Made available in DSpace on 2014-10-09T12:25:11Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:21Z (GMT). No. of bitstreams: 1 01015.pdf: 998775 bytes, checksum: 24043b75e9a372f6fca29bba4af963d3 (MD5) / Dissertacao (Mestrado) / IEA/D / Instituto de Química - Universidade de São Paulo - IQ/USP

Made available in DSpace on 2014-10-09T12:25:16Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:12Z (GMT). No. of bitstreams: 1 01248.pdf: 1789417 bytes, checksum: 5a973aecd1016836db674f63b72e6524 (MD5) / Dissertacao (Mestrado) / IEA/D / Faculdade de Ciencias Farmaceuticas, Universidade de Sao Paulo - CF/USP

Made available in DSpace on 2014-10-09T12:24:44Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:05:15Z (GMT). No. of bitstreams: 1 00882.pdf: 1586547 bytes, checksum: 0bb29ea8d486fa54c36c25f7b2200e8e (MD5) / Tese (Doutoramento) / IEA/T / Instituto de Energia Atomica - IEA

Made available in DSpace on 2014-10-09T12:24:01Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:53Z (GMT). No. of bitstreams: 1 00320.pdf: 1172919 bytes, checksum: 4d5e1e5e78a42ba78f889529faaf1838 (MD5) / Dissertacao (Mestrado) / IEA/D / Instituto de Química - Universidade de São Paulo - IQ/USP

This thesis describes the reductive functionalisation of the uranyl(VI) dication by metalation of the uranyl oxo-groups (O=UVI=O), using reductants from Group I, Group II, Group IV, Group XII and Group XIII as well as from the lanthanide and actinide series of the periodic table. Chapter 1 introduces uranium and nuclear waste, and gives an introduction into uranium(V) chemistry. It further compares the chemistry of uranyl(V) to neptunyl(V), with a specific focus on solid state interactions. The chemistry of the Pacman calixpyrroles is briefly introduced. These macrocyclic ligands form the basis for the synthesis of uranyl Pacman, which represents the major uranyl complex investigated in this thesis. Chapter 2 describes the reductive and catalytic uranyl oxo-group metalation using Group XIII and Group I reagents. It presents the reductive uranyl alumination using di-(iso-butyl)-aluminium hydride and Tebbe’s reagent to form the first Al(III)- uranyl(V) oxo complexes (AlIII-O-UV=O). The chapter shows how the transmetalation of these aluminated uranyl(V) complexes with alkali metal hydrides and alkyls leads to the formation of mono-metalated alkali metal uranyl(V) complexes (MI-O-UV=O). The combination of these two reactions is developed into a catalytic synthesis of the latter. The use of elemental alkali metals is described as another pathway of accessing alkali metal uranyl(V) complexes, carried out in collaboration with Dr. Rianne M. Lord. Chapter 3 describes the synthesis of the first Group IV uranyl(V) complexes, using low-valent titanium and zirconium starting materials. The chapter includes magnetic measurements on the first Ti(III)-uranyl(V) complex and a comparison of computational results regarding a selection of uranyl(V) complexes from this thesis. The magnetic measurements were carried out by Dr. Alessandro Prescimone, University of Edinburgh, and analysed by Dr. Nicola Magnani, Institute for Transuranium Elements, Karlsruhe, Germany. Theoretical calculations were carried out by Xiaobin Zhang and Prof. Dr. Georg Schreckenbach, University of Manitoba, Canada. The chapter further describes the reductive metalation of uranyl using elemental Mg, Ca and Zn and their respective metal halides. Chapter 4 describes the uranyl functionalisation using f-elements and their complexes. It describes the attempted mono-metalation using lanthanides and the formation of a Sm(III)-bis(uranyl(V)) complex. It further describes the uranyl reduction using actinides and the synthesis of the first U(IV)-uranyl(V) complex. The chapter further describes the first Np(IV)-uranyl(V) complex and the attempted synthesis of a Pu(IV)-uranyl(V) complex. These syntheses were performed in collaboration with Michał S. Dutkiewicz at the Institute for Transuranium Elements (ITU) in Karlsruhe, Germany. This work was carried out with the help of Dr. Christos Apostolidis and Dr. Olaf Walter and supervised by Prof. Dr Roberto Caciuffo. Chapter 5 describes the reductive uranyl functionalisation in a redox-active dipyrromethene ligand, collaboratively carried out with James R. Pankhurst and Lucy N. Platts. The synthetic work and analyses were performed jointly with Lucy N. Platts (master student under the supervision of the author); UV-vis spectra and cyclic voltammograms were recorded by James R. Pankhurst and Lucy N. Platts. The chapter presents the synthesis of a new uranyl(VI) complex and its two-electron reduction to uranium(IV) using a titanium(III) reductant. Additionally the chapter describes the reductive uranyl silylation in a dipyrromethane complex of which the ligand was designed by Dr. Daniel Betz. Section 6 describes the synthetic procedures. Section 7 gives references to the work of others. Section 8 shows the publication related to this thesis. Section 9 is a table of the complexes described in this thesis.

The framework of this PhD is the interpretation of Nuclear Magnetic Relaxation Dispersion experiments performed on solvated U4+, NpO2+ and PuO22+, which all have an f2 configuration. Unexpectedly the two actinyl ions have a much higher relaxivity than U4+. One possible explanation is that the electronic relaxation rate is faster for Uranium(IV) than for the actinyl ions. We address this problem by exploring the electronic spectrum of the three compounds in solution. A preliminary step is the computation of the electronic spectra of these three ions in gas phase. A two-step SOCI method has been used to investigate the spectroscopy in gas phase and in solution. The influence of electron correlation  (treated in the first step) and spin-orbit relaxation effects (considered in the second step) has been discussed thoroughly. The influence of the first hydration sphere and the bulk solvent effects has been investigated as well.Another issue that has been questioned is the accuracy of Density Functional Theory for the study of actinide species. This matter has been discussed by comparing its performance to wave-function based correlated methods. The chemical problem chosen was the water exchange in UO22+(H2O)5. This reaction can proceed via three pathways, the associative, the dissociative and the symmetric interchange. We looked at the two former ones using a model with one additional water in the second hydration sphere.The last part of the thesis dealt with the spectroscopy of coordinated Uranyl(V). Absorption spectrum of Uranyl(V) with various ligands has been recorded. The first sharp absorption band in the Near Infrared region were assigned to the Uranium centered 5f-5f transitions, but uncertainties remained for the assignment of transitions observed in the Visible region. We computed the spectra of naked UO2+ and [UO2(CO3)3]5- to elucidate the spectral changes induced by the carbonate ligands. / Cecile Danilo takes her PhD in collaboration with Uniersité Lille 1 under the cotutelle system

Minor actinides represent the long-term radiotoxicity of nuclear wastes. As one of their potential incineration options, partitioning and transmutation in fission reactors are seriously considered worldwide. If implemented, these technologies could also be a source of nuclear fuel materials required for sustainability of nuclear energy. The objective of this research was to evaluate performance characteristics of Very High Temperature Reactors (VHTRs) and their variations due to configuration adjustments targeting achievability of spectral variations. The development of realistic whole-core 3D VHTR models and their benchmarking against experimental data was an inherent part of the research effort. Although the performance analysis was primarily focused on prismatic core configurations, 3D pebble-bed core models were also created and analyzed. The whole-core 3D models representing the prismatic block and pebble-bed cores were created for use with the SCALE 5.0 code system. Each of the models required the Dancoff correction factor to be externally calculated. The code system DANCOFF-MCThe whole-core/system 3D models with multi-heterogeneity treatments were validated by the benchmark problems. Obtained results are in agreement with the available High Temperature Test Reactor data. Preliminary analyses of actinide-fueled VHTR configurations have indicated promising performance characteristics. Utilization of minor actinides as a fuel component would facilitate development of new fuel cycles and support sustainability of a fuel source for nuclear energy assuring future operation of Generation IV nuclear energy systems. was utilized to perform the Dancoff factor calculations.

Th.--Chim.--Toulouse--Inst. natl polytech., 1991. N°: 461. / Bibliogr. p. 203-216. Résumé en anglais et en français.

Made available in DSpace on 2014-10-09T12:23:12Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:47Z (GMT). No. of bitstreams: 1 00403.pdf: 2297146 bytes, checksum: 62d1c7710f3017305d9a11eaa8d59e9f (MD5) / Tese (Doutoramento) / IEA/T / Instituto de Química - Universidade de São Paulo - IQ/USP

Made available in DSpace on 2014-10-09T12:30:27Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:51Z (GMT). No. of bitstreams: 1 00976.pdf: 4121392 bytes, checksum: a2ce9913a7bf6c928a38c11fd97c887e (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP