``In-situ'' spectro-electrochemical studies of radionuclide-contaminated surface films on metals
The incorporation of heavy metal ions and radioactive contaminants into hydrous oxide films has been investigated in order to provide fundamental knowledge that could lead to the technological development of cost-effective processes and techniques for the decontamination of storage tanks, piping systems, surfaces, etc., in DOE nuclear facilities. The formation of oxide/hydroxide films was simulated by electrodeposition onto a graphite substrate from solutions of the appropriate metal salt. Synchrotron X-ray Absorption Spectroscopy (XAS), supplemented by Laser Raman Spectroscopy (LRS), was used to determine the structure and composition of the host oxide film, as well as the impurity ion. Results have been obtained for the incorporation of Ce, Sr, Cr, Fe, and U into hydrous nickel oxide films. Ce and Sr oxides/hydroxides are co-precipitated with the nickel oxides in separate phase domains. Cr and Fe, on the other hand, are able to substitute into Ni lattice sites or intercalate in the interlamellar positions of the brucite structure of Ni(OH){sub 2}. U was found to co-deposit as a U(VI) hydroxide. The mode of incorporation of metal ions depends both on the size and charge of the metal ion. The structure of iron oxide (hydroxide) films prepared by both anodic and cathodic deposition has also been extensively studied. The structure of Fe(OH){sub 2} was determined to be similar to that of {alpha}-Ni(OH){sub 2}. Anodic deposition from solutions containing Fe{sup 2+} results in a film with a structure similar to {gamma}-FeOOH. From the knowledge gained from the present studies, principles and methods for decontamination have become apparent. Contaminants sorbed on oxide surfaces or co-precipitated may be removed by acid wash and selective dissolution or complexation. Ions incorporated into lattice sites and interlamellar layers will require more drastic cleaning procedures. Electropolishing and the use of an electrochemical brush are among concepts that should be considered seriously for the latter cases. The incorporation of radionuclides into the structure of highly defective, insoluble oxides and clays should be considered for long-term storage and disposal. The establishment of a truly long-term (10 to 20 years) basic program on environmental science by DOE is strongly recommended. Avenues for future work are suggested.
- Research Organization:
- Argonne National Lab., IL (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 752916
- Report Number(s):
- ANL/CMT/RP-101081; TRN: US0001591
- Resource Relation:
- Other Information: PBD: 16 Feb 2000
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SURFACE CONTAMINATION
DECONTAMINATION
FILMS
CERIUM OXIDES
STRONTIUM OXIDES
CHROMIUM OXIDES
IRON OXIDES
URANIUM OXIDES
NICKEL OXIDES
CHEMICAL COMPOSITION
CRYSTAL STRUCTURE
CERIUM HYDROXIDES
STRONTIUM HYDROXIDES
CHROMIUM HYDROXIDES
IRON HYDROXIDES
URANIUM HYDROXIDES
NICKEL HYDROXIDES