A study was made of the defect influence upon U diffusion, and experiments were performed under reactor conditions. A thin UO2 layer, in direct contact with a Zr foil, was irradiated in a high-flux reactor. The fission product rate was about 3 x 1011ions/s, and the neutron flux was 5 x 1014/cm2s. The target temperature ranged from 470 to 490C. Under these conditions, Zr oxidation was observed before U diffusion. A model was proposed in order to deduce the apparent U diffusion coefficient from energy distribution broadening of a selected fission product (A = 90). It was found to be equal to 10−15cm2/s. The samples were implanted with 800keV U-ions to a dose of 1016/cm2, and were annealed under a pressure of 7.5 x 10−1Pa. No U diffusion was observed at up to 800C.

Thermal- and Radiation-Enhanced Diffusion of Uranium in Oxidised Zirconium. N.Bérerd, N.Moncoffre, A.Chevarier, Y.Pipon, H.Faust, H.Catalette: Surface and Coatings Technology, 2005, 196[1-3], 10-4

Figure 43

Interface Diffusivity of 18O in Nanocrystalline Monoclinic ZrO2