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Nuclear cross sections are the pillars onto which the transport simulation of particles and radiations is built on. Since the nuclear data libraries production chain is extremely complex and made of different steps, it is mandatory to foresee stringent verification and validation procedures to be applied to it. The work here presented has been focused on the development of a new python based software called JADE, whose objective is to give a significant help in increasing the level of automation and standardization of these procedures in order to reduce the time passing between new libraries releases and, at the same time, increasing their quality. After an introduction to nuclear fusion (which is the field where the majority of the V\&V action was concentrated for the time being) and to the simulation of particles and radiations transport, the motivations leading to JADE development are discussed. Subsequently, the code general architecture and the implemented benchmarks (both experimental and computational) are described. After that, the results coming from the major application of JADE during the research years are presented. At last, after a final discussion on the objective reached by JADE, the possible brief, mid and long time developments for the project are discussed., Le sezioni d'urto nucleari sono alla base della simulazione del trasporto di particelle e radiazioni. Poichè la catena produzione di librerie di dati nucleari è estremamente complessa e si compone di diversi passaggi, è opportuno prevedere stringenti procedure di verifica e validazione. Il lavoro di tesi qui presentato si è concentrato sullo sviluppo in python di un nuovo software, JADE, il cui obbiettivo è quello di aiutare significativemente nella automatizzazione e standardizzazione di queste procedure in modo tale da diminuire il tempo necessario per il rilascio di nuove versioni di queste librerie e allo stesso tempo aumentarne la qualità. Dopo un' introduzione alla fusione nucleare (ambito sul quale si è concentrata per il momento l'attività di V\&V) e alla simulazione del trasporto di particelle e radiazioni, vengono discusse le motivazioni che hanno portato allo sviluppo di JADE. Successivamente, sono descritti l'architettura generale del codice ed i benchmark, sia sperimentali che computazionali, che sono stati implementati. Inoltre, vengono riportati i risultati ottenuti dalle principali applicazioni di JADE effettuate durante gli anni di ricerca. Infine, dopo un ultima discussione conclusiva sugli obbiettivi raggiunti da JADE, vengono esaminati i possibili sviluppi a breve, medio e lungo periodo per il progetto.

A Plasma Focus device can confine in a small region a plasma generated during the pinch phase. When the plasma is in the pinch condition it creates an environment that produces several kinds of radiations. When the filling gas is nitrogen, a self-collimated backwardly emitted electron beam, slightly spread by the coulomb repulsion, can be considered one of the most interesting outputs. That beam can be converted into X-ray pulses able to transfer energy at an Ultra-High Dose-Rate (UH-DR), up to 1 Gy pulse-1, for clinical applications, research, or industrial purposes. The radiation fields have been studied with the PFMA-3 hosted at the University of Bologna, finding the radiation behavior at different operating conditions and working parameters for a proper tuning of this class of devices in clinical applications. The experimental outcomes have been compared with available analytical formalisms as benchmark and the scaling laws have been proposed. A set of Monte Carlo models have been built with direct and adjoint techniques for an accurate X-ray source characterization and for setting fast and reliable irradiation planning for patients. By coupling deterministic and Monte Carlo codes, a focusing lens for the charged particles has been designed for obtaining a beam suitable for applications as external radiotherapy or intra-operative radiation therapy. The radiobiological effectiveness of the UH PF DR, a FLASH source, has been evaluated by coupling different Monte Carlo codes estimating the overall level of DNA damage at the multi-cellular and tissue levels by considering the spatial variation effects as well as the radiation field characteristics. The numerical results have been correlated to the experimental outcomes. Finally, ambient dose measurements have been performed for tuning the numerical models and obtaining doses for radiation protection purposes. The PFMA-3 technology has been fully characterized toward clinical implementation and installation in a medical facility.

In the last decades, the possibility to generate plasma at atmospheric pressure gave rise to a new emerging field called plasma medicine; it deals with the application of cold atmospheric pressure plasmas (CAPs) or plasma-activated solutions on or in the human body for therapeutic effects. Thanks to a blend of synergic biologically active agents and biocompatible temperatures, different CAP sources were successfully employed in many different biomedical applications such as dentistry, dermatology, wound healing, cancer treatment, blood coagulation, etc.… Despite their effectiveness has been verified in the above-mentioned biomedical applications, over the years, researchers throughout the world described numerous CAP sources which are still laboratory devices not optimized for the specific application. In this perspective, the aim of this dissertation was the development and the optimization of techniques and design parameters for the engineering of CAP sources for different biomedical applications and plasma medicine among which cancer treatment, dentistry and bioaerosol decontamination. In the first section, the discharge electrical parameters, the behavior of the plasma streamers and the liquid and the gas phase chemistry of a multiwire device for the treatment of liquids were performed. Moreover, two different plasma-activated liquids were used for the treatment of Epithelial Ovarian Cancer cells and fibroblasts to assess their selectivity. In the second section, in accordance with the most important standard regulations for medical devices, were reported the realization steps of a Plasma Gun device easy to handle and expected to be mounted on a tabletop device that could be used for dental clinical applications. In the third section, in relation to the current COVID-19 pandemic, were reported the first steps for the design, realization, and optimization of a dielectric barrier discharge source suitable for the treatment of different types of bioaerosol.

Since last century, the rising interest of value-added and advanced functional materials has spurred a ceaseless development in terms of industrial processes and applications. Among the emerging technologies, thanks to their unique features and versatility in terms of supported processes, non-equilibrium plasma discharges appear as a key solvent-free, high-throughput and cost-efficient technique. Nevertheless, applied research studies are needed with the aim of addressing plasma potentialities optimizing devices and processes for future industrial applications. In this framework, the aim of this dissertation is to report on the activities carried out and the results achieved concerning the development and optimization of plasma techniques for nanomaterial synthesis and processing to be applied in the biomedical field. In the first section, the design and investigation of a plasma assisted process for the production of silver (Ag) nanostructured multilayer coatings exhibiting anti-biofilm and anti-clot properties is described. With the aim on enabling in-situ and on-demand deposition of Ag nanoparticles (NPs), the optimization of a continuous in-flight aerosol process for particle synthesis is reported. The stability and promising biological performances of deposited coatings spurred further investigation through in-vitro and in-vivo tests which results are reported and discussed. With the aim of addressing the unanswered questions and tuning NPs functionalities, the second section concerns the study of silver containing droplet conversion in a flow-through plasma reactor. The presented results, obtained combining different analysis techniques, support a formation mechanism based on droplet to particle conversion driven by plasma induced precursor reduction. Finally, the third section deals with the development of a simulative and experimental approach used to investigate the in-situ droplet evaporation inside the plasma discharge addressing the main contributions to liquid evaporation in the perspective of process industrial scale up.

In this dissertation are reported the most relevant results obtained during my three years Ph.D. project. An open-air plasma source has been developed to treat plastic and metallic films typically used in food packaging manufacturing. Among others, the DBD configuration was chosen due to its many advantages such as high intensity and uniformity of the treatment, possibility of operating in ambient air as well as ease of scale up. Biological experiments were performed to assess the microbial reduction induced by the plasma treatment. Different operative conditions have been tested in order to identify the most efficient configuration and two distinct behaviours have been observed: low-power density treatment allowed to achieve microbial inactivation values below log 2 independently on treatment time; high-power density treatment where the microbial reduction grew with increasing treatment time. Subsequently, the plasma discharge has been characterized by means of three investigation methods: thermal, electrical and optical absorption spectroscopy (OAS) analysis. The thermal and electrical analyses were employed to identify the best dielectric materials for food packaging manufacturing purposes. Once defined the optimal DBD configuration, OAS was used to measure the absolute concentration of ozone and nitrogen dioxide. Results showed that at low-power density the chemistry is governed by ozone; while at high-power density ozone is consumed by the poisoning effect and only nitrogen dioxide is detectable. Lastly, a numerical simulation has been used to deeper investigate the chemistry governing the plasma discharge; by means of PLASIMO a global model and a fluid model were implemented.

The use of atmospheric pressure plasmas for thin film deposition on thermo-sensitive materials is currently one of the main challenges of the plasma scientific community. Despite the growing interest in this field, the existing knowledge gap between gas-phase reaction mechanisms and thin film properties is still one of the most important barriers to overcome for a complete understanding of the process. In this work, thin films surface characterization techniques, combined with passive and active gas-phase diagnostic methods, were used to provide a comprehensive study of the Ar/TEOS deposition process assisted by an atmospheric pressure plasma jet. SiO2-based thin films exhibiting a well-defined chemistry, a good morphological structure and high uniformity were studied in detail by FTIR, XPS, AFM and SEM analysis. Furthermore, non-intrusive spectroscopy techniques (OES, filter imaging) and laser spectroscopic methods (Rayleigh scattering, LIF and TALIF) were employed to shed light on the complexity of gas-phase mechanisms involved in the deposition process and discuss the influence of TEOS admixture on gas temperature, electron density and spatial-temporal behaviours of active species. The poly-diagnostic approach proposed in this work opens interesting perspectives both in terms of process control and optimization of thin film performances.

When considering the dismantling of a PET cyclotron facility, considerable amount of low level solid radioactive waste has to be characterized and disposed of. Prediction of induced radioactivity is a challenging task since the activity produced varies considerably, depending on the type of accelerator, on its use and on the specific structure of the bunker: for this reason, each facility require its specific decommissioning strategy. This work is aimed at developing a Monte Carlo approach to a preliminary assessment of activation, to define an ad hoc decommissioning strategy and to identify possible countermeasures to be taken during the construction phase of the facility. In this work two main cases studies were analysed: The GE PETtrace facility of the Sant’Orsola-Malpighi Hospital (Bologna) and the IBA CYCLONE 18/9 facility of Inselspital (Bern). The Monte Carlo code FLUKA was used to model accurately the two facilities for activation assessment. Different kinds of experimental measurements were performed to evaluate MC models reliability in terms of neutron field and neutron activation. The main long lived radionuclides founded inside the bunkers walls were 152Eu, 154Eu, 134Cs, 54Mn, 46Sc, 57Co, 65Zn and 60Co, for both facilities. The nuclides with the highest activity concentrations were 60Co and 152Eu. The total activity concentration estimated after 20 years of cyclotron operating life was up to 4.10 Bq/g and up to 3.22 Bq/g respectively in Bologna and in Bern, exceeding in both cases the radiological exemption limit of 1 Bq/g. Monte Carlo simulation proved to be a very powerful and feasible tool in the planning of new biomedical cyclotron installations and in the definition of an optimized decommissioning strategy. The availability of an experimentally validated Monte Carlo model makes it possible to revise the traditional approach to activation assessment.

Cold Atmospheric pressure Plasma (CAP) devices are gaining great interest for their potentials in medical applications, ranging from the inactivation of microbial load to the induction of apoptosis in malignant cells. Therefore, the dissertation was focused on the development of a prototype CAP medical devices, based on Plasma Gun configuration, evaluating its performances in endodontic and oncology fields. Regarding dental applications, a biological investigation of the antibacterial efficacy of Plasma Gun source was carried out on realistic root canal models in collaborations with a group of dental practitioners. Furthermore, the CAP-derived enhancement of adhesion performances of tooth restoration was evaluated along the whole length of ex-vivo root canals. Concerning cancer applications, the CAP-induced apoptosis in Jurkat cells was tested and studied by means of cyto-toxicological analyses. This study represents the first step of a national research project aiming at evaluating the selectively induction of apoptosis in leukemia cell models. Finally, great effort was addressed to the study of optical spectroscopy techniques for the characterization and control of plasma processes: in particular, the poisoning effect of ozone, a molecule extremely relevant for biomedical applications, was investigated through the analysis of O3 and NOx kinetics.

Plasma assisted processes are a fundamental technology for the production of high valued-added materials. To meet the ever-changing demands for this kind of materials, the investigation and the optimization of plasma assisted processes is a fundamental issue. In this perspective, research activities must be carried out both for the more established plasma technologies and for the promising Cold Atmospheric Plasma (CAP) sources. This dissertation, organized in three main parts, is focused on the characterization and development of plasma assisted process and sources to produce high value-added materials. In the first part an integrated approach for the design and optimization of processes assisted by low power atmospheric pressure Radio Frequency (RF) thermal plasmas, based on the analysis and comparison of numerical and experimental results, is presented. The development of two processes performed by means of CAPs to modify the wettability of polymers are described in the second part. The first process concerns the functionalization of polymeric films; the second one the deposition of a hydrophobic coating on natural textiles. In the last part, the results achieved on the design and development of processes assisted by cold plasmas (whether low pressure or atmospheric pressure) for the realization of antibacterial coatings are presented.

Heavy Liquid Metal Cooled Reactors are among the concepts, fostered by the GIF, as potentially able to comply with stringent safety, economical, sustainability, proliferation resistance and physical protection requirements. The increasing interest around these innovative systems has highlighted the lack of tools specifically dedicated to their core design stage. The present PhD thesis summarizes the three years effort of, partially, closing the mentioned gap, by rationally defining the role of codes in core design and by creating a development methodology for core design-oriented codes (DOCs) and its subsequent application to the most needed design areas. The covered fields are, in particular, the fuel assembly thermal-hydraulics and the fuel pin thermo-mechanics. Regarding the former, following the established methodology, the sub-channel code ANTEO+ has been conceived. Initially restricted to the forced convection regime and subsequently extended to the mixed one, ANTEO+, via a thorough validation campaign, has been demonstrated a reliable tool for design applications. Concerning the fuel pin thermo-mechanics, the will to include safety-related considerations at the outset of the pin dimensioning process, has given birth to the safety-informed DOC TEMIDE. The proposed DOC development methodology has also been applied to TEMIDE; given the complex interdependence patterns among the numerous phenomena involved in an irradiated fuel pin, to optimize the code final structure, a sensitivity analysis has been performed, in the anticipated application domain. The development methodology has also been tested in the verification and validation phases; the latter, due to the low availability of experiments truly representative of TEMIDE's application domain, has only been a preliminary attempt to test TEMIDE's capabilities in fulfilling the DOC requirements upon which it has been built. In general, the capability of the proposed development methodology for DOCs in delivering tools helping the core designer in preliminary setting the system configuration has been proven.

Il presente lavoro di tesi ha riguardato lo studio dello smantellamento di un reattore gas grafite di potenza di I Gen. L’indagine è stata focalizzata in particolare al recupero della grafite irraggiata che ne costituisce il core. Viene presentata una descrizione referenziata del reattore e dei suoi componenti per mettere in evidenza la particolare architettura e le specifiche problematiche ad essa correlate. A valle di un’indagine sulle esperienze internazionali in merito al decommissioning e allo smantellamento di questi tipi di reattori, si forniscono una possibile sequenza di accesso alla cavità del reattore e una procedura per il suo smantellamento; si descrivono sommariamente le tecnologie di taglio e di handling, attualmente allo stato dell’arte, considerate come più idonee a questo tipo di applicazione. Vengono descritte le principali criticità della grafite nuclear grade ed illustrati i fenomeni caratteristici che ne determinano l’evoluzione nel reattore. Sulla base dei dati resi disponibili dalla Sogin S.p:A. e ricorrendo ai dati di letteratura per quelli non disponibili, è stato effettuato un assessment della grafite irraggiata costituente il nocciolo del reattore, rivolto in particolare a determinarne le caratteristiche meccaniche e la resistenza residua post-irraggiamento. Per valutare la possibilità di prelevare la grafite dal nocciolo è stato ipotizzato un dispositivo di presa che agganci per attrito i blocchi di grafite del moderatore attraverso il canale assiale. Infine è stata valutata la fattibilità di tale metodo attraverso una serie di simulazioni agli elementi finiti dirette a verificare la resistenza del blocco in varie condizioni di carico e vincolo. Come risultato si è dimostrata la fattibilità, almeno in via preliminare, del metodo proposto, determinando l’inviluppo di utilizzo del dispositivo di presa nonché la compatibilità del metodo proposto con le tecnologie di handling precedentemente individuate., The PhD thesis has been focused on the study of the decommissioning of a gas-graphite reactor of the I gen. The investigation was pointed in particular to the retrieval techniques of irradiated graphite of the core. It has been presented a description of the reactor and its components in order to show the architecture and the specific problems related to it. After a review of international experiences regarding the decommissioning and dismantling of these types of reactors, it has been proposed a sequence of access to the cavity of the reactor and a procedure for its dismantling; it has been described the state of art on the cutting and handling technologies, considered as the most suitable for this type of application. the characteristic phenomena which determine the evolution of the graphite in the reactor are described and the main criticality of the nuclear grade graphite are illustrated . Based on data made available by Sogin S.p A. and with the data from literature , it has been performed an assessment of the irradiated graphite of the pile, addressed in particular to determine the mechanical characteristics and the post-irradiation residual strength. To evaluate the possibility to retrireve the graphite from the core it has been proposed a concept design of gripping device that hooks the bored graphite moderator brick for friction through the axial channel. Finally it has been evaluated the feasibility of this method by a series of FEM simulations to verify the strenght of the bricks under various load conditions and constraints. The feasibility of the proposed method has been proved as well as the compatibility of the proposed method with the handling technologies previously identified and the working range of the gripper tool was given.

The aim of this paper is to compare the effects of different mechanisms underlying the synthesis of copper nanoparticles using an atmospheric pressure radio-frequency induction thermal plasma. A design oriented modelling approach was used to parametrically investigate trends and impact of different parameters on the synthesis process through a thermo-fluid dynamic model coupled with electromagnetic field equations for describing the plasma behaviour and a moment method for describing nanoparticles nucleation, growth and transport. The effect of radiative losses from Cu vapour on the precursor evaporation efficiency is highlighted, with occurrence of loading effect even with low precursor feed rate due to the decrease in plasma temperature. A method to model nanoparticle deposition on a porous wall is proposed, in which a sticking coefficient is employed to model particle sticking on the porous wall used to carry a quench gas flow into the chamber. Two different reaction chamber designs combined with different quench gas injection strategies (injection through a porous wall for “active” quenching; injection of a shroud gas for “passive” quenching) are analysed in terms of process yield and size distribution of the synthetized nanoparticles. Conclusion can be drawn on the characteristics of each quenching strategy in terms of throughput and mean diameter of the synthesized nanoparticles.

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.

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.

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.

This dissertation will be focused on the characterization of an atmospheric pressure plasma jet source with an application oriented diagnostic approach and the description of processes supported by this plasma source. The plasma source investigated is a single electrode plasma jet. Schlieren images, optical emission spectra, temperature and heat flux profiles are analyzed to deeply investigate the fluid dynamic, the chemical composition and the thermal output of the plasma generated with a nanosecond-pulsed high voltage generator. The maximum temperature measured is about 45 °C and values close to the room temperature are reached 10 mm down the source outlet, ensuring the possibility to use the plasma jet for the treatment of thermosensitive materials, such as, for example, biological substrate or polymers. Electrospinning of polymeric solution allows the production of nanofibrous non-woven mats and the plasma pre-treatment of the solutions leads to the realization of defect free nanofibers. The use of the plasma jet allows the electrospinnability of a non-spinnable poly(L-lactic acid) (PLLA) solution, suitable for the production of biological scaffold for the wound dressing.

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.

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.

In this work, the well-known MC code FLUKA was used to simulate the GE PETrace cyclotron (16.5 MeV) installed at “S. Orsola-Malpighi” University Hospital (Bologna, IT) and routinely used in the production of positron emitting radionuclides. Simulations yielded estimates of various quantities of interest, including: the effective dose distribution around the equipment; the effective number of neutron produced per incident proton and their spectral distribution; the activation of the structure of the cyclotron and the vault walls; the activation of the ambient air, in particular the production of 41Ar, the assessment of the saturation yield of radionuclides used in nuclear medicine. The simulations were validated against experimental measurements in terms of physical and transport parameters to be used at the energy range of interest in the medical field. The validated model was also extensively used in several practical applications uncluding the direct cyclotron production of non-standard radionuclides such as 99mTc, the production of medical radionuclides at TRIUMF (Vancouver, CA) TR13 cyclotron (13 MeV), the complete design of the new PET facility of “Sacro Cuore – Don Calabria” Hospital (Negrar, IT), including the ACSI TR19 (19 MeV) cyclotron, the dose field around the energy selection system (degrader) of a proton therapy cyclotron, the design of plug-doors for a new cyclotron facility, in which a 70 MeV cyclotron will be installed, and the partial decommissioning of a PET facility, including the replacement of a Scanditronix MC17 cyclotron with a new TR19 cyclotron., In questo lavoro, il codice Monte Carlo (MC) FLUKA è stato utilizzato per simulare il ciclotrone GE PETtrace (16.5 MeV) installato presso l’azienda ospedaliera “S. Orsola-Malpighi” (Bologna, IT), quotidianamente utilizzato per la produzione di radiofarmaci PET. Le simulazioni sono state effettuate per valutare diversi fenomeni e quantità d’interesse radiologico tra cui l’equivalente di dose ambientale nell’intorno dell’acceleratore, il numero di neutroni emessi per protone incidente e la loro distribuzione spettrale, l’attivazione dei componenti del ciclotrone e delle pareti del bunker, l’attivazione dell’aria interna al bunker ed in particolare la produzione di 41Ar, la resa a saturazione di radionuclidi d’interesse in medicina nucleare. Le simulazioni sono state validate, in termini di parametri fisici e di trasporto da utilizzare nel range energetico caratteristico delle applicazioni mediche, con una serie di misure sperimentali. Il modello MC validato è stato quindi applicato ad altri casi pratici quali lo studio di fattibilità della produzione diretta in ciclotrone di 99mTc, la produzione di radionuclidi ad uso medico con il ciclotrone TR13 (13 MeV) installato presso il centro di ricerca TRIUMF (Vancouver, CA), la progettazione completa del nuovo centro PET dell’ospedale “Sacro Cuore-Don Calabria” di Negrar (Verona, IT), incluso il ciclotrone ACSI TR19 (19 MeV), lo studio del campo di dose nell’intorno di un sistema di selezione dell’energia (degrader) di un ciclotrone per terapia, la progettazione di specifiche “porte a tappo” per un sito di produzione di radionuclidi ad uso medico, in cui verrà installato un ciclotrone da 70 MeV e sei diverse beam line, e per il parziale decommissioning di un centro PET e la sostituzione di un ciclotrone Scanditronix MC17 (17 MeV), attualmente installato, con una nuova unità TR19.

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.

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.

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.