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Title: Monte Carlo simulations of coupled diffusion and surface reactions during the aqueous corrosion of borosilicate glasses

Borosilicate nuclear waste glasses develop complex altered layers as a result of coupled processes such as hydrolysis of network species, condensation of Si species, and diffusion. However, diffusion has often been overlooked in Monte Carlo models of the aqueous corrosion of borosilicate glasses. Therefore, in this paper three different models for dissolved Si diffusion in the altered layer were implemented in a Monte Carlo model and evaluated for glasses in the compositional range (75 - x) mol% SiO2 (12.5 + x/2) mol% B2O3 and (12.5 + x/2) mol% Na2O, where 0 ≤ x ≤ 20%, and corroded in static conditions at a surface-area-to-volume ratio of 1000 m-1. The three models considered instantaneous homogenization (M1), linear concentration gradients (M2), and concentration profiles determined by solving Fick's 2nd law using a finite difference method (M3). Model M3 revealed that concentration profiles in the altered layer are not linear and show changes in shape and magnitude as corrosion progresses, unlike those assumed in model M2. Furthermore, model M3 showed that, for borosilicate glasses with a high forward dissolution rate compared to the diffusion rate, the gradual polymerization and densification of the altered layer is significantly delayed compared to models M1 and M2. Finally,more » models M1 and M2 were found to be appropriate models only for glasses with high release rates such as simple borosilicate glasses with low ZrO2 content.« less
Authors:
 [1] ;  [2] ;  [3]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Fundamental and Computational Sciences Directorate
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Energy and Environmental Sciences Directorate
  3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Energy and Environment Directorate
Publication Date:
OSTI Identifier:
1286710
Grant/Contract Number:
AC05-00OR22725; AC05-76RL01830
Type:
Accepted Manuscript
Journal Name:
Journal of Non-Crystalline Solids
Additional Journal Information:
Journal Volume: 408; Journal ID: ISSN 0022-3093
Publisher:
Elsevier
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org:
USDOE Office of Nuclear Energy (NE); USDOE Office of Environmental Management (EM); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
97 MATHEMATICS AND COMPUTING; 36 MATERIALS SCIENCE Monte Carlo; Borosilicate glasses; Diffusion; Alteration layer; Kinetics