Hydriding kinetics of Zry-4 samples was studied in the temperature range from 350 to 450 deg C at 50 atm of pure hydrogen pressure. We dexcribe a simple surface treatment performed at room temperature that minimises the difficulties associated with the oxide layer always present in Zr-based alloys surface. Two stages where hdrogen uptake rate is constant with time characterise the kinetics absorption. An initial one with low hydrogen uptake and an activation energy of 84 KJ/mol probably due to an oxygen rich zone in the Pd/Zry-4 interface. The second stage related with the constant growth of a hydride layer of about 5 mm thick. The found activation energy for this second process is of 54 KJ/mol.
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