An international study on THM modelling of the full-scale heater experiment at Mont Terri laboratory

Journal Article · Fri Jan 03 00:00:00 EST 2025 · Geomechanics for Energy and the Environment

DOI:https://doi.org/10.1016/j.gete.2024.100631· OSTI ID:2566092

Graupner, Bastian Johannes ^[1]; Thatcher, Kate ^[2]; Friedenberg, Larissa ^[3]; Guo, Ruiping ^[4]; Hadgu, Teklu ^[5]; Hou, Wenbo ^[6]; Kaiser, Sonja ^[7]; Kim, Taehyun ^[8]; Park, Chan-Hee ^[9]; Lee, Changsoo ^[8]; Matteo, Edward ^[5]; Nagel, Thomas ^[7]; Newson, Rebecca ^[2]; Pan, Peng-Zhi ^[6]; Pitz, Michael ^[10]; Rutqvist, Jonny ^[11]; Thiedau, Jan ^[12]; Urpi, Luca ^[13]

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1. Swiss Federal Nuclear Safety Inspectorate (ENSI), Brugg (Switzerland)
2. Quintessa Ltd., Warrington (United Kingdom)
3. Society for Plant and Reactor Safety (GRS) (Germany)
4. Nuclear Waste Management Organization (NWMO), Toronto, ON (Canada)
5. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sandia National Lab. (SNL-CA), Livermore, CA (United States)
6. Chinese Academy of Sciences (CAS), Peking (China)
7. Technische Universität Bergakademie Freiberg (Germany)
8. Korea Atomic Energy Research Institute (KAERI), Daejeon (Korea, Republic of)
9. Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon (Korea, Republic of)
10. Technische Universität Bergakademie Freiberg (Germany); Federal Institute for Geosciences and Natural Resources, Hannover (Germany)
11. Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
12. Federal Institute for Geosciences and Natural Resources, Hannover (Germany)
13. CSD Aarau (Switzerland)

We present results from an international model comparison study of the Full-Scale Emplacement (FE) experiment in Opalinus Clay at the Mont Terri Laboratory, Switzerland. Based on a provided parameter set the teams decided which parameters they adopted for their models, whether they considered the excavation and the ventilation phase in addition to the heating phase and if they included technical features like the shotcrete or the EDZ. The teams were able to reproduce the measured parameters temperature, relative humidity and pore pressure. The modelled results for temperature agree very closely between the teams especially in the sensors in Opalinus Clay. All teams were able to reproduce the redistribution of water in the bentonite backfill due to heating. The evolution of the relative humidity showed similar trends with differences in the intensity of the dry out effect. To model the pore pressure evolution is more complex because it comprises the full interaction of the coupled THM processes. The spread between the pore pressure modelled by the teams was larger, with some teams overestimating the pressure increase due to heating and some teams overestimating the extent of drainage. The agreement of modelled results with measurements improves with larger distance to the heater. We conclude that the EDZ and the shotcrete potentially influence the behaviour of the rock causing higher differences closer to the heater. Further research is needed to better implement those influences into the models. Based on the calibrated models, the future evolution of temperature, relative humidity and pore pressure was predicted over the next 10 years following a change of the heat power applied in 2023 and 2024. Again, the predicted temperatures agree very closely between the teams. Most teams do not expect an increase in relative humidity during the next 10 years after the initial dry-out.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 2566092
• Journal Information: Geomechanics for Energy and the Environment, Journal Name: Geomechanics for Energy and the Environment Vol. 41; ISSN 2352-3808
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
FE experiment in Mont Terri
Opalinus Clay
coupled thermal-hydraulic-mechanical models
deep geological repository
heat emission
pore pressure evolution