The Study of Oxidation/Reduction Volatilization

The Study of Oxidation/Reduction Volatilization

6 Asia-Pacific Symposium on Radiochemistry
September 17 ~ 22, 2017 • ICC Jeju • Jeju Island, Korea
th
The Study of Oxidation/Reduction Volatilization Technology for the UO2 Simulated Fuel
Tan Cunmin,1 Cao Shiwei, 2 Qin Zhi3
Institute of Modern Physics, Chinese Academy of Sciences, No. 509 Nanchang Rd,
730000, Lanzhou, China. E-mail: [email protected]
2
Institute of Modern Physics, Chinese Academy of Sciences, No. 509 Nanchang Rd,
730000, Lanzhou, China. E-mail: [email protected]
3
Institute of Modern Physics, Chinese Academy of Sciences, No. 509 Nanchang Rd,
730000, Lanzhou, China. E-mail: [email protected]
1
As an advanced dry head-end processing of spent fuel reprocessing, the Oxidation/Reduction volatilization technology
will use for pulverizing uranium oxide ceramic pellets, decladding, and removal of most of volatile and semi-volatile fission
elements, 3H, 14C, Kr, Xe, I, Cs, Ru and Tc, from fuel prior to main treatment process. The AIROX and ORIOX process,
including circulation of oxidation in oxygen atmosphere and reduction in hydrogen atmosphere，researched on international
at present, is considered to be the first choice for head-end processing.
In the AIROX process, fuel decladding can be accomplished oxidatively.[1,2] In oxidative decladding, the fuel pin is
punctured and then heated in air (400 to 600℃) so that the oxidation of UO2(10.96 g/cm3) to U3O8(8.3 g/cm3) powder can
then be easily separated from the cladding. The U3O8 is then reduced in hydrogen at 600 to 1000℃ to regenerate UO2. The
Oxidation/Reduction steps are performed at high enough temperatures to cause the release of volatile fission products.[3] The
ORIOX process is an improvement on the AIROX process. Oxidation is performed at a higher temperature (1200℃) than in
the AIROX process resulting in a more effective removal of the volatile fission products. [4, 5]
In this paper, the UO2 powder was pressed into simulated pellets by tablet machine at 10 MPa and sintered at 1700 ℃
for 7 hours in an atmosphere of 4% H2/Ar. In oxidative process at different conditions above 300 ℃, the UO2 simulated
pellets all showed good pulverization results. Fig.1(a, b) shows the three cycles of a oxidation at 450℃ in air/50% O2/Ar and
a reduction at 700℃ in 4% H2/Ar for UO2 simulated pellets. The particle size of two conditions are both less than 10 microns
and the UO2 simulated fuel will separate from the cladding easily. Based on these, our group studied the UO2 real fuel pellets
in 3 cycle Oxidation/Reduction process. As Fig.1(c) shown, the average particle size is larger than simulated fuel because of
different preparation process.
a
b
c
Fig.1 Particle size (a) UO2 simulated pellets--Oxidation: 50% O2-Ar, 450℃, 4 h; Reduction: 4% H2-Ar, 700℃, 4 h；
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6 Asia-Pacific Symposium on Radiochemistry
September 17 ~ 22, 2017 • ICC Jeju • Jeju Island, Korea
th
(b) UO2 simulated pellets--Oxidation: air, 450℃, 4 h; Reduction: 4% H2-Ar, 700℃, 4 h;
(c) UO2 real fuel pellets--Oxidation: air, 450℃, 4 h; Reduction: 4% H2-Ar, 700℃, 4 h.
The XRD patterns of simulated and real pellets after the complete oxidation and reduction are shown in Fig.2. The result
is in agreement with standard parameter of U3O8 and UO2, which confirmed chemical conversion of Uranium can be fully
realized.
More in-depth research for volatile and semi-volatile elements of the UO2 simulated pellets in Oxidation/Reduction
cycle process is our present work in order to lay a foundation for the advanced dry head-end processing of spent fuel
reprocessing.
ACKNOWLEDGMENTS
The present work is supported by the CAS Strategic Priority Research Program (XDA03010402).
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