An evaluation of hydrided Zircaloy-4 cladding fracture behavior by X-specimen test

Hydrogen embrittlement is one of the major degradation mechanisms of Zircaloy (Zry) fuel cladding at high burnups. In this study, a novel technique, named X-specimen test method, was developed to analyze the effects of hydrogen concentration and temperature on the fracture properties of Zry-4 cladding. The X-specimens were machined from the cladding sections hydrogen-charged to the target hydrogen concentrations between 150 and 1200 ppm. The toughness values for the as-received Zry-4 cladding specimens at room temperature and 300 °C were very reproducible. The toughness values for Zry-4 cladding at room temperature decreased significantly as hydrogen concentration increased. However, the toughness value at 300 °C was not sensitive to hydrogen concentration.