High level nuclear waste glass corrosion in synthetic clay pore solution and retention of actinides in secondary phases

• Published in: Journal of nuclear materials Vol. 385; no. 2; pp. 456 - 460
• Main Authors: Bosbach, D., Luckscheiter, B., Brendebach, B., Denecke, M.A., Finck, N.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 31.03.2009; Elsevier
• Subjects: Applied sciences; Controled nuclear fusion plants; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Fuels; Installations for energy generation and conversion: thermal and electrical energy; Nuclear fuels; 61.05.cj; 28.41kw; 91.67Pq; Actinide; Clay; Crystalline phase; X ray absorption spectrometry; Corrosion; Concentration effect; Laser; High level radioactive waste; Fluorescence; Iron; Speciation; Nuclear reactor
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2008.12.044

The corrosion of the simulated high level waste glass GP WAK1 in synthetic clay pore solution was studied in batch-type experiments at 323 and 363K with special focus on the effect of high carbonate concentration in solution. The corrosion rate after 130 days was <10−4gm−2d−1 – no significant effect of the carbonate was identified. During glass corrosion, crystalline secondary phases (powellite, barite, calcite, anhydrite and clay-like Mg(Ca,Fe)-silicates) were formed. To obtain a molecular level picture of radionuclide speciation within the alteration layer, spectroscopic methods have been applied including grazing incidence X-ray absorption spectroscopy (XAS) to study the structural changes in the coordination of uranyl upon alteration layer formation. The number of equatorial oxygen atoms increases from 4 in the bulk glass to 5 in the alteration layer. Furthermore, reduced coordination symmetry was found. Hectorite, a frequently observed secondary clay mineral within the glass alteration layer, was synthesized in the presence of trivalent f-elements (e.g. Eu) and structurally characterized using time-resolved laser fluorescence spectroscopy. Structural incorporation into the octahedral layer is indicated.