This research deals with the development and calibration of numerical models of fuel rods based on quasi-static and vibration experiments performed on intact (unirradiated) rods. The original rod configuration exhibits a gap between the cladding and pellets that may be reduced, or even closed, after irradiation due to the swelling of the pellets, leading to bonding between the pellets and cladding. In this paper two cases are investigated. First, the pellets are bonded to the cladding, with the pellets just in contact with one another (de-bonded). Second the pellets are in contact with the cladding and with one another without bonding. Due to limited availability of irradiated fuel rods and their restricted workability, the experiments were performed on unirradiated surrogate copper claddings with steel pellets, and the bonding was simulated using adhesive epoxy. The experiments were conducted with fixtures that represent pin supports. The results obtained on the vibration response of surrogate copper rods, indicate that bonding of the pellets and cladding results in a total rod flexural rigidity equal to the rigidity of the copper cladding and up to 15% of the flexural rigidity of the pellets. For the case of pellet-cladding in contact, the contribution of the steel pellets to the total rod flexural rigidity is negligible.
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