Int J Thermophys (2012) 33:311–329 DOI 10.1007/s10765-012-1161-9 Design and Validation of a High-Temperature Comparative Thermal-Conductivity Measurement System C. Jensen · C. Xing · C. Folsom · H. Ban · J. Phillips Received: 20 September 2011 / Accepted: 17 January 2012 / Published online: 31 January 2012 © Springer Science+Business Media, LLC 2012 Abstract A measurement system has been designed and built for the specific appli- cation of measuring the effective thermal conductivity of a composite, nuclear-fuel compact (small cylinder) over a temperature range of 100 ◦ C to 800 ◦ C. Because of the composite nature of the sample as well as the need to measure samples pre- and post- irradiation, measurement must be performed on the whole compact non-destructively. No existing measurement system is capable of obtaining its thermal conductivity in a non-destructive manner. The designed apparatus is an adaptation of the guarded- comparative-longitudinal heat flow technique. The system uniquely demonstrates the use of a radiative heat sink to provide cooling which greatly simplifies the design and setup of such high-temperature systems. The design was aimed to measure thermal- conductivity values covering the expected range of effective thermal conductivity of the composite nuclear fuel from 10 W · m -1 · K -1 to 70 W · m -1 · K -1 . Several mate- rials having thermal conductivities covering this expected range have been measured for system validation, and results are presented. A comparison of the results has been made to data from existing literature. Additionally, an uncertainty analysis is presented finding an overall uncertainty in sample thermal conductivity to be 6 %, matching well with the results of the validation samples. Keywords Comparative method · High-temperature measurement · Nuclear fuel compact · Thermal-conductivity measurement · Uncertainty analysis C. Jensen (B ) · C. Xing · C. Folsom · H. Ban Department of Mechanical & Aerospace Engineering, Utah State University, Logan, UT 84322, USA e-mail: colby.jensen@aggiemail.usu.edu J. Phillips Idaho National Laboratory, Idaho Falls, ID 83415, USA 123