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Nuclear Science and Engineering
Fusion Science and Technology
Study indicates pilot facility could significantly reduce waste volumes
Waste disposal start-up Deep Isolation and fusion tech company SHINE Technologies have announced the completion of a collaborative study assessing the costs of disposing of radioactive byproducts from a pilot spent nuclear fuel recycling facility.
Matthew D. Zimmer, Igor A. Bolotnov
Nuclear Science and Engineering | Volume 194 | Number 8 | August-September 2020 | Pages 708-720
Technical Paper | doi.org/10.1080/00295639.2020.1722543
Articles are hosted by Taylor and Francis Online.
Recent advancements in computing power allow utilization of state-of-the-art direct numerical simulations (DNSs), coupled with interface tracking techniques, to perform fully resolved simulations of complex two-phase flows, such as flow regime transitions. Studying the highly resolved temporal and spatial information produced from these virtual experiments can advance our understanding of the phenomenon and inform coarser models. With these improved models, better predictions of flow regime behavior and location in boiling water reactors can be made.
The presented research uses the PHASTA code, which employs the level set method for interface tracking, to examine the mechanisms of flow regime transition, specifically the slug-to-bubbly and slug-to–churn-turbulent regime transitions. The DNS was validated using theoretical and experimental work found in open literature. Different geometries, including pipes and minichannels, were explored in order to improve the fundamental understanding of the complex flow phenomenon. Using advanced analysis techniques, the transient flow properties were analyzed at resolutions not available to other methods. The numerical data analysis allows for calculation of both time and spatially averaged properties as well as local instantaneous properties. Possible mechanisms for the transition are discussed. Examples include liquid kinetic energy/surface tension energy balance and interfacial shear forces in the liquid film. It is also noted that the transition out of slug flow can take at least two pathways: interfacial wave-induced instability development in the Taylor bubble, leading to its disintegration, or strong bubble shearing at the tail of the bubble.