Abstract

Body-centered cubic structured γ U-Mo fuels have been developed for high performance research reactors. The formation of Xe gas bubble superlattice (GBS) in irradiated U-Mo fuels reduces the volumetric swelling of the fuels. In this study, atom probe tomography (APT) was used to measure the characteristics of the Xe GBS, including chemical composition, number density, and volume fraction of the gas bubbles, as well as the characteristics of the solid fission products, in neutron irradiated U-10 wt.% Mo fuel. It was found that in the bubbles (∼2 nm in diameter) that form the GBS are enriched with Xe with depletion of U as compared to the matrix. However, the atomic concentration of Xe is not 100%, suggesting the bubbles are not pure Xe. There is a significant fraction of Xe atoms remaining in the BCC U-Mo matrix, indicating some solubility. These observations are different from conventional assumptions. In addition, Nd clusters/precipitates arrange themselves in a superlattice structure of their own, separate from the Xe GBS. Despite limitations of APT in measuring gas bubbles and the associated uncertainty in obtaining accurate compositions, results provide new insights into the characteristics of fission product superlattice in irradiated U-Mo fuels.

Department(s)

Materials Science and Engineering

Publication Status

Full Text Access

Comments

National Nuclear Security Administration, Grant NA-212

Keywords and Phrases

Atom probe tomography; Neutron irradiated U-Mo fuel; Solid fission products clustering/segregation; Xe gas bubble superlattice

International Standard Serial Number (ISSN)

2589-1529

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2026 Elsevier, All rights reserved.

Publication Date

01 May 2026

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