Development of an in-pile technique for thermal conductivity measurement

Thermophysical properties of advanced fuels and materials during irradiation must be known prior to their use in existing, advanced, or next generation reactors. Fuel thermal conductivity is one of the most important properties for predicting fuel performance and reactor safety. This paper discusses a joint Utah State University (USU) Idaho National Laboratory / (INL) project, which is being conducted with assistance from the Institute for Energy Technology at the Halden Reactor Project (IFE HRP), to investigate in-pile fuel thermal conductivity measurement methods using a surrogate fuel rod. The methods use a surrogate fuel rod with Joule heating to simulate volumetric heat generation to gain insights about in-pile detection of thermal conductivity. Initial investigations have focused on a carbon structural foam, CFOAM®, a product of Touchtone Research Laboratory as a surrogate material because of its electrical and thermal properties. This paper describes the method used to evaluate in-pile thermal conductivity measurement methods. A description of the test setup and preliminary results are presented. Thermal conductivity values obtained by this technique are compared with thermal property data obtained from standard thermal property measurement techniques, such as laser flash, differential scanning calorimetry, and pushrod dilatometry.