Controlling the oxygen potential to improve the densification and the solid solution formation of uranium–plutonium mixed oxides

Assessing the oxygen stoichiometry during the sintering of (U, Pu)O 2 fuel

“…The second peak between 300 and 600°C is directly linked to the reduction of UO 2+x into UO 2,00 [4]. A third smaller peak appears around 900°C which also results from the reduction process of UO 2+x into UO 2,00 .…”

“…The latter sets the nature and the concentration of point defects which govern diffusion mechanisms inside the material [2]. The oxygen partial pressure, pO 2 , of the sintering gas in equilibrium with MOX pellets needs to be precisely controlled; otherwise it may induce a large dispersion in the critical parameters for fuel manufacturing [2][3][4]. Among these parameters, the oxygento-metal ratio (O/M) after sintering defines many properties of the fuel in operation (thermal conductivity, mechanical properties, fuel-cladding interaction, etc.).…”

Influence of the oxygen potential on the sintering of UO2–45% PuO2

“…It appears that densification begins at lower temperatures within oxidizing atmospheres. Recently, Berzati et al [13,14] confirmed this result on UO 2 -30% PuO 2 mixtures and showed that both densification and solid solution formation occur at a lower temperature when the oxygen potential increases. The effect of plutonium concentration on the relationship between sintering http://dx.doi.org/10.1016/j.jeurceramsoc.2015.05.006 0955-2219/© 2015 Elsevier Ltd. All rights reserved.…”

“…Sodium-cooled fast reactors (SFRs) are envisaged in France and an experimental prototype, ASTRID, is being currently under development [12]. Mixed uranium-plutonium oxide (MOX) fuel with plutonium content close to 30% is considered as candidate fuel for such reactor, and the research work regarding its fabrication is under progress [13][14][15][16][17].…”

“…It is well known that the diffusion coefficient of U and Pu in U 1−y Pu y O 2±x for a given temperature varies by 4-5 orders of magnitude with oxygen potential [18,19]. Furthermore, several studies [14,19,20] were undertaken to evaluate the oxygen potential influence on the densification of UO 2 -y% PuO 2 mixtures (with y = 0, 20, 50, 76 and 100) as a function of PuO 2 content. It appears that densification begins at lower temperatures within oxidizing atmospheres.…”