Stainless steel and the nickel-base alloy Inconel are metals with nuclear applications, either in power plants or for geological disposal. Inconel 625 is used in steam generators in nuclear power plants. Grade 316L stainless steel is used for reactor internals and is also considered as a candidate containment material for nuclear waste in some geological disposal concepts. In many disposal concepts, highly alkaline cementitious materials are used, either as an immobilization matrix, or as buffer/backfill material. During disposal, conditions eventually will become anoxic due to the consumption of oxygen by e.g. corrosion processes. During the anoxic period, corrosion of Inconel 625 and 316L grade stainless steel will produce hydrogen gas, which may endanger the safety of the underground disposal facility.
Experimental data on the long-term corrosion rate of Inconel 625 and 316L grade stainless steel under highly alkaline and anoxic conditions are scarce. Therefore, at SCK•CEN, an experimental programme was launched with the aim to directly measure the evolved hydrogen gas, allowing us to obtain a precise determination of the low corrosion rates associated with Inconel and stainless steel under highly alkaline and anoxic conditions (oxygen content of less than 10 ppb). Our measurement technique is based on off-line gas chromatography.
In this paper, the results obtained during the first six months of exposure to a cementitious environment (pH 13.5) will be discussed.
stainless steel 316L, Ni alloy Inconel 625, alkaline, corrosion rate, gas chromatography, anoxic