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Title: Conversion of nuclear waste to molten glass: Formation of porous amorphous alumina in a high-Al melter feed

Abstract

The transition of Al phases in a simulated high-Al high-level nuclear waste melter feed heated at 5 K min-1 to 700°C was investigated with transmission electron microscopy, 27Al nuclear magnetic resonance spectroscopy, the Brunauer-Emmett-Teller method, and X-ray diffraction. At temperatures between 300 and 500°C, porous amorphous alumina formed from the dehydration of gibbsite, resulting in increased specific surface area of the feed (~8 m2 g-1). The high-surface-area amorphous alumina formed in this manner could potentially stop salt migration in the cold cap during nuclear waste vitrification.

Authors:
ORCiD logo; ; ; ; ORCiD logo
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1340744
Report Number(s):
PNNL-SA-118421
Journal ID: ISSN 0022-3115; 39392; 830403000
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Nuclear Materials; Journal Volume: 483; Journal Issue: C
Country of Publication:
United States
Language:
English
Subject:
Nuclear waste vitrification; amorphous alumina; high-Al HLW; Environmental Molecular Sciences Laboratory

Citation Formats

Xu, Kai, Hrma, Pavel, Washton, Nancy, Schweiger, Michael J., and Kruger, Albert A.. Conversion of nuclear waste to molten glass: Formation of porous amorphous alumina in a high-Al melter feed. United States: N. p., 2017. Web. doi:10.1016/j.jnucmat.2016.11.005.
Xu, Kai, Hrma, Pavel, Washton, Nancy, Schweiger, Michael J., & Kruger, Albert A.. Conversion of nuclear waste to molten glass: Formation of porous amorphous alumina in a high-Al melter feed. United States. doi:10.1016/j.jnucmat.2016.11.005.
Xu, Kai, Hrma, Pavel, Washton, Nancy, Schweiger, Michael J., and Kruger, Albert A.. Sun . "Conversion of nuclear waste to molten glass: Formation of porous amorphous alumina in a high-Al melter feed". United States. doi:10.1016/j.jnucmat.2016.11.005.
@article{osti_1340744,
title = {Conversion of nuclear waste to molten glass: Formation of porous amorphous alumina in a high-Al melter feed},
author = {Xu, Kai and Hrma, Pavel and Washton, Nancy and Schweiger, Michael J. and Kruger, Albert A.},
abstractNote = {The transition of Al phases in a simulated high-Al high-level nuclear waste melter feed heated at 5 K min-1 to 700°C was investigated with transmission electron microscopy, 27Al nuclear magnetic resonance spectroscopy, the Brunauer-Emmett-Teller method, and X-ray diffraction. At temperatures between 300 and 500°C, porous amorphous alumina formed from the dehydration of gibbsite, resulting in increased specific surface area of the feed (~8 m2 g-1). The high-surface-area amorphous alumina formed in this manner could potentially stop salt migration in the cold cap during nuclear waste vitrification.},
doi = {10.1016/j.jnucmat.2016.11.005},
journal = {Journal of Nuclear Materials},
number = C,
volume = 483,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2017},
month = {Sun Jan 01 00:00:00 EST 2017}
}
  • During nuclear waste vitrification, a melter feed (generally a slurry-like mixture of a nuclear waste and various glass forming and modifying additives) is charged into the melter where undissolved refractory constituents are suspended together with evolved gas bubbles from complex reactions. Knowledge of flow properties of various reacting melter feeds is necessary to understand their unique feed-to-glass conversion processes occurring within a floating layer of melter feed called a cold cap. The viscosity of two low-activity waste (LAW) melter feeds were studied during heating and correlated with volume fractions of undissolved solid phase and gas phase. In contrast to themore » high-level waste (HLW) melter feed, the effects of undissolved solid and gas phases play comparable roles and are required to represent the viscosity of LAW melter feeds. This study can help bring physical insights to feed viscosity of reacting melter feeds with different compositions and foaming behavior in nuclear waste vitrification.« less
  • The rate of batch-to-glass conversion is a primary concern for the vitrification of nuclear waste, as it directly influences the life cycle of the cleanup process. This study describes the development of an advanced model of the cold cap, which augments the previous model by further developments on the structure and the dynamics of the foam layer. The foam layer on the bottom of the cold cap consists of the primary foam, cavities, and the secondary foam, and forms an interface through which the heat is transferred to the cold cap. Other model enhancements include the behavior of intermediate crystallinemore » phases and the dissolution of quartz particles. The model relates the melting rate to feed properties and melter conditions, such as the molten glass temperature, foaminess of the feed, or the heat fraction supplied to the cold cap from the plenum space. The model correctly predicts a 25% increase in melting rate when changing the alumina source in the melter feed from Al(OH)3 to AlO(OH). It is expected that this model will be incorporated in the full glass melter model as its integral component.« less
  • Gases evolve from nuclear waste melter feed during conversion to glass in response to heating. This article is focused on oxygen mass balance based on the stoichiometry of feed melting reactions and evolved-gas analysis data. Whereas O 2-producing and -consuming batch-melting reactions are complete in the reacting and primary-foam layers of the cold cap, O 2 from redox reactions continues to evolve as long as melt temperature increases, and thus generates secondary foam. Also, we discuss the relationship between the oxygen mass balance and the temperature-dependent iron redox ratio and the O 2 partial pressure, as they evolve during themore » feed-to-glass conversion.« less