Development of Crystal‐Tolerant Waste Glasses

Matyáš, Josef; Vienna, John D.; Kimura, Akihiko; Schaible, Micah J.; Tate, Rachel M.

doi:10.1002/9780470930991.ch5

Cited by 26 publications

(26 citation statements)

References 8 publications

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“…Three glasses were formulated from previously used baseline glass 2 by varying component fractions of NiO, Fe 2 O 3 , and Cr 2 O 3 . The remaining components were kept in the same proportions as in the baseline glass.…”

Section: Methodsmentioning

confidence: 99%

“…1 The major factor limiting waste loading in Hanford high-level waste (HLW) glasses is the precipitation, growth, and subsequent accumulation of spinel crystals [Fe, Ni, Mn, Zn, Sn][Fe, Cr] 2 O 4 in the glass discharge riser of the melter during idling. 2,3 These crystals can reach a size of a few hundreds of micrometers and because of their high density (~5.3 × 10 3 kg/m 3 ) settle down fast, forming a thick sludge layer that prevents the discharge of the molten glass into stainless steel canisters.…”

Section: Introductionmentioning

confidence: 99%

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The Effects of Glass Doping, Temperature and Time on the Morphology, Composition, and Iron Redox of Spinel Crystals

Matyáš

Amonette

Kukkadapu

et al. 2014

Ceramic Transactions Series

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Precipitation of large crystals/agglomerates of spinel and their accumulation in the pour spout riser of a Joule-heated ceramic melter during idling can plug the melter and prevent pouring of molten glass into canisters. Thus, there is a need to understand the effects of spinel-forming components, temperature, and time on the growth of crystals in connection with an accumulation rate. In our study, crystals of spinel [Fe, Ni, Mn, Zn, Sn][Fe, Cr] 2 O 4 were precipitated from simulated high-level waste borosilicate glasses containing different concentrations of Ni, Fe, and Cr by heat treating at 850 and 900°C for different times. These crystals were extracted from the glasses and analyzed with scanning electron microscopy and image analysis for size and shape, with inductively coupled plasma-atomic emission spectroscopy and atom probe tomography for concentration of spinel-forming components, and with wet colorimetry and Mössbauer spectroscopy for Fe 2+ /Fe total ratio. High concentrations of Ni, Fe, and Cr in glasses resulted in the precipitation of crystals larger than 100 µm in just two days. Crystals were a solid solution of NiFe 2 O 4 , NiCr 2 O 4 , and ɤ-Fe 2 O 3 (identified only in the high-Ni-Fe glass) and also contained small concentrations of less than 1 at% of Li, Mg, Mn, and Al. INTRODUCTIONThe U.S. Department of Energy is building the Waste Treatment and Immobilization Plant at the Hanford Site in Washington State to remediate 55 million gallons of radioactive waste that is being temporarily stored in 177 underground tanks. The plan is to vitrify the waste into a durable borosilicate glass with Joule-heated ceramic melters. To do this efficiently and costeffectively, the waste loading in the glasses must be maximized.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Effects of Glass Doping, Temperature and Time on the Morphology, Composition, and Iron Redox of Spinel Crystals

Matyáš

Amonette

Kukkadapu

et al. 2014

Ceramic Transactions Series

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“…At this temperature, a significant volume of large octahedral crystals of spinel [Fe, Ni, Mn, Zn][Fe, Cr] 2 O 4 can precipitate in the glass (Izak et al 2001). Matyáš et al (2010b) demonstrated that these crystals rapidly settle, forming a thick sludge layer with rates up to 0.6 mm/day. This settling rate is fast enough to form a few cm thick sludge layer that can partially or completely block the riser during idling, thereby preventing molten glass from discharging during normal operation.…”

Section: Introductionmentioning

confidence: 99%

“…The settling of spinel crystals in molten glasses (Matyáš et al 2010b;LaMont and Hrma 1998;Kloužek et al 2001;Matlack et al 2009) as well as transparent liquids (Matyáš et al 2011(Matyáš et al , 2010a was researched in the laboratory. Lamont and Hrma (1998) observed the parabolic shape of the settling front indicating that the settling crystals generated a convective cell within the melt.…”

Section: Introductionmentioning

confidence: 99%

“…Kloužek et al (2001) determined that the measured settling distances between the glass level and the uppermost crystals in the centerline of the crucible were less than 10% smaller than the distances calculated with the modified Stoke's law. Matyáš et al (2010b) determined the accumulation rate of crystals as a function of spinel forming components and noble metals, and revealed a beneficial effect of suppressing the crystal size and accumulation rate through additions of Fe and noble metals. Matlack et al reported that the high-crystal content glasses of up to 4.2 vol% at 950°C have been successfully discharged from the DuraMelter® DM-100 after about 8 days of melter idling at 950°C (Matlack et al 2009).…”

Section: Introductionmentioning

confidence: 99%

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HLW Glass Studies: Development of Crystal-Tolerant HLW Glasses

Matyáš¹,

Huckleberry²,

Rodriguez³

et al. 2012

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iii SummaryTen glasses were prepared from high-level waste (HLW) AZ-101 simulant and additives. Eight of them were evaluated with a double crucible test for the effect of Cr, Ni, Fe, Al, Li, and RuO 2 on the accumulation rate of spinel crystals in the glass discharge riser of the HLW melter. The thicknesses of accumulated layers were incorporated into previously developed model of spinel settling (Matyáš et al. 2010a). In addition, the liquidus temperature (T L ) of glasses was measured and their crystallinity in mass % of spinel determined for heat-treatments at various temperatures for 24 h. The remaining two glass compositions enriched with Rh 2 O 3 and RuO 2 were investigated with scanning electron microscopy (SEM) and x-ray tomography for agglomeration of particles and impact of agglomerates on accumulation rate.The experimental study of spinel accumulation indicated that high concentrations of spinel-forming constituents in the glass can produce settling layers of a few cm thick in a few weeks. An excessive agglomeration of spinel in high-Ni-Fe glass (Ni1.5/Fe17.5) with agglomerates bigger than 500 µm resulted in the accumulation rate ~53.8 µm/h, which will produce ~2.6 cm thick layer in just 20 days of melter idling and can potentially plug the riser. Can noble metals decrease significantly this accumulation rate? There is an indication that they can. Additions of RuO 2 (in the form of ruthenium nitrosyl nitrate) to high-Ni glass (Ni1.5) effectively slowed down or stopped the spinel accumulation because of their effect on decreasing the average crystal size below 10 µm. Can the accumulation of thick but noncompacted spinel layer prevent the plugging of the riser? Maybe it can. Then, the additions of Al 2 O 3 and Li 2 O to glasses containing high concentration of spinel constituents might be the way. These components slowed down the growth of individual crystals but promoted the formation of a dendritic network of large needle-like spinel structures, which resulted in the non-compacted layers. There is a reasonable chance that spinel crystals locked in this configuration can be removed with glass during the pouring into canister.The previously developed model (Matyáš et al. 2010a) predicts well, R 2 = 0.981, the accumulation of crystals in the glasses with no or small-scale agglomeration, in which spinel settles as individual crystals and/or as clusters of a few crystals. But, in the case of excessive agglomeration, observed in the Ni1.5/Fe17.5 glass, the model under predicts the thicknesses of deposited layers. This under prediction was getting gradually worse with time as an increased number of larger agglomerates formed. Another factor that was not depicted by the model and that affected greatly the accumulation of spinel was the formation of 3D network of spinel needle-like structures in the Ni1.5/Al10 and Ni1.5/Li.38 glasses, which prevented a formation of a dense settled layer.The T L 's of tested glasses as determined with optical microscopy was between 950 to 1105°C. We have also measured the mass ...

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