STUDIES OF FUEL-CLAD MECHANICAL INTERACTION AND RESULTING INTERACTION FAILURE MECHANISM

Fuel performance studies at the Halden reactor have given valuable information on how various design parameters affect the mechanical interaction between fuel and cladding. The experiments have also indicated how the interaction is dependent on burnup and on the actual power history of the fuel rod. Based on this experience, a simple graphical model has been proposed for the prediction of interaction between fuel and cladding as a function of power history and burnup. This concept, referred to as '%'iso- gap curves'%', clearly demonstrates the importance of avoiding an increase in power at high burnup.