Numerical study of the THM effects on the near-field safety of a hypothetical nuclear waste repository—BMT1 of the DECOVALEX III project. Part 2: Effects of THM coupling in continuous and homogeneous rocks

A. Millard (1) , A. Rejeb (2) , M. Chijimatsu (3) , L. Jing (4) , J. de Jonge (5) , M. Kohlmeier (6) , T.S. Nguyen (7) , J. Rutqvist (8) , M. Souley (9) , Y. Sugita (10)

1 CEA - Commissariat à l'énergie atomique et aux énergies alternatives
2 IRSN - Institut de Radioprotection et de Sûreté Nucléaire
3 HC - Hazama Corporation
4 KTH - Royal Institute of Technology [Stockholm]
5 Eberhard Karls Universität Tübingen = Eberhard Karls University of Tuebingen
6 Leibniz Universität Hannover=Leibniz University Hannover
7 CNSC - Canadian Nuclear Safety Commission
8 LBNL - Lawrence Berkeley National Laboratory [Berkeley]
9 INERIS - Institut National de l'Environnement Industriel et des Risques
10 JNC - Japan Nuclear Cycle Development Institute

An evaluation of the importance of the thermo-hydro-mechanical couplings (THM) on the performance assessment of a deep underground radioactive waste repository has been made as a part of the international DECOVALEX III project. It is a numerical study that simulates a generic repository configuration in the near field in a continuous and homogeneous hard rock. A periodic repository configuration comprises a single vertical borehole, containing a canister surrounded by an over-pack and a bentonite layer, and the backfilled upper portion of the gallery. The thermo-hydro-mechanical evolution of the whole configuration is simulated over a period of 100 years. The importance of the rock mass's intrinsic permeability has been investigated through scoping calculations with three values: 10−17, 10−18 and 10−19 m2. Comparison of the results predicted by fully coupled THM analysis as well as partially coupled TH, TM and HM analyses, in terms of several predefined indicators of importance for performance assessment, enables us to identify the effects of the different combinations of couplings, which play a crucial role with respect to safety issues. The results demonstrate that temperature is hardly affected by the couplings. In contrast, the influence of the couplings on the mechanical stresses is considerable.

Keywords: Thermo-hydro-mechanical couplings; Performance assessment; Radioactive wastes

Domains: Engineering Sciences [physics]; Mechanics [physics.med-ph]

A. Millard, A. Rejeb, M. Chijimatsu, L. Jing, J. de Jonge, et al.. Numerical study of the THM effects on the near-field safety of a hypothetical nuclear waste repository—BMT1 of the DECOVALEX III project. Part 2: Effects of THM coupling in continuous and homogeneous rocks. International Journal of Rock Mechanics and Mining Sciences, 2005, 42 (2005), pp.731-744. ⟨ineris-00175383⟩