Mews, Paul Aaron (2007-12). Evaluation of zirconium-iron-rhenium alloys as surrogates for a technetium alloy waste form. Master's Thesis. Thesis uri icon


  • Stainless steel - zirconium alloys were developed by the US Department of
    Energy Laboratories as metallic waste forms for noble metal fission products. This
    thesis evaluates iron-zirconium-rhenium alloys to establish a technical basis for using
    metal waste form alloys for technetium-99 immobilization. Rhenium is used as a
    surrogate for Tc-99 since Tc is not naturally available and Re is metallurgically similar
    to Tc.
    The iron-zirconium system has two eutectic compositions, Fe-15 wt % Zr and Zr-
    16 wt% Fe. Ten test samples were successfully cast in yttrium oxide crucibles at
    1600?C, half near each eutectic composition, with Re amounts varying from 2.5 to 12.5
    weight percent.
    A scanning electron microscope (SEM) with energy dispersive X-ray
    spectroscopy (EDS) capability was employed to determine the phase structure and phase
    composition of each sample. Iron rich samples were found to form up to three phases,
    with the rhenium content favoring the intermetallic phases: 1) an Fe solid solution phase,
    2) an FeZr2-type intermetallic with 11 wt % or less Re, and 3) a second intermetallic with about 18 wt % Re. Zirconium rich samples formed as many as five distinct phases:
    1) a Zr solid solution phase, 2) a Zr3Fe-type intermetallic with as much as 13 wt% Re, 3)
    a rhenium-zirconium intermetallic, 4) another Fe-Zr intermetallic with very little Re, and
    5) a Fe-Re intermetallic.
    Potentiostatic and potentiodynamic electrochemical tests were performed using
    sulfuric acid to evaluate the corrosion resistance of each sample. These tests found that
    the zirconium rich samples were very corrosion resistant but became increasingly
    susceptible at higher rhenium concentrations. The iron rich samples were not very
    resistant to corrosion under the test conditions; there was no notable trend in corrosion
    behavior related to the introduction of rhenium.

publication date

  • December 2007