Kinetic study of the effect of a sudden change in temperature during the reduction of U3O8 into UO2 by hydrogen

In the non-isothermal approach to the determination of kinetic constants, t he mathematical analysis of the a-time curve is based on the assumption of a rate equation, which in some cases, is not consistent with the isothermal curves. For example, during the reduction of U3O8 by hydrogen, we have sho wn from isothermal and isobaric experiments that a model of nucleation and anisotropic growth was able to fit the experimental rate curves. This makes the analysis of non-isothermal experiments very complex. A first attempt t o solve this problem is presented here, in which the effect of a sudden cha nge in the reaction temperature during an experiment is analysed. Taking in to account the differences due to the sudden change in the calculation of t he rate, a good agreement was found between the calculated and experimental d alpha /dt vs. a curves. (C) 2001 Elsevier Science B.V. All rights reserv ed.