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Title: X-ray tomography of feed-to-glass transition of simulated borosilicate waste glasses

The feed composition of a high level nuclear waste (HLW) glass melter affects the overall melting rate by influencing the chemical, thermophysical, and morphological properties of a relatively insulating cold cap layer over the molten phase where the primary feed vitrification reactions occur. Data from X ray computed tomography imaging of melting pellets comprised of a simulated high-aluminum HLW feed heated at a rate of 10°C/min reveal the distribution and morphology of bubbles, collectively known as primary foam, within this layer for various SiO 2/(Li 2CO 3+H 3BO 3+Na 2CO 3) mass fractions at temperatures between 600°C and 1040°C. To track melting dynamics, cross-sections obtained through the central profile of the pellet were digitally segmented into primary foam and a condensed phase. Pellet dimensions were extracted using Photoshop CS6 tools while the DREAM.3D software package was used to calculate pellet profile area, average and maximum bubble areas, and two-dimensional void fraction. The measured linear increase in the pellet area expansion rates – and therefore the increase in batch gas evolution rates – with SiO 2/(Li 2CO 3+H 3BO 3+Na 2CO 3) mass fraction despite an exponential increase in viscosity of the final waste glass at 1050°C and a lower totalmore » amount of gas-evolving species suggest that the retention of primary foam with large average bubble size at higher temperatures results from faster reaction kinetics rather than increased viscosity. However, viscosity does affect the initial foam collapse temperature by supporting the growth of larger bubbles. Because the maximum bubble size is limited by the pellet dimensions, larger scale studies are needed to understand primary foam morphology at high temperatures. This temperature-dependent morphological data can be used in future investigations to synthetically generate cold cap structures for use in models of heat transfer within a HLW glass melter.« less
Authors:
ORCiD logo [1] ;  [2] ;  [3] ;  [3] ;  [4] ;  [5] ;  [5] ;  [5]
  1. North Carolina State Univ., Raleigh, NC (United States)
  2. Idaho National Lab. (INL), Idaho Falls, ID (United States)
  3. Academy of Sciences of the Czech Republic (ASCR), Prague (Czech Republic)
  4. Tokyo Inst. of Technology (Japan)
  5. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
Report Number(s):
INL/JOU-16-39470
Journal ID: ISSN 0002-7820; TRN: US1702317
Grant/Contract Number:
AC07-05ID14517
Type:
Accepted Manuscript
Journal Name:
Journal of the American Ceramic Society
Additional Journal Information:
Journal Volume: 100; Journal Issue: 9; Journal ID: ISSN 0002-7820
Publisher:
American Ceramic Society
Research Org:
Idaho National Lab. (INL), Idaho Falls, ID (United States)
Sponsoring Org:
USDOE Office of Nuclear Energy (NE); USDOE Office of Environmental Management (EM)
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; image analysis; pellet melting; waste glass
OSTI Identifier:
1361493
Alternate Identifier(s):
OSTI ID: 1378386