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Article Dans Une Revue Journal of the American Ceramic Society Année : 2023

Transient melt formation and its effect on conversion phenomena during nuclear waste vitrification – HT‐ESEM analysis

Miroslava Vernerová
  • Fonction : Auteur
Jaroslav Kloužek
  • Fonction : Auteur
Petra Cincibusová
Martina Kohoutková
  • Fonction : Auteur
Radek Pezl
  • Fonction : Auteur
Pavel Ferkl
Pavel Hrma
  • Fonction : Auteur
Renaud Podor
Albert Kruger
  • Fonction : Auteur

Résumé

Abstract Although the vitrification of nuclear waste has a decades‐long history, numerous opportunities still exist to improve its efficiency and to increase the waste loading in glass. This is especially true for the vitrification of low‐activity waste (LAW), which has been historically treated by other immobilization technologies and is less mature than high‐level waste (HLW) vitrification. In this work, we address one of the least understood phenomena during the conversion of nuclear waste feeds to glass—the formation of molten salt and transient glass‐forming melt. Using high‐temperature environmental scanning electron microscopy (HT‐ESEM) in combination with X‐ray diffraction, thermogravimetry, and evolved gas analysis, we have analyzed the complex chemical reactions and phase transitions as they occur during melting of representative HLW and LAW melter feeds. We evaluated the compositions of amorphous phases and the fractions of salt components, and estimated the fractions of molten salt phases present in the feeds as a function of temperature. We show that the maximum fraction of molten salts is ∼4 % and ∼28 % during HLW and LAW feed melting, respectively, and discuss the possibility of molten salt migration in LAW feeds. We also argue that the presence of significant fractions of molten salt phase can hinder the retention of rhenium (and, hence, radioactive technetium), and discuss how the properties of molten salt phase and transient glass‐forming melt are related to primary foam formation and behavior. Finally, we summarize key unanswered questions requiring further research to increase the understanding of the conversion process and enhance the nuclear waste vitrification efficiency.

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Chimie
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Origine : Publication financée par une institution
Licence : CC BY - Paternité

Dates et versions

hal-04487934 , version 1 (20-03-2024)

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Richard Pokorný, Miroslava Vernerová, Jaroslav Kloužek, Petra Cincibusová, Martina Kohoutková, et al.. Transient melt formation and its effect on conversion phenomena during nuclear waste vitrification – HT‐ESEM analysis. Journal of the American Ceramic Society, 2023, 107 (3), pp.1691-1705. ⟨10.1111/jace.19361⟩. ⟨hal-04487934⟩
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