Applied Chemistry for Engineering (공업화학)

The Korean Society of Industrial and Engineering Chemistry (한국공업화학회)
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High Temperature Oxidation Behavior of Nd-doped $UO_2$

네오듐 고용 이산화우라늄의 고온 산화거동

  • Published : 2013.06.10
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Abstract

The phase change of $(U_{1-x}Nd_x)_3O_8$ powder produced by oxidation of Nd-doped $UO_2$ pellet at $500^{\circ}C$ was investigated by high temperature oxidation heat treatment at $900{\sim}1500^{\circ}C$ under an air atmosphere. The XRD analysis results showed that the formation of $(U_{1-y}Nd_y)O_{2+z}$ phase and $U_3O_8$ phase from metastable $(U,Nd)_3O_8$ phase initiated at a temperature of $1000^{\circ}C$. The relative integrated intensity of $(U_{1-y}Nd_y)O_{2+z}$ phase to $U_3O_8$ phase increased with increasing of the oxidation temperature from 1100 to $1500^{\circ}C$. And also, it was found from the SEM observation that the particle size of $(U_{1-y}Nd_y)O_{2+z}$ phase increased with increasing of the oxidation temperature. However, electrone probe X-ray microanalyzer (EPMA) analysis results showed that Nd contents in $(U_{1-y}Nd_y)O_{2+z}$ phase decreased with increasing of the oxidation temperature. This behavior on the ground of XRD, SEM, and EPMA analysis data could be interpreted in terms of the transportation of U ions from $U_3O_8$ phase into $(U_{1-y}Nd_y)O_{2+z}$ phase through the interface of two phases during high temperature oxidation.

$(U_{1-x}Nd_x)O_2$ 소결체를 $500^{\circ}C$에서 산화하여 얻은 $(U_{1-x}Ndx)_3O_8$ 분말의 상변화를 $900{\sim}1500^{\circ}C$의 공기 중에서 고온 산화 열처리를 하여 조사하였다. $1100^{\circ}C$ 이상의 온도로 산화 열처리할 경우에 Nd 농도가 높은 $(U_{1-y}Nd_y)O_{2+z}$ 상과 $U_3O_8$ 상이 생성됨을 확인하였으며, 산화 열처리 온도가 높아질수록 $(U_{1-y}Nd_y)O_{2+z}$ 상에서의 Nd 농도는 감소하였다. 산화 열처리 온도의 증가에 따라서 $U_3O_{8-w}$ 입자로부터 $(U_{1-y}Nd_y)O_{2+z}$ 입자로의 U 양이온 및 Nd 양이온이 두 입자의 계면을 통해 농도 구배에 따른 확산에 의해서 $(U_{1-y}Nd_y)O_{2+z}$ 상 내에 U의 농도는 증가하고 Nd의 농도는 감소하게 된다. 이러한 현상은 산화 열처리 온도증가에 따라서 $U_3O_8$ 상에 대한 $(U_{1-y}Nd_y)O_{2+z}$ 상의 X-선 회절피크의 적분강도비 증가와 $(U_{1-y}Nd_y)O_{2+z}$ 상의 입자가 커지는 것과 연관하여 해석할 수 있었다.

Keywords

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