As an important structural component in CANDU reactor, the pressure tube, made of coldworked Zr-2.5Nb, experiences a neutron flux under high pressure and elevated temperature during the reactor operation. Notches, existing as defects in the pressure tube, are usually the location where stress concentration and crack initiation happens, which seriously degrade the performance of the pressure tube. However, the concentrated stress at the notch area is expected to be relieved by thermal creep, reducing the possibility of crack occurrence. In this study, synchrotron X-ray diffraction experiments were conducted to collect the lattice strains near the notch in both irradiated and unirradiated Zr-2.5Nb samples which had experienced a thermal creep process for different time periods. Strain maps of the notch area were created for each sample. Stress relaxation over the time is discussed for both parallel and perpendicular to the loading direction and also compared between {10 -10} and {0002} orientations. A FE model was set up for the unirradiated materials, which was verified by the experimental results. This work provides an understanding of the stress relaxation near a notch in Zr-2.5Nb and the stress/strain distribution during the thermal creep, which provides valuable information on the assessment of the reactor operation. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2012-09-20 19:39:30.593

In laboratory experiments, I study strongly-coupled dusty plasma levitated in a glow-discharge plasma. Dusty plasma is an arrangement of small dust particles in a plasma background of electrons, ions, and neutral gas. The dust particles are negatively charged because they collect electrons and ions from the background plasma. Depending on the experimental setup, the plasma's electric field can help to balance the dust particles against gravity. The high dust charge causes dust particles to repel each other, while confinement forces prevent their escape. The dust particles cannot easily move past one another, and instead organize themselves into highly-ordered structures. The neutral gas also plays a key role in these experiments. Depending on the relative motion between gas and dust particles, the neutral gas can either impede dust motion or it can drive the dust into motion. In this thesis, I report the findings of three separate experiments. In the first experiment, I use a spherically-shaped dusty plasma (Yukawa ball) as an indicator of a flow of neutral gas, called thermal creep flow. In the second and third experiments, I study naturally occurring dust-density waves, which propagate within the volume of a dusty plasma that has many horizontal layers. In Ch.2 of this thesis, I study thermal creep flow (TCF), which is a flow of gas driven by a temperature gradient along a solid boundary. Stripes on a glass box are heated by laser beam absorption, leading to both TCF and a thermophoretic force. A stirring motion of the dust particle suspension is observed. By eliminating all other explanations for this motion, I conclude that TCF at the boundary couples by drag to the bulk gas, causing the bulk gas to flow, thereby stirring the suspension of dust particles. This result provides an experimental verification that TCF in the slip-flow regime causes steady-state gas flow in a confined volume. In Ch.3, I observe the growth of a naturally occurring dust-density wave (DDW) using high-speed imaging. This low-frequency wave (∼ 25 Hz) grows in amplitude as it propagates downward through a dusty plasma. I measure the wave's linear growth rate using a phase-sensitive analysis method. For the conditions studied here, the growth rate increases as gas pressure decreases. At a critical gas pressure that I observe, a balance between an ion-flow instability and dissipation by neutral gas drag determines a threshold for wave propagation. A linear dispersion relation is derived, taking into account effects of strong coupling, to compare to the experiment. In Ch.4, I observe the development of nonlinearity in the naturally occurring dust-density wave by measuring harmonics of the fundamental. Using high-speed imaging, I measure amplitudes, wave numbers and growth rates for the fundamental and its harmonics. The amplitudes of the harmonics exhibit a strong exponential increase with diminishing gas pressure, and they saturate at lower gas pressures. My measurements show that the wave numbers and growth rates of harmonics are near integer multiples of the fundamental.

Les travaux menés durant cette thèse ont abouti à la fabrication d'un microsystème fluidique de détection de gaz innovant portatif, bas coût et incluant un pompage thermique. Le microcapteur de gaz utilisé est inséré dans un microcanal. Un chauffage intégré permet au microcapteur de bien fonctionner. Il permet aussi la création du phénomène de thermal creep qui est à l'origine de l'écoulement du gaz à détecter le long du canal vers le microcapteur. Le gradient de température le long du canal et les dimensions sont des paramètres essentiels de l'étude.Des simulations microfluidiques et thermiques ont permis de définir les dimensions du microcanal ainsi que les matériaux les plus adéquats. Deux types de microsystèmes ont ensuite été réalisés. Le dispositif de chauffage intégré a été calibré afin d'étudier le gradient thermique réel. Une étude des performances du microcapteur sous ammoniac a été réalisée. Nous avons pu notamment déterminer la température optimale de détection. Puis des tests dans une cellule de détection ont été réalisés avec le microsystème complet. / My thesis work led to develop an innovative fluidic microsystem for gas detection. It is portable, cheap and has an integrated thermal pumping. The gas microsensor used is inserted into a microchannel. Its integrated heater allows the well detection. It also allows the creation of thermal creep phenomenon, which is at the origin of the gas flow along the channel which will be detected by the microsensor. The choices of both microchannel dimensions and the temperature gradient are the most important parameters. Thus, microfluidic and thermal simulations were performed to define the microchannel dimensions and the most suitable materials natures. Two microsystems were processed with clean room technologies. The integrated heater was calibrated to study the real thermal gradient. A study of the performance of the microsensor was performed under ammonia. We could include determining the optimal temperature sensing. Then the microsystem was studed using in a special detection cell.

学位授与大学：京都大学 ; 取得学位: 博士(工学) ; 学位授与年月日: 2007-09-25 ; 学位の種類: 新制・課程博士 ; 学位記番号: 工博第2860号 ; 請求記号: 新制/工/1420 ; 整理番号: 25545 / Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第13389号 / 工博第2860号 / 新制||工||1420(附属図書館) / 25545 / UT51-2007-Q790 / 京都大学大学院工学研究科航空宇宙工学専攻 / (主査)教授 青木 一生, 教授 稲室 隆二, 教授 斧 髙一 / 学位規則第4条第1項該当

The essence of performance-based structural fire safety design of steel building structures is the ability to predict thermal and structural response to fire. An important aspect of such predictions is the ability to evaluate strength of columns at elevated temperatures. Columns are critical structural elements, and failure of columns can lead to collapse of a structure. The ability of steel columns to carry their design loads is greatly affected by timeand temperature-dependent mechanical properties of steel at high temperatures due to fire. It is well known that structural steel loses strength and stiffness with temperature, especially at temperatures above 400 °C. Further, the reductions in strength and stiffness of steel are also dependent on the duration of exposure to elevated temperatures. The time-dependent response or creep of steel plays a particularly important role in predicting the collapse load of steel columns subjected to fire temperatures. Specifically, creep of steel leads to the creep buckling phenomenon, where the critical buckling load for a steel column depends not only on slenderness and temperature, but also on duration of exposure to fire temperatures. The main focus of the research summarized in this dissertation is on a testing program to investigate the effects of time-dependent material behavior or creep on buckling of steel columns subjected to fire. Material characterization tests were conducted at temperatures up to 1000 °C to evaluate tensile and creep properties of ASTM A992 steel at elevated temperatures. In addition, buckling tests on W4×13 wide flange columns under pin-end conditions were conducted to characterize short-time and vii creep buckling phenomena at elevated temperatures. The column test results are further used to verify analytical and computational tools developed to model the time-dependent buckling of steel columns at elevated temperatures. Test results are also compared against code-based predictions such as those from Eurocode 3 and the AISC Specification. Results of the research study presented in this dissertation clearly indicate that thermal creep of steel has a very large effect on strength of steel columns at high temperatures due to fire. The effect of creep on column capacity at high temperatures can be predicted using analytical and computational approaches presented in this dissertation. / text

Capacitance manometer with sensors maintained at temperatures above the temperature of the vacuum vessel may read a higher gas pressure than the true value. This arises due to a transport process of molecules induced by molecule-surface collisions called thermal transpiration effect. Thermal transpiration effect depends on the pressure, the temperature gradient, gas, geometry and surface properties of the interconnecting pipe between the capacitance manometer and the vacuum vessel. To determine the height of the thermal transpiration effect for the biomolecular gas tetrahydrofuran, an experimental setup has been built. Its suitability to measure the thermal transpiration effect has been tested. Measurements of thermal transpiration effects for nitrogen and tetrahydrofuran have been analyzed with the semi-empirical Takaishi-Sensui equation. The coefficients of the Takaishi-Sensui equation can be used to determine the magnitude of the thermal transpiration effect for different temperature gradients, diameters of the interconnecting pipe and pressures.

En raison du développement croissant des MEMS (Micro Electro Mechanical Systems), l'étude des écoulements de liquide ou de gaz et des transferts thermiques dans des conduites, chauffées ou non, dont le diamètre hydraulique est de l'ordre de quelques microns, a suscité un nombre considérable de travaux au cours des vingt dernières années. À cette échelle, le nombre de Knudsen peut être important (Kn>0,01), ce qui donne naissance à des phénomènes de glissement, de saut de température et de pompage thermique qui s'ajoutent aux effets de compressibilité, telles que la puissance due aux forces de pression et à la puissance des contraintes visqueuses et aux variations des propriétés du fluide avec la température. Dans les modélisations de la littérature, ces phénomènes sont rarement pris en compte simultanément et sont souvent partiellement négligés, sans justification. Notre démarche consiste à proposer une modélisation des micro-écoulements gazeux se rapprochant au mieux de la réalité en prenant en compte tous les phénomènes et à étudier les effets de chacun d'entre eux. L'étude est, en premier lieu, menée en utilisant un code commercial, résolvant les équations de conservation par la méthode des volumes finis et adapté par le biais de sous-programmes développés au cours de cette thèse. Des validations ont été effectuées pour des problèmes allant des plus simples (incompressibles, non glissants) aux plus complexes (compressibles, glissants). Cette étude a permis de mettre en évidence les problèmes liés à la modélisation quand les nombres de Péclet des écoulements sont inférieurs à l'unité (Pe < 1). Dans ce cas, les effets de diffusion inverse sont dominants et l'utilisation d'extensions à l'amont de la conduite devient incontournable. Les effets de compressibilité qui se traduisent par des détentes du gaz près de la sortie de la conduite (accélération + refroidissement) ont été analysés. Enfin, des comparaisons ont été effectuées avec des solutions analytiques d'écoulements compressibles et glissants, supposés isothermes en imposant de faibles variations de pression. Nous avons pu montrer que ces solutions restent valables, même lorsque les variations de pression sont importantes parce que les détentes ne sont localisées que près de la sortie de la conduite et n'influencent donc pas les propriétés globales de l'écoulement. La suite du travail a été réalisée à l'aide d'un code de calcul développé au laboratoire et validé pour les écoulements à grandes échelles. Des conditions aux limites de glissement ont été introduites afin de l'adapter à la problématique de ce travail de thèse. Compte-tenu de ses performances (précision et rapidité des calculs en particulier), ce code a permis de réaliser une étude paramétrique sur une large gamme de pressions d'entrée et de sortie, de telle sorte à balayer tous les types d'écoulements : de peu à très compressibles et de peu à très glissants. Les résultats sont d'abord présentés pour des écoulements quasi-isothermes puis comparés aux solutions analytiques afin de tester ces dernières sur une plus large gamme de pression. Enfin, de nouveaux résultats ont été obtenus pour des écoulements chauffés. Des corrélations, en fonction des paramètres adimensionnels caractéristiques de ces écoulements, ont été obtenues pour les modèles complets à l'aide d'un logiciel de statistiques et de plans d'expériences. Des comparaisons à des modèles simplifiés ont été effectuées pour évaluer les erreurs commises lorsque certains termes sont négligés / These phenomena are rarely taken into account all at once, at least one of them is neglected and often without justification. Our approach is to get as close as possible to reality by taking into account all the phenomena that appear at once and then to study the effect of the phenomena most often overlooked. First, the study is conducted using a commercial code for solving the conservation equations by the finite volume method. Validations were performed for problems ranging from the simplest (incompressible, non-slip flow) to the more complex (compressible, slip flow). This study highlighted the problems associated with simulations when the flows Peclet numbers are less than unity (Pe <1). In this case, the inverse diffusion effects are dominant and the use of extensions at the upstream becomes unavoidable. In addition, compressibility effects were identified; they have resulted in expansions of the gas near the exit of the pipe (acceleration + cooling). Finally, comparisons were made with analytical solutions of compressible slip flows assumed isothermal by imposing small variations of pressure. We showed that these solutions remain valid even if the pressure variations are important because the detents are located only near the exit of the pipe. In this case, they do not affect the properties of the flow. Further works were carried out using an in-house computer code, previously developed and validated in the laboratory for flows with large scales and for which slipping limits conditions have been added so that it can properly resolve slip flows. In view of its accuracy and performances in terms of CPU-time, the code allowed us to achieve a parametric study on a wide range of input and output pressures, so as to sweep all runoff from few to very compressible and few to very slip flow. The results were first presented for quasi-isothermal flow, which subsequently were compared to analytical solutions to test these ones on a wider range of pressure. Finally, the results were made for heated flows. Correlations have been obtained for a complete model using a statistical based software and design of experiments. Comparisons to simplified models were performed to assess the inaccuracies linked to the omission of terms often overlooked in the literature

No description available.

In dry interim storage of spent nuclear fuel, thermal creep is one of the major threats to the fuel cladding integrity due to the constant decay heat generation from the fission products and minor actinides in the fuel, and the increase in fuel rod internal pressure which is present after burnup. Plenty of research has been done on either empty cladding tubes irradiated in a research reactor, or on spent fuel that is defueled prior to the examination. This type of research excludes the effects of the pellet-cladding bonding that may be present after burnup, where the bonding might have significant effects on the thermal creep behavior. Therefore, this work aims to construct and validate an experimental model that is designed to perform thermal creep tests on as-received spent nuclear fuel, where the pellet-cladding bonding is still intact, in order to gain knowledge in the causal relation that the pellet-cladding bonding has on the thermal creep phenomenon during dry storage. The experimental model is validated by a number of qualification tests, as well as a series of creep tests on unirradiated Zircaloy-4 tubes. The results are compared to the literature which shows the reproducibility of the model, which further supports its validity. / I torrt mellanförvar av använt kärnbränsle så är termisk krypning en av de främsta farhågorna för kapslingens fysiska integritet genom sönderfallsvärmen från klyvningsprodukter och andra aktinider, samt det förhöjda interna trycket i kapslingen som är närvarande efter utbränning. Åtskillig forskning har gjorts på antingen tomma kapslingsrör som är bestrålade i en forskningsreaktor, eller på använt bränsle där bränslekutsen är urborrad innan undersökning. Denna typ av forskning utelämnar effekten av kuts-kapsling bindningen som uppstår under uppbränning, där bindningen kan ha en betydande effekt på kapslingens beteende under termisk krypning. Därför så dedikeras detta arbete till att konstruera och validera en experimentell modell som är designad till att utföra tester av termisk krypning på opåverkat använt bränsle, där kuts-kapsling bindningslagret fortfarande är intakt, för att lära om bindningslagrets effekt på fenomenet termisk krypning under torrt mellanförvar. Den experimentella modellen är validerad genom ett antal kvalificeringstester, samt en serie av kruypningstester på obestrålade Zircaloy-4 rör. Resultaten är jämförda mot litteraturen, vilket visar reproducerbarheten hos modellen, som i sin tur understöder modellens validitet.