Effects of Ba(NO3)2 content on yellow phase formation and chemical durability of vitrified waste glass

Lian, Qihui; Zhang, Zhuangsen; Wang, Bin; Ying, Yao; Zhao, Xiaofeng; Wu, Lei

doi:10.1016/j.jnoncrysol.2022.121933

Cited by 2 publications

(2 citation statements)

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“…The residual low-density salt phase consisting of sulfates, chromates, and molybdates tends to segregate from the glass melt, forming the so-called "yellow phase", the formation of which limits the waste loading in the glass. Yellow phase has been a topic of research around the world, including the US, [75][76][77][78] France, 79,80 Japan, 81,82 the UK, 83,84 and also China, [85][86][87][88] where first waste vitrification facilities have recently been constructed and will need to immobilize nuclear waste containing significant concentrations of sulfate. Significant advancements have been achieved, for example showing that the salt segregation can be suppressed by the redistribution of oxides from the original glass frit to the waste simulant, by glass composition reformulation, or by milling the frit into powder, but, as a recent review noted, an industrial solution has not yet been implemented.…”

Section: Segregation Of Molten Salts Yellow Phase Formationmentioning

confidence: 99%

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

Pokorný,

Vernerová,

Kloužek

et al. 2023

J Am Ceram Soc.

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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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Section: Segregation Of Molten Salts Yellow Phase Formationmentioning

confidence: 99%

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

Pokorný,

Vernerová,

Kloužek

et al. 2023

J Am Ceram Soc.

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“…to sequester sulfate anions as BaSO 4 from simulated Hanford LAW solutions. In our previous work, 20,21 SO 4 2− ions present in the simulated HLW as Na 2 SO 4 can be sequestrated in the form of BaSO 4 by adding Ba(NO 3 ) 2 solution, and the formation of the yellow phase can be effectively reduced during vitrification.…”

Section: Introductionmentioning

confidence: 97%

In situ study of microstructural evolution of borosilicate glass–sulfate mixture at high temperatures

Lian,

Yao,

Jiang

et al. 2024

J Am Ceram Soc.

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Microstructural evolution of borosilicate glass–sulfate (BaSO4 or Na2SO4) mixture was observed in situ using a high‐temperature confocal scanning laser microscope. The phase compositions and sulfate retention of the mixture at different temperatures were also examined. The results indicate that for the glass–BaSO4 sample (abbreviated as BS), the borosilicate glass begins to melt at about 900°C, and the triangular BaSO4 crystals grow obviously between 900°C and 1100°C. At temperatures above 1100°C, the BaSO4 crystals gradually melt and decompose. For the glass–Na2SO4 sample (abbreviated as NS), strip‐shaped BaSO4 crystals begin to form at about 820°C after the borosilicate glass melting, and then gradually melt with further increasing temperature. When the temperature increases to 1000°C, the upper layer of the NS sample possesses Na2SO4, LiNaSO4, and BaSO4 phases, while the lower layer possesses an amorphous phase. Moreover, the SO3 retention in the BS sample remains almost unchanged with temperature increases from 900°C to 1100°C, and then decreases with further increasing temperature. The SO3 retention retained in the NS sample decreases rapidly at temperatures above 900°C. These findings can provide a guidance for vitrifying sulfur‐rich high‐level liquid waste.

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Effects of Ba(NO3)2 content on yellow phase formation and chemical durability of vitrified waste glass

Cited by 2 publications

References 30 publications

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

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

In situ study of microstructural evolution of borosilicate glass–sulfate mixture at high temperatures

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