Characterisation of hot isostatically pressed (HIPed) hollandite wasteform-canister interaction zone
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Date
2024-02
Journal Title
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Publisher
Elsevier
Abstract
A potential hollandite wasteform for immobilising waste containing Cs, Ba, Sr, and Rb, projected from a solvent extraction process that separates Cs/Sr from spent nuclear fuel, was fabricated via hot isostatic pressing (HIPing) within a stainless-steel (SS) canister at 1250 °C / 30 MPa / 2 h. Before HIPing, 2 wt.% Ti metal was added to the precursor, as a redox control additive. Detailed elemental profiling and microstructural analysis at the interaction zone between the wasteform and the SS HIP canister were thoroughly investigated with transmission electron microscopy (TEM) using a lamella extracted by focused ion beam (FIB) milling, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The interaction zone towards the wasteform was ∼20–30 µm in distance and in this region, a hollandite composition with varying chemistry was observed relative to the bulk wasteform. Moreover, the regular Cr-oxide layer, often observed previously for HIPed Synroc-type materials, was not present due to the achievement of reducing condition by adding Ti-metal as redox additive and simultaneous diffusion of canister material towards the ceramic. Predominant Cr-diffusion was observed with incorporation in the hollandite phase along with minor Fe, Mn and Co from the SS canister. This study provides a detailed understanding of the HIP canister – wasteform interaction zone for a hollandite-rich wasteform design for the first time. Importantly, no deleterious phases were formed that may otherwise reduce the performance of the wasteform. This study further demonstrates the flexibility of HIPing as a consolidation process for the treatment of radioactive wastes. © 2023 Elsevier B.V.
Description
All authors thank the Australian Institute of Nuclear Science and Engineering (AINSE) scholarship for financial support, Analytical Centre of the University of New South Wales (UNSW) and the Nuclear Materials Development and Characterisation (NMDC) for technical support. We also acknowledge help from Dr. Charlie Kong for assistance with focussed ion beam milling, Ian Watson and Iveta Kurlapski for assistance with sample preparation, Neil Webb for HIPing, and Nuclear Science and Technology (NST) at ANSTO for material characterisations.
Keywords
Hollandite, Chemistry, Cesium, Bromine, Strontium, Rubidium, Nuclear fuels, Stainless steels, Electron microscopy, Oxides, Synroc process, X-ray diffraction, Solvent extraction, Waste forms
Citation
Mann, J., Farzana, R., Aughterson, R. D., Dayal, P., Sorrell, C. C., Koshy, P., & Gregg, D. J. (2024). Characterisation of hot isostatically pressed (HIPed) hollandite wasteform-canister interaction zone. Journal of Nuclear Materials, 589, 154863. doi:10.1016/j.jnucmat.2023.154863