Oxygen potential of hypo-stoichiometric Lu-doped UO2

Abstract

a b s t r a c tOxygen potentials of hypo-stoichiometric Lu-doped UO 2 , (U 0.80 Lu 0.20 )O 2Àx , were experimentally investigated by thermogravimetric analysis using H 2 O/H 2 gas equilibria at 1173, 1273 and 1473 K. The oxygen potentials of (U,Lu)O 2Àx were higher than those of other forms of rare earth-doped UO 2 , specifically (U,Nd)O 2Àx , (U,Gd)O 2Àx , and (U,Er)O 2Àx . Slope analyses for plots of oxygen potential versus deviation from stoichiometry indicated that (U 0.80 Lu 0.20 )O 2Àx had a similar defect structure to that of the other forms of rare earth-doped UO 2 . A relationship between the effective ionic radii and oxygen potentials was found for the hypo-stoichiometric rare earth-doped UO 2 .

Oxygen non-stoichiometries in (Th0.7Ce0.3)O2−x

“…4. It is thought that DS O 2 and DH O 2 reflect information on defect structures [16]. A similarity between the profile of DS O 2 for (Th 0.7 Ce 0.3 )-O 2Àx and that for CeO 2Àx is observed, while the profiles of DH O 2 are different between those in mean Ce valence ranging from 3.6 to 3.9.…”

Oxygen potential of hypo-stoichiometric La-doped UO2

“…and 8, respectively. Oxygen potentials of (U 0.8 RE 0.2 )O 2-x : RE=Lu [6], Er [12], Gd [4], La (this study)…”

“…According to Eqs. (6)(7)(8), the slopes 1/n of the plot of log ΔG values by following relations: ΔG is generally considered to be a stability of the oxygen vacancy in the fluorite solid solution with oxygen hypo-stoichiometry. Thus, in the hypo-stoichiometric range, it could be that at the given O/M ratio, the larger the absolute value of 2 O ΔG is, the higher the stability of the oxygen vacancy is.…”

“…They reported that there were little different in the oxygen potentials of (U,Ln)O 2±x with different Ln elements. Osaka et al [6] have, however, shown that the oxygen potential of (U,Lu)O 2-x was notably higher than those of other (U,Ln)O 2-x . Since high burnup fuels have a variety of lanthanide compositions as fission products according to the fuel specification, such difference in oxygen potential of (U,Ln)O 2±x should be clarified.…”

“…against -logx become 1/3, 1/4 and 1/5 respectively. Thus, the defect structures of (U,La)O 2-x at 1173 K and 1273 K are considered as the vacancy cluster given by Eqs (6). and(8).…”