Thermo-Hydro-Mechanical-Chemical processes in geological disposal of radioactive waste – An example of regulatory research

Abstract

Deep geological disposal is being considered in Canada and many other countries as the most viable option for the long-term management of radioactive waste. The disposal method consists of emplacing the waste in a repository built at hundreds of metres depth in a suitable host rock. A multi-barrier system, that includes the host rock formation as a major component, would be provided in order to protect humans and the environment from the harmful effects of the waste for very extensive time periods. Many events and processes are expected to occur during the lifetime of the repository, such as heat generation from the waste, seismicity and glaciation. As a result of those events and processes the Thermal-Hydraulic-Mechanical-Chemical (THMC) regimes in the natural and engineered components of the multi-barrier system will be perturbed, and the evolution of the THMC regimes and how this evolution affects the multi-barrier performance need to be understood. The Canadian Nuclear Safety Commission (CNSC), Canada’s nuclear regulator, has been conducting independent experimental and theoretical research on coupled THMC processes for several decades. As part of this research, the CNSC used experimental data from laboratory tests and large-scale experiments at underground research laboratories (URL) in order to develop a mathematical framework for the simulation of coupled processes in engineered and natural barriers for geological disposal. In this paper, we describe that mathematical framework and show examples of how it was adapted and applied to several situations: water and gas injection experiment at an URL, a heater experiment at an URL, and the effects of nine glacial cycles in a sedimentary rock formation.

Cited as: Nguyen, T.S. Thermo-Hydro-Mechanical-Chemical processes in geological disposal of radioactive waste – An example of regulatory research. Advances in Geo-Energy Research, 2018, 2(2): 173-189, doi: 10.26804/ager.2018.02.06

References

Abdi, H., Labrie, D., Nguyen, T.S., et al. Laboratory investigation on the mechanical behaviour of Tournemire argillite. Can. Geotech. J. 2014, 52(3): 268-282.

Al, T., Beauheim, R., Crowe, R., et al. OPG’s Deep Geologic Repository for Low & Intermediate Level Waste-Geosynthesis. Nuclear Waste Management Organization, report NWMO DGR-TR-2011-11, 2011.

Biot, M.A. General theory of three dimensional consolidation. J. Appl. Phys. 1941, 12(2): 155-164.

Bishop, A.W., Blight, G.E. Some aspects of effective stress insaturated and partly saturated soils. G ´eotechnique 1963, 13(3): 177-197.

Gens, A., Vaunat, J., Garitte, B., et al. In situ behaviour of a stiff layered clay subject to thermal loading: observations and interpretation. Geotechnique 2007, 57(2): 207-228.

Grasle, W., Plischke, I. Laboratory Testing (LT) Experiment: Mechanical behavior of Opalinus clay, Final report from Phase 614. BGR, Germany, Mont Terri Project Technical Report, 2009.

Le, D., Nguyen, T.S. Hydromechanical response of a bedded argillaceous rock formation to excavation and water injection. Can. Geotech. J. 2014, 52(1): 1-17.

Marschall, P., Trick, T., Lanyon, G.W., et al. Hydro-Mechanical evolution of damaged zones around a micro-tunnel in a claystone formation of the Swiss Jura mountains. The 42nd US Rock Mechanics Symposium (USRMS), San Francisco, California, 29 June-2 July, 2008.

Martin, C.D., Chandler, N.A. The progressive fracture of Lac du Bonnet granite. Int. J. Rock Mech. Min. Sci. 1994, 31(6): 643-659.

Nasir, O., Fall, M., Nguyen, T.S., et al. Modeling of the thermo-hydro-mechanical-chemical response of sedimen-tary rocks of Ontario to past glaciations, Int. J. Rock Mech. Min. 2012, 64: 160-174.

Nasir, O., Nguyen, T.S., Barnichon, J.D., et al. Simulation of the hydromechanical behaviour of bentonite seals for the containment of radioactive wastes. Can. Geotech. J. 2017, 54(8): 1055-1070.

Nguyen, T.S., B ¨orgesson, L., Chijimatsu, M., et al. A case study on the influence of THM coupling on the near-field safety of a spent fuel repository in sparsely fractured granite. J. Environ. Geol. 2009, 57(6): 1239-1254.

Nguyen, T.S., Le, D.A. Simultaneous gas and water flow in a damage-susceptible bedded argillaceous rock. Can. Geotech. J. 2014, 52(1): 18-32.

Nguyen, T.S., Le, D.A. Development of a constitutive model for a bedded argillaceous rock from triaxial and true triaxial tests. Can. Geotech. J. 2015, 52(8): 1072-1086.

Nguyen, T.S., Li, Z., Barnichon, J.D., et al. Modelling a heater experiment for radioactive waste disposal. Environ. Geotech. 2017, 1-14.

Nguyen, T.S., Selvadurai, A.P.S., Armand, G. Modelling the FEBEX THM experiment using a state surface approach. Int. J. Rock Mech. Min. 2005, 42(5-6): 639-651.

Noronha, J. Deep geological repository conceptual design report-crystalline/sedimentary rock. Nuclear Waste Man-agement Organization, report APM-REP-00440-0015 R001, 2016.

Sevadurai, A.P.S., Nguyen, T.S. Scoping ananalyses of the coupled thermal-hydrological-mechanical behaviour of the rock mass around a nuclear fuel waste repository. Eng. Geol. 1997, 47(4): 379-400.

Terzaghi, K.V. Die berechnung der durchlassigkeitsziffer des tones aus dem verlauf der hydrodynamishen Spa-nnungserscheinungen, akademie der wissenschaften in wien. Mathematish-Naturwissen-Schaftiliche Klasse 1923, 132: 125-138.

Tsang, C.F. Introduction to Coupled Processes. New York, USA, Academic Press, 1987.

Wileveau, Y. THM behaviour of host rock (HE-D) experiment: progress report. Part 1. Mont Terri Project, Technical Report TR 2005-03, 2005.