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Abstract
In the framework of a law voted in 1991, it has been decided that the management of French high-level nuclear waste (HLW) should be studied along three main lines: (a) transmutation of actinides in fast breeder reactors, (b) long-term interim storage of waste containers (whether containing vitrified waste or spent fuel elements canisters) for a maximum period of 300 yr, and (c) geological disposal of the containers after the interim storage period.
The last two lines of research, among other problems, bring up the question of the long-term corrosion behavior of the containers. The Commissariat à l’Énergie Atomique (CEA) is in charge of the researches concerning the transmutation of the actinides and the long-term interim storage.
As interim storage is concerned, extended studies are being carried out at the CEA in order to predict the environmental conditions of an interim storage facility and the consequent corrosion of the HLW containers over a period of 300 yr.
A dry corrosion phase of a minimum duration of 100 yr was identified, followed by an atmospheric corrosion phase of a maximum duration of 200 yr. Phenomenological models were developed to obtain an estimate of the total corrosion damage during interim storage.
Results led to a conservative estimate of a corroded thickness of metal comprised between 0.35 and 1 mm, hence, <2% of the wall thickness of the overpacks.
Because of the extended period of time considered, this estimate, partly based on the extrapolation of experimental results, has to be reinforced. Mechanistic modeling of the elementary processes is currently in progress and has already given encouraging results for both the dry and atmospheric corrosion phases.