The Impact of Kinetics on Nepheline Formation in Nuclear Waste Glasses

Amoroso, Jake W.

doi:10.2172/1011079

Cited by 10 publications

(13 citation statements)

References 9 publications

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“…The main interest in these glasses was that they are all very similar compositions but one (24) forms no nepheline while the other two form large amounts of nepheline; HLW-E-ANa-13(3Al-3Si) [13] is significantly basic and forms a large fraction of nepheline by CCC treatment.  Position in ternary (~18 Na 2 O-30 Al 2 O 3 -52 SiO 2 in wt%): HLW-E-ANa-04 [4]; this glass formed nepheline like most in the previous group but had different levels of Na/Si/Al.  Position in ternary (~30 Na 2 O-37 Al 2 O 3 -33 SiO 2 in wt%): IWL-HAC5-1 has an extreme composition compared to normal borosilicate waste glasses with very low Si and high Al but with substantial Na.…”

Section: Selection Of Glasses For Studymentioning

confidence: 93%

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Nepheline crystallization in boron-rich alumino-silicate glasses as investigated by multi-nuclear NMR, Raman, & Mössbauer spectroscopies

McCloy

Washton

Gassman

et al. 2015

Journal of Non-Crystalline Solids

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A spectroscopic study was conducted on six simulant nuclear waste glasses using multi-nuclear NMR, Raman, and Mössbauer spectroscopies exploring the role of Si, Al, B, Na, and Fe in the glass network with the goal of understanding melt structure precursors to deleterious nepheline crystal formation. NMR showed two sites each for Al, Si, and Na in the samples which crystallized significant amounts of nepheline, and B speciation changed, typically resulting in more B(IV) after crystallization. Raman spectroscopy suggested some of the glass structure is composed of metaborate chains or rings, thus significant numbers of non-bridging oxygen and a separation of the borate from the aluminosilicate network. Mössbauer, combined with Fe redox chemical measurements, showed Fe playing a minor role in these glasses, mostly as Fe 3+ , but iron oxide spinel forms with nepheline in all cases. A model of the glass network and allocation of non-bridging oxygens (NBOs) was computed using experimental B(IV) fractions which predicted a large amount of NBO consistent with Raman spectra of metaborate features. local charge balance on the oxygens of alkaline-earth boro-aluminate crystals, where results from 11 B and 27 Al magic angle spinning (MAS)-NMR stressed the importance of three-coordinated oxygen O(III), where parentheses here and elsewhere denote nearest neighbor coordination, and indicated the importance of Al(V) and Al(VI) in all composition ranges [19]. In another example, Du and Stebbins [12] presented a modified Dell and Bray-type model [20] to include aluminum (i.e., alkali-alumino-borosilicate) and to describe boron speciation. Various tetrahedra compete for sodium, the modifier generally preferring Al, then B, then Si [21]. Tetrahedra building, on the other hand, is believed to start with Si then proceed to Al(IV), Fe(IV), and B(IV) (if present), as long as charged tetrahedron nearneighbor avoidance is maintained [12,22].Both boron and aluminum coordination are affected by modifier-cation field strength. In aluminoboro-silicates containing both Na and Ca, increasing the amount of Ca increases Al(V) [13], but has been said to increase B(IV) [23] or decrease it [13]. It has been shown in aluminoborates that higher-fieldstrength cations (e.g., Mg), can shift the normally encountered "chemical ordering" (i.e., Al and B tetrahedra avoidance due to Coulomb repulsion) seen in Na and Ca aluminoborates to the "statistical random mixing" of tetrahedra seen in Mg alumino-borate [24], and to an extent in Ca alumino-borosilicates [13]. Higher coordinated alumina units, Al(V) and Al(IV), can be charge compensated by 2 + cations (Ca, Mg) or 3 + cations (B, Al, La), and at the same time tend to "stabilize" B(IV) tetrahedra, acting as weakly positive ions themselves [19,24,25].Effects of differing Al/B ratios are explained by the local charge balance model [19], as B(III) is needed to stabilize units containing the charged Al(IV), so as more Al is added, the fraction of B(III) increases relative to B(IV) [23]. It has also been shown by ...

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Section: Selection Of Glasses For Studymentioning

confidence: 93%

“…By performing CCC heat treatments, the goal is to replicate the upper-bound crystallization behavior of a HLW glass [3]. Recently, simulations have been made of canister thermal profiles considering different pour schemes [3], and different cooling curves have been examined to study crystallization in crucible studies [4].…”

Section: Nuclear Waste Glassesmentioning

confidence: 99%

Nepheline crystallization in boron-rich alumino-silicate glasses as investigated by multi-nuclear NMR, Raman, & Mössbauer spectroscopies

McCloy

Washton

Gassman

et al. 2015

Journal of Non-Crystalline Solids

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show abstract

“…As stated previously, surface crystallization appears to dominate the nepheline crystallization observed in CCC treated samples in the laboratory. 6 Whereas the CCC simulates the cooling profile of the glass at 51" along the centerline of the filled canister, both the glass and crucible are heat treated together in the laboratory test. Thus, the glass/crucible interface is exposed to the same temperatures as the centerline portion of the glass in an actual canister; however, as shown in Figure 3-13 and Figure 3-18, the cooling profiles of the glass at the canister centerline and at the canister inside wall vary significantly.…”

Section: Radial Temperature Datamentioning

confidence: 99%

“…Three areas of focused research are suggested: 1) Glass-surface interface effects-It has been shown that nepheline crystallization in HLW glass is dominated by surface/interface crystallization in the CCC crucible test. 6 The CCC test is currently performed in Pt/Au alloy crucibles. Experiments to determine the effect of different materials, specifically the canister material, on crystallization should be performed.…”

Section: Path Forwardmentioning

confidence: 99%

“…3,5 Indeed, it has been shown that kinetic effects exist and impact the measured nepheline crystallization in HLW glass. 6 As a result, experimental studies at SRNL are ongoing to understand the impact of kinetics on nepheline crystallization and to develop improved methods of preventing nepheline crystallization in HLW glass during processing.…”

Section: Introductionmentioning

confidence: 99%

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Computer Modeling of High-Level Waste Glass Temperatures Within DWPF Canisters During Pouring and Cool Down

Amoroso¹

2011

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Observation of nepheline crystallization in the Na₂O-B₂O₃-Al₂O₃-SiO₂ system for the vitrification of zeolites absorbing Cs

Sawada

Kida

Shimizu

et al. 2021

Journal of Nuclear Science and Technology

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The Impact of Kinetics on Nepheline Formation in Nuclear Waste Glasses

Cited by 10 publications

References 9 publications

Nepheline crystallization in boron-rich alumino-silicate glasses as investigated by multi-nuclear NMR, Raman, & Mössbauer spectroscopies

Nepheline crystallization in boron-rich alumino-silicate glasses as investigated by multi-nuclear NMR, Raman, & Mössbauer spectroscopies

Computer Modeling of High-Level Waste Glass Temperatures Within DWPF Canisters During Pouring and Cool Down

Observation of nepheline crystallization in the Na₂O-B₂O₃-Al₂O₃-SiO₂ system for the vitrification of zeolites absorbing Cs

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The Impact of Kinetics on Nepheline Formation in Nuclear Waste Glasses

Cited by 10 publications

References 9 publications

Nepheline crystallization in boron-rich alumino-silicate glasses as investigated by multi-nuclear NMR, Raman, & Mössbauer spectroscopies

Nepheline crystallization in boron-rich alumino-silicate glasses as investigated by multi-nuclear NMR, Raman, & Mössbauer spectroscopies

Computer Modeling of High-Level Waste Glass Temperatures Within DWPF Canisters During Pouring and Cool Down

Observation of nepheline crystallization in the Na2O-B2O3-Al2O3-SiO2 system for the vitrification of zeolites absorbing Cs

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Observation of nepheline crystallization in the Na₂O-B₂O₃-Al₂O₃-SiO₂ system for the vitrification of zeolites absorbing Cs