Application of archaeological analogues for a repository safety case; Arguments supporting the waste container lifetime

Yoshikawa, Hideki; Ueno, Kenichi; Yui, Mikazu

In the Japanese HLW safety case, a carbon steel container (overpack) was designed with a 1000 year lifetime, based on a corrosion allowance of 40 mm derived from laboratory data obtained under anaerobic conditions. Analogue studies have been conducted to increase confidence in the robustness of this design basis. Using X-ray computer tomography (X-CT) to measure corrosion rate, about 40 samples of iron archaeological artifacts, which were found at Japanese ancient monuments after burial underground for a few hundred to one thousand years, were analyzed. The their corrosion rates are more than one order of magnitude less than the design allowance of 40 mm / ka, which supports the argument that the designed corrosion allowance is conservative.