Hydrogen Behavior and Mechanism of Cr-Coated Zirconium Alloy Cladding During Simulated LOCA Tests

Extensive research has been conducted on accident-tolerant coatings for zirconium alloy claddings, while study of the hydrogen behavior during simulated loss-of-coolant accidents (LOCAs) has seemingly been overlooked. However, research on the effect of hydrogen on the performance of zirconium alloy claddings is crucial. Therefore, simulated LOCA tests with different oxidation durations were performed on uncoated and Cr-coated claddings. A series of microstructural analysis techniques were used to characterize the distribution of hydrogen and oxygen elements, as well as the evolution of microstructural characteristics, aiming to explore the hydrogen behavior and mechanism of Cr-coated zirconium alloy claddings during simulated LOCA tests. The results showed that no hydrogen absorption occurred in the uncoated claddings during the tests. The uncoated claddings formed a relatively simple microstructure with dense zirconia that prevented hydrogen diffusion into the zirconium alloy matrix. In contrast, severe hydrogen absorption occurred in the Cr-coated claddings. A complex microstructure consisting of interleaved oxide and metallic phases was formed in the Cr-coated claddings during the tests, which facilitated hydrogen absorption into the cladding matrix and is the main reason for the severe hydrogen absorption of Cr-coated claddings during LOCAs.