Hydraulic conductivity and specific storage of bentonite following prolonged thermal exposure

The scope of this study was to determine the hydraulic properties of a specimen of bentonite which had previously been exposed to elevated temperatures during the Canister Retrieval Test (CRT) performed at the Äspö Hard Rock Laboratory. A series of well-constrained hydraulic measurements were performed on a specimen of compact bentonite, that had been situated close to the canister, yielded a mean hydraulic conductivity of 4.77x10-14 m/s (standard deviation = 0.49 x10-14 m/s) using fluxes ranging from 1.6 to 4.6 µl/h and a mean specific storage coefficient for the same range of flux of 1.64x10-5 m-1 (standard deviation = 0.61 x10 5 m-1). Data from this study are in close agreement with observations for unaltered saturated bentonite. Based on these observations, the BGS find no evidence for an adverse increase in hydraulic conductivity of bentonite as a result of its exposure to temperatures up about 80ºC for around 5 years.