Corrosivity of different natural groundwaters from repository sites

In Finland, the repositories for low and intermediate-level waste (LLW and ILW) are situated at three different geographical locations in deep granite bedrock where the waste containers can be subjected to anoxic groundwater containing microbes. The composition of groundwater varies in terms of chemistry and microbial activity in different locations. In this study, groundwater from three repository areas was analyzed in respect of chemistry and microbial community. Corrosion tendency of three steel grades, carbon steel AISI/SAE 1005 and stainless steels AISI 304 and 316L, was studied in these groundwater environments using electrochemical methods. As a reference, measurements were also performed in simulated groundwater without microbes. The measurements show that corrosivity of the water and thus the steels’ performance differs depending on its location of origin. Also, the groundwater differed remarkably in in their chemical composition as well as abundance and diversity of microbial community. Consequently, the local environment has to be considered when evaluating the long-term safety of disposal of nuclear waste.