URANIUM AND OXYGEN SELF-DIFFUSION IN UO2

Uranium self-diffusion coefficients in hyperstoichiometric uranium dioxide UO2 + x (0.005 ≤ x ≤ 0.217) were determined in the temperature range 1275-1650 °C by means of the alpha spectrum degradation method. The results can be fitted, in the composition range 0.03 < x < 0.20, with the Arrhenius equation: D = 0.13 x2 [1 + 103 x3] exp (-85 000/RT)cm2/sec. Oxygen self-diffusion in massive UO2 samples has been studied by means of mass spectrometry (using a spark or laser source), proton 18O (p, α) 15N reaction and ionic mass analyzer. In the temperature range 780-1250 °C, oxygen diffusion in stoichiometric samples can be represented by the equation: D = 0.26 exp (-59 300/RT) cm2/sec. A considerable enhancement of D with small stoichiometry deviations has been evidenced at 800 °C. © 1969.