Radionuclides in Irradiated Graphite of Industrial Uranium–Graphite Reactors: Effect of Irradiation and Thermochemical Treatment on the Graphite Structure

The structure of irradiated graphite from decommissioned industrial uranium–graphite reactors was studied. The extent of disturbance of the graphite structure is closely correlated with temperature and integral neutral fluence. The perfection of the structure of graphite samples (data of X-ray diffr...

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Bibliographic Details
Published in:Radiochemistry (New York, N.Y.) N.Y.), 2018-11, Vol.60 (6), p.664-671
Main Authors: Shiryaev, A. A., Volkova, A. G., Zakharova, E. V., Nikolsky, M. S., Averin, A. A., Dolgopolova, E. A., Yapaskurt, V. O.
Format: Article
Language:English
Subjects:
Chemistry
Chemistry and Materials Science
Chemistry/Food Science
Correlation
Crystal lattices
Domains
Fish
Fluence
Graphite
Heat treatment
Irradiation
Mapping
Nuclear Chemistry
Oxidation
Radioactivity
Radioisotopes
Raman spectroscopy
Reactors
Spatial distribution
Spectrum analysis
Thermal shock
Uranium
X-ray diffraction
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Summary:The structure of irradiated graphite from decommissioned industrial uranium–graphite reactors was studied. The extent of disturbance of the graphite structure is closely correlated with temperature and integral neutral fluence. The perfection of the structure of graphite samples (data of X-ray diffraction and Raman spectroscopy) does not correlate with their radioactivity, which is due to low absolute concentration of the radionuclides. Mapping of the samples using Raman spectroscopy reveals spatial heterogeneity of the distribution of graphite lattice damages, which casts doubt on the representativeness of the spectra of individual points. The spatial distribution of domains differing in the crystal lattice perfection was studied for the first time and was compared with the radionuclide distribution. Satisfactory correlation between the radiographic and spectroscopic mapping data is observed for some samples. Irradiated graphite is strongly textured and contains amorphous microvolumes, which are probably radionuclide carriers. Thermochemical treatment (oxidation in O 2 , thermal shock) leads to degradation of the irradiated graphite structure on the submicron level, accompanied by a drastic decrease in the mechanical strength of the samples.
ISSN:1066-3622
1608-3288
DOI:10.1134/S1066362218060164