This work is part of the research on the design of MYRRHA primary system. MYRRHA, a multipurpose research facility, being developed at SCK-CEN, is based on the Accelerator Driven System (ADS) concept. This research facility intends to show the applicability of the ADS principle, and aims to demonstrate, among other objectives, the feasibility of efficient transmutation of high-level nuclear waste. The present study investigates, mainly, the thermo-mechanical behaviour of the core support bundle, fuel assemblies and core devices, in particular, the deformation in terms of the displacement and gaps distribution. To reach this goal, which is arduous, an efficient modeling methodology based on the finite element method has been devised. An effective solution strategy has been formulated to carry out a highly challenging analysis due to severe numerical issues and instabilities, making the solutions particularly difficult to reach for some cases. Analysis cases are differentiated by some friction coefficient values; and the presence or not of a spring pre-compression force. Despite serious convergence issues, converged solutions have been achieved for all the cases studied. From the results analysis, a remarkable feature observed is the stability of the solutions obtained. And, on the whole, the value of the friction coefficient used does not change significantly the displacement, the gaps patterns, and the stresses. Similarly, account of the pre-compression force does not affect much the global behaviour. The kinematic quantities found should be useful for some preliminary reactivity predictions of the reactor.