High‐Temperature Hemispherical Spectral Emittance of Uranium Oxides at 0.65 and 0.70 μm

Hemispherical spectral emittances were measured for uranium oxides. The compositions ranged from UO 1.05 to UO 2,20 the bulk densities from about 8 to more than 10.6 g/cm 3 , the apparent porosities from less than 0.5 to 19.0%, and the temperatures from about 450° to about 2400°K. The data were taken at wavelengths of 0.656 and 0.70 μm. The emittance is high in all cases (from about 0.70 to above 0.90) and increases with increasing wavelength. The emittance is not strongly sensitive to temperature, porosity, density, surface finish, or stoichiometry. The high emittance values are linked to the absorption edge observed for uranium oxides in the visible portion of the spectrum.