HIGH-TEMPERATURE VOLUME OXIDATION OF ZIRCONIUM ALLOYS IN AIR

This work studies the oxidation processes of zirconium alloys alloyed with niobium at high temperatures (900–1200 ℃). 
The objects of the study were samples of iodide zirconium, E110 and E125 alloys, and fuel rod simulators made of E110 alloy. The results showed differences in the oxidation kinetics for three groups of samples. Samples of iodide zirconium (group I) demonstrated a linear increase in mass with increasing temperature. Zirconium alloys with niobium (group II) showed a maximum increase in mass at 950–1000 ℃, after which oxidation slowed down. Fuel rod simulators (group III) oxidized in a similar manner to group II, but with a smaller amplitude of changes. The shape of the samples had a significant effect on the oxidation kinetics. Fuel rod simulators oxidized faster due to cracking of the oxide layer, which contributed to more intensive access of the oxidizing environment to the metal. The activation energy of oxidation for iodide zirconium (113 kJ/mol) and fuel rod simulators (59 kJ/mol) was experimentally determined. The work revealed the influence of the composition and geometry of the samples on the high-temperature oxidation process, which can be useful for the development of more oxidation-resistant materials for nuclear reactors, as well as for the reprocessing of spent fuel assemblies using the volume oxidation method. 

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