Hydrogen effects on thermal diffusivity and electrical resistivity of zircaloy cladding

Thermal diffusivity measurements on Zirconium-based cladding materials have historically been a chal-lenge due to the difficulty to measure on specimens with curved geometries, including nuclear grade Zircaloy cladding materials. In this work, we first used laser flash analysis method and four-probe con-figuration method to measure the thermal diffusivity and electrical resistivity of Zircaloy tubes respec-tively, which show good agreement with Zircaloy plates in this work, as well as previously published data. The consistent results proved the applicability of the laser flash analysis setup and four-probe con-figuration method for investigating thermal diffusivity and electrical resistivity of Zircaloy tubes. We fur-ther investigated the hydrogen effect on thermal diffusivity and electrical resistivity of Zircaloy. Hydrogen plays significant roles in the thermal diffusivity of Zircaloy, which depends on the hydrogen concentra-tion. For higher hydrogen contents (1130 and 1820 wppm in this work), where phase transformation (alpha-Zr + 8-hydride -> alpha-Zr + beta-Zr) occurs at 567 degrees C, thermal diffusivity decreases as a function of tem-perature at the alpha-Zr + 8-hydride phase regime, while increase at higher temperature at the alpha-Zr + beta-Zr phase regime. For low hydrogen concentration, where hydride dissolved into alpha-Zr matrix phase at higher temperature, the thermal diffusivity is lower than non-hydrided Zircaloy-4 with similar temperature -dependent trends. Such observation demonstrates the hydrogen effects on reducing thermal diffusivity of alpha-Zr phase. Hydrogen increases the electrical resistivity of Zircaloy. Similar to thermal diffusivity re-sults, the phase transformation causes a reversal of temperature-dependent trends in electrical resistivity results in Zircaloy-4 with higher hydrogen contents.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

In this study, the thermal diffusivity and electrical resistivity of Zircaloy tubes were measured using the laser flash analysis and four-probe configuration methods, respectively. The results showed good agreement with the measurements of Zircaloy plates and previously published data. Further investigations revealed the significant effects of hydrogen on the thermal diffusivity and electrical resistivity of Zircaloy.