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Dans les nouvelles centrales nucléaires dites 4ème génération, comme d’ailleurs les anciennes, le dioxyde d’uranium devra opérer dans des milieux hostiles de températures et d’irradiation avec la présence des produits de fission (PF) et des particules alpha (α). Le fonctionnement dans ces conditions extrêmes induira des déplacements d’atomes et dégradera les propriétés thermiques et mécaniques du combustible UO2. La compréhension du comportement des défauts lacunaires, des PF et de l’hélium est cruciale pour prévoir le comportement du dioxyde d’uranium au sein de ces futures installations nucléaires. La première partie de cette thèse est consacrée à l’étude des défauts lacunaires induits par l’implantation de krypton et d’iode (quelques MeV) dans l’UO2 polycristallin et leurs stades de recuits. L’analyse par spectroscopie d’annihilation de positons (PAS) a permis de mettre en évidence la création de défauts de Schottky VU-2VO dans le cas des implantations iode et la formation de clusters lacunaires contenant du gaz pour les implantations krypton. L’évolution en température de ces défauts générés dépend des paramètres d’implantation (nature des ions, énergie, fluence). Cette étude a montré les rôles importants que peuvent jouer les défauts lacunaires et la présence des gaz de fission dans l’évolution du matériau UO2. Ensuite, nous nous sommes intéressés à l’étude et à la caractérisation, par PAS et les techniques d’analyse par faisceau d’ions (NRA/C et RBS/C), du comportement de l’hélium dans l’UO2. Les mesures de NRA/C et RBS/C révèlent une localisation d’une grande fraction d’hélium dans les sites interstitiels octaédriques de la matrice UO2. La localisation de l’hélium reste stable dans ces sites pour T< 600°C, évoluent légèrement entre 600 et 700°C et devient aléatoire à 800°C. Les mesures PAS mettent en évidence trois stades d’évolution des défauts lacunaires : la recombinaison par migration des interstitiels d’oxygène, l’agglomération des défauts entre 600 et 800°C et leur dissociation et élimination lorsque la température augmente. Ces résultats suggèrent que le transport d'hélium est assisté par les défauts lacunaires. / In the new fourth generation nuclear plants, as in the old ones, uranium dioxide must operate in hostile environments of temperature and irradiation with the presence of fission products (FP) and alpha particles (α). Operation in these extreme conditions will induce atoms displacements and degrade the thermal and mechanical properties of UO2 fuel. Understanding the behavior of induced vacancy defects, FP and helium is crucial to predict the uranium dioxide behavior in the future nuclear reactors. The first part of this thesis is dedicated to the study of vacancy defects induced by krypton and iodine implantation (a few MeV) in the UO2 polycrystalline and of their evolution under annealing. Analysis by positron annihilation spectroscopy (PAS) has highlighted the creation of Schottky defects VU-2VO in the case of iodine implantations and formation of vacancy clusters containing the gas for krypton implantation. The temperature evolution of these defects depends on the implantation parameters (nature of the ion energy, fluence). This study showed the important roles that can play vacancy defects and the presence of fission gases in the evolution of UO2 material. Then we were interested in the study of the helium behavior in UO2 its location and migration, agglomeration and interaction with vacancy defects by using PAS and ion beam analysis (NRA/C and RBS/C). The NRA/C and RBS/C characterizations showed a localization of a large helium fraction in the octahedral interstitial sites of the UO2 matrix. The helium location in these sites remains stable for T <600°C, changing slightly between 600 and 700°C and becomes random at 800°C. Positron annihilation spectroscopy reveals three stages of vacancy defects evolution : The recombination with oxygen interstitial migration, defects agglomeration between 600 and 800°C and their dissociation and elimination when the temperature increases. These results suggest that the He transport is assisted by the vacancy defects.

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Cette thèse est consacrée à l'étude de l'interaction d'ions multichargés avec des particules métalliques de taille nanométrique. Ce travail a eu pour but d'étudier les processus fondamentaux ainsi que d'éclairer leur rôle comme radio-sensibilisants dans le traitement de cancer par hadronthérapie. Le nouveau dispositif développé dans ce cadre consiste en une source d'agrégats de type magnétron, d'une chambre de dépôt afin de permettre la caractérisation de la taille des nanoparticules neutres par analyse microscopique, et d'un spectromètre de masse par temps de vol capable de détecter des systèmes positivement chargés jusqu'à une masse de 50 000 ua. Les études de collisions ont été réalisées avec des agrégats de Bi (2 nm ; 200 atomes) et de Ag (6 nm ; 5000 atomes). Dans le deux cas, le processus de capture multiélectronique crée un système multichargé. Dans le cas du Bi, une grande partie fragmente par la fission asymétrique émettant des petits fragments. Dans le cas des particules plus grandes (Ag), les systèmes multichargés ne fragmentent pas, par contre des petits fragments sont aussi observés mais ils sont le produit de la pulvérisation de la nano-surface lors de collisions pénétrantes. En perspective, des expériences seront réalisées avec des nanoparticules métalliques fonctionnalisées ainsi que le comptage des électrons émis lors de la collision. / This thesis presents a study of the interaction of multiply charged ions with metallic nano-sized particles both in the context of fundamental processes and possible applications as radiosensitizers in nanoparticle-enhanced hadrontherapy. For this purpose a new experimental set-up has been constructed based on a magnetron-discharge cluster source, a deposition chamber for analyzing the size of neutral nanoparticles with AFM and TEM techniques and a time-of-flight mass spectrometer able to detect positively charged particles with masses up to 50 000 amu. Collision studies were performed with Bi clusters of 2nm in diameter, containing 200 atoms, as well as Ag nanoparticles (6 nm, 5000 atoms). In both cases multi-electron capture leads to the formation of multiply charged systems. In the Bi case a large fraction fragments by asymmetric fission emitting small singly charged fragments. In the case of large Ag nanoparticles multiply charged systems are stable. However, small size fragments are formed due to sputtering of the nano-surface in penetrating collisions. Future experiments will be performed with functionalized metal nanoparticles, aiming to count the number of electrons emitted after ion collisions.

Php4 is a subunit of the CCAAT-binding protein complex that has a negative regulatory function during iron deprivation in the fission yeast Schizosaccharomyces pombe. Under low iron conditions, Php4 fosters the repression of genes encoding iron using proteins. In contrast, under iron-replete conditions, Php4 is inactivated at both transcriptional and post-transcriptional levels. Our group has already described that Php4 is a nucleo-cytoplasmic shuttling protein, which accumulates into the nucleus during iron deficiency. On the contrary, Php4 is exported from the nucleus to the cytoplasm in response to iron abundance. Php4 possesses a leucine-rich NES (93LLEQLEML100) that is necessary for its nuclear export by the exportin Crm1. Our current study aims at understanding the mechanism by which Php4 is imported in the nucleus during iron starvation. Through microscopic analyses using different mutant strains, we showed that the nuclear localization of Php4 is independent of the other subunits of the CCAAT-binding core complex namely Php2, Php3 and Php5. Deletion mapping analysis of Php4 identifies two putative nuclear localization sequences (NLSs) in Php4 (171KRIR174 and 234KSVKRVR240). Using chimeric proteins that consist of GFP fused to Php4, we engineered substitutions of the basic amino acid residues 171AAIA174 and 234ASVAAAA240 and analyzed the functionality of both NLSs. We observed that both monopartite NLSs play critical role for Php4 nuclear localization. We also observed that mutant strains of cut15+, imp1+ or sal3+ exhibited defects in nuclear targeting of Php4, revealing that nuclear accumulation of Php4 is dependent on two karyopherin α (Imp1 and Cut15) and one karyopherin β (Sal3) receptors. Consistently, the Php4-mediated repression activity is abolished in the absence of two functional NLSs. Moreover, loss of Imp1, Cut15 or Sal3 resulted in increased expression of isa1+, which is a target gene of Php4. Co-immunoprecipitation assay (Co-IP) reveals physical interaction of Php4 with Imp1, Cut15 and Sal3 in vitro. Collectively, our results demonstrate that Php4 has two distinct NLS regions responsible for its nuclear localization. Furthermore, karyopherin α and β receptors play a role in the nuclear import of Php4. Because Php4 is essential for growth under low iron conditions, the presence of two NLSs would ensure the protein to reach its nuclear destination when cells undergo a transition from iron-sufficient to iron-limiting conditions.

Acenes have been explored by a number of research groups in the field of organic electronics with a particular emphasis on transistor materials. This group has been actively studying acene‐based organic semiconductors for more than a decade using a crystal engineering approach and has developed acene derivatives for applications in field‐effect transistors, light‐emitting diodes, and photovoltaics. In addition to organic electronics, crystal engineering has important applications in a number of other fields, quite notably in the design of metal‐organic frameworks. Chapters 2 and 3 of this dissertation focus on applying crystal engineering to the synthesis of acene derivatives for use as solid‐state, long‐wavelength fluorescent organic dyes in the field of biomedical imaging. More specifically, this work studied the synthesis and properties of dioxolane‐functionalized pentacenes and hexacenes. One of these pentacene derivatives has already been demonstrated in biomedical imaging which may lead to improved treatment of tuberculosis. The dioxolane‐functionalized hexacene is still under evaluation for bioimaging applications. Chapters 4 and 5 focus on crystal engineering in relation to organic electronics. Chapter 4 deals with fine‐tuning of crystal packing and demonstrated that small differences in molecular structure can result in significant changes to the solid‐state structure which affects semiconductor properties. Finally, chapter 5 studies the use of singlet fission in photovoltaics and demonstrated that this process does occur in a solar cell incorporating a hexacene derivative. Pentadithiophenes were also synthesized for singlet fission photovoltaics, but they have yet to be studied further.

Ce travail de thèse se compose d'une partie théorique et d'une partie expérimentale. Nous combinons et utilisons les codes de transport de haute énergie LAHET, de basse énergie MCNP et le code d'activation CINDER. Nos calculs de validation des codes montrent que LAHET néglige la dissociation coulombienne du deutéron. En ajoutant cette contribution, nous obtenons un bon accord avec les données. Nous concluons également que LAHET reproduit bien la production d'isotopes si le modèle de fission ORNL est utilise pour des cibles avec z > 90. Le modèle de fission RAL donne des distributions isotopiques trop larges et ne reproduit pas les données en valeur absolue. Nous examinons différentes combinaisons de faisceaux (projectile, énergie), de cibles de spallation et de cœur de réacteur pour la production de neutrons, l'amplification d'énergie et la production de faisceau radioactif par fission. Nous montrons que les réactions (d, xn) pourraient apporter un certain nombre d'avantages importants, comparées aux réactions (p, xn). Nous concluons que l'utilisation de deutérons au lieu de protons devrait conduire a des intensités de faisceau primaire plus élevées, a un prix réduit du système et a moins de problèmes de radioprotection. Dans le projet SPIRAL Phase-II au GANIL, nous proposons la combinaison d(100 MeV)+Be→xn+U pour une production optimum de noyaux riches en neutron dans la région de masse 75≤A≤160. Cependant, la production de gaz de tritium dans la cible de conversion devrait être soigneusement étudiée. Nous prouvons également que l'utilisation des cibles de conversion de métal plus lourd peut poser des problèmes de radioprotection plus graves. Notre travail expérimental est directement relié aux investigations théoriques. Nous mesurons les distributions en énergie de protons produits par des deutérons de 100 et de 200 MeV sur 8 cibles minces (Be, C, Al, Ni, Nb, Ta, Pb et U) et dans la région angulaire 8° ≤ θp ≤ 120°. Les deux expériences ont été réalisées au LNS (Saclay, france) et au NAC (Faure, Afrique du Sud). Les données de bonne qualité (10% en valeur absolue et un seuil en énergie de 4-8 MeV) sont bien reproduites par le modèle LAHET amélioré pour les réactions (d, xp) et, par conséquent, pour les réaction (d, xn).

A model of the generation and release of fission gas, as well as the total swelling over time, was created. It uses an ideal spherical fuel grain with a time-dependent radius. UO2 and quasi-homogeneous SBR MOX fuels were simulated with this model, and the results were compared to a fixed grain radius model of gaseous swelling. Gaseous swelling and fission gas release were calculated for temperatures from 1600 K to 2200 K. The grain growth of UO2 was found to decrease the time needed to saturate the intergranular boundaries as compared to simple diffusion without grain growth. Small temperatures increased the time required for saturation, as did small rates of grain growth. Gaseous swelling was within the range of values found by experimental data.

The SABR fusion-fission hybrid concept for a fast burner reactor, which combines the IFR-PRISM fast reactor technology and the ITER tokamak physics and fusion technology, is adapted for a fusion-fission hybrid reactor, designated SABrR. SABrR is a sodium-cooled 3000 MWth reactor fueled with U-Pu-10Zr. For the chosen fuel and core geometry, two configurations of neutron reflector and tritium breeding structures are investigated: one which emphasizes a high tritium production rate and the other which emphasizes a high fissile production rate. Neutronics calculations are performed using the ERANOS 2.0 code package, which was developed in order to model the Phenix and SuperPhenix reactors. Both configurations are capable of producing fissile breeding ratios of about 1.3 while producing enough tritium to remain tritium-self-sufficient throughout the burnup cycle; in addition, the major factors which limit metal fuel residence time, fuel burnup and radiation damage to the cladding material, are modest.

A General Description of Fission Observables (GEF) version 2016/1.2 is a software which simulates various types of fission. The main objective of this project is to compare the proton induced fission with the neutron induced fission of the same fissioning system. The proton induced fission was recently introduced to GEF and is relatively untested. Furthermore another task is to study the energy dependence in the same compound nucleus. The project will focus on simulating and comparing 238U(p,f) with 238Np(n,f) and 239Np*(f) as well as 232Th(p,f) with 232Pa(n,f) and 233Pa*(f ). The simulations were also compared to experimental data acquired by the division of applied nuclear physics at Uppsala University. The results show that the p-induced channel behaves very similar to the Compound Nucleus (CN) channel in contrary with the (n,f) channel. However when comparing the simulated data to the experimental data, there seems to be clear differences.