Effects of HCO3- on the kinetics of UO2 oxidation by H2O2
2006 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 358, no 2-3, 202-208 p.Article in journal (Refereed) Published
The effect of HCO3- on the kinetics of UO2 oxidation by H2O2 in aqueous solution has been studied using powder suspensions where the concentration of H2O2 was monitored as a function of time. By varying the UO2 surface to solution volume ratio second order rate constants were obtained for HCO3- concentrations ranging from 0 to 100 mM. The second order rate constant increases linearly with HCO3- concentration from 0 to approximately 1 mM. Above 1 mM HCO3- the rate constant is 4.4 × 10-6 m min-1 independent of [HCO3-]. This indicates that the kinetics of the reaction depends on both oxidation and dissolution below 1 mM HCO3- while at higher concentrations it is solely governed by oxidation. Hence, the rate constant obtained at HCO3- concentrations above 1 mM is the true rate constant for oxidation of UO2 by H2O2. The results also imply that the reaction between HCO3- and oxidized UO2 on the UO2 surface (i.e. HCO3- facilitated dissolution) is limited by diffusion (ca 10-3 m min-1 in the present system). Furthermore, the experimental results were used to estimate the oxidation site density of the powder used (126 sites nm-1) and the rate constant for dissolution of UO22 + from the UO2 surface (7 × 10-8 mol m-2 s-1).
Place, publisher, year, edition, pages
2006. Vol. 358, no 2-3, 202-208 p.
F0700, U0200, W0200
IdentifiersURN: urn:nbn:se:kth:diva-6360DOI: 10.1016/j.jnucmat.2006.07.008ISI: 000242254200012ScopusID: 2-s2.0-33750371503OAI: oai:DiVA.org:kth-6360DiVA: diva2:11051
QC 201009102006-11-172006-11-172011-01-21Bibliographically approved