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dc.rights.licenseRestricted to current Rensselaer faculty, staff and students. Access inquiries may be directed to the Rensselaer Libraries.
dc.contributorLian, Jie
dc.contributorJi, Wei
dc.contributorLiu, Li (Emily)
dc.contributorLewis, Daniel
dc.contributor.authorScott, Spencer M.
dc.date.accessioned2021-11-03T08:56:44Z
dc.date.available2021-11-03T08:56:44Z
dc.date.created2018-02-21T14:02:52Z
dc.date.issued2017-12
dc.identifier.urihttps://hdl.handle.net/20.500.13015/2138
dc.descriptionDecember 2017
dc.descriptionSchool of Engineering
dc.description.abstractMaterial limitations are the most significant obstacles to the implementation of advanced nuclear fuel cycles. These limitations occur throughout the nuclear cycle and include key components of the fuel cycle such as the thermal performance and phase stability of reactor fuels, the capacity for radionuclides to be separated from waste streams, and the suitability of waste forms materials to sequester the most volatile radionuclides present in spent nuclear fuel. This work outlines attempts to address key issues to the implementation of advanced nuclear fuel cycles through both the development of novel materials tailored for the nuclear applications of concern and an elucidation of the underlying mechanisms that drive the interactions of interest in the studied materials.
dc.description.abstractCs2SnCl6 defect perovskites were studied for their thermal stabilities and sinterability using spark plasma sintering, as well as their applicability to applications in the back end of the nuclear fuel cycle such as separations. The synthesis, consolidation, and characterization of Cs2SnCl6 powders and pellets were outlined, indicating promise for liquid nuclear waste stream separations of Cs and Cl. Cs2SnCl6 was synthesized using a simple solution-based approaching, resulting in a pure Cs2SnCl6 starting powder with particle sizes ranging from 200 to 500 nm. Spark plasma sintering was demonstrated to be suitable for the consolidation of Cs2SnCl6 pellets, achieving ≥ 94% theoretical density without decomposition products visible via X-ray diffraction. The thermal decomposition mechanism of Cs2SnCl6 was elucidated, appearing to decompose into the precursors, CsCl and SnCl4, above 600 °C, with the loss of volatilized SnCl4 occurring concurrently with decomposition. This mechanism was supported by the X-ray diffraction results of the pellets consolidated by spark plasma sintering, with pellets sintered at elevated temperatures displaying CsCl signals, suggesting the partial decomposition of Cs2SnCl6 and the loss of SnCl4.
dc.description.abstractGraphene-based materials were investigated as sorbent materials for the segregation of elemental iodine from the off-gas from the reprocessing of spent nuclear fuel. The maximum iodine sorption capacities of several graphene-based materials were determined, as well as the effects of specific surface area, defect concentration, oxygen functional group concentration, and pore size distribution on the maximum sorption capacity. Iodine’s sorption kinetics on graphene were shown to be dominated by the specific surface and defect concentration, while the pore size distribution significantly impacted the desorption kinetics, as evidenced by the two-stage desorption in graphene aerogels with increasing temperature. The sorption mechanism of I2 on graphene was demonstrated to be driven by van der Waals forces, confirming prior density functional theory calculations for the sorption of halogens on two-dimensional materials.
dc.description.abstractThe phase stability of the ThO2-La2O3 system has been investigated for its applications in the fabrication of nuclear fuels, as well as the potential interactions in spent nuclear fuel. La2O3 was incorporated into the ThO2 matrix through a mechanical synthesis technique, high energy ball milling, resulting in a solid solution Th1 xLaxO2 0.05x. Spark plasma sintering was used to consolidate ThO2 and Th1 xLaxO2 0.05x powders into dense pellets under varying conditions. The non-equilibrium heating conditions of SPS was shown to facilitate the localized phase segregation in Th1-xLaxO2-0.05x, resulting in La-rich and La-deficient zones on the sub-micron scale, beyond 1600 °C.
dc.description.abstractDefect perovskites were introduced as a potential waste form for the sequestration of volatile iodine present in spent nuclear fuel. Cs2SnI6, Cs2SnCl6-xIx, and Cs3Bi2I9 were synthesized using solution-based approaches, resulting in iodine contents varying from 11 to 66 wt %. The thermal stabilities of the defect perovskites were measured using thermogravimetric analysis, displaying thermal stabilities ranging from 300 °C to 500 °C. Spark plasma sintering was shown to fully densify Cs2SnI6 and Cs3Bi2I9, without decomposition visible in via X-ray diffraction, at 200°C and 250 °C, respectively. Cs2SnCl6-xIx pellets displayed a degree of decomposition above 250 °C, with the pellet sintered at 250 °C displaying a low degree of consolidation. Water dissolution of Cs2SnI6 and Cs2SnCl6-xIx suggested rapid dissolution, unsuitable for waste form applications, however the dissolution of Cs3Bi2I9 powder was shown to be more gradual, with the bulk retention of Cs3Bi2I9 phase after a week of powder dispersion in water, accompanied by the emergence of a BiOI pattern in X-ray diffraction. Hydroxyapatite – Cs2SnCl6-xIz encapsulation in a core-shell structure using spark plasma sintering at 700 °C was shown capable of retaining both iodine and chlorine during consolidation, suggesting spark plasma sintering may be suitable for the consolidation of heterogeneous waste assemblies containing volatile radionuclides.
dc.language.isoENG
dc.publisherRensselaer Polytechnic Institute, Troy, NY
dc.relation.ispartofRensselaer Theses and Dissertations Online Collection
dc.subjectNuclear engineering and science
dc.titleDevelopment of materials for advanced nuclear fuel cycle applications
dc.typeElectronic thesis
dc.typeThesis
dc.digitool.pid178828
dc.digitool.pid178829
dc.digitool.pid178830
dc.rights.holderThis electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.
dc.description.degreePhD
dc.relation.departmentDept. of Mechanical, Aerospace, and Nuclear Engineering


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