Separate-Effects Tests for Studying Temperature-Gradient-Driven Cracking in UO₂ Pellets

A variety of normal operation and accident scenarios can generate thermal stresses large enough to cause cracking in ceramic fuel pellets. Cracking pellets lead reduced heat removal, higher centerline temperatures, localized stress the cladding—all which impact performance. It is important experimentally characterize mechanical behaviors pellet both before after cracking, would help improve models performance codes such as BISON. However, in-reactor observation measurement are very challenging due harsh environment design rods involved. Recently, an experimental pellet-cracking test stand was developed for separate-effects testing under operations temperature conditions using imaging capture surface temperatures order evaluate optical evolution real time. Experiments were performed depleted uranium dioxide (UO2) pellets, useful collecting valuable data development validation models. combination induction resistance heating used create gradients similar those seen a reactor environment. Characterization conducted cracking. The patterns moderately different from expected typical because variations microstructures. when actual these experiments reproduced computational with sufficient precision, out-of-pile on UO2 provides relevant modeling purposes.