Oxidation of UO2(s) in aqueous solution

Abstract

Abstract:In this review the kinetics and mechanism of oxidative dissolution of UO 2 (s), mainly under conditions of relevance for the safety assessment of a deep geological repository for spent nuclear fuel, are discussed. Rate constants for the elementary processes involved (oxidation of UO 2 and dissolution of oxidized UO 2 ) are used to calculate the rates of oxidative UO 2 (s) dissolution under various conditions (type of oxidant, oxidant concentration and HCO 3 -/CO 3 2-concentration) for which experimental data are also available. The calculated rates are compared to the corresponding experimental values under the assumption that the experimental numbers reflect the steady-state conditions of the system. The agreement between the calculated rates and the corresponding experimental ones is very good, in particular for the higher rates. In general, the calculated rates are somewhat higher than the experimental numbers. This can be due partly to the use of initial concentrations rather than steady-state concentrations in the calculations. The kinetic data are also used to quantitatively discuss the dynamics of spent nuclear fuel dissolution under deep geological repository conditions. © Versita Warsaw and Springer-Verlag Berlin Heidelberg.

On the impact of reactive solutes on radiation induced oxidative dissolution of UO2

“…The solution contained 10 mM HCO À 3 and NaCl (2 M Table 2. The solution (containing the UO 2 pellet) was irradiated in a 137 Cs c-source Table 1 Rate constants for the oxidation of UO 2 by the products of radiolysis of water containing HCO À 3 [5,6]. Gammacell 1000 Elite from MDS Nordion with dose rate 0.15 Gy s À1 (determined by Fricke dosimetry [29]).…”

“…The solutions were saturated by different gases (inert gas, N 2 O, Air) in order to vary the conditions by changing the initial yields of radiolysis products. N 2 O promotes the production of OH Å (which in turn is converted to CO ÅÀ 3 in the presence of carbonate) by conversion of the solvated electron according to reaction (5).…”

“…Since oxidative dissolution of the UO 2 matrix of spent nuclear fuel is a key issue in the safety assessment of a future deep repository the process has been subject to extensive investigations over the years [1,5]. Relatively fresh spent nuclear fuel has sometimes been used in these experimental studies.…”

Factors influencing the rate of radiation-induced dissolution of spent nuclear fuel

“…The kinetics and mechanisms of surface reactions on UO 2 have also been studied quite extensively during the past decade. Most of the current knowledge in this field has recently been summarized in a review paper [10].…”

Radiation Effects on Materials Used in Geological Repositories for Spent Nuclear Fuel

“…As can be understood, this is quite an extensive task, and there is a vast body of the scientific literature covering this topic. Research on this topic has been summarized in several reviews [21][22][23].…”