Accurate prediction of fuel cladding integrity during LOCA reflood requires time-resolved data that couple thermal-hydraulic conditions with thermo-mechanical response, especially for high-burnup rods under elevated internal pressure. Two out-of-pile large-break LOCA (LBLOCA) reflood experiments with initial rod internal pressures of 30 bar (LP) and 50 bar (HP) were conducted at the ICARUS facility (KAERI) by using Zircaloy-4 cladding under quasi-similar conditions. These LOCA experiments produced simultaneous measurements of cladding surface temperature, rod internal pressure, collapsed water level, and cladding deformation. The HP test ruptured earlier (104 s) than the LP test (186 s) at a lower normalized rupture temperature ( T* ) of 0.70 and 0.72, respectively, indicating a reduced time and thermal margin of cladding failure at higher pressure. The creep-driven ballooning continued during the early reflood, and the collapsed water level remained below the rupture elevations (0.76 – 0.77 m) until failure, indicating steam-dominated cooling at the failure location. Cladding post-test 3D measurements showed nearly identical rupture elevations for both cases, with a larger opening area in HP, and higher circumferential strain in LP. The resulting integral dataset supports validation and improvement of coupled LOCA analysis models for cladding creep, ballooning, and burst.
Ali et al. (Fri,) studied this question.