Survey of binary oxide fuel manufacturing and quality control

Phase studies in the UO2–Gd2O3 system

“…The interdiffusion processes decrease the sintering rate and shift densification to higher temperatures. Assmann et al [8] complemented this proposition by verifying that the diffusion coefficients in the UO 2 -Gd 2 O 3 system show a complex dependence on the U:Gd:O ratio in the oxide phases formed. Peehs et al [12] detected the presence of the (U 0.5 Gd 0.5 )O 2 phase in sintered UO 2 -Gd 2 O 3 pellets; however, their report did not discuss the possible participation of that phase in the sintering blockage mechanism.…”

“…Nevertheless, the incorporation of Gd 2 O 3 powder into the AUCderived UO 2 powder by the most attractive commercial method of dry mechanical blending leads to difficulties while obtaining sintered UO 2 -Gd 2 O 3 pellets with the minimum required density [7,8], due to the deleterious effect of the Gd 2 O 3 on the traditional UO 2 sintering behavior. Several studies have investigated the sintering of UO 2 -Gd 2 O 3 mixed oxides, several of them indicated difficulties in sintering fuel pellets with the minimal specified density, of around 94% of the theoretical density.…”

Remarks on the sintering behavior of UO2–Gd2O3 fuel

“…Various studies [2,3] have verified that the incorporation of Gd 2 O 3 powder into AUC-derived UO 2 powder by dry mechanical blending leads to difficulties in preparing sintered UO 2 -Gd 2 O 3 pellets with the minimum required density, due to the deleterious effect of Gd 2 O 3 on the traditional UO 2 sintering behavior. The sintering curves show that the lower sintered densities are due to the abnormal sintering behavior of UO 2 -Gd 2 O 3 fuel, compared to the sintering behavior of traditional UO 2 fuel.…”

Synthesis of UO2 and ThO2 doped with Gd2O3

“…The reference methods for industrial production of Gd 2 O 3 -doped UO 2 nuclear fuel are solely based on powder metallurgy (also called ''solid-state synthesis'') [31], while for fundamental studies of doped UO 2 and ThO 2 systems, one often prefers to go via a homogeneous solution followed by co-precipitation or sol gel routes towards the powder precursors. In the specific case of Gd 2 O 3 -doped UO 2 production, powder metallurgical routes were described by Grossman et al [32], Yuda and Une [33], and Riella et al [34], coprecipitation processes by Manzel and Dörr [35], Fukushima et al [36], Miyake et al [37], Riella et al [34], Leyva et al [38], and Durazzo et al [39], and sol gel routes by Gündüz et al [40,41].…”