After one-two years of normal operation in a LWR, the fuel–cladding gap may close,
as a result of as a result of several phenomena and processes, including the different thermal
expansion and swelling of both the fuel and the cladding (Pellet Cladding Interaction). In this
equilibrium state, a significant increase of local power (like a transient power ramp, i.e. power
increase in the order of 100kW/m-h), induces circumferential stresses in the cladding. In presence
of corrosive fission products (i.e. iodine) and beyond specific stress threshold, material dependent,
cracks typical of stress corrosion may appear and grow-up: this phenomenon is called stress
corrosion cracking (SCC). The cracks of the cladding may spread out from the internal surface,
causing the fuel failure. The objective of the activity (performed in the framework of the IAEA
CRP FUMEX III), is to validate the TRANSURANUS models relevant in predicting the fuel
failures due to PCI/SCC during power ramps. Focus is given on the main phenomena, which are
involved or may influence the cladding failure behavior. The database selected is the Studsvik
BWR Super-Ramp Project, which belongs to the “public domain database on nuclear fuel
performance experiments for the purpose of code development and validation – International Fuel
Performance Experiments (IFPE) database” by OECD/NEA. It comprises the data of sixteen
BWR fuel rods, that have been modeled and simulated with suitable input decks. The burn-up
values range between 28 and 37 MWd/kgU. Eight rods, of KWU standard type, are subjected to
fast ramps, the remaining rods experience slow ramps and are of standard GE type
