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A Study on the Oxidation Behaviorof Uranium
Abstract
The intermetallic compound of aluminum-dispersed UsSi, is used for
Hanaro Reactor(Korea Multipurpose Research Reactor, KMRR) and
U-Zr alloy nuclear fuel is under the development for a Liquid Metal
Reactor in KAERI. Depleted uranium wastes are generated in forms of
chips, scraps and powder during the manufacturing processes of
alloy-type nuclear fuels. As a radioactive waste treatment method has
not yet been fixed for these wastes, they are currently being stored in
a temporary storage house for later treatment. When storing
depleted uranium wastes, careful handling is required due to their very
high oxidation rates.
To determine the oxidation mechanism and the oxidation rate of
depleted uranium wastes, and to find important factors to be considered
in their treatment, an experiment was carried out by varying the
heating rates of an Air-Controlled Oxidizer. The experiment showed
that depleted uranium wastes are pulverized by oxidation because of
the density difference and then converted to U3O8. The grain size of
pulverized powder decreases with increased temperature.
The oxidation rate is different depending on the alloy composition of
the wastes. The oxidation rate of the U~Si alloy waste per unit area
against temperature is as follows :[ -85.8W/>«o/|
dwldt = 6.92 x 106 e\ RT I mg/ cm2 h
That for U-Zr alloy waste is as follows '•I -57.Q2/fe//mo/|
dwl dt = 8.46 x 10 7 e \ RT I mg/ cm2 h
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S.
Table 1. Analysis of impurity content(ppm) in l^Si sample 15
Table 2. Oxidation rates of U-3.9 wt% Si with air 28
Table 3. Program of thermogravimetric analyzer. 37
Table 4. Reaction rate constants for the oxidation of U-10wt% Zr
on air 46
Table 5. Oxdton rates of U-10 wt% Zr in air 47
Table 6. Oxidation rates of UO2 with air 52
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Fig. 1. Microstructure of the specimen before oxidation(x200) 16
Fig. 2. XRD pattern of initial specimen 17
Fig. 3. A Schematic diagram of oxidation test equipment 18
Fig. 4. Shape of a specimen after oxidation at 250°C 21
Fig. 5. Shape of a specimen after oxidation at 275°C 22
Fig. 6. Shape of a specimen after oxidation at 300°C 23
Fig. 7. Shape of a specimen after oxidation at 325°C 24
Fig. 8. XRD pattern change after oxidation of U~Si 26
Fig. 9. Weight gain vs time curve for the oxidation at 250-300°C 29
Fig. 10. Weight gain vs time curve for the oxidation at 325-400°C ••••30
Fig. 11. Rate of weight gain versus 1000/T 31
Fig. 12. Schematic diagram of thermogravimetric analyzer. 36
Fig. 13. Shape of a specimen after oxidation at 350°C 38
Fig. 14. Shape of a specimen after oxidation at 450°C 39
Fig. 15. Shape of a specimen after oxidation at 500°C 40
Fig. 16. XRD pattern change after oxidation of U~Zr 42
Fig. 17. Weight gain vs time curve for the oxidation at 250-300^ 43
Fig. 18. Time dependence of the weight gain at 300-500°C 44
Fig. 19. Rate of weight gain versus 1000/T 45
Fig. 20. Shape of a specimens after oxidation in air 49
Fig. 21. XRD pattern change after oxidation of UO2 50
Fig. 22. Weight gain vs time curve for the oxidation at 300-500T: 53
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Fig. 23. Rate of weight gain versus 1000/T 54
Fig. 24. Shape of DU chips before the oxidation experiment 56
Fig. 25. Shape of samples after oxidation. 58
Fig. 26. XRD pattern change after oxidation. 59
Fig. 27. Weight gain vs time curve for the oxidation at 250-500°C 61
Fig. 28. Rate of weight gain(%) versus 1000/T. 63
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BIBLIOGRAPHIC INFORMATION SHEET
Performing Qrg.Report No.
Sixxisoring Org.Report No. Standard Report No. M S Subject Code
KAERI / TR-987/98
Title/Subtitle
A Study on the Oxidation Behavior of Uranium
Project Manager/Dept.(or Main Author)
Taekook Kim (Rad Waste Treatment Facility Dep.)
Researcher/Dept
Kweonho Kang(RWTF), Kiljeang Kim(RWTF), Dsik Kang(RWTF),Kyung whan Jung(RWTF)
Pub. Place Tae jon Pub. Org. KAERI Pub. Date 1998.3
Page 80 P. HI and Tab. Yes ( v ), No ( ) Size 26 cm.
Note
Classified Open ( v ), Outside ( ), Class Report. TypeTechenical
Report
Sponsoring Org. Contract No.
Abstract
When storing depleted tiranium wastes, careful handling is required due to
their very high oxidation rates.
To determine the oxidation mechanism and oxidation rate of depleted
uranium wastes, the most important factors to be considered in their treatment
, an experiment was carried out by varying the heating rates of the
Air-Controlled Oxidizer. The experiment, showed that depleted uranium
wastes are pulverized after complete oxidation because of the density difference
and then converted to UO2, U3O7, U3O8. The grain size of pulverized powder
decreases with increased temperature.
Subject Keywords
Depleted uranium wastes, Oxidation mechanism, Oxidation rate,Air-Controlled Oxidizer, UO2, U3O3, U-Si. U-Ti alloy.
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