The flash method has been extended to measure thermal diffusivity in the radial direction at high temperatures, and in the presence of substantial radiation heat losses. Radial effects in this instance, arise because only a small portion of the front surface of the sample is exposed to the energy source. The present effort complements a recently published study in which thermal diffusivity was measured in the axial direction. In that study, substantial radial heat flow and axial radiation heat losses were experienced. Both methods were used to test the same samples of an isotropic material (POCO AXM‐5Qgraphite) and an anisotropic material (reactor‐grade graphite). Results show that thermal diffusivity in the radial direction can be measured for both isotropic and anisotropic material without accounting for the large radiation heat losses. These results are also compared with those based on the conventional flash method using smaller samples.
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