부산대학교 도서관

ABSTRACTInteraction tests between UO2and Zr were performed at precisely controlled high temperatures between 1840 and 2000°C (±2.5°C for 1900, 1920, 1930, 1940, and 2000°C, ±10°C for 1840 and 1890°C, respectively), to understand the interaction mechanism in detail. A Zr rod was inserted in a UO2crucible and then heat-treated at a fixed temperature in an Ar-gas flow for 10 min. After heating in the range of 1890 to 1930°C, the Zr rod was deformed to a round shape, in which the post-analysis detected the significant diffusion of U into the Zr region and the formation of a dominant α-Zr(O) matrix and a small amount of U-Zr-O precipitates. An abrupt process of liquefaction was observed in the sample heated at around 1940°C or higher. Furthermore, the post-analysis results suggested the detailed liquefaction mechanism: (1) the higher oxygen concentration in the α-Zr(O) matrix suppressed the liquefaction progress, due to the variation in the equilibrium state; (2) the U-Zr-O melt formation progressed by the selective dissolution of Zr from the matrix, corresponding to the reverse variation of the oxygen concentration in the matrix; (3) the selective diffusion of U could occur via the U-Zr-O melt.