Grain size effects on the aqueous durability of Gd2Zr2O7 ceramics as high-level radioactive wastes matrix and its leaching mechanism

Gd 2 Zr 2 O 7 ceramic is considered as one of the most promising host minerals for the immobilization of high-level radioactive wastes . Here, the effects of grain size on the aqueous durability of Gd 2 Zr 2 O 7 ceramics were studied. Two kinds of leaching experiments were used to research Gd 2 Zr 2 O 7 ceramic powders and bulks with different grain sizes (5 nm, 78 nm, 1 μm and 18 μm). The results demonstrate that the normalized leaching rates decrease with the increase of grain size. Through characterization and analysis, it is concluded that the hydrolysis reactions of Gd 2 Zr 2 O 7 occur in the leaching experiment and the hydrolysates are Gd(OH) 3 and Zr(OH) 4 . Besides, all the samples after leaching exhibit slight lattice contraction, which decreases with the increase of crystal grain size. The influence of leaching on the elemental distribution is most significant for the sample with grain size of 5 nm. This study has theoretical guiding significance for the application of Gd 2 Zr 2 O 7 immobilization.