Characteristics of alteration layers formed on simulated HLW glass under silica-saturated solutions

シリカ飽和溶液中にて高レベル放射性廃棄物模擬ガラス表面に形成される変質層の特性

前田 敏克; 堀田 克敏*; 臼井 秀雄; 馬場 恒孝

Maeda, Toshikatsu; Hotta, Katsutoshi*; Usui, Hideo; Bamba, Tsunetaka

Static corrosion tests were conducted for simulated HLW glass in silica saturated solutions, and the characteristics of alteration layers formed on the glass were investigated. The depth profiles of elements at the surface of corroded glass were observed by use of SIMS. In each pH condition, alteration layer formed at the glass surface, where soluble elements such as B (boron) and Na depleted, while Si and Al remained to an equal degree of that in pristine glass. The thickness of the layer increased with decrease in solution pH. It is consistent with a hypothesis that ion exchange by oxonium ion controls the glass dissolution rate under near-saturated condition. On the other hand, the thickness of the layer was not proportionate to time and the growth rate decreased with time, providing that diffusive mass transfer in alteration layer contribute to as a rate limiting reaction.