Fused Deposition Modelling (FDM) is one of the most widespread additive manufacturing technologies due to its relatively low cost and simplicity. Usually, printed parts have an internal structure (infill) that is not produced with 100% material density. This strategy is adopted to save material and time thanks also to the fact that when a component is loaded, stress are concentrated on its skin rather than in the internal section. Furthermore, infill structure can have different densities and topology. Slicer software have various configurations that can be exploited to produce internal structures: according to All3DP [1], some are intended for functional parts while others are more indicated to prototypes only. Aim of this work, is to compare the effect of different infill topologies produced using Ultimaker CURA [2] slicing software on material mechanical properties. Preliminary experimental activity has been carried out in order to determine the most suitable printing temperature. MaCh3D, an innovative miniaturized universal testing machine [3] was used to perform uniaxial tensile tests. Results underline the difference between different kind of infill in term of mechanical properties, given the same infill density across all specimens. Additionally, in order to evaluate infill percentage effect on mechanical properties, some of the most performing infill from the characterisation activity have been selected and specimens produced with 20%, 50%, 80% infill percentage. In the end, both infill topology as well as density impacts on mechanical properties.

No abstract

No abstract

To support the feasibility and the deployment of LFRs one of the main issues to be solved is the reliability of structural materials to be exposed to liquid metal coolant. Particularly the Liquid Metal Embrittlement (LME) of steels is of interest for nuclear reactors and spallation sources projects because structural materials for these systems are selected according to their corrosion resistance, irradiation embrittlement and compatibility with the coolant. This study was performed in the framework of MYRRHA project, a new-generation sub-critical reactor (based on the Accelerator Driving System concept) that uses Lead-Bismuth Eutectic (LBE) as coolant. LME phenomenon has been investigated by performing theoretical and experimental activity profiting and basing on the results obtained for the T91 m/f steel in contact with LBE. This paper first reviews the model of Kamdar: weak points and contradictions are highlighted. From an experimental point of view to verify the occurrence of LME, Slow Strain Rate Tensile tests were performed on the AISI 316L in LBE environment at SCK-CEN laboratories. Besides, a fracture surface analysis was carried out together with a microstructural analysis by using that Scanning Electron Microscopy. This was done in order to confirm the results obtained by the mechanical tests and to look for impurities in the metallic matrix. These impurities are an interesting feature in case of high scatter in the results. Indeed one of the difficulties was the opacity and conductivity of the medium. The methodological approach and the procedure are also duly described along with preliminary results.

Safety and security aspects are of meaningful importance in the design of nuclear facilities. In this study, the attention is so focused on the potential damaging effects that a large civilian airplane impact could bring in safety relevant structures, like a superficial repository similar to El Cabril one. Safety performances of such a type of superficial disposal facility, subjected to the aircraft impact and fuel burning, have been analysed and discussed. Conservative assumptions have been made: normal impact on the lateral repository surface, fire scenario based on the amount of fuel burnt. Load functions (calculated with the Riera approach) and the maximum temperature reached by fuel during its combustion were used as input (boundary condition) in the numerical simulations as well as the damaging phenomena occurring in the concrete structure. Numerical analyses, by MARC© code, allowed to simulate the thermo-structural performances of the superficial repository. The obtained results showed that a repository wall thickness, ranging from 0.6 to 0.9 m, is not sufficient to prevent the penetration of wall itself. Despite the ongoing concrete degradation phenomena, the global strength of the repository seemed to be guaranteed.