Progress in Development of a Technique to Measure the Axial Thermal Diffusivity of Irradiated Reactor Fuel Pellets

Abstract

A new technique, based on pulsed high-energy (≈12 MeV) electron-beam heating, is being developed for measuring the thermal diffusivity of irradiated reactor fuel. This paper reports on the continuing development work required to establish a practical technique for irradiated materials at high temperatures (1000 to 1500 °C). This includes studies of the influence of thermocouple surface contact resistance, of the sheath and the pellet mounting system, of internal cracks in the pellet, and of the chamber atmosphere. Calibrations with a NIST standard and measurements on fresh UO₂ were done. Progress during the past year in these various areas is reviewed, and initial experiments with a specimen of high-burnup CANDU fuel are discussed.