Design and performance of an improved thermo-optometric equipment for the measurement of the solidus and liquidus at high temperatures

Experimental determination of solidus and liquidus in reactive systems at very high-temperatures requires special equipment and is rather complex. In the present study, we describe setting up an experimental facility based on the “spot-technique.” It was demonstrated that this setup could be used to measure phase transformation temperatures involving liquids in refractory systems that comprise reactive and radioactive components, in the range of 1273 K–2273 K, by using a thermo-optometric technique, namely, the “spot-technique.” The equipment and the method were validated by measuring the melting points of high purity metals, namely, gold, copper, nickel, and zirconium. A measurement accuracy of ±2 K could be realized at temperatures as high as 2128 K. The solidus and liquidus temperatures of nuclear reactor fuels as well as some binary alloys were also measured by using this setup. The research involved in building this equipment and the key features of the equipment and method are described in detail.