In the context of global warming, nuclear energy is a carbon-free source of power and so is a meaningful option for energy production without CO 2 emissions. Currently, there are more than 440 commercial nuclear reactors, accounting for about 15% of electric power generation in the world, and there has not been a major accident in over 20 years. The world's fleet of nuclear power plants is, on average, more than 20 years old. Even though the design life of a nuclear power plant is typically 30 or 40 years, it is quite feasible that many nuclear power plants will be able to operate for longer than this.

This paper gives an overview of the main corrosion issues related to the French program of the geological disposal of high-level nuclear wastes (HLNW). In addition to summarizing some specifics of the “dossier 2005 Argile” (clay underground repository concept, HLNW mainly composed of glass matrix, etc.), the French approach for the selection of the material (non-alloy steel) of HLNW overpacks is underlined with the combination of experimental work and semi-empirical modeling for estimation of service lifetimes, mechanistically based modeling for more robust and reliable prediction, and the use of archaeological artefacts to provide a database for testing and validating models.

In France, the reference concept for the geological disposal of high-level waste (HLW) consists of horizontal micro-tunnels, containing carbon steel casing and overpacks (around a stainless steel container containing vitrified waste). The overpacks and casing will be exposed to an environment that will evolve over time: from a hot and humid atmosphere containing oxygen, to an anoxic environment saturated with water at the geothermal temperature. Lots of corrosion experiments have been performed in representative environments to study steel corrosion modes (general corrosion, pitting and crevice corrosion, stress corrosion cracking, hydrogen embrittlement…) while taking into account the influence of temperature, radiation, mechanical stresses and microorganisms. Some key results have influenced the design of the HLW disposal cell, including the carbon steel grades and dimensions of the casing and overpacks, or the addition of an alkaline grout material between the casing and the host rock. This paper is part of a supplement on the 6th International Workshop on Long-Term Prediction of Corrosion Damage in Nuclear Waste Systems .