Laser heating investigation of the high-temperature interaction between zirconium and UO2
Abstract
In order to simulate, on a laboratory scale, the high-temperature interaction between cladding and nuclear fuel, a laser heating technique has been used to investigate the liquid-solid transitions in three compositions close to the section Zr-UO2. In fact, near the Zr-rich corner of the U-Zr-O ternary phase diagram, no experimental data are available in literature. A clear melting-solidification thermal arrest has been observed in the Zr-richer (14 molpercent UO2) composition. A double transition has been recorded for the compositions with higher uranium dioxide content (10.6 molpercent and 15 molpercent UO2). Interestingly, the lowest temperatures at which the second thermal arrests occur in the latter two compositions are lower than the melting point retained for pure Zr (2125 K approximately). This suggests the presence, in this part of the phase diagram, of a minimum liquefaction point. Emissivity of the investigated samples has been obtained with a multi-wavelength pyrometer within the grey-body assumption, which is reasonable in a narrow wavelength range between the visible and the near infrared spectral domain.