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Title: The Controversial Role of Inter-diffusion in Glass Alteration

Abstract

Current kinetic models for nuclear waste glasses (e.g. GM2001, GRAAL) are based on a set of mechanisms that have been generally agreed upon within the international waste glass community. These mechanisms are: hydration of the glass, ion exchange reactions (the two processes are referred as inter-diffusion), hydrolysis of the silicate network, and condensation/precipitation of partly or completely hydrolyzed species that produces a porous and amorphous layer and crystalline phases on surface of the altered glass. Recently, a new idea with origins in the mineral dissolution community has been proposed that excludes inter-diffusion process as a potential rate-limiting mechanism. To understand how the so-called interfacial dissolution/precipitation model can change the current understanding of glass behavior, a key experiment used to account for this model was replicated to further revisit the interpretation. This experiment was performed at 50°C, with SON68 glass, in static mode, deionized water and S/V ratio of 10 m-1 for 6 months. It turn out that glass alters in an intermediate kinetic regime between the forward and the residual rate. According to previous and new solid characterizations, it is concluded that neither a simple inter-diffusion model nor the interfacial dissolution precipitation model can account for the observed elemental profilesmore » within the alteration layer. More generally, far and close-to-saturation conditions must be distinguished and literature provides evidences that inter-diffusion takes place in slightly acidic conditions and far from saturation. However, closer to saturation, when a sufficiently dense layer is formed, a new approach is proposed requiring a full description of chemical reactions taking place within the alteration layer and involving water molecules as it is thought that water accessibility to the pristine glass is the rate-limiting process.« less

Authors:
; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1339831
Report Number(s):
PNNL-SA-118572
Journal ID: ISSN 0009-2541
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Chemical Geology
Additional Journal Information:
Journal Volume: 440; Journal ID: ISSN 0009-2541
Publisher:
Elsevier
Country of Publication:
United States
Language:
English

Citation Formats

Gin, Stephane, Neill, Lindsay, Fournier, M., Frugier, Pierre, Ducasse, T., Tribet, M., Abdelouas, Abdessalam, Parruzot, Benjamin, Neeway, James J., and Wall, Nathalie. The Controversial Role of Inter-diffusion in Glass Alteration. United States: N. p., 2016. Web. doi:10.1016/j.chemgeo.2016.07.014.
Gin, Stephane, Neill, Lindsay, Fournier, M., Frugier, Pierre, Ducasse, T., Tribet, M., Abdelouas, Abdessalam, Parruzot, Benjamin, Neeway, James J., & Wall, Nathalie. The Controversial Role of Inter-diffusion in Glass Alteration. United States. doi:10.1016/j.chemgeo.2016.07.014.
Gin, Stephane, Neill, Lindsay, Fournier, M., Frugier, Pierre, Ducasse, T., Tribet, M., Abdelouas, Abdessalam, Parruzot, Benjamin, Neeway, James J., and Wall, Nathalie. Tue . "The Controversial Role of Inter-diffusion in Glass Alteration". United States. doi:10.1016/j.chemgeo.2016.07.014.
@article{osti_1339831,
title = {The Controversial Role of Inter-diffusion in Glass Alteration},
author = {Gin, Stephane and Neill, Lindsay and Fournier, M. and Frugier, Pierre and Ducasse, T. and Tribet, M. and Abdelouas, Abdessalam and Parruzot, Benjamin and Neeway, James J. and Wall, Nathalie},
abstractNote = {Current kinetic models for nuclear waste glasses (e.g. GM2001, GRAAL) are based on a set of mechanisms that have been generally agreed upon within the international waste glass community. These mechanisms are: hydration of the glass, ion exchange reactions (the two processes are referred as inter-diffusion), hydrolysis of the silicate network, and condensation/precipitation of partly or completely hydrolyzed species that produces a porous and amorphous layer and crystalline phases on surface of the altered glass. Recently, a new idea with origins in the mineral dissolution community has been proposed that excludes inter-diffusion process as a potential rate-limiting mechanism. To understand how the so-called interfacial dissolution/precipitation model can change the current understanding of glass behavior, a key experiment used to account for this model was replicated to further revisit the interpretation. This experiment was performed at 50°C, with SON68 glass, in static mode, deionized water and S/V ratio of 10 m-1 for 6 months. It turn out that glass alters in an intermediate kinetic regime between the forward and the residual rate. According to previous and new solid characterizations, it is concluded that neither a simple inter-diffusion model nor the interfacial dissolution precipitation model can account for the observed elemental profiles within the alteration layer. More generally, far and close-to-saturation conditions must be distinguished and literature provides evidences that inter-diffusion takes place in slightly acidic conditions and far from saturation. However, closer to saturation, when a sufficiently dense layer is formed, a new approach is proposed requiring a full description of chemical reactions taking place within the alteration layer and involving water molecules as it is thought that water accessibility to the pristine glass is the rate-limiting process.},
doi = {10.1016/j.chemgeo.2016.07.014},
journal = {Chemical Geology},
issn = {0009-2541},
number = ,
volume = 440,
place = {United States},
year = {2016},
month = {11}
}