Oxidation behaviour of unirradiated sintered UO2 pellets and powder at different oxygen partial pressures, above 350°C

Françoise Valdivieso (1, 2, 3) , Michèle Pijolat (1, 2, 3) , V. Francon (1, 2, 3) , François Byasson (1, 2, 3) , A. Feugier (4) , Véronique Peres (4)

1 ProcESS-ENSMSE - Département Procédés et évolution des systèmes avec solides
2 SPIN-ENSMSE - Centre Sciences des Processus Industriels et Naturels
3 LPMG-EMSE - Laboratoire des Procédés en Milieux Granulaires
4 FBFC

The oxidation of sintered UO2 pellets and powder into U3O8 has been studied by thermogravimetry at 370°C, under controlled oxygen partial pressures (PO2 ranging from 2-40 kPa). Sigmoidal curves of oxidation weight gain were measured for both pellet and powder test samples. The rate of oxidation increased as the oxygen partial pressure increased. It has been shown, by simultaneous TG-DSC, that the reaction proceeds in a pseudo steady state. An experimental methodology based on temperature or PO2 jumps has shown that the assumption of a rate-limiting step is validated, and a mean value of activation energy for the formation of U3O8 of 103 kJ.mol-1 was estimated.

Keywords: U3O8; kinetics; oxygen partial pressure; pseudo steady state; rate-limiting step

Domains: Chemical and Process Engineering

Françoise Valdivieso, Michèle Pijolat, V. Francon, François Byasson, A. Feugier, et al.. Oxidation behaviour of unirradiated sintered UO2 pellets and powder at different oxygen partial pressures, above 350°C. Journal of Nuclear Materials, 2006, 354 (1-3), pp.85-93. ⟨10.1016/j.jnucmat.2006.02.096⟩. ⟨hal-00409379⟩