The diffusion coefficient of oxygen into alpha-uranium at 323 °K determined by grazing angle X-ray diffraction technique

Abstract

The diffusion of oxygen into uranium is of scientific interest for the understanding the kinetics of corrosion. In practical applications it is critical to know the amount of oxygen penetrating into the bulk metal because it has a direct impact on material properties, like ductility and embrittlement. Oxygen diffusion coefficients (ODC) into metals are often very difficult to obtain. Typically, they are measured by determining the concentration of oxygen isotopes as a function of depth into the metal. Isotope-sensitive detection is used in conjunction with materials removal usually carried out by sputtering, which is often very difficult and time-consuming. In this paper we instead employ a grazing angle XRD technique to accurately measure changes in lattice parameters near the surface. We use the observed the expansion of the metal unit cell as oxygen diffuses into the matrix during oxidation. The amount of oxygen concentration is approximated based on U3O8 which has the same structure uranium but higher concentration of atomic oxygen. We estimated that the ODC of oxygen into uranium at 323°K at 1 ATM to be D = 3.76 × 10−27 m2/sec which is extremely small as previously noted.

Keywords

• Oxygen diffusion into metals
• X-ray diffraction technique
• Uranium
• Oxidation