Giovanni Pugliese

Film thickness is the most important parameter of a lubricated contact. Its evaluation in a cam-follower contact is not easy due to the continuous variations of speed, load and geometry during the camshaft rotation. In this work, experimental apparatus with a system for film thickness and shape estimation using optical interferometry, is described. The basic principles of the interferometric techniques and the color spaces used to describe the color components of the fringes of the interference images are reported. Programs for calibration and image analysis, previously developed for point contacts, have been improved and specifically modified for line contacts. The essential steps of the calibration procedure are illustrated. Some experimental interference images obtained with both Hertzian and elastohydrodynamic lubricated cam-follower line contacts are analyzed. The results show program is capable of being used in very different conditions. The methodology developed seems to be promising for a quasi-automatic analysis of large numbers of interference images recorded during camshaft rotation.

To safely transport radioactive materials it is required that the packaging system must be able to guarantee their containment and confinement (via its integrity assurance) avoiding any additional dose exposure (respect of ALARA principle). The engineering system has thus to be designed to ensure safety features by complying/satisfy specific safety requirements, like the IAEA Safety Standards No. TS-R-1 and No. SSR-6. In this framework, the present study is intended to investigate and analyse the performance of an Italian CC-440 package, for the transport of low and intermediate level radioactive waste, subjected to the inclined free drop test. To the purpose numerical analysis simulating the drop test and performed by the FEM MSC Marc code are presented and discussed. In doing that a validation analysis of the numerical tool, based on available experimental data, has been carried out. The results obtained, in terms of stress, strains, acceleration, etc., showed that even if the packaging system components suffered local deformation, the magnitude of these effects would not determine an unacceptable loss of the safety features

In the transportation of radioactive waste, the package is designed as the major engineered system capable to ensure the containment and provide safety functions, such as radiation shielding, structural integrity against external mechanical and thermal loads, dissipation of the decay heat, etc. Packaging systems are designed in accordance to rigorous acceptance requirements, like the International Atomic Energy Agency (IAEA) ones, so to provide protection to human being and environment against radiation exposure and contamination, particularly in reference accident scenarios including, as it is widely known in literature, drop, puncture, fire and submersion tests. The scope of the present study is to evaluate the structural response and performance in a free drop test condition of a new Italian packaging system that should be used for the transportation of low and intermediate level radioactive wastes. For this purpose the carried out numerical analyses are presented and discussed. The numerical analyses, performed by the finite element MARC® code, simulate the behaviour of the packaging system components: the overpack, gasket, cover lid, bolts and a concrete matrix representative of the radioactive content. The obtained results for 1.2 m horizontal drop, on a flat and unyielding surface, were critically analysed and also compared to the experimental ones obtained from the experimental test campaign performed at the Unipi test facility on the new Italian packaging system considered. The stress and acceleration values indicate that the package, although rather local deformations in correspondence of bolts and secondary lid, is capable to withstand the dynamic loading generated during the drop test without any unacceptable loss of the safety features.

Nuclear reactors have to be maintained in a critical state so as to keep the chain fission process stationary and under control. Nuclear stability considerations dictate that the geometry of the core be closely controlled at all times: therefore any modification of it must be predictable, compatible with the requirements of the interfacing reactor systems and safely manageable by (intrinsic and engineered) control mechanisms. This study deals with the evaluation of the deformation of core (and restraint system) geometry due to dynamic perturbations. This deformation may determine, at large or small extent, an assembly compaction, that is generally characterized by a radial inward displacement and, eventually, results in an insertion of reactivity. To the aim it is of meaningful importance to set up and develop an overall and reliable methodological approach to be used in designing the core system (all structures and components characterizing the core region) and evaluating its performance under operation and accident condition. In particular a LMR reactor configuration similar to the Advanced Lead-cooled Fast Reactor European Demonstrator - ALFRED (300 MWth) has been considered. The assessment of the dynamic behaviour of a LMR core is particularly needed for seismic design purposes: these solicitations could deform the core system and fuel assembly. A preliminary finite element model, in which all the core sub-assemblies were represented as masses distributed on the supporting plate, was carried out in order to investigate the dynamic response of the structures once confidence was established by sensitivity analyses of size and type of the adopted elements. The preliminary results indicate that the core region is undergoing local deformations (of about 3 cm) that could influence the normal reactor operation. Although any deformation influences the normal reactor operation, it is expected that the reactivity specifically related to this deformation will not pose concerns to the safe manageability of the associated abnormal operation.

The aircraft impact accident has become very significant in the design of a nuclear facilities, particularly, after the tragic September 2001 event, that raised the public concern about the potential damaging effects that the impact of a large civilian airplane could bring in safety relevant structures. The aim of this study is therefore to preliminarily evaluate the global response and the structural effects induced by the impact of a military or commercial airplane (actually considered as a “beyond design basis” event) into a near surface radioactive waste (RWs) disposal facility. The safety evaluation was carried out according to the International safety and design guidelines and in agreement with the stress tests requirements for the security track. To achieve the purpose, a lay out and a scheme of a possible near surface repository, like for example those of the El Cabril one, were taken into account. In order to preliminarily perform a reliable analysis of such a large-scale structure and to determine the structural effects induced by such a types of impulsive loads, a realistic, but still operable, numerical model with suitable materials characteristics was implemented by means of FEM codes. In the carried out structural analyses, the RWs repository was considered a “robust” target, due to its thicker walls and main constitutive materials (steel and reinforced concrete). In addition to adequately represent the dynamic response of repository under crashing, relevant physical phenomena (i.e. penetration, spalling, etc.) were simulated and analysed. The preliminary assessment of the effects induced by the dynamic/impulsive loads allowed generally to verify the residual strength capability of the repository considered. The obtained preliminary results highlighted a remarkable potential to withstand the impact of military/large commercial aircrafts, even in presence of ongoing concrete progressive failure (some penetration and spalling of the concrete wall) of the impacted area.