In-situ spectroelectrochemical studies of radionuclide contaminated surface films on metals and the mechanism of their formation and dissolution. 1997 annual progress report
- Argonne National Lab., IL (US). Chemical Technology Div.
- Northern Illinois Univ., DeKalb, IL (US). Physics Dept.
- Naval Surface Warfare Center, Bethesda, MD (US). Carderock Div.
'The incorporation of radioactive contaminants into corrosion product scales on metals is being investigated using in-situ spectroscopic and electrochemical techniques. To facilitate the study, stable isotopes are used initially, while the corrosion films are simulated by electrodeposition of the appropriate oxide (hydroxide) onto a graphite substrate. Synchrotron x-ray absorption spectroscopy (XAS) is used to determine the structure and composition of the host oxide film, as well as the local structure of the impurity ion. Results on the incorporation of Sr and Ce into surface films of Ni(OH){sub 2} and NiOOH are reported. Cathodically deposited Ni(OH){sub 2} was found to be mainly in the {alpha} form while anodically prepared NiOOH consists of Ni{sup +2} and Ni{sup +4} phases. Sr in the films consists mainly of Sr{sup 2+} which appears to be coordinated to oxygen atoms and is likely to exist as small domains of co-precipitated material. Ce in Ni(OH){sub 2} exists mainly as Ce{sup +3} and as a Ce{sup +4} species when co-deposited with NiOOH. The structure of the Ce{sup +4} phase appears similar to a Ce(OH){sub 4} standard. However, x-ray diffraction and laser Raman measurements indicate that the latter chemical formulation is probably incorrect and that the material is more likely to be a disordered hydrous cerium oxide. Ce chemisorbed on Ni(OH){sub 2} and NiOOH films is predominantly in the +3 valency state. Iron oxide films prepared by anodic deposition from borate buffer solution containing Fe{sup +2}, has been found by XAS to consist mainly of {alpha} FeOOH. The latter has been found by others to be the constituent of the corrosion film on iron; this lends credence to the present simulation approach. Future work will involve studies on the incorporation of radioactive Sr, Ce, and Cs, as well as U, into nickel and iron oxide films. Investigations on the structure and composition of chromium oxide films, the effect of temperature on the energetics and mechanism of incorporation of heavy metal ions, as well as the subsequent dissolution of the films by electroreduction and anodic oxidation, will be undertaken.'
- Research Organization:
- Argonne National Lab., Chemical Technology Div., IL (US)
- Sponsoring Organization:
- USDOE Office of Environmental Management (EM), Office of Science and Risk Policy
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 13675
- Report Number(s):
- EMSP-55380-97; ON: DE00013675
- Country of Publication:
- United States
- Language:
- English
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