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This work presents first a study of the national and international laws in the fields of safety, security and safeguards. The international treaties and the recommendations issued by the IAEA as well as the national regulations in force in France, the United States and Italy are analyzed. As a result of this, a comparison among them is presented. Given the interest of the Japan Atomic Energy Agency for the aspects of criminal penalties and monetary, also the Japanese case is analyzed. The main part of this work was held at the JAEA in the field of proliferation resistance (PR) and physical protection (PP) of a GEN IV sodium fast reactor. For this purpose the design of the system is completed and the PR & PP methodology is applied to obtain data usable by designers for the improvement of the system itself. Due to the presence of sensitive data, not all the details can be disclosed. The reactor site of a hypothetical and commercial sodium-cooled fast neutron nuclear reactor system (SFR) is used as the target NES for the application of the methodology. The methodology is applied to all the PR and PP scenarios: diversion, misuse and breakout; theft and sabotage. The methodology is applied to the SFR to check if this system meets the target of PR and PP as described in the GIF goal; secondly, a comparison between the SFR and a LWR is performed to evaluate if and how it would be possible to improve the PR&PP of the SFR. The comparison is implemented according to the example development target: achieving PR&PP similar or superior to domestic and international ALWR. Three main actions were performed: implement the evaluation methodology; characterize the PR&PP for the nuclear energy system; identify recommendations for system designers through the comparison.

The first part of this work deals with the inverse problem solution in the X-ray spectroscopy field. An original strategy to solve the inverse problem by using the maximum entropy principle is illustrated. It is built the code UMESTRAT, to apply the described strategy in a semiautomatic way. The application of UMESTRAT is shown with a computational example. The second part of this work deals with the improvement of the X-ray Boltzmann model, by studying two radiative interactions neglected in the current photon models. Firstly it is studied the characteristic line emission due to Compton ionization. It is developed a strategy that allows the evaluation of this contribution for the shells K, L and M of all elements with Z from 11 to 92. It is evaluated the single shell Compton/photoelectric ratio as a function of the primary photon energy. It is derived the energy values at which the Compton interaction becomes the prevailing process to produce ionization for the considered shells. Finally it is introduced a new kernel for the XRF from Compton ionization. In a second place it is characterized the bremsstrahlung radiative contribution due the secondary electrons. The bremsstrahlung radiation is characterized in terms of space, angle and energy, for all elements whit Z=1-92 in the energy range 1–150 keV by using the Monte Carlo code PENELOPE. It is demonstrated that bremsstrahlung radiative contribution can be well approximated with an isotropic point photon source. It is created a data library comprising the energetic distributions of bremsstrahlung. It is developed a new bremsstrahlung kernel which allows the introduction of this contribution in the modified Boltzmann equation. An example of application to the simulation of a synchrotron experiment is shown.

This work presents results from experimental investigations of several different atmospheric pressure plasmas applications, such as Metal Inert Gas (MIG) welding and Plasma Arc Cutting (PAC) and Welding (PAW) sources, as well as Inductively Coupled Plasma (ICP) torches. The main diagnostic tool that has been used is High Speed Imaging (HSI), often assisted by Schlieren imaging to analyse non-visible phenomena. Furthermore, starting from thermo-fluid-dynamic models developed by the University of Bologna group, such plasma processes have been studied also with new advanced models, focusing for instance on the interaction between a melting metal wire and a plasma, or considering non-equilibrium phenomena for diagnostics of plasma arcs. Additionally, the experimental diagnostic tools that have been developed for industrial thermal plasmas have been used also for the characterization of innovative low temperature atmospheric pressure non equilibrium plasmas, such as dielectric barrier discharges (DBD) and Plasma Jets. These sources are controlled by few kV voltage pulses with pulse rise time of few nanoseconds to avoid the formation of a plasma arc, with interesting applications in surface functionalization of thermosensitive materials. In order to investigate also bio-medical applications of thermal plasma, a self-developed quenching device has been connected to an ICP torch. Such device has allowed inactivation of several kinds of bacteria spread on petri dishes, by keeping the substrate temperature lower than 40 degrees, which is a strict requirement in order to allow the treatment of living tissues.

Since the Three Mile Island Unit 2 (TMI-2), accident in 1979 which led to the meltdown of about one half of the reactor core and to limited releases of radioactive materials to the environment, an important international effort has been made on severe accident research. The present work aims to investigate the behaviour of a Small Modular Reactor during severe accident conditions. In order to perform these analyses, a SMR has been studied for the European reference severe accident analysis code ASTEC, developed by IRSN and GRS. In the thesis will be described in detail the IRIS Small Modular Reactor; the reference reactor chosen to develop the ASTEC input deck. The IRIS model was developed in the framework of a research collaboration with the IRSN development team. In the thesis will be described systematically the creation of the ASTEC IRIS input deck: the nodalization scheme adopted, the solution used to simulate the passive safety systems and the strong interaction between the reactor vessel and the containment. The ASTEC SMR model will be tested against the RELAP-GOTHIC coupled code model, with respect to a Design Basis Accident, to evaluate the capability of the ASTEC code on reproducing correctly the behaviour of the nuclear system. Once the model has been validated, a severe accident scenario will be simulated and the obtained results along with the nuclear system response will be analysed.

La corretta modellizzazione della zona del riflettore dei sistemi GEN III+ è un passaggio fondamentale per un’accurata predizione dei parametri di cella il cui valore influenza direttamente la distribuzione di potenza su tutto il nocciolo. Tale esigenza si è resa ancora più stringente dopo la constatazione che il fenomeno del “tilt power” risulta essere più amplificato nei noccioli nucleari equipaggiati con un riflettore pesante. Per tali ragioni, nel presente lavoro di tesi si è dedicata particolare attenzione alle metodiche di modellizzazione ed alla generazione delle sezioni d’urto efficaci omogenee ed agli assembly discontinuity factors (ADF) nella zona di riflessione. Il codice deterministico utilizzato per il calcolo è SCALE 6.1.3. La notevole differenza nelle proprietà neutroniche associata ad un’elevata eterogeneità geometrica tra un nocciolo ed un riflettore hanno suggerito di effettuare un’analisi preliminare sul sistema riflettente GEN II proposto nel benchmark NEA-NSC-DOC (2013) per testare la capacità di SCALE 6.1.3 di effettuare un corretto calcolo di cella adottando una modellizzazione monodimensionale assembly/riflettore. I risultati ottenuti sono confrontati con quelli presentati nel benchmark e e con quelli valutati attraverso il codice Monte Carlo SERPENT 2.0 confermando la capacità di calcolo di SCALE 6.1.3. L’analisi sulla modellizzazione dei sistemi riflettenti GEN III+ è stata effettuata ricavando il valore dei parametri di cella per configurazioni omogenee ed una serie di configurazioni geometriche esatte che comprendono tutte le modellizzazioni del sistema riflettente lungo la direzione angolare del riflettore. Si è inoltre effettuata un’analisi di sensitività su parametri operativi e sui parametri di codice. Si è infine effettuato un calcolo in color-set per indagare l’influenza degli effetti 2-D sui parametri di cella. I risultati prodotti rappresentano un contributo migliorativo nella conoscenza dei parametri di cella di riflettore e potranno essere utilizzati per una più precisa valutazione del fenomeno del tilt nei sistemi GEN III+. / In GEN III+ systems the correct modelization of the reflector zone is a key step for an exact prediction of the cell parameters whose values directly affect the radial power distribution of the core system. This need has become even more necessary after the discovery of the amplification of the “tilt power” phenomenon in the GEN III+ nuclear core. For this reason, special care is taken in the modelization methodology and in the generation of reflector homogenized cross-section and discontinuity factor (DFs) on the reflector zone. The deterministic package code used for the cell data calculation is SCALE 6.1.3 suite. The strong difference in the neutronic properties at core/reflector interface combined with a high geometric heterogeneity between a core and a reflector system have suggested to perform a preliminary analysis on the GEN II reflector system as presented by NEA-NSC-DOC (2013) benchmark with the aim of testing the capability of the deterministic code to perform a correct calculation on a 1-D assembly/reflector modelization. The results, which are in good agreement with those evaluated with SERPENT 2.0 Monte Carlo code, confirmed the capability of SCALE code to perform cell data reflector calculations. The modelization analysis on the GEN III+ reflector system has been performed for two homogeneous configurations and for a series of exact heterogeneous zones along the angular direction of the reflector. It has been also realized a sensitivity analysis on operational and code parameters. Finally, it was performed a 2x2 color-set calculation to investigate the 2-D geometry effects on the numerical values of cell reflector parameters. The final results are an improvement in the scientific knowledge of the reflector cell data values. These values can be used in a EPR nodal code calculation for a more accurate assessment of the core power distribution and of the “power tilt” values.

Widely employed for a steadily increasing number of industrial processes and experimental studies, plasma can be considered as one of the most pervasive and promising technology of our time. Differently from thermal plasmas, the potentialities offered by non-equilibrium plasmas, especially if working at atmospheric pressure, are still far away to be totally understood, since the surprising and sometimes unpredictable results, coming from studies carried out all over the world, bring out the growing versatility of this technology and its suitability for many applications intersecting our daily lives. The present dissertation, organized in two parts, is focused to present and discuss the results obtained from the Ph.D research activities carried out in the wide field of plasma and materials. The first part of the work is mainly aimed at investigating the potentialities of cold atmospheric plasmas (CAP) for the modification of materials, coating deposition and crosslinking of polymers. In the first two chapters, the conventional techniques and the CAP approaches most employed to carry out the processes will be briefly summarized. In the other chapters, organized by topic, the results achieved during the Ph.D research activities in the fields of surface material modification, coating deposition and crosslinking of polymers will be presented and discussed. The second part of the dissertation is linked to the investigation of the potentialities of plasma-induced chemistry in a liquid environment for the synthesis of nanostructures. Similarly to the first one, the second part of the dissertation will present an overview on the conventional and CAP assisted methods for nanostructures synthesis; moreover, in the second part of the last chapter, the Ph.D experimental activities aimed at synthesising CuO quantum dots in a liquid environment will be illustrated.

The first part of this work reports the elementary theory of the atomic photoeffect presented in a form that is suited for practical numerical calculation. A detailed derivation of subshell cross sections for both excitation and ionization, comprising the angular distributions of emitted photoelectrons, is presented taking into account the effect of the polarization of the photons. The theoretical formulas have been implemented in a computer program PHOTACS that calculates tables of excitation and ionization cross sections for any element and subshell. Numerical calculations are practicable for excitations to final states with the principal quantum number up to about 20 and for ionization by photons with energy up to about 2 MeV. The effect of the finite width of atomic energy levels is accounted for by convolving the calculated subshell cross section with a Lorentzian profile. The second part of this work reports unfolding strategies for correcting a radiation measurement from the effects of the detector-pulse handling circuitry system. These strategies comprise the correction from the effects of pulse pile-up (PPU) and the detector response function (DRF). A first principles balance equation for second order PPU is derived and solved for the particular case of rectangular pulse shape. A Monte Carlo (MC) strategy is then implemented in the code MCPPU (Multi-shape pulse pile-up correction) allowing handling more general cases. Regarding the DRF, computed with deterministic or MC codes, it is presented the new tool RESOLUTION which introduces in the computed DRF the effects of energy resolution and incomplete charge collection. In the end the computer program UMESTRAT (Unfolding Maximum Entropy STRATegy) is presented in an updated version which include a new constrain to the total number of photons of the spectrum, which can be easily determined by inverting the diagonal efficiency matrix.

In modern nuclear technology, integral reactor parameter uncertainty evaluation plays a crucial role for both economic and safety purposes. Target accuracies for operating and future nuclear facilities can be obtained only if the available simulation tools, such that computational platforms and nuclear data, are precise enough to produce reduced biases and uncertainties on target reactor parameters. The quality of any engineering parameter uncertainty quantification analysis strongly depends on the reliability related to the covariance information contained in evaluated libraries. To propagate properly nuclear data uncertainty on nuclear reactor parameters, science-based variance-covariance matrices are then indispensable. The present work is devoted to nuclear data covariance matrices generation for reactivity loss uncertainty estimations regarding the Jules Horowitz Reactor (JHR), a material testing facility under construction at CEA-Cadarache (France). During depletion, in fact, various fission products appear and the related nuclear data are often barely known. In particular, the strenuous and worldwide recognized problem of generating fission product yields covariances has been mainly considered. Present nuclear data libraries such as JEFF or ENDF/B do not have complete uncertainty information on fission yields, which is limited to only variances. The main goal of this work is to generate science-based and physically consistent fission yields covariances to be associated to the existing European library JEFF-3.1.1. Variance-covariance matrices have been evaluated using CONRAD (COde for Nuclear Reaction Analysis and Data assimilation, developed at CEA-Cadarache) for the most significant fissioning systems.

The dissertation focuses on several aspects of non-equilibrium atmospheric plasma technology, also known as cold atmospheric plasma (CAP) technology, including the design, the diagnostic and the optimization of CAP sources for biomedical applications. The first part of the dissertation concerns the characterization of a single electrode atmospheric pressure plasma jet (APPJ) through various diagnostic techniques, including ICCD and Schlieren high speed imaging. First, the results for the APPJ freely expanding in atmosphere are presented along with the detailed description of the methodology developed for the ICCD analysis of plasma discharges driven by sub-microsecond voltage pulses. Second, results on the investigation on the APPJ source while impinging on a liquid substrate are shown to highlight the influence of the presence of the liquid substrate on the characteristics of the plasma discharge. In the second part of the dissertation focuses on the application of CAP technology in various branches of the medical field. The applications reported in this dissertation include: plasma treatment of soft reline palatal obturators prostheses for bacterial decontamination and reduction of bacteria adhesion; plasma direct and indirect treatment of L5178Y lymphoma cells to investigate the fundamental mechanisms promoting cell death and cell-cycle arrest; plasma treatment of tooth root canal dentin in standard dental procedures for the enhancement of the adhesion of resin composites for dental restorations. Overall, all findings support the feasibility of these plasma applications and help in the understanding of some of their governing mechanisms.