A mathematical model to describe the alpha dose rate from a UO2 surface

A model to determine the dose rate of a planar alpha-emitting surface, has been developed. The approach presented is a computationally efficient mathematical model using stopping range data from the Stopping Ranges of Ions in Matter (SRIM) software. The alpha dose rates as a function of distance from irradiated UO2 spent fuel surfaces were produced for bench-marking with previous modelling attempts. This method is able to replicate a Monte Carlo (MCNPX) study of an irradiated UO2 fuel surface within 0.6 % of the resulting total dose rate and displays a similar dose profile

Structure and Phase Transitions of Metastable Hexagonal Uranium Thin Films

We report a simple technique for the synthesis of uniaxially textured, metastable hexagonal close-packed-like uranium thin films with thicknesses between 175-2800 \r{A}. The initial structure and texture of the layers have been studied via X-ray diffraction and reflectivity and the time-dependent transitions of the samples into various orientations of orthorhombic ${\alpha}$-U have been mapped by similar techniques. The final crystallographic orientations of each system and the timescales on which the transitions occur are found to depend on the lattice parameters of the original layer. The absence of the ${\alpha}$-U (001) orientation in the transition products suggests that the transitions in these layers are mediated by mechanisms other than the [110] transverse acoustic phonon mode previously suggested for the cubic ${\gamma}$-U(110) to hcp-U(00.1) to ${\alpha}$-U(001) displacive phase transition. Alternative transition pathways are discussed

Synchrotron x-ray scattering of magnetic and electronic structure of UN and U2N3 epitaxial films

We examine the magnetic ordering of UN and of a closely related nitride, U2N3, by preparing thin epitaxial films and using synchrotron x-ray techniques. The magnetic configuration and subsequent coupling to the lattice are key features of the electronic structure. The well-known antiferromagnetic (AF) ordering of UN is confirmed, but the expected accompanying distortion at Tn is not observed. Instead, we propose that the strong magneto-elastic interaction at low temperature involves changes in the strain of the material. These strains vary as a function of the sample form. As a consequence, the accepted AF configuration of UN may be incorrect. In the case of cubic a-U2N3, no single crystals have been previously prepared, and we have determined the AF ordering wave-vector. The AF Tn is close to that previously reported. In addition, resonant diffraction methods have identified an aspherical quadrupolar charge contribution in U2N3 involving the 5f electrons; the first time this has been observed in an actinide compound

XPS Study of Ion Irradiated and Unirradiated UO2 Thin Films

XPS determination of the oxygen coefficient k O =2+x and ionic (U 4+ , U 5+ and U 6+ ) composition of oxides UO 2+x formed on the surfaces of differently oriented (hkl) planes of thin UO 2 films on LSAT (Al 10 La 3 O 51 Sr 14 Ta 7 ) and YSZ (yttria-stabilized zirconia) substrates was performed. The U 4f and O 1s core-electron peak intensities as well as the U 5f relative intensity before and after the 129 Xe 23+ and 238 U 31+ irradiations were employed. It was found that the presence of uranium dioxide film in air results in formation of oxide UO 2+x on the surface with mean oxygen coefficients k O in the range 2.07-2.11 on LSAT and 2.17-2.23 on YSZ substrates. These oxygen coefficients depend on the substrate and weakly on the crystallographic orientation. On the basis of the spectral parameters it was established that uranium dioxide films AP2,3 on the LSAT substrates have the smallest k O values, and from the XRD and EBSD results it follows that these samples have a regular monocrystalline structure. The XRD and EBSD results indicate that samples AP5-7 on the YSZ substrates have monocrystalline structure, however, they have the highest k O values. The observed difference in the k O values, probably, caused by the different nature of the substrates: the YSZ substrates provide 6.4% compressive strain, whereas (001) LSAT substrates result only in 0.03% tensile strain in the UO 2 films. 129 Xe 23+ irradiation (92 MeV, 4.8 × 10 15 ions/cm 2 ) of uranium dioxide films on the LSAT substrates was shown to destroy both long range ordering and uranium close environment, which results in increase of uranium oxidation state and regrouping of oxygen ions in uranium close environment. 238 U 31+ (110 MeV, 5 × 10 10 , 5 × 10 11 , 5 × 10 12 ions/cm 2 ) irradiations of uranium dioxide films on the YSZ substrates were shown to form the lattice damage only with partial destruction of the long range ordering

Preocupações de carreira e adaptabilidade : estudo exploratório com uma amostra de candidatos a sargentos e oficiais do Exército Português

Tese de mestrado, Psicologia (Psicologia dos Recursos Humanos, do Trabalho e das Organizações), Universidade de Lisboa, Faculdade de Psicologia, 2010O presente trabalho consiste num estudo exploratório sobre as preocupações de carreira e as dimensões da adaptabilidade, baseando-se na Perspectiva de Desenvolvimento da Carreira de Donald Super e na Perspectiva Construtivista de Mark Savickas. Pretende-se, ainda, contribuir para a investigação acerca do Inventário sobre Adaptabilidade, que se encontra ainda em estudo no âmbito de um Projecto Internacional. Foram aplicados o Inventário das Preocupações de Carreira e o Inventário sobre Adaptabilidade a uma amostra de 75 adultos candidatos a Sargentos e Oficiais do Exército Português. Os resultados obtidos tendem a confirmar as hipóteses de investigação formuladas, apontando para a relação entre a variável idade e as tarefas de desenvolvimento das fases da carreira Exploração e Estabelecimento, para a predominância das dimensões Confiança e Cooperação, e para a relação entre preocupações de carreira e dimensões da adaptabilidade. Apresentam-se as conclusões do presente estudo, algumas limitações deste e futuras linhas de investigação. Tecem-se também algumas considerações sobre as implicações do estudo para as práticas de gestão de carreira.This work is an exploratory study about the career concerns and the dimensions of adaptability, based on the Perspective of the Career Development of Donald Super and the Constructivist Perspective of Mark Savickas. It is also intended to contribute to the research on the Career Adapt-Abilities Inventory, which is still under investigation as part of an International Project. The Career Concerns Inventory and the Career Adapt-Abilities Inventory were applied to a sample of 75 adult candidates to Sergeants and Officers of the Portuguese Army. The results seem to confirm the research hypotheses, pointing to the relation between the variable age and the developmental tasks of the Exploration and Establishment career phases, to the predominance of the dimensions Cooperation, and Confidence and also to the relation between career concerns and adaptability dimensions. The findings of this study, some of its limitations and future research paths are presented. Some reflections are also discussed in what concerns the study's implications for the career management practices