[2E01-07] Evaluation of physical properties of nuclear fuel

[2E07] Study on crystal structure of U_1-yLn_yO_2-x(Ln=Gd, Er) solid solution

*MAO VAN PHAM¹, Tatsumi Arima¹, Yaohiro Inagaki¹, Kazuya Idemitsu¹, Daisuke Akiyama², Takayuki Nagai³, Yoshihiro Okamoto³ (1. Kyushu Univ., 2. Tohoku Univ., 3. JAEA)

Keywords:UO2, burnable poison, crystal structure, XRD, XAFS

UO₂-LnO_1.5 (Ln=Gd, Er; LnO_1.5=0-40 mol%) samples were prepared, sintered at 1700 ^oC for 4 hours under reduction condition. The effect of LnO_1.5 doping on the crystal structure of UO₂-LnO_1.5 samples was evaluated by XRD and XAFS measurements. LnO_1.5 doping into UO₂ reduced the lattice parameter of UO₂-LnO_1.5 solid solution. The interatomic distances of U-O and Ln-O in U_1-yLn_yO_2-x decreased with a very small change when LnO_1.5 is added. The change of crystal structure results from doping of LnO_1.5 (the formation of oxygen vacancies) and oxidation U⁴⁺ to U⁵⁺.