This work examines the isotopic composition and abundance of helium in a number of different crustal environments with a view to understanding its production and transport in the crust. The work was largely carried out using existing instrumentation, but a dedicated interface was also built to allow computer control of a quadrupole mass spectrometer for rare gas abundance pattern determination. Conventional calculations of the radiogenic <SUP>3</SUP>He/<SUP>4</SUP>He production ratio based on the assumption of a chemically homogeneous composition cannot adequately account for the <SUP>3</SUP>He/<SUP>4</SUP>He ratio in waters from the Carnmenellis Granite of SW England. Alpha tracking and back-scattered electron microscopy show that the majority of the U and Th are concentrated in volumetrically insignificant accessory minerals. A new model has been devised, taking this heterogeneity into account, to explain the Carnmenellis data. Helium isotopic analysis of the granite itself revealed isotopic disequilibrium with the circulating waters. This may be related to differential release of <SUP>3</SUP>He and <SUP>4</SUP>He associated with different formation sites. A survey was made of the helium abundance and isotopic composition of groundwaters from the Pannonian Basin of Hungary in order to study the behaviour of mantle-derived fluids in an area of major recent crustal extension and volcanism. More than 80 samples were analysed covering most of the basin, and almost all contained a component of mantle-derived helium. Although <SUP>3</SUP>He/<SUP>4</SUP>He ratio is not clearly correlated with the surface expression of volcanism, it may act as an indicator of intrusion at depth. The <SUP>3</SUP>He flux through the Hungarian crust is ≈4 atoms.cm<SUP>-2</SUP>.s<SUP>-2</SUP>. If the mechanism of extraction is partial melting, then by analogy with melt production at mid-ocean ridges, addition of a 20-40 metre layer of basalt (for 5-10% partial melting) must be added to the Hungarian crust in a million years to support the present day <SUP>3</SUP>He flux.

The chemical binders used to make sand molds and cores thermally decompose and release gas when subjected to the high temperature conditions in sand casting processes. Computational models that predict the evolution of the binder gas are being introduced into casting simulations in order to better predict and eliminate gas defects in metal castings. These models require knowledge of the evolved binder gas mass and molecular weight as a function of temperature, but available gas evolution data are limited. In the present study, the mass and molecular weight of gas evolved from PUNB bonded sand are measured as a function of temperature for use with binder gas models. Thermogravimetric analysis of bonded sand is employed to measure the binder gas mass evolution as a function of temperature for heating rates experienced in molds and cores during casting. The volume and pressure of gas evolved from bonded sand are measured as a function of temperature in a specially designed quartz manometer during heating and cooling in a furnace. The results from these experiments are combined with the ideal gas law to determine the binder gas molecular weight as a function of temperature. Thermogravimetric analysis reveals that the PUNB binder significantly decomposes when heated to elevated temperatures, and the PUNB binder gas mass evolution is not strongly influenced by heating rate. During heating of PUNB bonded sand at a rate of 2°C/min, the binder gas molecular weight rapidly decreases from 375 g/mol at 115°C to 99.8 g/mol at 200°C. The molecular weight is relatively constant until 270°C, after which it decreases to 47.7 g/mol at 550°C. The molecular weight then steeply decreases to 30.3 g/mol at 585°C and then steeply increases to 47.2 g/mol at 630°C, where it remains constant until 750°C. Above 750°C, the binder gas molecular weight gradually decreases to 33.3 g/mol at 898°C. The present measurements are consistent with the molecular weights calculated using the binder gas composition data from previous studies. The binder gas is composed of incondensable gases above 709°C, and the binder gas partially condenses during cooling at 165°C if the bonded sand is previously heated below 507°C.

Theoretical models are used in support of the I2S-LWR (Integral Inherently Safe LWR) project for a direct comparison of fuel swelling and fission gas bubble formation between U₃Si₂ and UO₂ fuels. Uranium silicide is evaluated using a model developed by Dr. J. Rest with the fuel in a amorphous state. The uranium dioxide is examined with two separate models developed using a number of papers. One model calculates the swelling behavior with a fixed grain radius while the second incorporates grain growth into the model. Uranium silicide rapidly becomes amorphous under irradiation. The different mechanisms controlling the swelling of the fuels are introduced including the knee point caused by the amorphous state for the U₃Si₂. The outputs of each model are used to compare the fuels.

Orientador: Osvair Vidal Trevisan / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica e Instituto de Geociencias / Made available in DSpace on 2018-08-11T00:41:26Z (GMT). No. of bitstreams: 1 Okabe_ClarissaPaiva_M.pdf: 2059387 bytes, checksum: 7eca532809c263ddd5b0b3751c823f20 (MD5) Previous issue date: 2006 / Resumo: Campos no Canadá e na Venezuela contendo reservatórios de óleo espumoso apresentaram recuperação primária da ordem de 10 a 15 % maior do que a estimada por simuladores numéricos Black-Oil. Além do alto fator de recuperação, foram observadas outras características não convencionais, como baixa razão gás-óleo e alta manutenção da pressão de reservatório. Esta discrepância entre o fator de recuperação estimado e o real é atribuída ao fato de que os simuladores Black-Oil não descrevem adequadamente o comportamento do gás em óleos espumosos. Nesta pesquisa são descritos e comparados três modelos numéricos de óleo espumoso propostos para o simulador pseudo-composicional CMG Stars. Estes modelos permitem descrever as etapas de evolução do gás, que compreendem desde a nucleação das bolhas de gás, o crescimento das bolhas, até a formação de uma fase conectada de gás, com reações cinéticas. Além disso, admite a presença de diferentes formas de gás ¿ gás em solução, gás preso, gás disperso e gás livre - nas fases gás e óleo. A mobilidade da fase gás é avaliada por uma composição de curvas de permeabilidade relativa ao gás. Com o estudo da influência de alguns parâmetros, algumas características típicas de reservatórios de óleo espumoso são explicadas, como a baixa produção de gás, o escoamento do gás na forma dispersa, a alta saturação crítica de gás e as altas razões de produção de óleo / Abstract: Fields in Canada and Venezuela, which contain foamy oil reservoirs, have exhibited a primary oil recovery on the order of 10 to 15 % greater than the recovery estimated by black-oil simulators. Besides the high oil recovery, other unusual characteristics have been observed, as low gas-oil ratio and high reservoir pressure maintenance. Such discrepancy between estimated and the actual oil recovery factor is attributed to the fact that black-oil simulators do not describe adequately gas behavior in foamy oils. In the present study, three numerical models of foamy oil behavior are described and compared using the pseudo-compositional simulator CMG Stars. These models allow describing the steps of gas evolution, since the nucleation of the gas bubbles, the bubble growing, until its connection to form a free phase, via kinetic reactions. The model admits the presence of different forms of gas ¿ solution gas, entrained gas, dispersed gas and free gas ¿ in the oil and gas phases. The mobility of the gas phase is evaluated by a composition of relative permeability curves. After the study on the influence of some parameters, some typical characteristics of the foamy oil reservoirs are explained, as the low gas production, the dispersed gas flow, the high critical gas saturation and the high oil production rates / Mestrado / Reservatórios e Gestão / Mestre em Ciências e Engenharia de Petróleo

The aim of the project was to develop a method to measure and studythe degree of activation of the negative electrode (MH) in a NiMH battery.This was done by characterization of the gases produced during charge of a battery – O2 and H2 – using a Gas Chromatograph. The current applied in the very first charge of the battery was varied in order to examine how this affects the gas evolution. In the developed method, batteries were charged to 8Ah with 9A, after which a gas sample was taken and analyzed with Gas Chromatography. An additional goal was to use the method to examine the difference in activation between virgin and recycled negative electrode material. A module charged stepwise with 0.07C followed by 0.2C had the lowest share of H2 after two cycles, indicated best activation. However, a higher amount of H2 in the beginning of the activation process could possibly enhance the degree of activation during the following cycles. The method indicated that the module with recycled MH was better activated than the virgin MH. To improve the technique, repeated measurements to get better statistics should be done. Gas samples should be taken at dV/dt=0 in order to take samples at same SoC. The charge current should be adjusted so that the same C rate is always used. This would make the results easier to interpret.

A procedure to evaluate the leaching properties of radionuclides from irradiated graphite waste has been developed by combining ANSI 16.1 (USA) and NEN 7345 (Netherlands) standardised diffusion leaching techniques. The ANSI 16.1 standard has been followed to the acquire the leachates and to determine the leach rate/ diffusion coefficient and NEN 7345 standard technique has been used to determine the diffusion mechanism of radionuclides. The investigation employs simulated Drigg groundwater as a leachant using semi-dynamic technique for the production of leachate specimens. From gamma spectroscopy analysis the principal radionuclides present in terms of activity were 60Co, 137Cs, 134Cs, 155Eu, 133Ba and 46Sc. The dominant radionuclides are 60Co, 134Cs and 133Ba which together account for about 91 % of the total activity. The 91 % can be broken down into 73.4 % 60Co, 9.1 % 134Cs and 8.1 % 133Ba. Analysis of total beta and total beta without tritium activity release from Magnox graphite was measured using liquid scintillating counting. Preliminary results show that there is an initial high release of activity and decreases when the leaching period increases. This may be due to the depletion of contaminants which were absorbed by the internal pore networks and the surface. During the leaching test approximately 275.33 ± 18.20 Bq of 3H and 106.26 ± 7.01 Bq of 14C was released into the leachant within 91 days. Irradiation induced damages to the nuclear graphite crystal structure have been shown to cause disruption of the bonding across the basal planes. Moreover, the closures of Mrozowski cracks have been observed in nuclear graphite, the bulk property are governed by the porosity, in particular, at the nanometre scale. Therefore, knowledge of the crystallite structure and porosity distribution is very important; as it will assist in understand the affects of irradiated damage and location and the mechanism of the leaching of radionuclides. The work reported herein contributed several key findings to the international work on graphite leaching to offer guidance leading toward obtaining leaching data in the future: (a) the effective diffusion coefficient for 14C from graphite waste has been determined. The diffusion process for 14C has two stages resulting two different values of diffusion coefficient, i.e., for the fast and slow components; (b) the controlling leaching mechanism for 3H radionuclide from graphite is shown to be surface wash–off; and for that of 14C radionuclide the initial controlling leaching mechanism is surface wash-off following by diffusion which is the major transport mechanism ; (c) The weight loss originates from the open pore structure which has been opened up by radiolytic oxidation; at the higher weight losses much of the closed porosity in the graphite has been opened. The investigation indicates that weigh loss has a major influence on the leaching of elements from the irradiated graphite; and (d) the analysis of the pores in nuclear graphite can be categorised into three types. These three types of pores are: (1) small pores narrow which are slit-shaped pores in the binder phase or matrix, (2) gas evolution pores or gas entrapment pores within the binder phase or matrix and (3) lenticular pores which are large cracks within the filler particles. It is shown in this thesis that by using tomography to study the morphology of the different pores coupled with the distribution of impurities an understanding of the role of porosity in leaching is possible.