An investigation of the thermal conductivity of Zr-2.5%Nb reactor alloy

Experimental data are obtained for the thermal conductivity coefficient of zirconium containing 2.5% niobium. The investigated temperature range of 400 to 1600 K covers the range of existence of hexagonal (alpha-phase) and cubic (beta-phase) structural modifications of the alloy. The low-temperature and high-temperature structures differ by the value of the temperature derivative of the thermal conductivity coefficient. The thermal cycling of sample under vacuum of 10(-3) Pa leads to a gradual decrease in thermal conductivity, which is especially pronounced at low temperatures. The available data on electrical resistance for the alpha-phase region are used to estimate the Lorentz function. The obtained values of Lorentz number are indicative of the predominating part played by the electron mechanism of thermal conductivity in the alloy. The values of thermal conductivity measured for the beta-phase are used to determine the electrical conductivity of the alloy.