The encapsulation of a small molecule inside a fullerene cage through advances in synthetic chemistry have created a new platform to study the dynamics of a freely rotating and translating quantum rotors entrapped inside a symmetric cage potential. These endohedral fullerene complexes are of great interest because the fullerene cages uniquely provide the entrapped molecules a high level of isolation, homogeneity, symmetry and stability. The endohedral fullerene complexes discussed in this thesis are the H2@C60, H2@C70 and H2O@C60. Both variants of small molecules studied in this thesis, H2 and H2O, exhibits spin isomerism, where the spins of both protons in the molecule are able to combine either symmetrically with total spin I=1 (ortho) or anti-symmetrically with total spin I=0 (para). The H2@C60 is the union between the simplest molecule and the most symmetrical molecule in the universe. This thesis discusses the temperature dependence of cold neutron scattering study in this complex to investigate the statistical distribution of the energy states. The H2@C70 is a less symmetric endohedral fullerene which has a prolate ellipsoidal symmetry cage. This thesis discusses the low temperature thermal neutron scattering and the temperature dependence of cold neutron scattering investigations in the complex to study the effect of the ellipsoidal cage on the quantum dynamics of the molecules. H2O@C60 is different to the dihydrogen variant of the small molecule endohedral fullerenes because H2O has a permanent electric dipole moment and is less symmetric than H2. The quantum dynamics of the H2O@C60 is investigated using low temperature thermal neutron scattering, temperature dependence cold neutron scattering and milli-Kelvin NMR. Unlike the dihydrogen endohedral fullerenes, the H2O@C60 also exhibits slow nuclear spin-isomer conversion at low temperatures. This low temperature ortho-H2O to para-H2O conversion process is investigated with both INS and NMR to study the conversion mechanism.

La radioactivité deux-protons est un mode de décroissance du noyau atomique ne se produisant que pour des noyaux extrêmement riches en protons, situés au-delà de la limite de cohésion proton des noyaux (drip line). Prédit dans les années 1960, ce phénomène n’a été mis en évidence expérimentalement qu’en 2002 avec l’observation de la décroissance de 45Fe. Jusqu’à maintenant, seuls quatre noyaux se désintégrant par radioactivité deux-protons étaient connus : 45Fe, 48Ni, 54Zn et 19Mg. La recherche de nouveaux émetteurs a été menée lors d’une expérience avec le dispositif EURICA-WAS3ABi au centre RIKEN Nishina en 2015. La décroissance de 59Ge, 63Se, 67Kr et 68Kr a été observée pour la première fois. La radioactivité deux-protons de 67Kr a pu être étudiée ainsi que la décroissance bêta et l’émission retardée de protons de noyaux exotiques de la région. Une chambre à projection temporelle ou TPC (Time Projection Chamber) conçue par le CENBG (2004-2011) a permis d’étudier les corrélations entre les protons pour 45Fe et 54Zn. Une deuxième génération de TPC est développée au sein de la collaboration ACTAR TPC (ACtive TARget for TPC). Ce détecteur doit permettre une vraie reconstruction tridimensionnelle de l’énergie déposée par les particules dans le volume actif, afin d’obtenir une reconstruction des traces plus performantes que l’ancienne TPC. L’électronique générique GET (General Electronics for TPCs) gère le traitement et l’acquisition des signaux. La caractérisation de l’électronique GET ainsi que du démonstrateur de la TPC au CENBG est le deuxième aspect de ce travail de thèse. / Two-proton radioactivity is a decay mode of proton-rich nuclei located beyond the proton nuclear existence limit (drip line). Predicted in the 1960s, this process was observed for the first time in 2002 in the 45Fe decay study. Only four two-proton emitters were known so far: 45Fe, 48Ni, 54Zn and 19Mg. A search for new emitters was performed with the EURICA- WAS3ABi setup at the RIKEN Nishina center in 2015. The decay of 59Ge, 63Se, 67Kr and 68Kr was observed for the first time. Two-proton radioactivity of 67Kr together with the beta and delayed proton decay of exotic nuclei in the region were studied. A time projection chamber (TPC) developed at the CENBG (2004-2011) enabled the study of the correlations between the protons for 45Fe and 54Zn. A second generation of TPC is under construction within the ACTAR TPC (ACtive TARget for TPC) collaboration. This detector enables a reconstruction in three dimensions of the energy deposited in the active volume which allows a more efficient reconstruction of the tracks as compared to the previous TPC. The generic electronics GET (General Electronics for TPCs) manages the processing and acquisition of the signals. The characterisation of the GET electronics and the TPC demonstrator at CENBG is devoted to the second aspect of this PhD work.

The work described in this thesis was conducted at the University of Nottingham in the Sir Peter Mansfield Imaging Centre, between September 2011 and 2014. Subject motion in high- resolution magnetic resonance imaging (MRI) is a major source of image artefacts. It is a very complex problem, due to variety of physical motion types, imaging techniques, or k-space trajectories. Many techniques have been proposed over the years to correct images for motion, all looking for the best practical solution in clinical scanning, which would give cost- effective, robust and high accuracy correction, without decreasing patient comfort or prolonging the scan time. Moreover, if the susceptibility induced field changes due to head rotation are large enough, they will compromise motion correction methods. In this work a method for prospective correction of head motion for MR brain imaging at 7 T was proposed. It would employ innovative NMR tracking devices not presented in literature before. The device presented in this thesis is characterized by a high accuracy of position measurements (0.06 ± 0.04 mm), is considered very practical, and stands the chance to be used in routine imaging in the future. This study also investigated the significance of the field changes induced by the susceptibility in human brain due to small head rotations (±10 deg). The size and location of these field changes were characterized, and then the effects of the changes on the image were simulated. The results have shown that the field shift may be as large as |-18.3| Hz/deg. For standard Gradient Echo sequence at 7 T and a typical head movement, the simulated image distortions were on average equal to 0.5%, and not larger than 15% of the brightest voxel. This is not likely to compromise motion correction, but may be significant in some imaging sequences.

Geological disposal of radioactive wastes currently stored at Earth's surface is now the favoured management pathway for these materials. Typically, intermediate level wastes (ILW) are grouted and emplaced in a geological disposal facility (GDF) which will be backfilled, possibly with cementitious materials. Post-closure leaching of the cementitious materials in a GDF is expected to create hyperalkaline conditions in and around the repository, resulting in mineral alteration and crystallisation, both within the engineered barrier and host rock; creating a persistent chemically disturbed zone (CDZ). Iron derived from within the host rock as a result of alkaline breakdown of Fe-bearing silicate minerals (e.g. biotite, chlorite); corrosion products formed within the repository; or iron contained within the waste; will form secondary iron (oxyhydr)oxide minerals. The formation and re-crystallisation of these reactive mineral phases may sequester radionuclides through a host of processes: surface-mediated reduction to less soluble forms; adsorption onto, and/or incorporation into stable secondary or tertiary iron oxide phases. Therefore iron (oxyhydr)oxides will be key to the fate of radionuclides potentially released from within radioactive wastes disposed of in a GDF.In this study, the fate of U(VI) and Tc(VII) was considered during crystallisation of ferrihydrite to more stable iron oxide phases (e.g. hematite and magnetite) and, in three synthetic cement leachates (pH 13.1, 12.5, 10.5) designed to reflect the early-, middle- and late-stage evolution of the CDZ. XRD and SEM/TEM have been used to characterise the mineralogy during crystallisation. Partitioning of U(VI) and Tc(VII) between the solid and solution has been followed throughout, with chemical extractions used to determine the distribution of the radionuclides adsorbed to, and incorporated within the solid. Synchrotron-based XAS techniques have been utilised to probe the oxidation state and molecular scale bonding environment of the radionuclides associated with the solids. The data suggest that: U(VI) is incorporated into the hematite structure in place of Fe(III), in a distorted octahedral environment with elongation of the uranyl bond; Tc(VII) is reduced to Tc(IV) and incorporated into the octahedral site within the magnetite structure in place of Fe(III), and is retained in the same environment even after extensive oxidation of the magnetite to maghemite; and that U(VI) may also be incorporated as U(V) or U(VI) into the magnetite structure, with similar recalcitrant behaviour during oxidation. These results highlight the importance of mineral reactions within the CDZ as potentially significant pathways for immobilising radionuclides released from a GDF.

The task of this master´s thesis is to write a theory of radiation sensing, describe the function of GPS and design the measuring system which can measure the radioactive background and these values assigned to the current GPS coordinates.

Auf der Grundlage umfangreicher Originaldokumente aus staatlichen Archiven in Prag und Wien zeichnen die Autoren anhand zahlreicher Briefe, Aktennotizen und weiterer Aufzeichnungen die Rolle der Joachimstaler Uranbergwerke bei der Bereitstellung von Pechblende nach, die als Mineral M. und P. Curie die Entdeckung des Elementes Radium ermöglichten. Bürokratische Eitelkeiten, akademische Vorurteile und sich überschneidende Interessen der K.u.K. Verwaltung in Wien haben die durchaus denkbare Entdeckung des Radiums in österreichischen Laboratorien erfolgreich verhindert.

In the years 2014-2015 a radiohydrogeochemical survey was carried out in the Tanvald granite body. Tanvald granite is a two-mica granite body located on the southern edge of the Krkonoše-Jizera Pluton, in the Lusatian part of the Saxony and Thuringian zone of the Variscan orogenic belt. The aim of the survey was to find radioactive water, the 222 Rn volume activity of which exceeds 1500 Bq/l. Such water is - under the Act no. 164/2001 Coll. - considered as radioactive mineral water. The result was a found of 20 water sources meeting this condition and many other sources approaching this value. In terms of the findings, the most important area is Dlouhý Most, where 8 of the radioactive water resources exceeding 1500 Bq/l were found. The most important of these is probably the source TGR/11 with the 222 Rn volume activity 2449 Bq/l. A cluster of water sources with a slightly higher conductivity (exceeding 300 µS/cm) appears in the Dlouhý Most area. Chemical analysis of the most important of them (TG1/15) showed that it is water of the Na-Ca-Cl type, probably contaminated by a run-off from the motorway, which is salted in winter. Another important site is the Kokonín fault area. At this important geological structure a total of four springs of radioactive water with the 222 Rn volume activity greater...

Radiohydrochemical exploration took place in east part of the "smrčinský" pluton between "Skalná-Plesná-Bad Brambach in years 2016-2018. The main aim of the exploration was location and thorough research of possible occurrence of waters with radioactive concretation higher than 1500 Bq/l. That is a value for radioactive mineral waters given by the "lázeňským" law number 164/2001 Sb. Most important area is Plesná-south where was discovered several springs with values exceeding 5000 Bq/l. Eminent spring is called "Břetislav-Radonka" and lies one kilometre southwest from the train station Plesná-Šneky with an activity of about 12.5 kBq / l 222 Rn and a flow rate of about 2.5 l / min. It is the most active surface discharge of radon mineral water in the Czech Republic Another significant source area is north of Skalna - north. These springs were discovered almost 60 years ago, Dr. Marie Zukriegelová. The main source of this area was named after its discoverer - the "Marie Z" spring with an activity of 5800 Bq / l 222 Rn.Further the research focused on historical radioactive conduit which were used to supply village Skalné with water. The conduit was separated on two "branches" and the younger one was built ten years after the first one. In both pipes were found radioactive waters and the most important...

The Karoo has been receiving considerable attention since the early 1970’s when uranium mining was at its peak, with numerous research studies being instigated to look at all aspects of uranium mining. It has recently been observed that there seems to be resurgence in uranium exploration in and around the town of Beaufort West. A study on the transport mechanisms of uranium and thorium in fractured-rock aquifers, initiated in the hope of understanding the actual processes controlling radionuclide mobilisation, is reported here. Hydrochemical investigations of the various boreholes were sampled for water quality in June, 2009. The hydrochemical description is typical of shallow fresh groundwater, changing composition to a more sulphate hydrochemical facies along the flow path. While the geochemistry of groundwater in the study area seems to have minimal effects on uranium concentrations, the low levels of uranium in boreholes sampled suggest the importance of hydrological and lithological variability on the measured concentrations. Nevertheless, the uranium concentration is within the recommended levels as specified in the US-EPA, WHO and SA water quality guidelines and thus poses no immediate threat to the general public. Analysis of pumping and tracer tests, reveals that the fractured-rock aquifer can be highly transmissive and that transport can take place via multiple flow paths having different hydraulic properties. Tracer diffusing into stagnant water zones within fracture asperities and the rock matrix are seen as an important retardation mechanism, that has implications for remediation should the aquifer be contaminated by radionuclides. In terms of conceptualising flow at a local scale, aperture sizes ranging from (563-828ìm) along with high flow velocities (1.90E-03m/s), points to the importance of bedding-plane fractures as conduits of groundwater flow. The groundwater flow has been influenced by dolerite dykes creating compartments isolated from each other, suggesting a highly complex aquifer system. Based on the conceptual model, it is shown that these structures can create unique, site specific flow conditions. The integration of all available data into the conceptual model provides an effective research tool that can be built upon as a basis for further research. / Dissertation (MSc)--University of Pretoria, 2010. / Geology / unrestricted

Versuche mit radioaktiven Stoffen im Schulunterricht unterliegen der Strahlenschutzverordnung. Die Broschüre enthält wichtige Schutzvorschriften, die von Schulleitern und Lehrkräften im Umgang mit natürlichen und künstlichen radioaktiven Stoffen zu beachten sind. Die Vorschriften betreffen Erwerb, Lagerung, Kennzeichnung und Dokumentation von radioaktiven Stoffen sowie die personelle Organisation des Strahlenschutzes an Schulen.