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Journal Articles Journal of Nuclear Materials Year : 2022

Water uptake-induced pressure development by French bituminized radioactive waste products in nearly constant volume conditions

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Abstract

In this paper, the water uptake and leaching behavior of two simulated French Bituminized Waste Products (BWP) has been investigated in nearly constant volume conditions. The resulting pressure development was monitored over approximately half a decade for two BWP samples, varying one from the other by their inorganic load and composition. Pressure development induced by water uptake is mainly the result of (1) an osmotic phenomenon due to the presence of soluble salts (e.g. NaNO3) surrounded by bitumen and (2) recrystallization of the poorly soluble Na2SO4 into its decahydrate form. Differences are found in the pressure generation rate of the two studied simulated French BWP, though a much larger difference is seen when comparing the results of the French BWP to Belgian BWP, i.e. Eurobitum. The higher pressure increase rate in the French BWPs can be attributed to the differences in the soluble salt content, the inorganic load, the content of recrystallizing salts, but also to the presence of insoluble salts such BaSO4, which seems to facilitate the water uptake rate in the French BWP. The faster hydration in French BWP results in a larger fraction of salts becoming available for osmosis and recrystallization within a relatively short time frame, thereby explaining the faster pressure generation. Furthermore, the preferential pathways for water ingress along the BaSO4 crystals seem to be unavailable, or only to a lesser extent, for out-diffusion of dissolved salts, possibly due to partial blockage by other insoluble salts. After a certain hydration period, the pressure stabilizes when the pressure generating phenomena are fully counteracted by the leaching of soluble salts through out-diffusion, reconsolidation of pores in highly leached parts of the BWP, and/or some creep of the BWP into voids. For one of the French BWP, this already occurred after ~1 year of hydration.
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Dates and versions

cea-03617086 , version 1 (23-03-2022)

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Jean-Baptiste Champenois, Arnaud Poulesquen, Joseph Lautru, Nele Bleyen, Steven Smets, et al.. Water uptake-induced pressure development by French bituminized radioactive waste products in nearly constant volume conditions. Journal of Nuclear Materials, 2022, 561, pp.127741. ⟨10.1016/j.matlet.2020.127741⟩. ⟨cea-03617086⟩
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