Secondary hydriding criteria under irradiation conditions

► Paper is related to criteria of secondary hydriding in fuel rods with a primary failure. ► Massive cladding hydriding occurs when hydrogen-to-steam ratio in the gas phase is high. ► But some in-pile data cannot be explained using the criteria found in out-of-pile tests. ► It is shown that under irradiation, the threshold for massive hydriding is different. ► Data obtained from tests in research reactors support this conclusion.