The problem presented here concerns fuel assemblies for which the stochastic loads induced by turbulent fluid forces have to be identified. The simplified model used for this identification is composed of two coupled subsystems:(1) A nonlinear subsystem which is accurate and contains the quantity of interest (2) A linear subsystem which is less accurate and contains model uncertainties which have to be taken into account. Others sources of uncertainties are to be taken into account in the stochastic loads identification process: uncertainties concerning the stochastic loads and measurements errors. The identification is carried out using the moments method and the maximum likelihood method. Finally, the stochastic simplified computational model on which the identified stochastic loads are applied is used to construct statistics of the fretting wear of the fuel rods.