Comparative modelling approaches of hydro-mechanical processes in sealing experiments at the Tournemire URL

Abstract of the journal article published in Environmental Earth Sciences
January 2017

Authors:
A. Millard
Commissariat à l’énergie atomique et aux énergies alternatives (France)

T. S. Nguyen
Canadian Nuclear Safety Commission

N. Mokni and J.D. Barnichon
Institut de Radioprotection et de Sûreté Nucléaire (France)

K.E. Thatcher and A.E. Bond
Quintessa (UK)

A. Fraser-Harris and C. McDermott
University of Edinburgh (UK)

R. Blaheta, Z. Michalec and M. Hasal
Institute of Geonics CAS, Czech Republic

O. Nasir
Geofirma, Ottawa, Canada

H. Yi and O. Kolditz
UFZ, Germany

Abstract:

In this paper, a comparative modelling exercise from the DECOVALEX-2015 project is presented. The exercise is based on in situ experiments, performed at the Tournemire Underground Research Laboratory (URL), run by the Institut de Radioprotection et de Sûreté Nucléaire (IRSN), in France. These experiments aim at identifying conditions (e.g., technical specifications, design, construction and defects) that will affect the long-term performance of swelling clay-based sealing systems, which is of key importance for the safety of underground nuclear waste disposal facilities.

A number of materials are being considered as seals; the current work focuses on a 70/30 MX80 bentonite–sand mixture initially compacted at a dry density of 1.94 Mg/m³. The performance of the sealing plug involves at least three different important components: the hydro-mechanical behaviour of the bentonite–sand core, the overall permeability of the surrounding argillite, and the influence of the technological gap between the core and the argillite.

Two particular tests have been selected for a comparative modelling exercise: the WT-1 test, which was designed to study the rock mass permeability, and the PT-A1 test, which aimed at quantifying the evolution of the hydro-mechanical field within the bentonite–sand core.

A number of independent teams have worked towards modelling these experiments, using different codes and input parameters calibrated on additional small-scale laboratory experiments. Their results are compared and discussed.

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