plug operation. Part II: Bentonite contact journal June 2017
Reactive Transport of Chemicals in Compacted Bentonite under Nonisothermal Water Infiltration journal October 2018
Ion exchange selectivity in clay is controlled by nanoscale chemical–mechanical coupling journal October 2019
Thermal–hydraulic–mechanical (THM) behaviour of a large-scale in situ heating experiment during cooling and dismantling journal October 2012
Experimental study of the transformation of smectite at 80 and 300°C in the presence of Fe oxides journal March 2004
Coupled THM analysis of a full-scale test for high-level nuclear waste and spent fuel disposal under actual repository conditions during 18 years of operation   journal January 2022
Bentonite evolution at elevated pressures and temperatures: An experimental study for generic nuclear repository designs journal August 2014
EQ3/6, a software package for geochemical modeling of aqueous systems: Package overview and installation guide (Version 7.0) report September 1992
Reactive Transport Modelling of the Long-Term Interaction between Carbon Steel and MX-80 Bentonite at 25 °C journal November 2021

Similar Records

A Coupled THMC model of FEBEX mock-up test
Journal Article · Mon Sep 15 00:00:00 EDT 2008 · Physics and Chemistry of the Earth · OSTI ID:971675

A coupled THMC model of a heating and hydration laboratory experiment in unsaturated compacted FEBEX bentonite
Journal Article · Sat May 01 00:00:00 EDT 2010 · Journal of Hydrology · OSTI ID:985334

A coupled THC model of the FEBEX in situ test with bentonite swelling and chemical and thermal osmosis
Journal Article · Fri Apr 01 00:00:00 EDT 2011 · Journal of Contaminant Hydrology · OSTI ID:1050728

Related Subjects