Dissertations / Theses on the topic 'Recycle fuel'

The purpose of this research is to develop a methodology for a thorium fuel recycling analysis that provides results for isotopics and radio-toxicity evaluation and analysis. This research is motivated by the need to reduce the long term radiological hazard in spent nuclear fuel, which mitigates the mixing hazard (radiotoxicity and chemical toxicity) and decay heat load on the repository. The first part of the thesis presents comparison of several once-through cases with uranium and thorium fuels to show how transuranics build up as fuel is depleted. The once-through analysis is performed for the following pairs of comparison cases: low enriched uranium dioxide (UOX) vs. thorium dioxide with 233UOX (233U-ThOX), natural uranium dioxide mixed with transuranic oxides (U-TRUOX) vs. thorium dioxide mixed with transuranic oxides (Th-TRUOX), natural uranium dioxide mixed with weapons grade plutonium dioxide (U-WGPuOX) vs. thorium dioxide mixed with weapons grade plutonium dioxide (Th-WGPuOX), natural uranium dioxide mixed with reactor grade plutonium dioxide (U-RGPuOX) vs. thorium mixed with reactor grade plutonium dioxide (Th-RGPuOX). The second part of the research evaluates the thorium fuel equilibrium cycle in a pressurized water reactor (PWR) and compares several recycling cases with different partitioning schemes. Radio-toxicity results of the once-through cycle and multi-recycle calculations demonstrate advantages for thorium fuel and reprocessing with respect to long term nuclear waste management.

Currently, the United States is investigating methods to close the nuclear fuel cycle and increase the use of nuclear power for electricity and cogeneration applications. Congress has called for and held hearings in an attempt to determine an appropriate path forward for reprocessing of nuclear fuel. However, each current proposed method presents a different set of attributes with regards to: Complexity, safety, wastes, and proliferation risks. This thesis provides a decision analysis methodology for approaching the reprocessing issue. The presented methodology builds on the previous work done in the 1970s. Further, current reprocessing technologies which are capable of processing the oxide fuels utilized in the majority of United States reactors are evaluated across ten attributes related to reprocessing performance. A weighted total score is provided for each reprocessing method in order to separate the technological from political or emotional issues related to selection of a process. While it is not the goal of this thesis to select a particular best technology, application of this methodology results in the selection of the COmbined EXtraction (COEX) technology when equal weighting is put on the attributes as defined. It is unlikely that a decision maker will approach this decision with equal weighting; however, actual decision maker weightings are known only to the decision makers. By altering the weightings, different technologies are selected.

To mitigate the global greenhouse gases (GHGs) emissions, carbon dioxide (CO2) capture and storage (CCS) has the potential to play a significant role for reaching mitigation target. Oxy-fuel combustion is a promising technology for CO2 capture in power plants. Advantages compared to CCS with the conventional combustion technology are: high combustion efficiency, flue gas volume reduction, low fuel consumption, near zero CO2 emission, and less nitrogen oxides (NOx) formation can be reached simultaneously by using the oxy-fuel combustion technology. However, knowledge gaps relating to large scale coal based and natural gas based power plants with CO2 capture still exist, such as combustors and boilers operating at higher temperatures and design of CO2 turbines and compressors. To apply the oxy-fuel combustion technology on power plants, much work is focused on the fundamental and feasibility study regarding combustion characterization, process and system analysis, and economic evaluation etc. Further studies from system perspective point of view are highlighted, such as the impact of operating conditions on system performance and on advanced cycle integrated with oxy-fuel combustion for CO2 capture. In this thesis, the characterization for flue gas recycle (FGR) was theoretically derived based on mass balance of combustion reactions, and system modeling was conducted by using a process simulator, Aspen Plus. Important parameters such as FGR rate and ratio, flue gas composition, and electrical efficiency etc. were analyzed and discussed based on different operational conditions. An advanced evaporative gas turbine (EvGT) cycle with oxy-fuel combustion for CO2 capture was also studied. Based on economic indicators such as specific investment cost (SIC), cost of electricity (COE), and cost of CO2avoidance (COA), economic performance was evaluated and compared among various system configurations. The system configurations include an EvGT cycle power plant without CO2 capture, an EvGT cycle power plant with chemical absorption for CO2 capture, and a combined cycle power plant. The study shows that FGR ratio is of importance, which has impact not only on heat transfer but also on mass transfer in the oxy-coal combustion process. Significant reduction in the amount of flue gas can be achieved due to the flue gas recycling, particularly for the system with more prior upstream recycle options. Although the recycle options have almost no effect on FGR ratio, flue gas flow rate, and system electrical efficiency, FGR options have significant effects on flue gas compositions, especially the concentrations of CO2 and H2O, and heat exchanger duties. In addition, oxygen purity and water/gas ratio, respectively, have an optimum value for an EvGT cycle power plant with oxy-fuel combustion. Oxygen purity of 97 mol% and water/gas ratio of 0.133 can be considered as the optimum values for the studied system. For optional operating conditions of flue gas recycling, the exhaust gas recycled after condensing (dry recycle) results in about 5 percentage points higher electrical efficiency and about 45 % more cooling water consumption comparing with the exhaust gas recycled before condensing (wet recycle). The direct costs of EvGT cycle with oxy-fuel combustion are a little higher than the direct costs of EvGT cycle with chemical absorption. However, as plant size is larger than 60 MW, even though the EvGT cycle with oxy-fuel combustion has a higher COE than the EvGT cycle with chemical absorption, the EvGT cycle with oxy-fuel combustion has a lower COA. Further, compared with others studies of natural gas combined cycle (NGCC), the EvGT system has a lower COE and COA than the NGCC system no matter which CO2 capture technology is integrated.<br>QC 20111123

The stability of hydrogen peroxide (H2O2) is a critical factor for the brightening of mechanical pulps. Inorganic ions, including Fe, Mn and Cu catalytically decompose H2O2. These troublesome metals promote the rapid transformation of H2O2 to nonselective hydroxyl radicals that degrade the cellulose fibres and decrease yields.<br>The interaction of aqueous metal•complexes with magnesium metal (Mg°) or bimetallic mixtures of magnesium with either palladium (Pd°/Mg°) or silver (Ag°/Mg°) were optimized to remove metals (Mn, Cu and Fe) from solution with concomitant release of the complexing reagent. The analyte metals were removed by both cementation on the surfaces of the excess Mg° and by precipitation as hydroxides. Overall, the reactions were rapid (3 or 10 min) and very efficient. The accelerators (Ag or Pd) were deposited on the surfaces of the Mg°. In a separate study, the excess of Mg° could be reused to mediate more metals removal without apparent loss of reactivity. Among the other iminodiacetate analogs (CDTA, MEDTA, EGTA, HEDTA, DPTA and MTBE), the EGTA and HEDTA proved to be possible substitutes for both efficient metal removal of Mn, Cu and Fe from solution and efficient release of chelating reagent. The measurement of particle size, performed by laser granulometry, demonstrated that smaller particles of precipitate were generated from metal-EDTA complexes by reaction with NaOH than by reaction with Pd°/Mg° bimetallic mixture. If the suspensions of particles were analyzed in the absence of ultrasound, the particles became aggregated into large flocs (up to 150 mum3 ). The reactivity of the bimetallic mixtures was exploited to remove Cu, Mn, Fe, Zn and Al that had been initially chelated with EDTA or DTPA from a thermomechanical pulp (TMP). After 15 min, the metals had been removed efficiently with the bimetallic mixtures. The EDTA released from the TMP filtrate could be recycled efficiently for a total of three cycles. On the other hand, the DTPA was not released as efficiently. Measurements of turbidity and chemical oxygen demand (COD) indicated no appreciable difference between the pulp samples with either chelating reagent. Residual H2O2 and ISO brightness measurements indicated no apparent differences among pulps that had been treated wi

The degree of waste paper recycling has been increasing steadily in North America over the last decade. Flotation is a popular method for removing ink from fibres (deinking) and is traditionally performed in mechanical cells. Column flotation has been proposed as an alternative to mechanical cells. In this work, open and packed laboratory and pilot-scale columns were operated to determine their relative merits and how they compare to a circuit of mechanical cells.<br>It was found that the type of sparger was critical for obtaining high flotation efficiencies. Fine porous stainless steel spargers (0.5 $ mu$m) produced flotation efficiencies which were equal to those of the mechanical cells. Packing was effective in increasing flotation efficiency when the coarse porous stainless steel sparger (100 $ mu$m) was used in the laboratory column and when the variable gap sparger was used in the pilot column.<br>The organic loss from all column configurations (laboratory and pilot-scale) was less than 3%.<br>The scale up procedure was evaluated using data from the laboratory column and pilot column dimensions. Finally, using data from the laboratory column, industrial columns were designed.

The objective of this study was to determine the effect of biological treatment, using a trickling filter, on recycle water from a sulphide concentrator. Activated carbon (AC) treatment was studied for comparative purposes.<br>Both biological AC treatment increased the recovery of chalcopyrite in a single mineral microflotation test, from approximately 5.5% to 14.4% and 7.2% respectively. However, major differences were observed between various samples when comparing the number and types of bubbles produced during frothing tests. As expected, the number of bubbles produced per given volume decreased following AC treatment, approaching that of tap water. However, after biological treatment, the number of bubbles was increased. It is suspected that the changes produced by biological treatment in the recycle water might produce organic matter more surface active than that initially found in the wastewater.

The possibility of using demolished concrete waste as aggregate in fresh concrete in the production of prestressed concrete beams is checked in this research. As opposed to the use for road foundations or as fill-in material the use of the Recycled Aggregate (RA) for concrete structures requires more tests and processing of results. In fact to be able to use a material for construction it is essential to assess more than just its compressive strength. After the physical and chemical characteristics of the RA and the properties of both the wet and hardened Recycled Aggregate Concrete (RAC) have been determined, it is important to check if the mathematical models and numerical correlation normally used for design of ordinary concrete (such as mix-design procedure, design codes, non-linear analysis) are suitable for RAC. For this reason the main task of this investigations has been to ensure that RAC has satisfactory mechanical performance for structural use and later to guarantee a consistency of the results using methods checked for RAC. A mix-design procedure suitable for RAC to attain the desired workability and the target strength was the first step. Tests on durability of RA and RAC have been performed and the results reported. Finally three 15.0 metres span prestressd beams cast with different percentages of RA (one with 100% of RA, one with 100% of Natural Aggregate NA, and one with 50% of RA and 50% of NA) have been tested. The results show that it is practicable to make prestressed concrete elements using concrete made with Recycled Aggregate and that these elements can have satisfactory and predictable mechanical performance.

The widespread use of glass fibre reinforced polymers (GFRP) over the last decades has led to an increasing amount of waste and a demand for recycling solutions. Mechanical, chemical and thermal GFRP recycling processes have been developed in academia but the commercialisation of GFRP recycling processes has proven to be difficult. The value of recycled glass fibres is low because their strength is usually reduced during recycling processes. Thermal recycling processes involve the exposure of GFRP waste to elevated temperatures to degrade the polymer matrix and extract the glass fibres. The room temperature strength of the glass fibres and organic sizings are degraded during thermal recycling processes which leads to a lower composite performance when the recycled fibres are processed into composites. The main objective of this thesis was to develop composites based on thermally recycled glass fibres that can compete with as received fibre composites. Polypropylene (PP) was chosen as matrix material because of its processability and its widespread use. First, an understanding of the structure performance relationship of glass fibre PP (GF/PP) composites was established and gaps in existing literature were studied. The addition of maleic anhydride grafted PP (MAPP) to injection moulded GF/PP composites correlated with an increase of the ultimate mechanical properties (tensile strength, strain at break) but too high MAPP contents resulted in a reduction of the ultimate mechanical composite properties and the composite modulus. The optimum MAPP content was observed to depend on the glass fibre content. The composite tensile test data was used to analyse the microstructural composite properties. It was concluded that the analysis of the composite tensile data based on the Kelly-Tyson model can be used as a screening tool to detect general trends of the interfacial adhesion between glass fibres and PP matrix. However, micromechanical tests like the microbond tests are still required for more detailed studies of the interfacial adhesion because the composite tensile properties are often affected by a number of interacting factors. Glass fibres were thermally degraded before composite processing to simulate a thermal recycling process. Thermal gravimetric analysis and microbond tests showed that all investigated commercial sizings degraded at thermal recycling temperatures. The ultimate mechanical composite properties were reduced when the glass fibres were thermally degraded. The drop of the composite performance was attributed to a reduction of the glass fibre strength and a low interfacial adhesion between fibres and PP. Most of the interfacial adhesion between thermally degraded glass fibres and PP was recovered when the MAPP content was optimised. However, the composite performance was still low compared to as received glass fibre composites because of the low fibre strength. It was concluded that the post treatment of thermally recycled glass fibres should include the regeneration of the fibre strength and the reactivation of the fibre surface functionality in order to increase the reinforcement potential of the fibres. Aminopropyltriethoxy silane (APS) and sodium hydroxide (NaOH) were applied to the thermally degraded glass fibres. Approximately 70 % of the tensile strength loss of injection moulded GF/PP composites was recovered when thermally degraded glass fibres were post treated with APS. Micromechanical analysis suggested that the APS regenerated glass fibres experienced similar stresses as the as received fibres. The increase of the glass fibre stress could not solely be explained by an increase of the interfacial adhesion between fibres and matrix. It was proposed that the APS treatment also led to an increase of the maximum glass fibre strength in the injection moulded composites. Thermally degraded glass fibres tend to form a fluffy mat during the NaOH treatment and could not be processed via extrusion compounding and injection moulding. A glass mat thermoplastic (GMT) process was set up over the course of this PhD to process NaOH treated glass fibres. The treatment of the thermally degraded glass fibres with NaOH led to an increase of the composite tensile strength. The increase of the composite tensile strength was correlated with an increase of the glass fibre strength. The APS treatment of the thermally degraded glass fibres also led to an increase of GMT composite tensile strength but the increase was lower compared to the injection moulded GF/PP composites. It was speculated that the effect of APS on the strength of thermally degraded glass fibres might be gauge length dependent. The optimum treatment of thermally recycled glass fibres might therefore depend on the final fibre length in the composite. An APS treatment might be suitable for injection moulded composites with glass fibres shorter than 1 mm while the NaOH treatments might be required for composites with longer fibres. To the author’s knowledge the work presented in this thesis shows for the first time that the reinforcement potential of thermally degraded glass fibres can be regenerated without hydrogen fluoride. Thus, this work might be a step towards the development of an economically viable GFRP recycling process.

L'objectif de ce travail est de valoriser des déchets de pneus usagés par pyrolyse afin d'obtenir un nouveau carburant comparable avec le gazole suivant la norme EN590. L'obtention de ce carburant était réalisée via l'optimisation des conditions de pyrolyse qui sont la température, la vitesse de chauffage (puissance de la résistance électrique) et du débit d'azote. Le rôle de l'azote est limité à purger le réacteur avant le début de la pyrolyse pour 30 minutes système. Le carburant produit est comparable au gazole avec un pouvoir calorifique de 45 MJ/kg, une densité de 0,85 et une teneur en goudron 7%<br>The objective of this work is to get alternative fuel comparable with the available diesel in the market following the EN590. The fuel getting was via optimization of pyrolysis conditions which are temperature, heating rate (power of electrical resistance) and inert gas flow rate. The optimum values are 465°C, 650 Watts and without inert gas flow rate. Inert gas role is limited to purge the system for 30 minutes before start the pyrolysis to get rid of oxidative gases. The obtained product is comparable with the diesel as it has GCV 45 KJ/kg, low density of 0,85 and 7% tar content

This study involves the use of an inline rheometer (ILR) for process control. The ILR is a melt viscosity sensor that is mounted directly in the main process stream. This type of installation minimizes the measurement delay time, which is important for sensors used in process control applications.<br>The ILR was used for the closed loop control of product viscosity of post-consumer recycled high density polyethylene crosslinking in a twin screw extruder. The manipulated variable is the feed rate of crosslinking agent. Internal model control, Dahlin control, and minimum variance control algorithms were successfully implemented.

The processing and reuse of end-of-life composite products in an environmentally friendly manner is one of the most important challenges facing the industry and community. The development of an economically viable process for regenerating the properties of thermally recycled glass fibres (GFs) would have major technological, societal, economic and environmental impacts. The ultimate goal of this project is to enable cost-effective regeneration of the mechanical properties of GFs which have been produced from thermal recycling of end-of-life glass reinforced structural composites from automotive and wind energy applications. This work investigates the loss, and regeneration, of GF strength after thermal degradation at typical GRP recycling temperatures. The mechanical properties of APS sized and water sized (uncoated) Boron-free-E-glass fibres were first characterised using a conventional single fibre tension test. A substantial higher average strength was obtained from the APS sized fibres. Further investigation with GFs, coated with different silanes was carried out to determine any beneficial effect on GF mechanical properties. It was found that ɣ-Methacryloxypropyltrimethoxy Silane (MPS) and ɣ-Glycidoxypropyltrimethoxy Silane (GPS) prepared for 24 hours at RT and solution medium pH 5-5.5 in deionised water and ɣ-Aminopropyltriethoxy Silane prepared at 830C for 5 hours at solution medium natural pH (ET APS) in deionised water showed the higher increases in GF mechanical properties. Moreover, it was found that preparing the hydrolysed APS solution at elevated temperatures, had a beneficial effect on GF strength in comparison to a solution prepared at RT over 24 h (RT APS). Further investigation was carried out to identify any changes to the final products in solution and any structural differences between APS prepared at RT and at ET, that would lead to a conclusion about the difference in mechanical properties achieved. Using techniques such as Nuclear Magnetic Resonance (1H NMR) and Fourier Transform Infrared Spectroscopy (FTIR), several differences were identified. The results showed that ET APS contained less ethanol in solution after preparation, showing a relationship between the preparation temperature and the ethanol lost from the solution. On the other hand, the FTIR spectra indicated a higher polymerisation level of the ET APS, which suggested that a higher polymer may positively affect the mechanical performance of GFs. Hydrolysis at elevated temperature was found to be a novel and relatively easy way to prepare APS that improves the beneficial effect on GF strength. Thermal degradation of the APS sized Boron-free-E-glass fibres was also investigated across a wide range of temperatures. The results suggested that at temperatures around 3500C, the APS coating on the GFs surface starts to degrade and disappear, consequently reducing the protection provided by the APS layer. The effect of high temperature on GFs also creates cracks and flaws that may also contribute to the strength loss seen in these results which are consistent with the creation of defects for high temperature. Two other chemical treatments were investigated for their ability to regenerate the mechanical properties of the thermally conditioned GFs. An acidic treatment with hydrochloric acid (HCl) 37% v/v did produce a small increase of the average fibre strength, whilst a base treatment using concentrated sodium hydroxide (NaOH) solution at high temperature (950C) substantially improved the mechanical properties of thermal conditioned GFs, achieving up to 200% increase in fibre strength in comparison with the thermally degraded GFs. The optimum NaOH treatment conditions were further characterised in terms of treatment time, NaOH concentration and GF surface state and the effect on GF surface (i.e. OH groups on the surface) and reactions that occur with the glass. It is concluded that a number of very promising treatments with the potential to regenerate the mechanical properties of GFs recycled from composites have been identified.

State highway agencies are searching for more cost-effective methods of rehabilitating roads. One sustainable solution is full-depth reclamation (FDR), a pavement rehabilitation technique that involves pulverizing and reusing materials from existing distressed pavements in place. There is, however, limited information on the long-term properties of these recycled materials. One important property, the elastic modulus, indicates the structural capacity of pavement materials and is highly recommended for design purposes by the Mechanistic Empirical Pavements Design Guide (MEPDG). The elastic modulus directly impacts selection of the overall pavement thickness, and an accurate estimation of the modulus is therefore key to a cost-effective pavement design. This thesis researched the modulus trends and functional properties of three in-service pavements rehabilitated with the FDR technique during the 2008 Virginia Department of Transportation (VDOT) construction season. Foamed asphalt (2.7% with 1% cement), asphalt emulsion (3.5%), and Portland cement (5%) were used as stabilizing agents for the FDR layers. Several deflection tests and distress surveys were conducted for the pavement sections before and after construction. An automated road analyzer (ARAN) was used to collect distress data over a period of 7 years. Deterioration models were developed to predict the durability of differently stabilized FDR pavements and compared to reference sections rehabilitated with traditional asphalt concrete (AC) overlays. The results of the moduli measured for the recycled base materials varied significantly over time. These changes were attributed to curing after construction, seasonal effects, and subgrade moisture. The structural capacity of the pavements improved irrespective of the stabilizing agent used. Rutting was higher for the foamed asphalt and emulsion sections. The International Roughness Index (IRI) was better for the cement stabilized sections compared asphalt stabilized sections. The Critical Condition Index (CCI) was similar for all treatments at the end of the evaluation period. The durability of the sections was comparable, with the cement stabilized FDR sections slightly outperforming the asphalt stabilized sections.<br>Master of Science<br>Replacing all roads in bad condition with new reconstruction or with traditional rehabilitation alternatives such as the mill and overlay will cost state highway agencies (SHAs) huge sums of funds. State departments of transportation are therefore seeking cost-effective ways to rehabilitate roads under their jurisdiction. An innovative technique being used by several SHAs today is full depth reclamation (FDR) which involves breaking down an existing roadway and immediately reusing the materials to construct a strengthened base layer for a new road. Despite the increasing use of FDR in recent years, several questions remain unanswered regarding the behavior of the strengthened base materials and their performance in the long-term under traffic loads. The elastic modulus is one material property that indicates the strength or structural capacity of pavement materials and usually impacts the selection of the overall thickness of the roadway. This thesis researched the modulus trends and functional properties of three in-service roadways rehabilitated with the FDR technique in 2008 by the Virginia Department of Transportation. Foamed asphalt (2.7% with 1% cement), asphalt emulsion (3.5%), and Portland cement (5%) were used to strengthen the FDR base layers. Several deflection tests and distress surveys were conducted for the pavement sections before and after construction. The moduli measured for the recycled base materials varied significantly over time. These changes were attributed to curing after construction, seasonal effects, and subgrade moisture. Long term performance monitoring of the projects showed that rutting was higher for the foamed asphalt and emulsion sections. The International Roughness Index (IRI), which gives an indication of the overall ride quality i.e. how smooth the pavement surface is, was better for the cement stabilized FDR sections compared to the asphalt stabilized counterparts. The structural capacity of the pavements improved irrespective of the stabilizing treatment used. The Critical Condition Index (CCI) was similar for all treatments at the end of the evaluation period. The durability of the sections was comparable, with the cement stabilized sections projected to last slightly longer than asphalt sections.

State highway agencies are searching for more cost-effective methods of rehabilitating roads. One sustainable solution is full-depth reclamation (FDR), a pavement rehabilitation technique that involves pulverizing and reusing materials from existing distressed pavements in place. There is, however, limited information on the long-term properties of these recycled materials. One important property, the elastic modulus, indicates the structural capacity of pavement materials and is highly recommended for design purposes by the Mechanistic Empirical Pavements Design Guide (MEPDG). The elastic modulus directly impacts selection of the overall pavement thickness, and an accurate estimation of the modulus is therefore key to a cost-effective pavement design. This thesis researched the modulus trends and functional properties of three in-service pavements rehabilitated with the FDR technique during the 2008 Virginia Department of Transportation (VDOT) construction season. Foamed asphalt (2.7% with 1% cement), asphalt emulsion (3.5%), and Portland cement (5%) were used as stabilizing agents for the FDR layers. Several deflection tests and distress surveys were conducted for the pavement sections before and after construction. An automated road analyzer (ARAN) was used to collect distress data over a period of 7 years. Deterioration models were developed to predict the durability of differently stabilized FDR pavements and compared to reference sections rehabilitated with traditional asphalt concrete (AC) overlays. The results of the moduli measured for the recycled base materials varied significantly over time. These changes were attributed to curing after construction, seasonal effects, and subgrade moisture. The structural capacity of the pavements improved irrespective of the stabilizing agent used. Rutting was higher for the foamed asphalt and emulsion sections. The International Roughness Index (IRI) was better for the cement stabilized sections compared asphalt stabilized sections. The Critical Condition Index (CCI) was similar for all treatments at the end of the evaluation period. The durability of the sections was comparable, with the cement stabilized FDR sections slightly outperforming the asphalt stabilized sections.<br>Master of Science

Cold Central Plant Recycling (CCPR) has been used by many state highway agencies to save material, money, time, and energy in pavement construction and rehabilitation. The objectives of this thesis were to: (1) perform an instrumented verification analysis, (2) evaluate the response and performance of two pavement configurations with a CCPR base layer through accelerated pavement testing (APT), and (3) construct models using mechanistic-empirical pavement design software for comparison with the APT results. The pavement configurations featured a 5-inch CCPR mixture with either a 3-inch or 1.5-inch SM-9.5D surface mixture. Each section was instrumented with strain gauges, pressure cells, and thermocouples. A heavy vehicle simulator (HVS) was used to load three replicate test sections in each lane, with the temperature controlled at 39°C at a depth of 1.5 inches. Results from the instrument verification analysis showed that the strain gauges and pressure cells used in the experiment recorded pavement responses with a high degree of repeatability. In addition, the loading condition variables (speed, wheel load, and tire inflation pressure) affected the response following the expected trends and did not affect the repeatability of the instruments. The average CV of all strain gauge and pressure cell signals was approximately 0.009 or 0.9%, and 0.004 or 0.4%, respectively. In terms of the rutting comparison, the sections with the 3-inch surface layer outperformed the sections with the thinner 1.5-inch surface layer. However, the age of the pavement at the start of testing significantly affected the rutting performance. After adjusting for the pavement age at the time of testing, the section with the thicker surface showed approximately half of the rutting of the section with the thinner surface. The results from preliminary ME Design analysis indicate that the software cannot model the studied APT sections using the default material properties and calibration factors available at the time of analysis. In particular, the software does not seem to be prepared to model the CCPR materials.<br>Master of Science

Les piles à combustible (PAC) de type PEMFC permettent d’assurer la conversion d’énergie chimique en énergie électrique en utilisant de l’hydrogène pouvant être produit à partir de sources renouvelables. La catalyse des réactions mises en jeu lors de cette conversion d’énergie nécessite l’utilisation de platine, dont les ressources sont faibles et la production (extraction et raffinage) complexe. De plus, du fait de son prix élevé, ce métal représente une part importante du coût de production des PEMFC. Aujourd’hui, le prix de cette technologie doit être réduit pour qu’elle soit économiquement compétitive et puisse être commercialisée à grande échelle. En outre, les charges en platine dans les électrodes de piles à combustible ne peuvent être réduites significativement sans altération de la performance et de la durabilité de ces systèmes. Donc, le développement d’une filière de recyclage pour assurer la récupération du Pt en fin de vie des PAC pourrait permettre une réduction du coût de production des PEMFC.Cette thèse a consisté à mettre en place une voie de recyclage du platine d’assemblages membrane-électrodes (AME) de PEMFC. Un procédé hydrométallurgique composé des étapes suivantes : (i) lixiviation, (ii) séparation et (iii) récupération du platine a été développé. Différentes alternatives de lixiviation (HCl/H2O2, HCl/HNO3), de séparation (par résine ou solvant), de récupération (sous forme de nanoparticules ou de sel) ont été testées. Le fonctionnement de ces processus de récupération du platine a alors été optimisé à partir de produits modèles (Pt/C et solutions synthétiques). Le choix de ces derniers a ensuite été orienté grâce à une étude d’analyse du cycle de vie (ACV) réalisée à l’échelle de l’AME.Enfin, 76% du platine contenu dans des AME composées de catalyseurs Pt-Co a pu être récupéré. Ce rendement a pu être obtenu après mise en place du procédé composé des étapes suivantes : (i) dissolution du Pt par lixiviation avec le mélange HCl/H2O2, (ii) séparation du cobalt sur résine échangeuse d’ions, (iii) récupération sous forme de nanoparticules par la voie polyol. Les résultats finaux d’ACV ont montré que le recyclage du platine permettrait une nette réduction des impacts environnementaux du cycle de vie d’AME de PEMFC<br>The proton exchange membrane fuel cells (PEMFC) can be used to convert chemical energy into electrical energy using hydrogen which can be produced from renewable sources. Platinum (Pt) is the best catalyst used to perform PEMFC electrochemical reaction catalysis. However Pt resources are low and his production (extraction and refining) is complex. Moreover the platinum price represents an important part of the PEMFC stack cost. Nowadays this technology is too expensive to be competitive with conventional energy conversion systems, and cannot be commercialized at a large scale. In addition, PEMFC electrode platinum loading could not be reduced without affecting the system performance and durability. Thus PEMFC production cost could be reduced by recovering platinum from used fuel cells.The main goal of this thesis was to develop a platinum recovery way from fuel cells membrane electrodes-assemblies (MEAs). In order to achieve this objective the following steps were combined in a hydrometallurgical process: (i) leaching, (ii) separation, (iii) recovery. Several alternatives were tested for each step: leaching (HCl/H2O2, HCl/HNO3), separation (resin or solvent), and platinum recovery (as nanoparticles or as a complex). These platinum recovery steps were optimized using Pt/C catalysts and synthetic solutions. Then life-cycle analysis (LCA) methodology has been used to help with the process selection.Finally, about 76% of the platinum contained in multi-metallic catalysts (PtCo/C) MEAs has been recovered. The following path has been followed in this case: (i) dissolution in HCl/H2O2 solution, (ii) separation from cobalt with an ion exchange resin, (iii) recovery has nanoparticles using the polyol process. The LCA study final results showed that a significant reduction of PEMFC MEA life-cycle environmental impact could be achieved by recycling Pt at these systems end-of-life

Les enrobés bitumineux sont des matériaux composites complexes constitués de plusieurs phases : granulats, liants bitumineux et vides. L'assemblage de ces phases définit une microstructure très complexe qui pilote la réponse macroscopique des enrobés. Classiquement, les réponses mécanique et thermique des enrobés sont caractérisées par des essais à l'échelle macroscopique en supposant que le matériau est homogène et isotrope. À l’échelle des constituants, la caractérisation de ces matériaux nécessite d’utiliser une technique de mesure disposant simultanément d’une bonne résolution spatiale et d’une bonne résolution de mesure. L’enjeu de ce travail est d’une part d’évaluer les possibilités d’utilisation de la méthode de la grille (MG) pour l’analyse des propriétés thermo-mécaniques des enrobés bitumineux, et d’autre part de caractériser, grâce à l’apport de cette méthode, l’effet de l’introduction d’agrégats d’enrobés (AE). L’étude expérimentale comprend des essais de compression et de traction ainsi que des essais de gel-dégel. Les champs cinématiques issus de la MG ont permis d'étudier la réponse de ces matériaux à des échelles allant de l’échelle du constituant jusqu’à celle de l’éprouvette. Les résultats obtenus ont également permis de valider une approche expérimentale innovante pour l’analyse des enrobés en permettant d’accéder à des informations fiables et riches à l’échelle de la microstructure. Certains aspects liés à l'impact du recyclage sur le comportement local de l’enrobé sont également fournis<br>Asphalt mixtures are complex composite materials constituted of several phases, namely aggregates, bituminous binder and voids. The assembly of these phases defines a highly complex microstructure, which drives the macroscopic response of asphalt mixtures. Classically, both the mechanical and the thermal responses of asphalt materials are characterized by using experiments at the scale of the mixture assuming that the material is homogeneous. At the scale of their constituents, these materials require a measurement technique featuring simultaneously both a good spatial resolution and a good strain resolution. To date, there are only few experimental studies available in the literature that describe the thermal and mechanical behavior of bituminous mixes at the scale of the constituent. The aim of this work is, on the one hand, to evaluate the possibilities of using the grid method (GM) for the analysis of the thermo-mechanical properties of asphalt mixtures and, on the other hand, to characterize the effect of the recycled asphalt pavement (RAP) inclusion on the local behavior of these materials. Full-field measurements provided by GM allow to study the response of these materials at scales ranging from the component to the mixture itself. These results enable us to validate an innovative experimental approach for the analysis of asphalts. It gives access to reliable and rich information at the scale of the microstructure. Some aspects related to the impact of RAP on the local behavior of asphalt were also provided

Le Zircaloy-4 est un alliage à base de zirconium (~ 98 % massique) constituant le gainage des assemblages nucléaires. Actuellement, les gaines de Zircaloy irradiées sont destinées au stockage géologique profond en raison de leur contamination en radioéléments (contamination issue du séjour en réacteur ainsi que du procédé de traitement). Elles sont classées en déchet de moyenne activité à vie longue suivant les recommandations de l'ANDRA (radioactivité : 10 6 - 10 9 Bq/g, périodes &gt; 31 ans). Les gaines de Zircaloy irradiées représentent une part importante de l'inventaire des assemblages, ~ 25 % en masse. Le recyclage du zirconium contenu dans les gaines pourrait donc présenter un intérêt économique, soit dans le but de revaloriser le zirconium par refabrication de gaines (avec la contrainte imposée par la présence résiduelle de 93Zr), soit à minima pour déclasser le déchet coque en faible activité. Ce travail de thèse a pour objectif d'étudier les voies potentielles pour le recyclage du zirconium contenu dans les gaines de Zircaloy irradiées, et plus précisément l'électroraffinage en milieux de fluorures fondus. L'étude de la composition des gaines de Zircaloy des combustibles nucléaires usés a tout d'abord été réalisée afin d'identifier les radiocontaminants présents dans les gaines irradiées. Ces éléments sont soit des produits d'activation (Cr, Fe, Ni, Co, Sn, ...), soit des produits de fission (H, Sr (+ Y), Cs (+Ba), Eu, ...) et les actinides (U, Pu, Am et Cm). Une étude électrochimique des ions zirconium (IV) a ensuite été réalisée dans le milieu LiF-NaF. Elle a permis d'en déterminer les mécanismes de réduction en zirconium métallique. Puis, une étude classique de nucléation/croissance a également permis d'optimiser les conditions opératoires (i.e. nature de la cathode, concentration de ZrF4 dans le sel, densité de courant appliquée...) pour l'obtention d'un dépôt de zirconium métallique adhérant sur cathode solide inerte. La dernière partie de ce travail s'est focalisée sur l'électroraffinage de tronçons de Zircaloy "frais", soit avant passage dans le réacteur. Une attention particulière a été portée sur le comportement des constituants d'alliage (Fe, Cr et Sn) vis-à-vis de l'avancement de dissolution de l'anode. Bien que les électroraffinages se soient portés sur un matériau non radioactif, la combinaison des approches thermodynamique et expérimentale a permis de proposer un premier dimensionnement du cœur de procédé. L'ensemble de ce travail permet d'avancer un premier scénario pour le traitement des gaines de combustibles usés<br>Zircaloy-4 is an alloy mainly composed of zirconium (~ 98%wt.) constituting the cladding of nuclear assemblies. Currently, used Zircaloy claddings are intended for deep geological storage due to their contamination by radioelements from the nuclear reaction and the reprocessing process. They are classified as long-lived intermediate-level waste according to ANDRA recommendations (radioactivity: 10 6 - 10 9 Bq/g, periods &gt; 31 years), as they represent 25%wt. of the assembly inventory. Zirconium recycling thus could present an economic interest, either to upgrade the zirconium by remanufacturing sheaths (with the constraint imposed by the residual presence of 93Zr), or to downgrade the cladding wastes into low activity waste. This thesis aims to study the potential routes for the recycling of zirconium contained in spent Zircaloy sheaths, and more precisely electrorefining in molten fluorides. The study of Zircaloy sheath composition of spent nuclear fuel was first carried out to identify the radioelements present in used claddings. These elements are either activation products (Cr, Fe, Ni, Co, Sn, etc.), or fission products (H, Sr (+ Y), Cs (+ Ba), Eu, etc.), or actinides (U, Pu, Am and Cm). An electrochemical study of the zirconium (IV) ions was carried out in LiF-NaF at 750 °C to determine its reduction mechanisms into metallic zirconium. Then, a nucleation / growth study was performed to optimize the operating conditions (ie nature of the cathode, concentration of ZrF4, current density applied, etc.), to obtain an adherent metal zirconium deposit on inert solid cathode. The last part of this work was focused on the electrorefining of "fresh" Zircaloy sections, i.e. before its stay in the reactor. Particular attention was paid to the behavior of the alloy constituents (Fe, Cr and Sn), during the electrolysis process. This work proposes a first scenario for the reprocessing of spent fuel claddings

L'humanité fait face à de nombreux défis dans le domaine de l'énergie: explosion de la demande, émissions de gaz à effet de serre, raréfaction de certaines ressources fossiles, pollution, etc. La réponse à ces défis passe en particulier par le développement de systèmes de conversion d'énergie à haute efficacité et à faibles impacts environnementaux. Elle requiert, de plus, la mise au point d'approches permettant d'évaluer ces impacts et de communiquer les résultats à un très large public. Le travail de thèse présenté est une contribution aux efforts menés pour satisfaire ces deux exigences. Il est composé de deux parties qui ont consisté respectivement: - à évaluer à l'aide d'une approche mâture les impacts environnementaux de l'électricité produite par un système de conversion d'énergie en cours de mise au point. Il s'agissait d'effectuer l'Analyse de Cycle de Vie (LCA) de l'électricité issue d'un "stack" de pile à combustible de type Solid Oxyde Fuel Cell (SOFC). L'étude visait à définir les conditions optimales de fabrication, d'utilisation et de recyclage de ce stack d'un point de vue environnemental, afin d'aider les concepteurs et utilisateurs dans leurs choix technologiques. - à mettre au point une approche permettant d'évaluer les impacts environnementaux de l'électricité produite par un système de conversion d'énergie mâture. Il s'agissait d'adapter les concepts d'Empreinte Ecologique et de Biocapacité afin qu'ils intègrent correctement la production d'électricité à partir de réacteurs nucléaires. L'étude visait à disposer d'un indicateur simple permettant d'évaluer les impacts environnementaux de ce type d'électricité<br>Humankind faces many challenges in the energy field: explosion in demand, greenhouse gas emissions, rarefaction of certain fossi! resources, pollution etc. The answer to these challenges lies in particular in the development of energy conversion systems with a high efficiency and low environmental impacts. Furthermore, it requires the development of approaches which enable to evaluate these impacts and communicate the results to a very wide audience. The work undertaken in this Phd thesis is a contribution to the efforts underway to me et this dual demand. It is made up of two parts which have consisted respectively: - in evaluating with a mature approach the environmental impacts of the electricity produced by an energy conversion system currently under development. The objective was to carry out a Life Cycle Analysis (LCA) of the electricity provided by a Solid Oxide Fuel Cell (SOFC) "stack". The study was aimed to define the optimal manufacturing, use and end-of-life conditions for this stack from an environmental point of view, in order to help the designers and users in their technological choices. - in developing an approach which allows the assessment of the environmental impacts of the electricity produced by a mature energy conversion system. The objective was to adapt the concepts of Ecological Footprint and Biocapacity in order that they properly integrate nuclear electricity production. The study was aimed to propose a simple indicator for evaluating the environmental impacts ofthis type of electricity

Le recyclage des assemblages membrane électrode (AMEs) des piles à combustible à membrane échangeuse de protons (PEMFC) est en enjeu important pour le développement du marché de ces piles fonctionnant à l’hydrogène. Dans ces AMEs se trouvent le platine (Pt), un métal précieux et rare qui conditionne majoritairement le coût total de la pile. Le recyclage du Pt est encore largement effectué par hydro ou pyrométallurgie ce qui entraîne le rejet de gaz toxiques et polluants dans l’environnement. Plusieurs études ont porté sur la mise en place d’une voie plus soutenable écologiquement que le traditionnel usage d’acides forts pour lixivier le platine. Le procédé proposé ici s’inscrit dans ce domaine de recherche en proposant une nouvelle voie de séparation des constituants de l’électrode de PEMFC en vu de leur recyclage par l’utilisation de liquides ioniques. Ceux-ci par leur stabilité thermique et chimique et leur non-volatilité peuvent permettre la mise en place d’un procédé de récupération du platine sûr. Après l’étude d’une sélection de liquides ioniques plusieurs d’entre eux, dont le P66614Cl (trihexyltetradécylphosphonium chlorure), ont permis la récupération du platine sous forme de nanoparticules détachées et stabilisées dans le liquide ionique. Une étude des interactions du liquide ionique avec chacun des composants de l’AME a permis de mieux comprendre les mécanismes d’extraction. Le liquide ionique interagit ainsi fortement avec l’ionomère présent dans la couche catalytique. Cette forte interaction ouvre la voie à un retraitement simultané du Nafion et du platine des AMEs<br>Recovery of the protons-exchange membrane fuel cell (PEMFC) membrane electrode assemblies (MEAs) is an important issue for the growing of the fuel cells market. These MEAs contain platinum (Pt), which as a precious metal mainly influences the total cost of fuel cells. The recycling of Pt is still based to a great extent on hydro or pyrometallurgical techniques which produce toxic and pollutant gas emissions. Some studies aimed to set up processes to recycle platinum in a more sustainable way than traditional metal lixiviation using strong acids. The study here is part of this research field and is about a new way to separate the different components of the PEMFC electrode using ionic liquids for the recycling of these valuable materials. These liquids possess excellent thermal and chemical stability and their non-volatility can be useful to set up a safer way to recover platinum. A selection of ionic liquids was studied and some of them, including the P66614Cl (trihexyltetradecylphosphonium chloride), could be use to recover Pt nanoparticles detached from their carbon support and stabilized in the ionic liquid. A study on the interactions of ionic liquids and the components of the MEA allowed the extraction mecanisms to be better understood. Thus the ionics liquids interact strongly with Nafion in the catalyst layer which allows Pt nanoparticles to be recovered. These strong interactions set the stage for the simultaneous recycling of Nafion and Pt from MEAs

Dans les réacteurs à fusion nucléaire, un échange constant de particules se développe entre le plasma et la paroi. Ce phénomène, appelé recyclage, présente un intérêt crucial pour ces réacteurs car, une fois le plasma établi, le recyclage représente la principale source de particules pour le plasma. Une connaissance complète du recyclage est donc essentielle pour assurer un contrôle fiable de la densité plasma ainsi qu'une performance optimale du réacteur. Cependant, les études in-situ du recyclage demeurent complexes. La modélisation numérique peut assister dans la compréhension de ce phénomène. Les codes de transport de plasma de bord présentent la description la plus avancée de l’interaction plasma-paroi. La description du recyclage reste néanmoins partielle : la réflexion atomique est déjà traitée tandis que la désorption moléculaire est fixée ad-hoc par l’utilisateur. Cette thèse de doctorat se concentre sur le développement d’une extension au code de transport SolEdge2D-EIRENE, dénommée D-WEE, dont l’objectif est de modéliser la dynamique de la désorption. Afin d’initialiser D-WEE, une séquence de décharges plasma est simulée pour modéliser l’opération d’un tokamak. La dynamique simulée pendant ces décharges est étudiée, révélant des comportements intéressants qui pourraient impacter l’opération du réacteur. Pour évaluer la pertinence de la simulation, une confrontation avec l'expérience est effectuée et révèle un accord qualitatif entre la chute de pression post-décharge simulée (avec une tendance en t^{-0.8}) et celle observée expérimentalement. Le taux de rétention simulé pendant la décharge est étudié et présente un accord qualitatif avec l'expérience<br>In all plasma devices, a constant exchange of particle develops between the plasma and the wall. This phenomenon, referred to as recycling, is of critical interest for those reactors as, once the plasma is established, particle recycling represents the main particle source for the plasma. A complete understanding of the recycling phenomenon is therefore essential to ensure a reliable plasma density control and optimum performance. However, the in-situ experimental study of recycling remains challenging. Modelling can assist in the understanding of this phenomenon.The edge-plasma transport codes present the most-advanced description of the plasma-wall interaction. However, the description of recycling remains partial: atomic reflection is already handled while molecular desorption is set ad-hoc by the code user. This PhD focuses on the development of an extension of the SolEdge2D-EIRENE transport code, named D-WEE, whose goal is to model the dynamics of desorption.To initialise D-WEE, a sequence of plasma discharges is simulated with D-WEE to model a tokamak operation. The simulated wall dynamics during those discharges is studied, reveling some interesting behaviours that could impact the reactor operation. To assess the relevance of the simulated wall dynamics, a confrontation to post-pulse experimental pressure measurement is performed which reveals a qualitative agreement between the temporal pressure drop obtained in the simulation (with a t^{-0.8} trend) and the one observed experimentally under ILW configuration. The retention rate during the discharge is also studied and reproduces qualitatively the experimental trends

Full-depth reclamation (FDR) in conjunction with cement stabilization is an established practice for rehabilitating deteriorating asphalt roads. Conventionally, FDR uses dry cement powder applied with a pneumatic spreader, creating undesirable fugitive cement dust. The cement dust poses a nuisance and, when inhaled, a health threat. Consequently, FDR in conjunction with conventional cement stabilization cannot generally be used in urban areas. To solve the problem of fugitive cement dust, the use of cement slurry, prepared by combining cement powder and water, has been proposed to allow cement stabilization to be utilized in urban areas. However, using cement slurry introduces several factors not associated with using dry cement that may affect road base strength, dry density (DD), and moisture content (MC). The objectives of this research were to 1) identify construction-related factors that influence the strength of road base treated with cement slurry in conjunction with FDR and quantify the effects of these factors and 2) compare the strength of road base treated with cement slurry with that of road base treated with dry cement. To achieve the research objectives, road base taken from an FDR project was subjected to extensive full-factorial laboratory testing. The 7-day unconfined compressive strength (UCS), DD, and MC were measured as dependent variables, while independent variables included cement content; slurry water batching temperature; cement slurry aging temperature; cement slurry aging time; presence of a set-retarding, water-reducing admixture; and aggregate-slurry mixing time. This research suggests that, when road base is stabilized with cement slurry in conjunction with FDR, the slurry water batching temperature; haul time; environmental temperature; and presence of a set-retarding, water-reducing admixture will not significantly affect the strength of CTB, provided that those factors fall within the limits explored in this research and are applied to a road base with similar properties. Cement content and cement-aggregate mixing time are positively correlated with the strength of CTB regardless of cement form. Additionally, using cement slurry will result in slightly lower strength values than using dry cement.

Abstract The main aim of the European Union’s waste legislation and the corresponding Finnish waste legislation is to reduce the production of waste. Further, the aims of the European Union’s growth strategy are to reduce the production of greenhouse gases, increase the use of renewable energy, and improve energy efficiency. According to the renewed Waste Tax Act, a waste tax has to be paid on all fly ashes that are deposited in landfills in Finland. A large amount of wood- and peat-based fly ashes are formed annually in Finland, and the amount is likely to increase in the future due to the increasing use of renewable energy. Previously, these ashes have mainly been deposited in industrial landfills, but the need to utilize the fly ashes has increased recently due to changes in waste legislation. In this thesis, several issues related to the utilization of wood- and peat-based fly ash were studied, with the general objective of improving the utilization potential of such ashes. As the first stage of this research, the suitability of willow ash for use as a fertilizer was studied. Willow ash would be well suited for use as a fertilizer due to its very high nutrient content. However, cadmium, a heavy metal, was found to be enriched in the ashes of the studied willow species. Due to this, special attention should be paid when choosing willow species for energy production. In the second stage of the research, the possibility of improving the strength development of wood- and peat-based fly ashes, as well as the possibility of stabilizing fly ash containing high amounts of heavy metals via the addition of cement and/or alkali activation, was investigated. Strength development was found to be dependent on the amount of reactive calcium and the ratio between that amount of reactive calcium and the sum of the reactive silicon, aluminum, and sulfur (Ca/(Si + Al + S)). The studied methods performed well in terms of stabilizing barium, copper, lead, and zinc. During the next stage, the effect of different chemical digestion methods, which are regulated by the Finnish waste legislation, on the utilization potential of fly ash was studied. The digestion method had a significant impact on the results of the potassium content analysis, which could affect the possibility of using fly ash as a fertilizer. As the final stage of the research, the co-granulation of ash with sewage sludge and lime was studied. From a technical point of view, the co-granulation was successful, although the compressive strength of the granules was low. Additionally, an insufficient nitrogen content was achieved with a sludge addition of 20-40 weight%<br>Tiivistelmä Euroopan unionin jätelainsäädännön ja sitä vastaavan suomalaisen lainsäädännön tavoitteena on ehkäistä jätteiden muodostumista. Euroopan Unionin kasvustrategian tavoitteena on vähentää kasvihuonekaasupäästöjä, lisätä uusiutuvan energian käyttöä ja parantaa energiatehokkuutta. Uudistetun jäteverolain mukaan kaikista kaato-paikoille sijoitetuista lentotuhkista tulee Suomessa maksaa jäteveroa. Suomessa puu- ja turveperäisiä lentotuhkia muodostuu vuosittain suuria määriä ja määrä tulee vielä kasvamaan uusiutuvan energiankäytön lisääntyessä. Aiemmin nämä tuhkat ovat päätyneet pääasiassa läjitykseen teollisuuden kaatopaikoille, mutta muuttuneen jätelainsäädännön seurauksena tarve hyödyntää lentotuhkia on lisääntynyt. Tässä väitöstyössä tutkittiin puu- ja turveperäisten tuhkien hyödyntämiseen liittyviä kysymyksiä. Työn yleistavoitteena oli parantaa tuhkien hyödyntämis-mahdollisuuksia. Tutkimuksen ensimmäisessä vaiheessa tutkittiin pajutuhkan soveltuvuutta lannoitteeksi. Pajutuhka soveltuisi hyvin lannoitteeksi erittäin hyvien ravinne-pitoisuuksien ansiosta. Raskasmetalleista kadmiumin havaittiin kuitenkin rikastuvan tutkittujen pajulajien tuhkiin. Tähän tulisi kiinnittää erityishuomiota, kun pajulajeja valitaan energiantuotantoa varten. Tutkimuksen toisessa vaiheessa selvitettiin mahdollisuutta parantaa turpeen ja puun lentotuhkien lujittumista sekä raskasmetallipitoisen lentotuhkan stabiloimista sementtilisäyksen ja/tai alkaliaktivoinnin avulla. Lujuuden kehitys riippui reaktiivisen kalsiumin määrästä sekä reaktiivisen kalsiumin määrän ja reaktiivisten piin, alumiinin ja rikin määrien summan välisestä suhteesta (Ca/(Si + Al + S)). Tutkitut menetelmät toimivat hyvin bariumin, kuparin, lyijyn ja sinkin stabiloinnissa. Seuraavassa vaiheessa selvitettiin Suomen lainsäädännössä määritettyjen kemiallisten hajotusmenetelmien vaikutusta tuhkan hyödyntämispotentiaaliin. Hajotusmenetelmällä oli suuri merkitys kaliumin pitoisuutta määritettäessä, mikä voi vaikuttaa lentotuhkan hyödynnettävyyteen lannoitteena. Viimeisessä vaiheessa tutkittiin tuhkan yhteisrakeistusta lietteen ja kalkin kanssa. Teknisesti yhteisrakeistus onnistui hyvin, mutta rakeiden puristuslujuus oli alhainen. Lisäksi 20 - 40 paino% lietelisäyksellä ei rakeisiin saatu riittävän korkeaa typpipitoisuutta

The MURE code is based on the coupling of a Monte Carlo static code and the calculation of the evolution of the fuel during irradiation and cooling periods. The MURE code has been used to analyse two different questions, concerning the mono-recycling of Am in present French Pressurized Water Reactor, and the conversion of high enriched uranium (HEU) used in the Miniature Neutron Source Reactor in Ghana into low enriched uranium (LEU) due to proliferation resistance issues. In both cases, a detailed comparison is made on burnup and the induced radiotoxicity of waste or spent fuel. The UOX fuel assembly, as in the open cycle system, was designed to reach a burn-up of 46GWd/T and 68GWd/T. The spent UOX was reprocessed to fabricate MOX assemblies, by the extraction of Plutonium and addition of depleted Uranium to reach burn-ups of 46GWd/T and 68GWd/T, taking into account various cooling times of the spent UOX assembly in the repository. The effect of cooling time on burnup and radiotoxicity was then ascertained. Spent UOX fuel, after 30 years of cooling in the repository required higher concentration of Pu to be reprocessed into a MOX fuel due to the decay of Pu-241. Americium, with a mean half-life of 432 years, has high radiotoxic level, high mid-term residual heat and a precursor for other long lived isotope. An innovative strategy consists of reprocessing not only the plutonium from the UOX spent fuel but also the americium isotopes which dominate the radiotoxicity of present waste. The mono-recycling of Am is not a definitive solution because the once-through MOX cycle transmutation of Am in a PWR is not enough to destroy all the Am. The main objective is to propose a "waiting strategy" for both Am and Pu in the spent fuel so that they can be made available for further transmutation strategies. The MOXAm (MOX and Americium isotopes) fuel was fabricated to see the effect of americium in MOX fuel on the burn-up, neutronic behavior and on radiotoxicity. The MOXAm fuel showed relatively good indicators both on burnup and on radiotoxicity. A 68GWd/T MOX assembly produced from a reprocessed spent 46GWd/T UOX assembly showed a decrease in radiotoxicity as compared to the open cycle. All fuel types understudy in the PWR cycle showed good safety inherent feature with the exception of the some MOXAm assemblies which have a positive void coefficient in specific configurations, which could not be consistent with safety features. The core lifetimes of the current operating 90.2% HEU UAl fuel and the proposed 12.5% LEU UOX fuel of the MNSR were investigated using MURE code. Even though LEU core has a longer core life due to its higher core loading and low rate of uranium consumption, the LEU core will have it first beryllium top up to compensate for reactivity at earlier time than the HEU core. The HEU and LEU cores of the MNSR exhibited similar neutron fluxes in irradiation channels, negative feedback of temperature and void coefficients, but the LEU is more radiotoxic after fission product decay due to higher actinides presence at the end of its core lifetime.

A process for recycling spent nuclear fuel cladding, a zirconium alloy (Zircaloy), into a metal powder that may be used for advanced nuclear fuel applications, was investigated to determine if it is a viable strategy. The process begins with hydriding the Zircaloy cladding hulls after the spent nuclear fuel has been dissolved from the cladding. The addition of hydrogen atoms to the zirconium matrix stresses the lattice and forms brittle zirconium hydride, which is easily pulverized into a powder. The dehydriding process removes hydrogen by heating the powder in a vacuum, resulting in a zirconium metal powder. The two main objectives of this research are to investigate the dehydriding process and to design, build and demonstrate a specialized piece of equipment to process the zirconium from cladding hulls to metal powder without intermediate handling. The hydriding process (known from literature) took place in a 95 percent argon - 5 percent hydrogen atmosphere at 500 degrees C while the dehydriding process conditions were researched with a Thermogavimetric Analyzer (TGA). Data from the TGA showed the dehydriding process requires vacuum conditions (~0.001 bar) and 800 degrees C environment to decompose the zirconium hydride. Zirconium metal powder was created in two separate experiments with different milling times, 45 minutes (coarse powder) and 12 hours (fine powder). Both powders were analyzed by three separate analytical methods, X-Ray Diffraction (XRD), size characterization and digital micrographs. XRD analysis proved that the process produced a zirconium metal. Additionally, visual observations of the samples silvery color confirmed the presence of zirconium metal. The presence on zirconium metal in the two samples confirmed the operation of the hydriding / milling / hydriding machine. Further refining of the hydride / milling / dehydride machine could make this process commercially favorable when compared to the high cost of storing nuclear waste and its components. An additional important point is that this process can easily be used on other metals that are subject to hydrogen embrittlement, knowing the relevant temperatures and pressures associated with the hydriding / dehydriding of that particular metal.

The nuclear waste currently generated in the United States is stored in spent fuel pools and dry casks throughout the country awaiting a permanent disposal solution. One efficient solution would be to remove the actinides from the waste and transmute these isotopes in a fast spectrum reactor. Currently this technology is unavailable on a commercial scale and a considerable amount of research and development is still required. An alternate solution is to reprocess and recycle the used fuel in thermal reactors, creating new fuel while reducing the amount of waste and its impact to the environment. This thesis examines the possibility of multi-recycling the transuranics (Pu, Np, Am, and Cm) in a standard pressurized water reactor (PWR). Two types of recycling strategies will be examined: one where Pu, Np, and Am are recycled (TRU-Cm) and a second where the previous isotopes as well as Cm are recycled (TRU+Cm). To offset the hardened neutron spectrum that results from the inclusion of the transuranics, a smaller fuel pin is employed to provide additional moderation. Computer simulations are used to model the in-reactor physics and long-term isotopic decay. Each fuel type is assessed based on the required U-235 enrichment, void coefficient, transuranic production/destruction, and radiotoxicity reduction as compared to a UOX and MOX assembly. It is found that the most beneficial recycling strategy is the one where all of the transuranics are recycled. The inclusion of Cm reduces the required U-235 enrichment, compared to the other multi-recycled fuel and, after a significant number of recycles, can result in the required enrichment to decrease. This fuel type also maintains a negative void coefficient for each recycle. The void coefficient of the fuel type without Cm becomes positive after the third cycle. The transmutation destruction of the two multi-recycled assemblies is less than that of a MOX assembly, but the transmutation efficiency of the multi-recycled assemblies exceeds the MOX assemblies. The radiotoxicity of both multi-recycled assemblies is significantly lower than the UOX and MOX with the TRU+Cm fuel being the lowest. When Curium is recycled only 28,000 years are required for the radiotoxicity of the waste to reach that of natural Uranium and when Cm is not recycled, the amount of time increases to 57,000 years.

碩士<br>國立臺北科技大學<br>資源工程研究所<br>102<br>Solid oxide fuel cell (SOFC) is one of the important novel energy technology. The SOFC of the cathode, anode and electrolyte are often rich in rare earth elements with high recovery value, such as cerium, gadolinium and lanthanum. In this study, sintered La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode material and NiO-Ce0.9Gd0.1O1.95 (NiO-GDC) anode material as a original material. Studies of rare earth recovery by solvent extraction, the study was planned by the Taguchi method and selected the L9 (34) orthogonal table to separate and recover the different elements and analysis of optimal parameters by Taguchi and Variation analysis. As a result, acid digestion method was found to be La, Sr, Co, Fe and Ni dissolution, and Ce, Gd achieve the separation effect. Taguchi analysis of acid-soluble obtain optimal parameters are acid category: nitric, acid concentration : 3M, reaction temperature : 60 ℃, reaction time : 2hr, sintered powder of La, Sr, Co, Fe leaching rate is up to 100 %. Acid containing La, Sr , Co, Fe element can synthesis LSCF powder by GNP combustion then synthesis LSCF powder and recovery GDC powder crystal the same Original powder by XRD. Synthesis LSCF powder and recover GDC powder can apply to SOFC electrode material to achieve the purpose of recycling.

碩士<br>國立臺北科技大學<br>資源工程研究所<br>104<br>Processing of flat-panel displays generates huge amount of wasted glass polishing powder, with high concentration of cerium and other elements such as lanthanum. According to the current statistics, consumption of polishing powder was approximately ten thousand tons per year in world. Nevertheless, wasted polishing powder was usually buried or burned. If the lanthanum and cerium compounds in the wasted polishing powder could be recycled, that will greatly reduce enterprise cost and implement waste circulation. Cathodes of SOFCs are the principal consisting of rare earth elements such as lanthanum and cerium. In this study, we recycled the lanthanum and cerium from wasted glass polishing powder by acid-solution method, and synthesized La0.85Sr0.05Ca0.1Fe0.8Co0.2O3-δ and Gd0.1Ce0.9O2-δ(LSCCF-GDC) composite cathode material for SOFCs by glycine-nitrate combustion (GNP) method. The results show that the recovery rates of lanthanum and cerium could accomplish up to 94.64% and 100% under 10N nitric acid solution within one hour. Comparing with the XRD data of the commercial LSCCF-GDC powder and the LSCCF-GDC product synthesized with chemicals, we find that the LSCCF-GDC was successfully synthesized with the recycled La & Ce solution by GNP method. The effect of adding ammonia to the product was also discussed, the grain size is finer and recovery rate of the product is higher without the addition of ammonia to the solution. The waste glass polishing slurry has a salvage value, the product is melt-ceramic sponges by GNP method that was considerable as catalyst and material of SOFC. Technology of this study is green and reduced half cost of production.

abstract: The project aims at utilization of hydrothermal liquefaction (HTL) byproducts like biochar to grow microalgae. HTL is a promising method to convert wet algal biomasses into biofuels. The initial microalgae liquefaction at a temperature of 300 °C for 30 minute, converted 31.22 % of the Galdieria sulphuraria and 41.00 % of the Kirchneriella cornutum into biocrude. Upon changing the reactor from a 100 ml to a 250 ml reactor, the yield in biocrude increased to 31.48 % for G. sulphuraria and dropped to 38.05 % for K. cornutum. Further, energy recoveries based on calorific values of HTL products were seen to drop by about 5 % of the 100 ml calculated values in the larger reactor. Biochar from HTL of G. sulphuraria at 300 °C showed 15.98 and 5.27 % of phosphorous and nitrogen, respectively. HTL products from the biomass were analyzed for major elements through ICP-OES and CHNS/O. N and P are macronutrients that can be utilized in growing microalgae. This could reduce the operational demands in growing algae like, phosphorous mined to meet annual national demand for aviation fuel. Acidic leaching of these elements as phosphates and ammoniacal nitrogen was studied. Improved leaching of 49.49 % phosphorous and 95.71 % nitrogen was observed at 40 °C and pH 2.5 over a period of 7 days into the growth media. These conditions being ideal for growth of G. sulphuraria, leaching can be done in-situ to reduce overhead cost. Growth potential of G. sulphuraria in leached media was compared to a standard cyanidium media produced from inorganic chemicals. Initial inhibition studies were done in the leached media at 40 °C and 2-3 vol. % CO2 to observe a positive growth rate of 0.273 g L-1 day-1. Further, growth was compared to standard media with similar composition in a 96 well plate 50 μL microplate assay for 5 days. The growth rates in both media were comparable. Additionally, growth was confirmed in a 240 times larger tubular reactor in a Tissue Culture Roller drum apparatus. A better growth was observed in the leached cyanidium media as compared to the standard variant.<br>Dissertation/Thesis<br>Masters Thesis Chemical Engineering 2017

Tese de doutoramento em Engenharia Civil<br>Nesta tese estudou-se o comportamento mecânico e ambiental de materiais granulares e muito particularmente os agregados processados das escórias de aciaria produzidas na Siderurgia Nacional, com o principal objectivo de promover a sua valorização (reciclagem) como material de construção nas infraestruturas de transporte e obras geotécnicas. Neste sentido, estabeleceu-se um programa experimental para a caracterização ambiental e mecânica, quer em laboratório, quer no campo, dos agregados processados das escórias de aciaria nacionais, bem como de dois materiais naturais (Saibro Granítico e Agregado Granítico), com o propósito de se compararem as suas propriedades. Em laboratório, o principal ensaio mecanicista utilizado para determinar as propriedades de deformabilidade dos materiais granulares tem sido o triaxial cíclico, desenvolvido durante este programa de investigação. Uma câmara triaxial com 150mm de diâmetro e 300mm de altura foi instrumentada internamente para medição directa da força aplicada e dos deslocamentos no provete de ensaio. Paralelamente ao estudo sobre a valorização dos agregados processados das escórias de aciaria nacionais efectuou-se um outro, relativo à influência do índice de vazios e da granulometria nas características de deformabilidade dos materiais granulares. Esse estudo envolveu a realização de ensaios triaxiais cíclicos, em provetes com diferentes granulometrias, combinando diferentes dimensões médias das partículas (D50) e diferentes índices de vazios. Os resultados do estudo mostraram, claramente, que as equações relativas ao índice de vazios obtidas sobre areias, e normalmente utilizadas em materiais granulares com fracções mais grossas, não descrevem o comportamento destes materiais, sobretudo quando bem compactados. Com base nos resultados obtidos propôs-se para a normalização do módulo de deformabilidade em relação ao índice de vazios uma nova expressão matemática que incorpora um factor que depende da granulometria dos materiais. Os resultados mostraram ainda que o módulo de deformabilidade dos materiais granulares depende da dimensão máxima das partículas e do D50. No campo, a avaliação dos desempenhos mecânico e ambiental dos materiais efectuou-se recorrendo à construção de um trecho experimental, integrado numa estrada nacional em serviço, constituído por três secções distintas. Numa foram utilizados apenas os dois materiais naturais (no aterro e nas camadas de leito do pavimento e base), noutra foi utilizado exclusivamente agregado processado (no aterro e nas camadas de leito do pavimento e base) e na restante aplicou-se o Saibro Granítico, no aterro e na camada de leito do pavimento, e o agregado processado, na camada de base. A avaliação do desempenho mecânico e ambiental dos materiais efectuou-se durante e após a fase de construção. A avaliação do desempenho mecânico durante a fase de construção realizou-se através do controlo dos parâmetros de estado e da deformabilidade dos materiais, com recurso a diferentes ensaios. A avaliação do desempenho mecânico, após a fase de construção, efectuou-se ao longo de dois anos, quer ao nível interno das camadas do pavimento com recurso a extensómetros e do aterro através de varões extensométricos instalados durante a fase de construção, quer ao nível do comportamento global do aterro através de campanhas de nivelamento topográfico de precisão e no pavimento com recurso a ensaios com deflectómetro de impacto pesado. A avaliação do desempenho ambiental efectuou-se, ao longo de um ano, com recurso a instrumentação original em Portugal nesta aplicação: instalação de dois lisímetros. Os resultados experimentais obtidos neste estudo mostraram que os agregados processados das escórias de aciaria nacionais são inertes e apresentam um desempenho mecânico superior ao dos materiais naturais, contribuindo decisivamente para a sua valorização em infraestruturas de transporte e obras geotécnicas. Presentemente, são comercializados pela Siderurgia Nacional como um novo material de construção, com Marcação CE e marca registada com a designação de Agregado Siderúrgico Inerte para a Construção (ASIC).<br>This thesis studied the mechanical and environmental behaviour of granular materials and more specifically processed steel slag aggregates produced in National Iron and Steel Company, with the primary objective of promoting their use (recycling) as a building material in transport infrastructures and geotechnical work. In this context an experimental programme was established in order to environmentally and mechanically characterise, both in laboratory and in the field, the national processed steel slag aggregates, in addition to two natural materials (Granitic gravel and Granite Aggregate), with the purpose of comparing their properties. In the laboratory, the main mechanical test used to determine the deformation properties of granular materials has been the precision cyclic triaxial, developed during this research programme. A triaxial chamber 150mm in diameter and 300mm in height was internally instrumented for the direct measurement of displacement and applied force. Parallel to the study for promoting processed aggregates of national steel slags another laboratory study was carried out on the influence of void ratio and grading on the deformation characteristics of granular materials. This study involved carrying out precision cyclic triaxial tests on specimens with different gradations, combined with different particle size average and different void ratios. The results of the study clearly showed that the equations for the void ratio obtained for sand, and normally used in granular material with coarser fractions, do not describe the behaviour of these materials especially when they are well compacted. Based on the results obtained, a new mathematical expression that incorporates a factor that depends on the gradation of the material is proposed for the normalisation of the modulus of deformability in relation to the void ratio. The results also showed that this modulus in the granular material depends on the maximum size of the particles and on the particle size average. In the field, the assessment of the mechanical and environmental performance of the materials was carried out at the construction of a full scale test integrated in a national road in use which consisted of three distinct sections. In one section, only the two natural materials were used (in the embankment, capping and base layers of pavement), in another section only processed aggregate was used (in the embankment, capping and base layers of pavement) and in the remaining section Granitic Gravel was used, in the embankment and the capping layers of pavement, and processed aggregate was used in the base layer. The assessment of the mechanical and environmental performance of the materials was done during and after the construction phase. The mechanical performance during the construction phase was evaluated by controlling the state parameters and the deformability of the materials by using different tests. After the construction phase this was done throughout two years by assessing the pavement layers by using strain gauges. Furthermore embankment performance was evaluated by using strain gauge rods installed during the construction phase as well by precision topographic levelling campaigns. The assessment of pavement performance was done by using tests with a heavy falling weight deflectometer. The assessment of the environmental performance was carried out throughout one year by means of two lysimeters, instrumentation that is original in Portugal in this application. The experimental results obtained in this study show that the aggregate of national processed steel slags are inert and have a better mechanical performance than that of natural materials, decisively contributing to the promotion of these recycled materials in transport infrastructures and geotechnical works. Presently, this new construction material, with EC marking, registered as a trademark under the name of Agregado Siderúrgico Inerte para a Construção (ASIC) [Inert Steel Aggregate for Construction - ISAC], has led to an increased demand in the national market with obvious benefits for the National Iron and Steel Company.