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Abstract
The textural characteristics of engineered clay barriers of deeply buried radioactive waste repositories are likely to change in response to hydro-thermo-mechanical stresses during the 10 000-year service and risk analysis period. Expected textural changes stem from a combination of processes, the most significant of which is smectite illitization. To pose significant risks of radionuclide release from buried waste canisters, illitization must, as a minimum, produce barrier textural changes that are significant within the timeframe in which radioactive activity is still significant. Besides, the canister must be damaged, principally through corrosion by substance-laden infiltrating moisture. In the current paper, simulations of three scenarios of illitization of a clay barrier that is initially 100% smectite under a temperature regime that does not exceed 150°C indicate that the accumulation of potassium ions () borne by infiltrating water close to the waste canister is likely to be insignificant within the first 1000 years of waste entombment. Some
are extracted from the infiltrating moisture to feed the illitization reaction which is herein assumed to occur with an activation energy of 1.17 × 10−5 J/mole.