Gas migration at the granite–bentonite interface under semirigid boundary conditions in the context of high-level radioactive waste disposal

Abstract

The corrosion of waste canisters in the deep geological disposal facilities (GDFs) for high-level radioactive waste (HLRW) can generate gas, which escapes from the engineered barrier system through the interfaces between the bentonite buffer blocks and the host rock and those between the bentonite blocks. In this study, a series of water infiltration and gas breakthrough experiments were conducted on granite and on granite–bentonite specimens with smooth and grooved interfaces. On this basis, this study presents new insights and a quantitative assessment of the impact of the interface between clay and host rock on gas transport. As the results show, the water permeability values from water infiltration tests on granite and granite–bentonite samples (10⁻¹⁹–10⁻²⁰ m²) are found to be slightly higher than that of bentonite. The gas permeability of the mock-up samples with smooth interfaces is one order of magnitude larger than that of the mock-up with grooved interfaces. The gas results of breakthrough pressures for the granite and the granite–bentonite mock-up samples are significantly lower than that of bentonite. The results highlight the potential existence of preferential gas migration channels between the rock and bentonite buffer that require further considerations in safety assessment.

Keywords

gas migration / GMZ granite–bentonite interface / low-permeability porous medium / semirigid boundary

References

[1] Agus SS, Schanz T, Fredlund DG. Measurements of suction versus water content for bentonite–sand mixtures. Can Geotech J. 2010; 47: 583-594.

[2] Akgün H, Koçkar MK. Evaluation of a sand bentonite mixture as a shaft/borehole sealing material. Appl Clay Sci. 2018; 164: 34-43.

[3] Alonso EE, Alcoverro J, Coste F, et al. The FEBEX benchmark test: case definition and comparison of modelling approaches. Int J Rock Mech Min Sci. 2005; 42(5/6): 611-638.

[4] Anderson TL. Fracture Mechanics: Fundamentals and Applications. CRC Press; 2017.

[5] Arnedo D, Alonso EE, Olivella S. Gas flow in anisotropic claystone: modelling triaxial experiments. Int J Numer Anal Methods Geomech. 2013; 37: 2239-2256.

[6] Birgersson M, Åkesson M, Hökmark H. Gas intrusion in saturated bentonite: a thermodynamic approach. Phys Chem Earth Parts A/B/C. 2008; 33(Supp 1): S248-S251.

[7] Bonin B, Colin M, Dutfoy A. Pressure building during the early stages of gas production in a radioactive waste repository. J Nucl Mater. 2000; 281(1): 1-14.

[8] Boulin PF, Bretonnier P, Vassil V, Samouillet A, Fleury M, Lombard JM. Sealing efficiency of caprocks: experimental investigation of entry pressure measurement methods. Mar Petrol Geol. 2013; 48: 20-30.

[9] Chen L, Liu YM, Wang J, et al. Investigation of the thermal-hydro-mechanical (THM) behavior of GMZ bentonite in the China-Mock-up test. Eng Geol. 2014; 172: 57-68.

[10] Chen L, Zhao X, Liu J, et al. Progress on rock mechanics research of Beishan granite for geological disposal of high-level radioactive waste in China. Rock Mech Bull. 2023; 2(3):100046.

[11] Chen ZG, Tang CS, Shen Z, Liu YM, Shi B. The geotechnical properties of GMZ buffer/backfill material used in high-level radioactive nuclear waste geological repository: a review. Environ Earth Sci. 2017; 76(7): 270.

[12] Cui L, Ye WM, Wang Q, Chen YG, Chen B, Cui YJ. Insights into determination of gas breakthrough in saturated compacted gaomiaozi bentonite. J Mater Civil Eng. 2020; 32(7):04020190.

[13] Cui LY, Masum SA, Ye WM, Thomas HR. Investigation on gas migration behaviours in saturated compacted bentonite under rigid boundary conditions. Acta Geotech. 2021; 17(6): 2517-2531.

[14] Cui LY, Ye WM, Wang Q, Chen YG, Chen B. Gas breakthrough tests on saturated GMZ01 bentonite using RCP technique with consideration of dry density effect. Japan Geotech Soc Special Publ. 2019; 7(2): 318-322.

[15] Davy C, Skoczylas F, Lebon P, Dubois T. Gas migration properties through a bentonite/argillite interface. Appl Clay Sci. 2009; 42(3/4): 639-648.

[16] Graham J, Halayko KG, Hume H, Kirkham T, Gray M, Oscarson D. A capillarity-advective model for gas break-through in clays. Eng Geol. 2002; 64(2/3): 273-286.

[17] Guo G, Fall M. Modelling of dilatancy-controlled gas flow in saturated bentonite with double porosity and double effective stress concepts. Eng Geol. 2018; 243: 253-271.

[18] Guo J, Liu J, Zhang Q, Cao S, Chen Z. Gas migration properties through saturated bentonite considering the interface effect. Geomech Geophys Geo Energy Geo Res. 2022; 8(2): 66.

[19] Gutiérrez-Rodrigo V, Martín PL, Villar MV. Effect of interfaces on gas breaktrough pressure in compacted bentonite used as engineered barrier for radioactive waste disposal. Process Saf Environ Prot. 2021; 149: 244-257.

[20] Harrington J, Horseman S. Gas Transport Properties of Clays and Mudrocks. 158. Geological Society; 1999: 107-124.

[21] Harrington JF, Horseman ST. Gas Migration in KBS-3 Buffer Bentonite: Sensitive of Test Parameters to Experimental Boundary Conditions (SKB Technical Report, TR-03-02). SKB; 2003.

[22] Harrington JF, Milodowski AE, Graham CC, Rushton JC, Cuss RJ. Evidence for gas-induced pathways in clay using a nanoparticle injection technique. Mineral Mag. 2012; 76(8): 3327-3336.

[23] Kim K, Rutqvist J, Harrington JF, Tamayo-Mas E, Birkholzer JT. Discrete dilatant pathway modeling of gas migration through compacted bentonite clay. Int J Rock Mech Min Sci. 2021; 137:104569.

[24] Liu JF, Cao XL, Ni HY, et al. Numerical modeling of water and gas transport in compacted GMZ bentonite under constant volume condition. Geofluids. 2021; 2021:4290426.

[25] Liu JF, Davy CA, Talandier J, Skoczylas F. Effect of gas pressure on the sealing efficiency of compacted bentonite–sand plugs. J Contam Hydrol. 2014; 170: 10-27.

[26] Liu JF, Guo JN, Ni HY, Zhang Q, Skoczylas F. Swelling and gas transport characteristics of saturated compacted bentonite/sand samples considering the scale effect. Geomech Energy Environ. 2021; 26:100227.

[27] Liu JF, Song SB, Ni HY, et al. Research on gas migration properties in a saturated bentonite/sand mixture under flexible boundary conditions. Soils Found. 2018; 58(1): 97-109.

[28] Liu JF, Song Y, Skoczylas F, Liu J. Gas migration through water-saturated bentonite–sand mixtures, COx argillite, and their interfaces. Can Geotech J. 2016; 53(1): 60-71.

[29] Marschall P, Horseman S, Gimmi T. Characterisation of gas transport properties of the opalinus clay, a potential host rock formation for radioactive waste disposal. Oil Gas Sci Technol. 2005; 60(1): 121-139.

[30] Ogata S, Yasuhara H. Numerical simulations for describing generation of excavation damaged zone: important case study at Horonobe underground research laboratory. Rock Mech Bull. 2023; 2(3):100063.

[31] Ortiz L, Volckaert G, Mallants D. Gas generation and migration in Boom Clay, a potential host rock formation for nuclear waste storage. Eng Geol. 2002; 64(2): 287-296.

[32] Oscarson DW, Hume HB. Diffusion of ¹⁴C in dense saturated bentonite under steady-state conditions. Trans Porous Media. 1994; 14(1): 73-84.

[33] Sato S, Otsuka T, Kuroda Y, Higashihara T, Ohashi H. Diffusion of helium in water-saturated, compacted sodium montmorillonite. J Nucl Sci Technol. 2001; 38(7): 577-580.

[34] Tawara Y, Hazart A, Mori K, et al. Extended two-phase flow model with mechanical capability to simulate gas migration in bentonite. Geol Soc Lond Special Publ. 2014; 400(1): 545-562.

[35] Villar MV, Sánchez M, Gens A. Behaviour of a bentonite barrier in the laboratory: experimental results up to 8 years and numerical simulation. Phys Chem Earth Parts A/B/C. 2008; 33(Supp 1): S476-S485.

[36] Wang J, Chen L, Su R, Zhao X. The Beishan underground research laboratory for geological disposal of high-level radioactive waste in China: planning, site selection, site characterization and in situ tests. J Rock Mech Geotech Eng. 2018; 10(3): 411-435.

[37] Watanabe Y, Yokoyama S. Self-sealing behavior of compacted bentonite–sand mixtures containing technological voids. Geomech Energy Environ. 2021; 25:100213.

[38] Watanabe Y, Yokoyama S, Shimbashi M, Yamamoto Y, Goto T. Saturated hydraulic conductivity of compacted bentonite–sand mixtures before and after gas migration in artificial seawater. J Rock Mech Geotech Eng. 2023; 15(1): 216-226.

[39] Wei T, Hu D, Zhou H, Lu J, Lü T. Influences of degree of saturation and stress cycle on gas permeability of unsaturated compacted Gaomiaozi bentonite. Eng Geol. 2019; 254: 54-62.

[40] Wen ZJ. Physical property of China's buffer material for high-level radioactive waste repositories. Chin J Rock Mech Eng. 2006; 25(4): 794-800.

[41] Wiseall AC, Cuss RJ, Graham CC, Harrington JF. The visualization of flow paths in experimental studies of clay-rich materials. Mineral Mag. 2015; 79(6): 1335-1342.

[42] Xu L, Ye WM, Ye B. Gas breakthrough in saturated compacted GaoMiaoZi (GMZ) bentonite under rigid boundary conditions. Can Geotech J. 2017; 54(8): 1139-1149.

[43] Xu L, Ye WM, Ye B, Chen B, Chen YG, Cui YJ. Investigation on gas migration in saturated materials with low permeability. Eng Geol. 2015; 197: 94-102.

[44] Ye WM, Xu L, Chen B, Chen YG, Ye B, Cui YJ. An approach based on two-phase flow phenomenon for modeling gas migration in saturated compacted bentonite. Eng Geol. 2014; 169: 124-132.

[45] Younglove BA, Hanley HJM. The viscosity and thermal conductivity coefficients of gaseous and liquid argon. J Phys Chem Ref Data1986; 15(4): 1323-1337.

[46] Zhang Q, Xie JL, Cao SF, Gao YF, Cheng JF. The buffer material saturation mechanism under different rock conditions in high-level radioactive waste repository. World Nucl Geosci. 2023; 40(2): 298-308.

RIGHTS & PERMISSIONS

2024 The Author(s). Deep Underground Science and Engineering published by John Wiley & Sons Australia, Ltd on behalf of China University of Mining and Technology.