Browsing by Author "Farzana, R"

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    Hot isostatically pressed (HIPed) fluorite glass‐ceramic wasteforms for fluoride molten salt wastes
    (John Wiley & Sons, Inc., 2020-06-07) Gregg, DJ; Vance, ER; Dayal, P; Farzana, R; Aly, Z; Holmes, R; Triani, G
    Molten pyroprocessing salts can be used to dissolve used nuclear fuel from a reactor allowing recovery of the actinides. Previously, ANSTO have demonstrated hot isostatically pressed (HIPed) sodalite glass‐ceramic wasteforms for eutectic (Li,K)Cl salts containing fission products, but this system cannot be used for the analogous molten alkali fluoride salts (eg, FLiNaK), which have utility in the application of the next generation of nuclear reactors. In this work, a novel glass‐ceramic composite wasteform has been prepared by HIPing, as a candidate for the immobilization of fission product‐bearing FLiNaK salts. The wasteform has been tailored to immobilize the high fluoride content of the waste within fluorite, whereas the waste alkali elements are incorporated in a durable sodium aluminoborosilicate glass, with total waste loadings of ~17‐21 wt% achieved. It was also demonstrated that the speciation of Mo‐ and Sb‐simulated fission products was altered by adding Ti metal due to a controlled redox environment. The resulting candidate wasteform has been studied by X‐ray diffraction and scanning electron microscopy, including the HIP canister‐wasteform interaction zone, and its performance assessed via leaching studies using the PCT and ASTM C1220 leaching protocols. Dr Vance very much enjoyed the challenge of wasteform design for problematic nuclear wastes, for which fission product‐bearing FLiNaK salts are a clear example. His ability to hone in on a wasteform solution with viable waste loadings that meet performance requirements was testament to his nearly 40 years experience in nuclear waste immobilization. The samples discussed in this work represent the last wasteform materials that he prepared. © 1999-2020 John Wiley & Sons, Inc.
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    Profiling hot isostatically pressed canister–wasteform interaction for Pu-bearing zirconolite-rich wasteforms
    (John Wiley & Sons, Inc, 2022-04-02) Dayal, P; Farzana, R; Zhang, YJ; Lumpkin, GR; Holmes, R; Triani, G; Gregg, DJ
    Zirconolite-rich full ceramic wasteforms designed to immobilize Pu-bearing wastes were produced via hot isostatic pressing (HIP) using stainless steel (SS) and nickel (Ni) HIP canisters. A detailed profiling of the elemental compositions of the major and minor phases over the canister–wasteform interaction zone was performed using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDS) characterization. Bulk sample analyses from regions near the center of the HIP canister were also conducted for both samples using X-ray diffraction and SEM-EDS. The sample with the Ni HIP canister showed almost no interaction zone with only minor diffusion of Ni from the inner wall of the canister into the near-surface region of the wasteform. The sample with the SS HIP canister showed ∼100–120 μm of interaction zone dominated by high-temperature Cr diffusion from canister materials to the wasteform with the Cr predominantly incorporated into the durable zirconolite phase. We also examined, for the first time, changes to the HIP canister wall thickness caused by HIPing and demonstrated that no canister wall thinning occurred. Instead, in the areas examined, the canister wall thickness was observed to increase (up to ∼20%) due to the compression occurring during the HIP cycle. Further, only sparse formation of (Cr, Mn)-rich oxide particles were noted within the HIP canister inner wall area immediately adjacent to the ceramic material, with no evidence for reverse diffusion of ceramic materials. Though the HIP canister–wasteform interaction extends to ∼120 μm when using an SS HIP canister for the system investigated, this translates to <<1 vol.% for an industrial scale HIPed wasteform. Importantly, the HIP canister–wasteform interactions did not produce any obviously less durable phases in the wasteform or had any detrimental impact on the HIP canister properties. © 2022 Commonwealth of Australia. Journal of the American Ceramic Society published by Wiley Periodicals LLC on behalf of American Ceramic Society.
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    Pyrochlore glass-ceramics for the immobilization of molybdenum-99 production wastes: demonstrating scalability and flexibility to waste stream variance
    (Elsevier, 2021-11) Farzana, R; Zhang, YJ; Dayal, P; Aly, Z; Holmes, R; Triani, G; Vance, ER; Gregg, DJ
    Pyrochlore glass ceramics have been fabricated via in-situ crystallization under reducing conditions by both sintering and hot isostatic pressing (HIPing) as candidate wasteforms for the acidic waste biproduct of Mo-99 radiopharmaceutical production. The tailored wasteform demonstrates flexibility in the wasteform design to receive the required waste variability, it also suitably passes high-level waste performance requirement, and successfully scales to 1 kg scale with 45 wt.% waste loading. U-rich pyrochlore as the major phase was confirmed by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy, with residual glass and minor secondary phases. The presence of both U4+ and U5+ valences in the wasteforms was revealed by diffuse reflectance spectroscopy. Addition of glass content had little influence on the pyrochlore composition but facilitated minor perovskite formation. The up-scaled dense, HIPed sample showed elemental releases of < 2 g/L for all elements in durability experiments. © 2021 Elsevier Ltd
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    Synroc technology: perspectives and current status (review)
    (John Wiley & Sons, Inc., 2020-06-22) Gregg, DJ; Farzana, R; Dayal, P; Holmes, R; Triani, G
    Dr Eric (Lou) Vance spent 32 years at the Australian Nuclear Science and Technology Organisation (ANSTO), where he was dedicated to the development of Synroc technology, a waste treatment solution for intractable nuclear wastes. The original form of Synroc, a multiphase ceramic wasteform based on stable and leach resistant titanate minerals, was invented by Australian scientists in the late 1970s. This formulation was directed toward the immobilization of PUREX wastes from the reprocessing of nuclear fuels. Synroc at ANSTO under the scientific leadership of Dr Vance since evolved beyond these original titanate ceramics into a waste treatment technology platform. This platform can be applied to produce glass, glass‐ceramic and ceramic wasteforms and offers distinct advantages in terms of waste loading and suppressing volatile losses. The platform therefore provides an opportunity to treat those waste streams that are problematic for glass matrices alone or existing vitrification process technologies. Such wastes include, for example, actinide‐bearing wastes, those that contain large proportions of refractory elements, those with significant fission product or corrosive volatile emissions and those wastes resulting from radiopharmaceutical production. The implementation of the latter will see the industrialization of Synroc technology via a first‐of‐a‐kind Synroc Waste Treatment Facility that is currently under construction at ANSTO. This paper will review Synroc technology, particularly noting the substantial and essential contributions from the late Dr Vance. The review will also provide some perspective on the development of the technology for nuclear waste immobilization and describe the significant recent advancements at ANSTO. © 1999-2020 John Wiley & Sons, Inc.