Evaluation of fretting wear occurrence on the surface of nuclear fuel rods of Zr–1Nb–1Sn-0.1Fe alloy: Effects of assembly misalignment and grid spring loading

A mechanical apparatus was developed to investigate the grid-to-rod fretting on nuclear assembly of Zr–1Nb–1Sn-0.1Fe alloy. Test apparatus allowed the performing of fretting tests on fuel rods at a frequency to 30 Hz, which was evaluated as the first natural frequency of a fuel rod. In addition, strain-gauges was employed to evaluate the misalignment effect on the mechanical behavior of the testing material. The surface damage intensity decreased from the central part, to the extremity of wear areas. The variation of wear areas revealed that the misalignment promoted premature wear because the intensification of fretting wear occurred by the appearance of complementary efforts. The confocal method suggested that wear residues under dry conditions remained adhered to the fretting surface. •The greater the rod misalignment over time, the greater the imbalance of its structural behavior to wear.•Areas of wear presented greater superficial damage in its central part evolving in a lower intensity to the extremities.•The confocal method suggests that the wear residues in the dry condition remained adhered to the worn surface.•Misalignment promotes an intensification of the fretting wear by the appearance of complementary efforts.