Predicting fretting wear due to turbulence-induced vibration in a wire-wrapped fuel assembly

The goal of this research is to predict to what extent fretting wear damage occurs in a wire-wrapped fuel assembly, as found in the MYRRHA design, due to vibrations induced by the turbulent Pb-Bi coolant flow. This was achieved in a procedure of four steps, of which each one is dedicated to a specific physical aspect and is using a specific methodology that is suitable in terms of cost and accuracy. In previous work, in-air experiments were performed on a bare and wire-wrapped fuel pin to assess the effect of the wire on the modal characteristics. This knowledge was used in the second step to create a fully coupled fluid-structure interaction simulation of a 7-pin bundle, lumping the effect of the wire in the material properties of the bare rods. From this the bundle modal characteristics in LBE were determined, which differ from in-vacuo modal characteristics due to the surrounding liquid causing inter-cylinder coupling and consequently coupled added-mass and damping effects. In the third step the fluctuating, turbulent pressure field was determined by large eddy simulations on a 19-pin wirewrapped bundle model. The information on the turbulent loads was used to generate a long force history, used in the final step to excite a finite-elements model of a single pin. The material properties in this model were tuned to reflect the modal characteristics determined in the second step. Contact with (rigid) neighbors was detected, which allowed extracting contact forces and work rates, eventually leading to an estimate of the cladding wear depth.