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Alteration of 29Si-doped SON68 borosilicate nuclear waste glass in the presence of near field materials
- Bouakkaz, Rachid, Abdelouas, Abdesselam, El Mendili, Yassine, David, Karine, Grambow, Bernd
- Applied geochemistry 2019 v.111 pp. 104436
- apatite, argillite, calcite, calcium sulfate, clay, corrosion, geochemistry, glass, leaching, magnesium sulfate, magnetite, pyrite, radioactive waste, siderite, silicon, stainless steel
- The leaching of ²⁹Si-doped SON68 French nuclear waste glass was investigated in Callovo-Oxfordian (COx) water in the presence of P235GH stainless steel and COx argillite. Experiments were carried out to understand the effect of near-field materials on the rate of glass dissolution and the migration of ²⁹Si in the claystone core. Tests were performed by using percolation cells containing glass and stainless steel sandwiched between two clay cores in two different combinations: glass/clay at 50 and 90 °C, and glass/steel/clay/at 90 °C. COx water was injected through the percolation cells at 120 bars (solution flow rate 0.05–0.38 mL d⁻¹). Results showed that the presence of steel did not enhance the dissolution rate of the glass despite the retention of ²⁹Si released from the glass on the corrosion products. The glass dissolution rate up to 17 months tends towards 10⁻⁴ and 10⁻³ g m⁻² d⁻¹ at 50 and 90 °C, respectively. The glass alteration in the presence of clay leads to the formation of calcite and Mg-silicates at 50 °C in addition to apatite and powellite at 90 °C. The main steel corrosion products were siderite, magnetite, ferrosilicates, pyrite, pyrrhotite, troilite and mackinawite. MgSO₄ and CaSO₄ were also identified in the presence of steel.