ANALISIS KOMPOSISI UNSUR, DENSITAS, MAKROSTRUKTUR, DAN FASA PADUAN U-6Zr-xNb PASCA UJI KOROSI

Abstract

ANALYSIS OF ELEMENTAL COMPOSITION, DENSITY, MACROSTRUCTURE, AND PHASE FORMATION OF U-6Zr-xNb ALLOY POST CORROSION TEST. Research on the elemental composition, density, macrostructure, and phase formation of U-6Zr-xNb alloy have been done after corrosion test. The alloy composition analysis had been done before the corrosion test which included uranium content analysis by potentiometric titration, impurity analysis with Atomic Absorption Spectroscopy (AAS), and U, Zr and Nb content analysis with X-Ray Fluorescence (XRF). The alloy composition analysis was aimed to ensure that U-6Zr-xNb fuel meets the quality requirements of nuclear fuel specifications. The density, macrostructure and phase test were done after the corrosion test. The density test is required as one of the parameters in calculating the corrosion rate, and the microstructure and alloy phase observations are required to determine the damage or corrosion products and the layers/phases formed after the occurance of corrosion. The results of the U-6Zr-xNb alloy composition analysis with XRF and potentiometric titration show that the uranium content is close to the expected level, whereas the impurity test with AAS shows high levels of impurities including Al, Fe and Si. Based on these results, U-6Zr-xNb fuel meets the requirements because the elements of Al, Fe and Si have low neutron absorption cross-section. The sample density test results of U-6Zr, U-6Zr-1Nb, U-6Zr-4Nb, and U-6Zr-7Nb were 16.9798 g/mL, 16.6115 g/mL, 15.594 g/mL, and 15.3564 g/mL respectively. Macrostructure observation of the post-corrosion alloy shows black spots which are the result of oxidation of U (IV) to U (VI). The U-6Zr-xNb alloy experiences the greatest corrosion in mineral-free water media. The damage to the alloy surface decreases as the weight percentage of Nb in the alloy increases. The results of post-corrosion alloy characterization using XRD show that the U-6Zr and U-6Zr-1Nb samples formed an α phase, while the U-6Zr-4Nb and U-6Zr-7Nb samples formed γ phase. The protective Nb₂O₅ oxide layer formed, however, is minute and unlikely to be detected by XRD.