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Consequences of the thermal transient on the evolution of the damaged zone around a repository for heat-emitting high-level radioactive waste in a clay formation: a performance assessment perspective

Abstract : A proper evaluation of the perturbations of the host rock induced by the excavation and the emplacement of exothermic wastes is essential for the assessment of the long-term safety of high-level radioactive waste disposals in clay formations. The impact of the periodthermal transient on the evolution of the damaged zone (DZ) has been explored in a recent European Commission project called TIMODAZ (Thermal Impact on the Damaged Zone Around a Radioactive Waste Disposal in Clay Host Rocks, 2006 — 2010). This paper integrates the scientific results of the TIMODAZ project from a performance assessment (PA) point of view, showing how these results support and justify key PA assumptions and the values of PA model parameters. This paper also contextualises the significance of the thermal impact on the DZ from a safety case perspective, highlighting how the project outcomes result into an improved understanding of the Thermo-Hydro-Mechanical behaviour of the host clays.The results obtained in the TIMODAZ project strengthen the assessment basis of the safety evaluation of the current repository designs. There was no evidence throughout the TIMODAZ experimental observations of a temperature-induced additional opening of fractures or of a significant permeability increase of the DZ. Instead, thermal-induced plasticity, swelling and creep behaviour seem to be beneficial to the sealing of fractures and to the recovery of a very low permeability in the DZ, close to that of an undisturbed clay host rock. Results from the TIMODAZ project indicate that the favourable properties of the clay host rock that guarantee the effectiveness of the safety functions of the repository system are expected to be maintained after the heating-cooling cycle. Hence, the basic assumptions usually made in PA calculations so far are expected to remain valid and the performance of the system should not be affected in a negative way by the thermal evolution of the DZ around a radioactive waste repository in clay host rock.
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https://hal.archives-ouvertes.fr/hal-01084202
Contributor : Pierre Delage <>
Submitted on : Tuesday, November 18, 2014 - 4:59:08 PM
Last modification on : Thursday, April 8, 2021 - 4:26:02 PM

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Y. Li, E. Weetjens, X. Sillen, T. Vietor, Xiaojian Li, et al.. Consequences of the thermal transient on the evolution of the damaged zone around a repository for heat-emitting high-level radioactive waste in a clay formation: a performance assessment perspective. Rock Mechanics and Rock Engineering, Springer Verlag, 2013, pp.3-19. ⟨10.1007/s00603-013-0409-4⟩. ⟨hal-01084202⟩

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