Hydrogen Effects on Cladding Performance during Simulated Loss of Coolant Accident Testing

Fresh Zircaloy cladding segments were charged with hydrogen and subjected to simulated Loss of Coolant Accident (LOCA) conditions to assess the impact of hydrogen on the cladding mechanical performance and rupture resistance. The cladding rupture temperature decreased by 10 °C for every 100 wppm H added into the system for two different internal pressurization cases. Post-test analysis showed a loss of ductility with increasing hydrogen content, evident through decreased balloon sizes, smaller rupture openings, and sharper rupture interfaces. Digital image correlation was used to map the cladding strain in situ for two cladding segments. An elevated intermediate temperature uniform strain was visible for the hydride cladding, occurring prior to the decreased ductility during balloon and rupture determined from posttest fractography and microscopy. The thermal stability of Zr alloys as a function of hydrogen concentration and the thermal stability of Zr hydride as a function of temperature are likely responsible for the uniform deformation behavior at intermediate temperatures. The present framework for rapid assessment of hydrogen effects on cladding rupture can be utilized as an initial comparison to high burnup cladding thermomechanical response to a LOCA, where local regions may contain high concentrations of precipitated Zr hydride phase.. Authors: Ridley, Mackenzie [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:0000000240432209); Bell, Samuel [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)]; Garrison, Ben [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:0000000316880682); Cinbiz, M. Nedim [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:0000000346268515); Capps, Nathan [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)]. DOE Contract: AC05-00OR22725. Subjects: 11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; 22 GENERAL STUDIES OF NUCLEAR REACTORS