A thermal conductivity and electromotive force measurement system for nuclear fuels and materials

The development of advanced nuclear fuels requires detailed understanding of their transmutation and micro-structural evolution. Alloy fuels have the advantage of high thermal conductivity and improved characteristics in fuel-cladding chemical reaction. However, information on thermodynamic and thermophysical properties is limited. The objective of this work was to develop an experimental system, integrated with thermal conductivity measurement capability to measure the thermodynamic properties of solid materials, from which an understanding of their phase change(s) can be determined. With the coupled system, both thermal conductivity and electromotive force (EMF) may be measured. In order to validate the system, the apparatus was employed to measure the EMF of several materials. As an initial calibration test, the EMF of Chromel was measured from 100 °C to 800 °C and compared with theoretical values. Subsequent EMF measurements were made for pure iron, iron-nickel alloy, and ANSI 1018 carbon steel rods. The measured phase transition temperatures were compared with the corresponding alloy equilibrium phase diagrams. The results indicate that the system is able to determine material phase change based on EMF measurement. In the future, this prototype system is to be adapted for hot-cell use on irradiated samples.