Viscosity measurement on high temperature melts, (1)

What is called high temperature melt such as molten salt or liquid metal has attracted notice as the thermal media in breeder reactors or nuclear fusion reactors, blanket materials or the regenerators for utilizing energy. However, investigation of the physical properties of these materials has not been performed much. The authors have designed and produced a measuring apparatus based on the oscillating cup method for trial, aiming at conducting the absolute measurement of the coefficient of viscosity with high accuracy over the temperature range up to 1800 K, for such high temperature melts. The potassium nitrate (KNO3) recommended as a standard material has been selected to evaluate the reliability of the apparatus. This paper first explains the principle of and the theoretical formula for the oscillating cup method, then the measuring apparatus, and in turn describes on the sample, the measured results and discussion. In the investigation this time, the measurement of the coefficient of viscosity was made with the accuracy of +- 1.1% and the reproducibility fo + 0.5% in the range from 623 to 973 K. The reliability of the apparatus has been ensured by the agreement of the results with past data at temperature below 740 K. At the same time, the actually measured results of the coefficient of viscosity were able to be obtained in the high temperature region for the first time. A new equation for calculating the coefficient of viscosity has been made by comparing the results with the reliable data obtained so far. (Wakatsuki, Y.)