Prediction of corrosion products of iron at a low‐level radioactive waste disposal facility in Japan

Abstract

Estimation of the volumetric expansion ratio due to the corrosion of metals is an essential part of the safety assessment of low‐level radioactive waste disposal facilities in Japan, because such volumetric expansion can disrupt the barrier function of these facilities. In the present study, the corrosion products of iron were predicted from potential–pH diagrams and the results of a synthesis test, and the volumetric expansion ratios of the corrosion products were evaluated. Under a basic set of conditions expected at a disposal facility over a storage period of a thousand to tens of thousands of years, Fe3O4, Fe2O3, and FeOOH were predicted as the major stable corrosion products of iron. The maximum volumetric expansion ratio determined from the true density of these products was 2.9, and the maximum volumetric expansion ratio, assuming the generation of voids in the corrosion products, was 3.7, which is the Pilling–Bedworth ratio of Fe(OH)2. The volumetric expansion ratio may increase in the presence of carbonate ions in a long‐term environment with a reduced pH.