リチウムまたはナトリウムを含むホウケイ酸塩ガラスの熱水変質過程におけるセシウムとストロンチウムの挙動 -高レベル放射性廃棄物固化体の安定性の評価-

概要

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In order to assess the long-term stability of high-level radioactive waste form, various compositions of lithium and sodium borosilicate glasses containing cesium and strontium have been treated under a hydrothermal condition (200 C and 1.54 MPa) for maximum 6 months. The formed phases are tridymite, low quartz, Li2SiO3, Li2Si2O 5 · xH2O, Li2Si2O5, Li42O5, searlesite (NaBSi2O5(OH) 2), and veatchite (Sr2[B5O8(OH)] 2[B(OH)3] · H2O) including some unidentified phases. The behaviors of cesium and strontium are quite different on the hydrothermal process. Cesium is not included in any of the solid phases. In contrast, strontium is an essential constituent of veatchite. Natural veatchite occurs usually as a constituent of evaporite, and hence the mineral is inferred not to be stable, when groundwater flows into a disposal site. The results suggest, accordingly, that in order to incorporate cesium and strontium into some of forming minerals, another element must be added to the glass composition.
2001-01-25