Mechanical analysis of fuel fretting problem Original Research Article

Fuel fretting is studied by contact mechanics approach. Shear force produced by flow-induced vibration is regarded as the major factor of the fuel fretting. Contact dimension is examined for the Korean PWR Fuel Assembly using finite element method. Axial direction is incorporated with transverse one for the shear force. As for the sequence of the shear, a closed rectangular as well as an oblique path are considered to simulate the actual behaviour due to the vibration. The shear stresses on the contact surface between fuel rod and spacer grid is evaluated numerically. It is supposed that a partial slip regime prevails on the contact at the early stage of fuel life. In case of gross slip, the present method can be applied without modification. The dissipation of friction energy on the contact is evaluated and discussed for a wear model and a spacer grid design.