Phase reversion kinetics of thermally decomposed (α + γ′) phases to γ-phase in U – 10 wt% Mo alloy

Newell, Ryan; Mehta, Abhishek; Keiser, Dennis D.; Sohn, Yong Ho

doi:10.1016/j.jnucmat.2019.151983

Cited by 7 publications

(1 citation statement)

References 28 publications

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“…Stabilized cubic γ-U alloys have been of interest as nuclear fuels since the early days of nuclear energy, and several different elements can be used as γ-stabilizers (Mueller et al, 1962;Bleiberg et al, 2019;Hofman et al, 1998). Although some gamma phase stability can be achieved with low concentrations of Mo, 10 wt % Mo additions notably improve stability of the meta-stable γ-U phase that may remain stable under irradiation due to the stabilizing effect of ballistic mixing (Dwight, 1960;Rest et al, 2006;MEYER et al, 2014;Newell et al, 2020;Lu et al, 2021). Irradiation testing has been performed on U-10Mo and U-7Mo alloys for research reactor applications under 250 °C (Waldron et al, 1958;Dwight, 1960;May 1962;Leenaers et al, 2004;Rest et al, 2006;Creasy, 2012;Smirnova et al, 2015;Newell et al, 2017;Kautz et al, 2021;Gates et al, 2019) and for higher temperature fast reactors (Walters et al, 1984;Kittel et al, 1993;Harp et al, 2018) above 500 °C.…”

Section: Introductionmentioning

confidence: 99%

Accelerated fission rate irradiation design, pre-irradiation characterization, and adaptation of conventional PIE methods for U-10Mo and U-17Mo

Doyle¹,

Massey²,

Richardson³

et al. 2023

Front. Nucl. Eng.

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Metallic U alloys have high U density and thermal conductivity and thus have been explored since the beginning of nuclear power research. Alloys of U with modest amounts of Mo, such as U-10 wt % Mo (U-10Mo), are of particular interest because the γ-U crystal structure in this alloying addition shows prolonged stability in reactor service. Historically, radiation data on U-10Mo fuels were collected in Na fast reactors or lower temperature research reactor conditions, but little is known about irradiation behavior, particularly swelling and creep, at irradiation temperatures between 250 and 500°C. This work discusses the methodology and pre-irradiation characterization results from a U-Mo irradiation campaign performed in the High Flux Isotope Reactor at Oak Ridge National Laboratory. U-10Mo and U-17Mo samples irradiations are being completed at temperatures ranging from 250 to 500°C to three targeted fission densities between 2 × 1020 and 1.5 × 1021 fissions per cubic centimeter. Swelling measurement of the specimen sizes studied here required development and assessment of new methods for volume determination before and after irradiation. Laser profilometry and X-ray computation tomography (XCT) were used to provide preirradiation characterization of samples to determine the error and applicability of each to determine swelling following irradiation. These outcomes are contextualized through use of BISON simulations performed to assess the predicted expansion of U-Mo fuels subjected to the irradiation conditions of this work. Use of existing BISON fuel performance models predicted a maximum of 7% swelling under the irradiation conditions of this study. Pre-irradiation characterization revealed the as-cast U-Mo fuel samples were uniformly large-grained fully cubic U crystals with small U-C/N bearing precipitates and pores distributed throughout. Samples were found to contain a bulk porosity between .4 and 3% because of the casting process. Local porosity in areas far from large, interconnected pores was found by Slice-and-View to be under .2%. Nanometer-sized precipitates rich in C and N were identified in all samples, likely because of impurities during the fabrication process. Dendritic bands were also observed throughout the samples. These bands were characterized by variable Mo content that deviated from the overall Mo content by 2–3 wt %. No other microstructural features were correlated to these bands. Mechanical properties were found to be slightly strengthened compared to literature reports of bulk U-Mo fuels due to the nano-scale precipitates throughout the sample.

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