Corrosion of carbon steel in compacted bentonite buffer materials using anaerobic corrosive microbial consortium

圧縮ベントナイト中における鉄腐食性菌叢による炭素鋼の腐食挙動

長岡 亨*; 平野 伸一*; 松本 伯夫*; 天野 由記   

Nagaoka, Toru*; Hirano, Shinichi*; Matsumoto, Norio*; Amano, Yuki

Microbially influenced corrosion of metallic container is one of concerns for nuclear waste disposal. Corrosion of carbon steel buried in compacted bentonite buffer materials was investigated using anaerobic corrosive microbial consortium. The buffer material was composed of 70% bentonite (Kunigel V1) and 30% silicate sand with different dry densities in test cells. Compacted buffer materials were incubated in nutrient medium with or without inoculation for one year at 30C and 50C. Corrosion rates were suppressed (9.4-12.9 mg/cm/year) with compacted densities of 1.3 and 1.6 Mg/m at 50C. In contrast, a high corrosion rate (52.0 mg/cm/year) was observed in the inoculated 1.0 Mg/m compacted buffer materials at 30C, and microbial analysis showed the highest microbial abundance and the high relative ratio of sulfate-reducing bacteria, such as sp.. These results are demonstrated that a sufficiently high dry density is one of the important key factors to suppress microbial activity in buffer material surrounding metallic containers, because of the physical characteristics such as small pores, low water activity, less nutrient supply caused by low hydraulic conductivity.