Investigation of the long term corrosion resistance of the overpack FY2006 (Contract research)

Tachikawa, Hirokazu*; Kawakubo, Fumie*; Shimizu, Akihiko*; Shibata, Toshio*; Azumi, Kazuhisa*; Inoue, Hiroyuki*; Sugimoto, Katsuhisa*; Tsuru, Toru*; Fujimoto, Shinji*

JAEA-Research 2007-086, 74 Pages, 2008/02

JAEA-Research-2007-086.pdf:5.96MB

The corrosion life time of the overpack has been investigated on the basis of experimental data and past research, assuming the ranging geological environment of Japan. However, some subject for the realization of the overpack design, such as the behavior of the overpack under high pH conditions, the behavior of the overpack with change of near-field environmental condition and the corrosion behavior of the welds have still been left. To take into account these conditions, expert committee composed of metal corrosion science experts were established in the Nuclear Safety Research Association and past research outcomes and the theory of safety assessment for long term corrosion resistance were investigated from the view points of metal corrosion science.

In-situ corrosion monitoring of Cu foil immersed in bentonite-contact solutions

Azumi, Kazuhisa*; Yajima, Jungo*; Nagai, Yuto*; Watanabe, Masatoshi; Taniguchi, Naoki; Shimizu, Akihiko*

no journal, , 

Copper have been considered for one of the candidates for container material for vitrified radioactive waste and has been thought to be corroded in the deep underground at the initial stage of underground depository. The underground water contains various ions including small amount of silica. In this study, corrosion rates of Cu foil immersed in various solutions with and without dissolved silica were monitored by using temperature-compensated resistometry and the foil surfaces were observed by using FE-SEM. It was found to suppress the corrosion of Cu foil with very small amount of dissolved silica in comparison to without silica. From Raman spectra of Cu samples, main corrosion product of these samples without dissolved silica solution was speculated to be CuO. However, the sample corroded in the solution with dissolved silica showed strong Raman peak, which seems to be indicate that the flat deposits were a kind of silicate with electric insulator property. Such silicate deposits might be swelled in the aqueous solution and were expected to suppress dissolution process of Cu ions.