SPECTRAL EMISSIVITY AND OPTICAL-PROPERTIES AT LAMBDA = 632.8 NM FOR LIQUID URANIUM AND ZIRCONIUM AT HIGH-TEMPERATURES

The spectral emissivities, refractive indices, and extinction coeffici ents of pure liquid uranium and zirconium were measured versus tempera ture by He-Ne laser polarimetry at a wavelength of 632.8 nm. The exper iments were conducted under containerless conditions using electromagn etic levitation and heating supplemented by CO2 laser beam heating. Cl ean liquid metal surfaces were achieved by heating the specimens to hi gh temperatures at which oxides evaporated and nitrides decomposed. Re sults were obtained for liquid uranium and zirconium in the temperatur e ranges 2000-2800 K and 2000-2600 K, respectively and included data f or liquid zirconium undercooled by 125 K. The spectral emissivity of z irconium was equal to 0.345 and was independent of temperature. The sp ectral emissivity of uranium increased with temperature from 0.272 at 2000 K to 0.294 at 2800 K. The melting temperature of zirconium was de termined from its emissivity and apparent melting temperature to be 21 25 +/- 11 K, in good agreement with values in the literature.