Corrosion of Copper as a Nuclear Waste Container Material in Simulated Anoxic Granitic Groundwater

Copper (Cu) is a candidate material for waste packages in geological disposal systems for high-level radioactive waste in Switzerland, Sweden, Finland, Japan, and Canada. This paper reports experimental tests of Cu in the context of radioactive waste disposal applications. Experimental tests of Cu general corrosion and hydrogen evolution were conducted under anoxic conditions (less than 10 ppb of O₂) using synthetic saline groundwater based on reference compositions of deep groundwaters in crystalline rock of the Canadian Shield. The results indicate that the Cu open-circuit potential and corrosion rates in anoxic waters were very sensitive to the residual O₂ concentration in solution. The corrosion rates ranged from submicrometer to micrometer per year, depending on the residual O₂ concentration level. The corrosion products were predominantly cuprous oxide (Cu₂O). Chlorine was present in corrosion products for tests exposed to synthetic saline groundwater, but more work is needed to assess its role in the corrosion process. Minute amounts of hydrogen were detected from the autoclave as test cell, however, they cannot be simply correlated to Cu corrosion because of complication of the autoclave material corrosion.