This paper describes a laboratory test program to measure the thermal conductivity of corrosion product deposits on the surface of a Pressurized Water Reactor (PWR) fuel rod under a variety of thermal hydraulic conditions. This thermal conductivity information is necessary to allow more accurate predictions of fuel rod surface temperatures in the presence of fuel deposits, commonly known as crud.In this paper, a four regime theory and methodology are proposed and utilized for crud thermal conductivity measurements and calculations. The relevant measurements were performed at the Westinghouse Advanced Loop Tester (WALT) facility, which is a single rod crud thermal-hydraulic test loop built at the Westinghouse Science and Technology Center (STC). This facility is described and then selected experiments and calculated results of this study are presented and discussed.Copyright © 2013 by ASME