Radiation-enhanced diffusion and fission gas release from recrystallised grains in high burn-up hbox{UO}_{2} nuclear fuel |
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Authors: | S. Bre´mier C. T. Walker |
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Affiliation: | European Commission, Joint Research Centre , Institute for Transuranium Elements , Postfach 2340, Karlsruhe, D-76125, Germany |
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Abstract: | The effective diffusion coefficient that gives a steady-state xenon concentration of 0.2-0.3wt% in the recrystallised grains of high burn-up UO 2 fuel is calculated to lie in the range 10 m 24 to 10 m 22 m 2 s m 1 . These values are one to three orders of magnitude lower than the value currently accepted for the radiation-enhanced diffusion coefficient. The time required to reach the steady-state concentration depends on the local fission rate, the grain size distribution and the precise magnitude of the radiation-enhanced diffusion coefficient, and can take from 2 to 10 years. Additional calculations reveal that substantially less than 10% of the fission gas inventory is released from the original UO 2 grains in the outer region of the fuel prior to recrystallisation. In contrast, with a diffusion coefficient of 10 m 22 m 2 s m 1 more than 80% of the fission gas is released from the recrystallised grains of the high burn-up structure in one year. |
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Keywords: | Radiation-enhanced Diffusion Fission Gas Release Recrystallisation High Burn-up Uo2 |
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