Challenges with vitrification of Hanford High-Level Waste (HLW) to borosilicate glass – An overview

Goel, Ashutosh; McCloy, John S.; Pokorný, Richard; Kruger, Albert A.

doi:10.1016/j.nocx.2019.100033

Cited by 94 publications

(149 citation statements)

References 121 publications

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“…1 In the United States, Al-rich high-level tank waste (HLW) will be vitrified at the Hanford Tank Waste Treatment and Immobilization Plant (WTP), where alumina interacts with chromium, nickel, manganese, iron, and zinc to form spinel in the melter. [2][3][4] This poses challenges to nuclear waste vitrification operations where spinel formation can reduce the efficiency of melters and lead to operational problems. 5,6 Additionally, glasses developed for HLW immobilization are expected to meet specific durability standards.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Al:Si and (Al + Na):Si ratios on the properties of the international simple glass, part II: Structure

Reiser

Parruzot

et al. 2020

J. Am. Ceram. Soc.

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High-alumina containing high-level waste (HLW) will be vitrified at the Waste Treatment Plant at the Hanford Site. The resulting glasses, high in alumina, will have distinct composition-structure-property (C-S-P) relationships compared to previously studied HLW glasses. These C-S-P relationships determine the processability and product durability of glasses and therefore must be understood. The main purpose of this study is to understand the detailed structural changes caused by Al:Si and (Al + Na):Si substitutions in a simplified nuclear waste model glass (ISG, international simple glass) by combining experimental structural characterizations and molecular dynamics (MD) simulations. The structures of these two series of glasses were characterized by neutron total scattering and 27 Al, 23 Na, 29 Si, and 11 B solid-state nuclear magnetic resonance (NMR) spectroscopy. Additionally, MD K E Y W O R D S aluminosilicates, borosilicate glass, international simple glass, molecular dynamics, nuclear magnetic resonance, scattering F I G U R E 1 Neutron total scattering structure factor spectra obtained from (A-B) experimental data and (C-D) MD simulation for (A, C) ISG-An and (B, D) ISG-AnN glasses.

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Section: Introductionmentioning

confidence: 99%

“…Si-[NBO] (Na + ), [3] B-[NBO] (Na + ), [4] B (mostly Ca 2+ ), [4] Al (nearly equally split Na + and Ca 2+ ), and [6] Zr (mostly Ca 2+ ). The network former-BO-network former linkages preferences were also tabulated; Si-O-Al and Al-O-Al were preferred at the expense of lower Si-O- [3] B and [3] B-O- [3] B linkages.…”

mentioning

confidence: 99%

Effects of Al:Si and (Al + Na):Si ratios on the properties of the international simple glass, part II: Structure

Reiser

Parruzot

et al. 2020

J. Am. Ceram. Soc.

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“…Although this processing constraint has been successfully used to ensure that HLW glasses processed through the Defense Waste Processing Facility (DWPF) display comparatively low leaching (ie, high chemical durability), it may also unnecessarily restrict waste loading, contributing to excessive life‐cycle duration and associated costs. While targeted waste loadings at DWPF are around 36 wt% 6 and are generally limited by other constraints (eg, liquidus temperature, viscosity, etc), 7 the HLW at Hanford contains significantly higher concentrations of Al 2 O 3 , 8 which limits the projected waste loading of a large portion of the glass processed through WTP to ~18 wt% if the ND constraint is applied 3,9 . Because of this reality, much research in the last decade has focused on understanding the factors that contribute to nepheline (NaAlSiO 4 ) formation in waste glasses containing relatively high levels of sodium and aluminum, in an attempt to find composition regions that are resilient to nepheline formation without adhering to the current ND 9‐12 .…”

Section: Introductionmentioning

confidence: 99%

Nepheline crystallization and the residual glass composition: Understanding waste glass durability

McClane

Amoroso

Fox

et al. 2020

Int J of Appl Glass Sci

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The vast majority of High‐Level Waste (HLW) originating from defense nuclear programs is sequestered and immobilized in borosilicate glass. Borosilicate glass is universally accepted for immobilizing HLW, but its efficiency has limitations based on the compositional makeup of the waste stream. The chemical durability of the glass is the most important factor in determining the longevity and usefulness of the final glass waste form. The primary detriment to this durability in glasses containing high levels of aluminum is nepheline (NaAlSiO4) crystallization, as it is generally accompanied by a measurable decrease in the glass's chemical durability. This work seeks to understand nepheline crystallization, within the context of thermal history, and to elucidate the influence of compositional shifts in the residual glass (after crystallization) on the measured durability. The results presented within show a distinct deviation in leaching behavior as a function of structural makeup (calculated Q units). This understanding will provide practical information required for broadening glass compositional regions needed to more efficiently vitrify HLW.

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“…Figure shows the deconvolutions on a few select compositions. As sulfur was added, the intensity of the Q 1 and Q 3 (1075/cm) units remained somewhat invariant after the initial SO 3 loading, whereas Q 2 (1015/cm) units decreased and Q 4 (1150/cm) units increased continuously with increasing SO 3 loading. The ratio of (Q 3 + Q 4 )/(Q 1 + Q 2 ) increased with increasing SO 3 additions, as shown in Table , indicating the overall Si–O network was polymerizing.…”

Section: Resultsmentioning

confidence: 93%

“…Safe storage of nuclear waste is an ongoing technical challenge that becomes more important with each passing year, in particular for the cleanup of the Hanford site in southeast Washington State, USA. 1 The processes for creating and extracting plutonium for nuclear weapons were performed at this site for 45 years, and ultimately led to the production of over 200 000 m 3 of radioactive waste now stored in 177 underground tanks. These tanks were not designed for longterm storage, and multiple tanks have started leaking radioactive waste into the ground.…”

Section: Motivationmentioning

confidence: 99%

Thermal properties of sodium borosilicate glasses as a function of sulfur content

et al. 2020

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Sulfur trioxide (SO3) additions, up to 3.0 mass%, were systematically investigated for effects on the physical properties of sodium borosilicate glass melted in air, with a sulfur‐free composition of 50SiO2–10Al2O3–12B2O3–21Na2O–7CaO (mass%). Solubility measurements, using electron microscopy chemical analysis, determined the maximum loading to be ~1.2 mass% SO3. It was found that measured sulfur (here as sulfate) additions up to 1.18 mass% increased the glass transition temperature by 3%, thermal diffusivity by 11%, heat capacity by 10%, and thermal conductivity by 20%, and decreased the mass density by 1%. Structural analysis, performed with Raman spectroscopy, indicated that the borosilicate network polymerized with sulfur additions up to 3.0 mass%, presumably due to Na2O being required to charge compensate the ionic SO42- additions, thus becoming unavailable to form non‐bridging oxygen in the silicate network. It is postulated that this increased cross‐linking of the borosilicate backbone led to a structure with higher dimensionality and average bond energy. This increased the mean free paths and vibration frequency of the phonons, which resulted in the observed increase in thermal properties.

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Challenges with vitrification of Hanford High-Level Waste (HLW) to borosilicate glass – An overview

Cited by 94 publications

References 121 publications

Effects of Al:Si and (Al + Na):Si ratios on the properties of the international simple glass, part II: Structure

Effects of Al:Si and (Al + Na):Si ratios on the properties of the international simple glass, part II: Structure

Nepheline crystallization and the residual glass composition: Understanding waste glass durability

Thermal properties of sodium borosilicate glasses as a function of sulfur content

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