Diffusion Barrier Selection from Refractory Metals (Zr, Mo and Nb) Via Interdiffusion Investigation for U-Mo RERTR Fuel Alloy

    Authors

    K. Huang; C. C. Kammerer; D. D. Keiser;Y. H. Sohn

    Comments

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    Abbreviated Journal Title

    J. Phase Equilib. Diffus.

    Keywords

    diffusion barrier; interdiffusion; multicomponent diffusion; nuclear; URANIUM-MOLYBDENUM ALLOY; DISPERSION FUEL; HIGH-DENSITY; MATRIX; AL; Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy &; Metallurgical Engineering

    Abstract

    U-Mo alloys are being developed as low enrichment monolithic fuel under the Reduced Enrichment for Research and Test Reactor (RERTR) program. Diffusional interactions between the U-Mo fuel alloy and Al-alloy cladding within the monolithic fuel plate construct necessitate incorporation of a barrier layer. Fundamentally, a diffusion barrier candidate must have good thermal conductivity, high melting point, minimal metallurgical interaction, and good irradiation performance. Refractory metals, Zr, Mo, and Nb are considered based on their physical properties, and the diffusion behavior must be carefully examined first with U-Mo fuel alloy. Solid-to-solid U-10 wt.%Mo versus Mo, Zr, or Nb diffusion couples were assembled and annealed at 600, 700, 800, 900 and 1000 A degrees C for various times. The interdiffusion microstructures and chemical composition were examined via scanning electron microscopy and electron probe microanalysis, respectively. For all three systems, the growth rate of interdiffusion zone were calculated at 1000, 900 and 800 A degrees C under the assumption of parabolic growth, and calculated for lower temperature of 700, 600 and 500 A degrees C according to Arrhenius relationship. The growth rate was determined to be about 10(3) times slower for Zr, 10(5) times slower for Mo and 10(6) times slower for Nb, than the growth rates reported for the interaction between the U-Mo fuel alloy and pure Al or Al-Si cladding alloys. Zr, however was selected as the barrier metal due to a concern for thermo-mechanical behavior of UMo/Nb interface observed from diffusion couples, and for ductile-to-brittle transition of Mo near room temperature.

    Journal Title

    Journal of Phase Equilibria and Diffusion

    Volume

    35

    Issue/Number

    2

    Publication Date

    1-1-2014

    Document Type

    Article

    Language

    English

    First Page

    146

    Last Page

    156

    WOS Identifier

    WOS:000333093800005

    ISSN

    1547-7037

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