The purpose of the following research is to explore molten regolith electrolysis (MRE) methodology for in-situ resource utilization (ISRU) of Highlands lunar regolith, to be explored during the initial Artemis missions. An analysis of potential commercial launch providers for MRE-equipment based on technology-readiness level (TRL), payload mass support, and $ USD/kg payload price is provided. SpaceX is ultimately proposed as a launch provider of MRE equipment following multi-factorial analysis, with the SpaceX Starship human landing system (HLS) variant proposed for supporting MRE payload. Finally, customers of regolith-derived oxygen, aluminum, and silicon are distinguished to form the business case for operating MRE equipment on the lunar surface.

No description available.

No description available.

No description available.

Corrosion is a major challenge in the use of molten fluoride salt as a coolant in molten salt reactors (MSRs). A promising way of satisfying the two requirements of high strength and corrosion resistance is to clad structural alloys with a corrosion resistant material. Four candidate cladding and structural alloy combinations—stainless steel 316L and Incoloy 800H structural alloys either diffusion bonded to Hastelloy N or electroplated with nickel—were thermally aged at 700 °C for two to eight months. Based on measured concentration profles, the diffusion resistance of the four material combinations was compared and diffusion results were extrapolated to an end of reactor lifetime. The most important conclusion from this work is that Hastelloy N is highly likely to be signifcantly more diffusion resistant than nickel. The difference in diffusion resistance between Incoloy 800H and stainless steel 316L is relatively small. Two methods were used for extrapolating experimental diffusion results: (1) a diffusion model and calculated diffusion coeffcients and (2) simulations with Thermo-Calc DICTRA. Some simulations were carried out with a corrosion boundary condition of near-zero chromium concentration, demonstrating the potential of simulations for predicting diffusionlimited corrosion in molten fluoride salts. A surprising result of these simulations is that decreasing the thickness of Ni plating did not increase the thickness of diffusion zones in underlying structural alloys. / Thesis / Master of Applied Science (MASc)

Nuclear energy presents environmental benefits, yet the challenge of radioactive waste management persists. Advanced solutions, such as Molten Salt Reactors (MSRs), require a more profound understanding of molten salt chemistry. This research aims to develop tools, including a depletion simulator, molten salt electrochemical simulator, and a fluoride-based thermodynamic reference electrode for electrochemical purification. The computationally inexpensive depletion simulator allows for exploration into extraction and processing strategies for molten salt reactors. An illustrative case study on Mo-99 production from MSRs demonstrates the practical application of the theoretical framework, emphasizing the need for optimization in extraction effectiveness and separation difficulty. The electrochemical simulator, employing first-principles models, contributes to both nuclear technology and the broader field of electrochemistry. Detailed analyses of linear sweep voltammetry (LSV) for uranium deposition, coupled with numerical simulations for diffusion coefficient measurements, enhance precision in experimental methodologies. The study into fluoride-based thermodynamic reference electrodes provides validation of boron nitride as a viable ion-exchange membrane permeation of oxide impurities as a contributing factor to reference electrode failure, and an investigation of an alternative reference electrode chemistry based on the equilibrium between U3+ and U4+. This novel reference electrode chemistry enabled electrochemical purification of fluoride-based salts which were characterized with square wave voltammetry and have less than 30 ppm O2-. In summary, this work not only advances theoretical understanding but also provides practical tools for nuclear energy and electrochemical processes. Its interdisciplinary approach of integrating theory, computation, and experimentation represents a significant stride toward the responsible and balanced utilization of nuclear power to address global energy needs and challenges.

The first Molten Salt Reactor (MSR) was designed and tested at Oak Ridge National Laboratory (ORNL) in the 1960's, but recent technological advancements now allow for new components, such as heat exchangers, to be created for the next generation of MSR's and molten salt-cooled reactors. The primary (fuel salt-to-secondary salt) heat exchanger (PHX) design is shown here to make dramatic improvements over traditional shell-and-tube heat exchangers when changed to a compact heat exchanger design. While this paper focuses on the application of compact heat exchangers on a Molten Salt Reactor, many of the analyses and results are similarly applicable to other fluid-to-fluid heat xchangers. The heat exchanger design in this study seeks to find a middle-ground between shell- and-tube designs and new ultra-efficient, ultra-compact designs. Complex channel geometries and microscale dimensions in modern compact heat exchangers do not allow routine maintenance to be performed by standard procedures, so extended surfaces will be omitted and hydraulic diameters will be kept in the minichannel regime (minimum channel dimension between 200 μm and 3 mm) to allow for high-frequency eddy current inspection methods to be developed. High aspect ratio rectangular channel cross-sections are used. Various plant layouts of smaller heat exchanger banks in a "modular" design are introduced. FLUENT was used within ANSYS Workbench to find optimized heat transfer and hydrodynamic performance. With similar boundary conditions to ORNL's Molten Salt Breeder Reactor's shell-and-tube design, the compact heat exchanger interest in this thesis will lessen volume requirements, lower fuel salt volume, and decrease material usage. / Master of Science

Nuclear energy has gained crucial importance since it has a minor impact on climate change and greenhouse gas releases; additionally, the other energy sources are insufficient to reach the world's energy needs without nuclear energy. Another sign that the Generation IV International Forum (Kelly, Gen IV International Forum: A decade of progress through international cooperation, 2014) has pointed out is to utilize uranium resources to the maximum and recycle spent nuclear fuel through burn-up in the Generation IV reactor designs, one of which is the molten salt reactor (MSR). Therefore, the MSR can use the spent nuclear fuel as a fresh fuel when the actinides recycle. That reprocessing of spent fuel could be one of the opportunities to contribute to future nuclear energy goals. This study aims to develop a modified pyroprocessing method to prepare molten salt fuels for MSR from spent oxide nuclear fuel that was burned in light water reactors (LWRs). The process diagram illustrated as (1) spent fuel treatment, (2) chopping and voloxidation of spent oxide fuel, (3) oxide reduction of spent fuel, and then depending on the fuel structure and composition for the MSR, it continues by one or two of the following; – electrorefining, – chlorination, and – fluorination. The subject of this study focused on oxide reduction in two categories: chemical reduction and electrochemical reduction. The system designs have been optimized in calcium salts since they have high calcium metal and calcium oxide solubility. The significant results indicated that both methods would substantially reduce the solid uranium dioxide pellet. The chemical reduction will reduce the total solid pellet at 850oC in the composition of 55.73mol%CaCl2-12.37mol%CaF2-26.58mol%Ca-5.32mol%UO2 over 12 hours. The total reduction in the electrochemical test is seen at 850oC during 12 hours with a salt composition of 79mol%CaCl2-17mol%CaF2-4mol%CaO. These oxide reduction mechanisms are convenient ways to reprocess spent oxide fuel from LWRs to utilize in the MSR. Additionally, the reduced fuel is also applicable to using other next-generation reactors. The prospect of this research is the explicit comparison between chemical and electrochemical methods in calcium salts. / M.S. / Nuclear energy is a crucial energy production to meet the world’s future energy needs. The 6 (six) next-generation reactor design has been determined based on their sustainability, economic, and peaceful application for the world. One of those designs is molten salt reactors (MSRs) which have more attention due to their fuel choice. Most MSRs use the reprocessed fuel from current reactors or the fuel with the breeder blanket that creates more fuel while the reactor operates. This study aims to provide a diagram showing the various steps involved in the preparation of molten salt fuel from spent oxide fuel, which is a mainly utilized form of fuel in current and previous operations. The flowsheet’s first step is the treatment of spent fuel that releases most of the decay heat. The second step is that spent fuel chopping and voloxidation, which meets the requirements of removing gas products and cladding material from used fuel. Afterward, the spent oxide fuel reduces into its metal form chemically or electrochemically in oxide reduction. Then, the molten salt fuel could be fabricated in n one or two more steps from reduced metals: electrorefining, chlorination, or fluorination. Chlorination and fluorination pass through the specific gas components to convert the metal forms into salt. Electrorefining could be applied to arrange the composition of the reduced metal, and this stage is strongly dependent on the MSR designs; it may get eliminated due to its unnecessity. The oxide mechanisms mentioned above were examined under different design conditions to acquire a total reduction of the fuel pellet in calcium salts. The chemical reduction and electroreduction experiments have shown the reduced whole pellet at 850oC with two different salt mixtures. The design impacts of the reduction mechanism were discussed extensively between chemical and electrochemical reductions to identify the benefits and limitations.

Στα πλαίσια της παρούσας διδακτορικής διατριβής έγινε προσπάθεια να μελετηθούν μέσω φασματοσκοπίας Raman τα δομικά και τα δυναμικά χαρακτηριστικά διαφόρων ανόργανων υγρών και γυαλιών σε μεγάλο θερμοκρασιακό εύρος. Αναπτύχθηκαν μέθοδοι, με τις οποίες επιτεύχθηκε η φασματοσκοπική μελέτη υλικών υψηλής καθαρότητας σε θερμοκρασίες έως και 2000oC. Τα φασματοσκοπικά δεδομένα Raman διαφόρων γυαλιών και υγρών περιορίζονται σε θερμοκρασίες έως 1000oC λόγω διαφόρων πειραματικών δυσκολιών που παρουσιάζονται σε μετρήσεις δονητικής φασματοσκοπίας σε υψηλές θερμοκρασίες. Η κυριότερη δυσκολία είναι η πολύ ισχυρή ακτινοβολία μέλανος σώματος, η οποία υπερκαλύπτει το ασθενές σήμα Raman μην επιτρέποντας από κάποιο σημείο και πέρα τη λήψη των φασμάτων. Προκειμένου να ξεπεραστούν οι πειραματικές δυσκολίες αναπτύχθηκε στα πλαίσια της παρούσας διδακτορικής διατριβής ένα σύστημα Raman που συνδυάζει τις «τεχνικές ελλείψεως δοχείου» (“containerless techniques”) και τη χρήση ενός laser υπερύθρου (CO2-laser) ως θερμαντική πηγή, επιτρέποντας τη λήψη φασμάτων για πρώτη φορά σε θερμοκρασίες έως και 2000oC. Οι «τεχνικές ελλείψεως δοχείου» χωρίζονται σε δύο κατηγορίες, την «τεχνική αιώρησης» του δείγματος (“levitation technique”) όπου το υλικό αιωρείται υπό μορφή υγρής σταγόνας σε κατάλληλης γεωμετρίας ακροφύσιο με χρήση προωθητικού αερίου και την «τεχνική αυτοϋποστήριξης» του δείγματος (“self-support technique”) όπου το υγρό υποστηρίζεται από τη στερεά φάση του ίδιου υλικού. Το βασικότερο πλεονεκτήμα του συνδυασμού της φασματοσκοπίας Raman, των «τεχνικών ελλείψεως δοχείου» και της θέρμανσης με χρήση ενός laser υπερύθρου είναι ο σημαντικός περιορισμός της θερμικής εκπομπής, αφού απουσιάζει η ισχυρή θερμική εκπομπή του φούρνου, δίνοντας τη δυνατότητα μελέτης υψηλότηκτων υλικών αποφεύγοντας μολύνσεις, ετερογενή πυρηνοποίηση, αντιδράσεις μεταξύ υλικών και δοχείων σε υψηλές θερμοκρασίες επιτρέποντας την εφαρμογή της επιθυμητής ατμόσφαιρας στο υπό εξέταση υλικό. Μελετήθηκαν με δονητική φασματοσκοπία Raman μη-οξυγονούχες (ZnCl2, ZnBr2, xZnCl2-(1-x)AlCl3) και οξυγονούχες (SiO2, K2Si4O9, xCaO-(1-x)SiO2, xCaO-(1-x)Al2O3) ενώσεις με ενδογενείς πειραματικές δυσκολίες, όπως πολύ υψηλά σημεία τήξης (~2000oC για την περίπτωση των οξειδίων), υψηλή υγροσκοπικότητα, μεγάλες τάσεις ατμών κ.α. ξεπερνώντας τους διαφόρους πειραματικούς περιορισμούς και πραγματοποιήθηκε προσπάθεια σύνδεσης ανάμεσα στο δομικό και δυναμικό χαρακτήρα τους λαμβάνοντας φάσματα Raman σε θερμοκρασιακό εύρος που περιλαμβάνει την κρυσταλλική, υαλώδη, υπέρψυκτη και υγρή κατάσταση. Από τις πληροφορίες που λαμβάνονται για τα τοπικά πολύεδρα συναρμογής σε μικρής κλίμακας τάξη μέσω φασματοσκοπίας Raman γίνεται προσπάθεια να διασαφηνιστεί ο ρόλος των «τροποποιητών του δικτύου» (“network modifiers”) κατά την εισαγωγή τους σε υλικά με πλήρως πολυμερισμένες, τρισδιάστατες, δικτυακές τετραεδρικές δομές (“network formers”). Η δομή σε ενδιάμεσης κλίμακας τάξη (φάσμα Raman χαμηλών συχνοτήτων), η κορυφή Boson, η ημιελαστική κορυφή και χαρακτηριστικά όπως ο εύθραυστος/ισχυρός χαρακτήρας και η μη-εκθετική/εκθετική συμπεριφορά των υπό μελέτη υλικών προσδιορίστηκαν συναρτήσει της θερμοκρασίας και τα αποτελέσματα αναλύονται στα πλαίσια θεωρητικών και φαινομενολογικών μοντέλων που αφορούν την υαλώδη μετάβαση. / e present the Raman spectroscopic results concerning the structure and the dynamics of several inorganic melts and glasses in a broad temperature range. The development of pioneering methods appropriate for high temperature material research and their combination with Raman spectroscopy provided spectroscopic results of high-purity materials at temperatures up to 2000oC. High-temperature Raman data are limited at temperatures below 1000oC due to several experimental difficulties concerning high-temperature vibrational measurements. The main difficulty is the intensive black body radiation, which overwhelms the weak Raman signal and consequently no spectrum can be recorded. In order to overcome the experimental difficulties, we developed a Raman setup, which combines the “containerless techniques” with the use of an infrared laser (CO2-laser) as a heating source permitting the recording of Raman spectra at temperatures up to 2000oC. The “containerless techniques” are divided in two main categories. The “levitation technique”, where the liquid sample is levitated using a nozzle with the appropriate geometry and a supporting gas and the “self-support technique”, where the liquid sample is supported from the solid part of the same material. The main advantage of the Raman spectroscopy-containerlees techniques-laser heating combination is the effective limitation of the black body radiation giving the opportunity to use the desirable atmosphere on the sample and study high-melting materials preventing contamination, heterogeneous nucleation, reactions between materials and containers at high temperatures. We studied several non-oxide (ZnCl2, ZnBr2, xZnCl2-(1-x)AlCl3) and oxide (SiO2, K2Si4O9, xCaO-(1-x)SiO2, xCaO-(1-x)Al2O3) systems with intrinsic experimental difficulties, such as high melting points (~2000oC), hygroscopic nature, high vapor pressures etc. We recorded Raman spectra in extensive temperature range covering the crystalline, the glassy, the supercooled and the molten state in order to elucidate the structure and the involved dynamics of these materials. Information concerning the local coordination polyhedra in short range order have been used for clarifying the role of “network modifiers” inside the fully polymerized threedimensional tetrahedral networks (“network formers”). The structure in medium range order (low-frequency Raman spectrum), the Boson peak, the Quasi-Elastic line and characteristics such as the fragile/strong character and the non-exponential/exponential behavior of these materials have been put under focus and the results are discussed in the framework of the current phenomenological status of the field.

Le procédé de traitement du combustible du réacteur à sels fondus (réacteur de génération IV) est un procédé multi-étape dans lequell’extraction des actinides et des lanthanides utilise la technique d’extraction réductrice. Le développement d’un modèle analytique a montré que la mise en contact du sel combustible LiF-ThF4 avec une phase métallique constituée d'un mélange Bi-Li permet l’extraction sélective et quantitative des actinides dans un premier temps, puis l’extraction quantitative des lanthanides dans un second temps. La maitrise de ce procédé nécessite la connaissance des caractéristiques des phases salines impliquées dans le procédé. Les études des propriétés physico-chimiques des sels fluorures fondus ont permis de développer une technique de mesure de la fluoroacidité dans ces milieux via une mesure potentiométrique. Cette technique a permis d’établir un classement de différents mélanges de fluorures fondus en fonction de leur acidité relative. Par ailleurs, une méthode de détermination de la solvatation de solutés dans ces milieux a également été développée par électrochimie afin d’approfondir la connaissance du sel combustible (en particulier solvatation de ThF4 par les ions F-).L'extraction réductrice met également en jeu une phase métallique liquide. Une technique de préparation de cette phase a été développée par électro-réduction de lithium sur une électrode liquide de bismuth en milieu LiCl-LiF. Cette technique permet un bon contrôle de la fraction molaire de lithium introduite dans le bismuth, paramètre essentiel à l’efficacité de l’extraction.Enfin, afin d'optimiser le procédé général de traitement multi-étapes, des méthodes électrochimiques ont été proposées afin de régénérer les différentes phases liquides (salines et métalliques) mise en jeu lors de l’extraction. / The fuel reprocessing of the molten salt reactor (Gen IV concept) is a multi-steps process in which actinides and lanthanides extraction is performed by a reductive extraction technique. The development of an analytic model has showed that the contact between the liquid fuel LiF-ThF4 and a metallic phase constituted of Bi-Li provide firstly a selective and quantitative extraction of actinides and secondly a quantitative extraction of lanthanides. The control of this process implies the knowledge of saline phase properties. Studies of the physico-chemical properties of fluoride salts lead to develop a technique based on potentiometric measurements to evaluate the fluoroacidity of the salts. An acidity scale was established in order to classify the different fluoride salts considered.Another electrochemical method was also developed in order to determine the solvation properties of solutes in fluoride F- environment (and particularly ThF4 by F-)In reductive extraction technique, a metallic phase is also involved. A method to prepare this phase was developed by electro-reduction of lithium on a bismuth liquid cathode in LiCl-LiF melt. This technique allows to accurately control the molar fraction of lithium introduced into the liquid bismuth, which is a main parameter to obtain an efficient extraction.