Flow-induced structure in a system of nuclear waste simulant slurries

Chang, Chingyi; Smith, Peter A.

doi:10.1007/bf00403539

Cited by 11 publications

(5 citation statements)

References 17 publications

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“…This behavior is termed rheopexy or antithixotropy. Similar behavior was previously observed with the NCAW simulant (Chang and Smith 1996). The 0.1 s-1 test did not show this behavior.…”

Section: Rheologysupporting

confidence: 88%

“…Simply, the silica renders the particles sticky. Similar behavior has been observed in sol gel films (Brinker and Scherer 1990) aad simulated nuclear waste suspensions containing frit (a silica source) particles (Chang and Smith 1996). In addition, mineral phases such as montmorillonite and kaolin (Heckroodt and Ryan 1978) have shown this behavior.…”

Section: Discussionsupporting

confidence: 67%

“…They measured the shear strength of a sample of sludge from Tank SY-102 using a Haake Viscometer equipped with a shear vane. They reported the shear strength to be 39,000 dynedcm2, which is equivalent to 3,900 Pa. Our measurements indicated a yield stress of approximately 2.7 Pa. Smith et al (1996) have shown that the values of stress obtained from a shear vane viscometer are not directly linked to the yield stress or shear strength of the material. It was shown that the error in measurement of yield stress dramatically increases with rotation rate of the shear vane due to inertial effects.…”

Section: Rl=mentioning

confidence: 50%

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Tank SY-102 waste retrieval assessment: Rheological measurements and pump jet mixing simulations

Onishi¹,

Shekarriz²,

Recknagle³

1996

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DISCLAIMERPortions of this document m y be illegible in electronic image products. Images are produced from the best available original document. Executive SummaryWastes stored in Hanford Tank 241-SY-10 are planned to be retrieved from the tank and transferred to 200 East Area through the new pipeline Replacement Cross Site Transfer System (RCSTS). This report describes results of the second phase (the detailed assessment) of a the SY-102 waste retrieval study, which is a part of the efforts to establish a technical basis for mobilization of the slurry, waste retrieval, and slurry transport. This second-phase study was performed to close uncertainty issues on Tank SY-102 waste retrieval identified under the previous preliminary assessment (Onishi and Hudson 1996). The uncertainties on the preliminary assessment were primariiy related to lack of data on waste characteristics and the assumption of the tank being fully mixed. To resolve these issues, this Phase 11 study 1) identified solid phases of the SY-102 waste by using transmission electron microscopy (TEMJ, 2) conducted laboratory experiments to measure rheology, zeta potential to evaluate solid agglomeration, and sedimentation, 3) measured particle size distributions of the wastes, and 4) simulated time-varying, three-dimensional, tank pump jet mixing.The Phase 11 study results confirms the validity of the assumptions and parameter selections used in the preliminary assessment (Onishi and Hudson 1996) and supports its conclusion that the SY-102 waste m i h g and heating do not adversely impact the waste retrieval operation. . Specific conclusions of this study are briefly summarized below.The Transmission Electron Microscopy results show that the morphology of the agglomerates is dominated by large size (2-5 pm x 10-30 pm) NaOH rods s~o u n d e d by finer primary particles of various materials. A large population of amorphous silica and iron hydroxide primary particles in the nanometer size range was' observed. Also, needle-like FeO(0H) agglomerates and sharp-edged plate-like y-A1203 particles were found. Irregt&x U-containing agglomerates and rectangular MCrcontaining particles were also present. The major 'crystalline phases observed include: micrometersized y-Al2O3, needle-like FeO(0H) and Al2Si4010. The minor crystalline phases observed were rodlike particles of hydroxylapatite, Cas(PO)3(OH) and single crystalline gibbsite, Al(OH)3. t rod-like particles of hydroxylapatite, Ca5(PO)3(OH) and single crystalline gibbsite, Al(Orn.3. The preliminary assessment study (Onishi and Hudson 1996) assumed the all Al solids to be gibbsite for the chemical reaction modeling. The current TEM identified Al solids to be y-Al2O3, Al$34010, and gibbsite.Gibbsite and y-A1203 are chemically similar. Moreover, existence of y-Al2O3 would slightly increase the amount of water in the solution, as compared with gibbsite. Moreover, since the sludge has a much smaller amount of Si than the amount of Al, the majority of Al is not expected to form a solid with Si. Thus, the prelimina...

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“…This behavior is termed rheopexy or antithixotropy. Similar behavior was previously observed with the NCAW simulant (Chang and Smith 1996). The 0.1 s-1 test did not show this behavior.…”

Section: Rheologysupporting

confidence: 88%

Section: Discussionsupporting

confidence: 67%

Section: Rl=mentioning

confidence: 50%

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Tank SY-102 waste retrieval assessment: Rheological measurements and pump jet mixing simulations

Onishi¹,

Shekarriz²,

Recknagle³

1996

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“…Thixotropic media are frequently encountered in large‐scale industrial processes including oil pipeline‐transport, red‐mud in minerals processing, and waste processing at superfund sites . In addition, thixotropic agents are prominent in consumer applications, such as beauty creams, and have even been proposed for gelled hydrocarbon fuel applications .…”

Section: Introductionmentioning

confidence: 99%

A constitutive equation for thixotropic suspensions with yield stress by coarse‐graining a population balance model

et al. 2016

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A population balance model appropriate for the shear flow of thixotropic colloidal suspensions with yield stress is derived and tested against experimental data on a model system available in the literature. Modifications are made to account for dynamic arrest at the onset of the yield stress, in addition to enforcing a minimum particle size below which breakage is not feasible. The resulting constitutive model also incorporates a structural based relaxation time, unlike existing phenomenological models that use the inverse of the material shear rate as the relaxation time. The model provides a reasonable representation of experimental data for a model thixotropic suspension in the literature, capturing the important thixotropic timescales. When compared to prevalent structure kinetics models, the coarse‐grained population balance equation is shown to be distinct, emphasizing the novelty of utilizing population balances as a basis for thixotropic suspension modeling. © 2016 American Institute of Chemical Engineers AIChE J, 63: 517–531, 2017

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“…Much of the Savannah River Site (SRS) high-level radioactive waste is in the form of alkaline suspensions of insoluble, inorganic (“sludge”) particulates. The chemical processing of the sludge to produce melter feed suitable for a glass melter involves the boiling of the sludge ( , ).…”

Section: Introductionmentioning

confidence: 99%

Foaming in Simulated Radioactive Waste

Bindal¹,

Nikolov²,

Wasan³

et al. 2001

Environ. Sci. Technol.

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Radioactive waste treatment process usually involves concentration of radionuclides before waste can be immobilized by storing it in stable solid form. Foaming is observed at various stages of waste processing like SRAT (sludge receipt and adjustment tank) and melter operations. This kind of foaming greatly limits the process efficiency. The foam encountered can be characterized as a three-phase foam that incorporates finely divided solids (colloidal particles). The solid particles stabilize foaminess in two ways: by adsorption of biphilic particles at the surfaces of foam lamella and by layering of particles trapped inside the foam lamella. During bubble generation and rise, solid particles organize themselves into a layered structure due to confinement inside the foam lamella, and this structure provides a barrier against the coalescence of the bubbles, thereby causing foaming. Our novel capillary force balance apparatus was used to examine the particle-particle interactions, which affect particle layer formation in the foam lamella. Moreover, foaminess shows a maximum with increasing solid particle concentration. To explain the maximum in foaminess, a study was carried out on the simulated sludge, a non-radioactive simulant of the radioactive waste sludge at SRS, to identify the parameters that affect the foaming in a system characterized by the absence of surface-active agents. This three-phase foam does not show any foam stability unlike surfactant-stabilized foam. The parameters investigated were solid particle concentration, heating flux, and electrolyte concentration. The maximum in foaminess was found to be a net result of two countereffects that arise due to particle-particle interactions: structural stabilization and depletion destabilization. It was found that higher electrolyte concentration causes a reduction in foaminess and leads to a smaller bubble size. Higher heating fluxes lead to greater foaminess due to an increased rate of foam lamella generation in the sludge system.

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Flow-induced structure in a system of nuclear waste simulant slurries

Cited by 11 publications

References 17 publications

Tank SY-102 waste retrieval assessment: Rheological measurements and pump jet mixing simulations

Tank SY-102 waste retrieval assessment: Rheological measurements and pump jet mixing simulations

A constitutive equation for thixotropic suspensions with yield stress by coarse‐graining a population balance model

Foaming in Simulated Radioactive Waste

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