Dissertation
FUNDAMENTAL STUDIES ON THE MORPHOLOGY AND EFFECTS OF URANIUM CARBIDE PARTICLES DURING CASTING IN URANIUM AND U-10MO METAL
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2022
DOI:
https://doi.org/10.7273/000004367
Handle:
https://hdl.handle.net/2376/118926
Abstract
There is a renewed interest in studying the fabrication of metallic nuclear fuel alloys for existing and new generation nuclear reactors. The United States High Performance Research Reactor conversion program seeks to reduce uranium isotopic enrichment of civilian research reactor fuel by substitution with a metallic form of high assay low enriched uranium (HALEU). The chosen fuel alloy is a monolithic metallic uranium alloyed with 10 weight percent molybdenum (U-10Mo). The fabrication of this fuel consists of a complex series of casting and thermomechanical processing steps that introduce impurities, such as carbon. The low solid solubility of carbon in uranium results in precipitation of secondary-phase uranium carbide (UC) particles that can impact the microstructure and fabrication of U-10Mo. To elucidate the formation, persistence, and impact of UCs in U-10Mo fabrication, a set of U-10Mo plates were cast with variable quantities of bulk carbon content. Stable 13C graphite was used to induce UC formation, and spatial isotopic mass spectrometry (NanoSIMS and atom probe tomography) was used to trace UC formation and migration in the matrix. Additionally, a U-10Mo thermomechanical process procedure including thermal homogenization, hot rolling, and cold rolling were performed to assess the microstructural evolution of U-10Mo as a function of UC content. Isotopic mass spectrometry displayed homogeneity of carbon isotopes across two different spatial scales. Quantitative image analysis of the U-10Mo grain size indicated that UCs influence the grain growth of thermomechanically-processed U-10Mo. Further, the thermomechanical processing impacted the size and morphology of UCs. In addition to U-10Mo alloy studies, the effect of cooling rate on UC inclusion morphology in unalloyed U metal was investigated. In general, UCs grew larger with slower cooling rates, and the two slowest cooling rates noticeably affected the mean inclusion circularity and ellipse aspect ratio. These results indicate that UC size and morphology is sensitive to thermomechanical processing and demonstrates that their presence and physical features could be controlled in the production of metallic nuclear fuels. Results of these studies will help optimize the U-10Mo fabrication process and improve fundamental knowledge of UC formation and persistence during melting and casting.
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Details
- Title
- FUNDAMENTAL STUDIES ON THE MORPHOLOGY AND EFFECTS OF URANIUM CARBIDE PARTICLES DURING CASTING IN URANIUM AND U-10MO METAL
- Creators
- Matthew Athon
- Contributors
- John S McCloy (Advisor)David P Field (Committee Member)Qizhen Li (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- School of Mechanical and Materials Engineering
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 218
- Identifiers
- 99900883039001842
- Language
- English
- Resource Type
- Dissertation