Evaluating the microstructure and origin of nonmetallic inclusions in as-cast U-10Mo fuel

JOURNAL OF NUCLEAR MATERIALS

卷:554

Article

Kautz, Elizabeth J.¹  Shahrezaei, Sina¹  Athon, Matthew²  Frank, Michael³  Schemer-Kohrn, Alan¹  Soulami, Ayoub⁴  Lavender, Curt¹  Joshi, Vineet V.¹  Devaraj, Arun⁴ 

[1] Pacific Northwest Natl Lab, Energy & Environm Directorate, Richland, WA 99354 USA

[2] Pacific Northwest Natl Lab, Natl Secur Directorate, Richland, WA 99354 USA

[3] Univ North Texas, Dept Mat Sci & Engn, Denton, TX 76207 USA

[4] Pacific Northwest Natl Lab, Phys & Computat Sci Directorate, Richland, WA 99354 USA

关键词: Casting;    metallic nuclear fuel;    U-10Mo;    uranium-molybdenum;    low-enriched uranium;    LEU;    atom probe tomography;   

DOI  :  10.1016/j.jnucmat.2021.152949

来源: Elsevier

【 摘 要 】

Low enriched uranium alloyed with 10 wt. % molybdenum (U-10Mo) has been identified as a promising alternative to highly enriched uranium oxide dispersion fuels for use in high performance research and test reactors. Manufacturing U-10Mo alloy fuel involves several complex thermomechanical processing steps and understanding of the microstructure and its evolution throughout the various fabrication steps is critical to enable the deployment of a reliable fuel production capability. Nonmetallic inclusions are often found in U castings and may affect subsequent fuel processing steps and microstructure evolution. Yet, the origin of these inclusions is not well established. To elucidate their origin and formation mechanisms, nonmetallic inclusions in U-10Mo castings were characterized on sub-nanometer to millimeter scale. Inclusion distribution, morphology, size, and composition were determined for the metallic fuel samples. Inclusions were estimated to comprise similar to 0.4 % of the fuel (by area), were identified at both grain boundaries and grain interiors, and were found to have varying morphologies (e.g., core-shell, elongated, blocky). All inclusions were either uranium carbides or oxides, or a combination of the two (i.e., dual-phase inclusions). Analysis of inclusions via atom probe tomography revealed that carbides and oxides were hypostoichiometric, with minor amounts of additional impurity elements present (e.g., Si, H). All analyzed inclusions were found to be enriched to similar to 20 at. % U-235, consistent with the surrounding gamma-UMo matrix and target enrichment for the low enriched U fuel, indicating that the inclusions formed during the downblending of highly enriched U metal with depleted U via the melting and casting processes. (C) 2021 Elsevier B.V. All rights reserved.

【 授权许可】

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