OBSERVATIONS ON THE OXIDATION OF BERYLLIUM IN CO$sub 2$ BY USE OF C$sup 14$$O$$sub 2$ AND AUTORADIOGRAPHIC TECHNIQUES
Because of the proposed use of beryllium as a fuelcladding material in a CO/sub 2/-cooled reactor, the compatibility of beryllium and CO/sub 2/ at elevated temperatures is of interest. The reported breakaway or nonprotective oxidation of beryllium in CO/sub 2/ under certain test conditions and the proposed relation of this phenomenon to carbon absorbed during the oxidation stimulated a brief study to determine the reaction products formed and their location. A limited number of tests were run at a pressure of 200 mm lig in C/ sup 14/O/sub 2/ at temperatures between 593 and 815 deg C for times up to 500 hr. The specimens were examined after test using metallographic, autoradiographic, and surface-counting techniques. It was found that the reaction products of the beryllium with CO/sub 2/ were BeO and Be/sub 2/C. The reaction proceeded along preferred longitudinal directions that seemed to be influenced by the voids present in the as-received materia1. The reaction advanced more rapidly in the longitudinal than in the transverse direction. Three possible mechanisms were proposed to account for the greater rate in the longitudinal direction based upon an excess concentration of vacancies in the oxide film from the voids, the segregation of impurity atoms around the voids, and the inability of the material to deform plastically in certain directions due to preferred orientations of the grains. It was found that the beryllium specimens increased in carbon content during exposure to CO/sub 2/. The carbon was found to remain associated with the reaction product and did not diffuse into the beryllium. (auth)
- Research Organization:
- Oak Ridge National Lab., Tenn.
- DOE Contract Number:
- W-7405-ENG-26
- NSA Number:
- NSA-17-034349
- OSTI ID:
- 4667273
- Report Number(s):
- ORNL-TM-622
- Country of Publication:
- United States
- Language:
- English
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