Abstract. Understanding and extracting systems information is a time consuming, demanding and expensive process. Complicating factors are cross-boundary communication methods and tools. We combine an informal and formal systems engineering method; Lean manufacturing principles and Model Based systems Engineering (MBSE) resulting in Dynamic A3 architecture. Dynamic A3 Architecture is a hierarchy of overviews from super-system to sub-system that the reader can navigate through active links. We applied the method to a lube oil system of a gas turbine package. We found that Dynamic A3 Architecture can ease internal and cross boundary communication, train new employees, facilitate knowledge capture, and share common understanding of the "system of interest". A functional sequence diagram, which is a hybrid of a state and functional diagram, can assist in early validation of process applications.
A fiber-based Raman spectroscopy system was commissioned in an inert atmosphere for in situ analysis of high temperature molten salts. Speciation of samarium chloride was studied in the LiCl-KCl eutectic system at 500 °C. Raman spectra indicated trivalent samarium forms an octahedral SmCl63- complex with two detectable vibration modes. Chemical reduction experiments were conducted to investigate the coordination of divalent samarium in the same eutectic salt. The resulting spectra are reported and discussed in terms of complex formation and behavior of divalent samarium ions. Trivalent samarium was electrochemically reduced in situ and Raman spectra obtained were compared with those resulting from chemical reduction experiments. The spectra suggest divalent samarium ions form in LiCl-KCl only temporarily and spontaneously disproportionate into a mixture of trivalent samarium ions and metallic samarium.
Molten salt systems are under consideration for both energy generation and used fuel processing as part of the nuclear fuel cycle. Generation IV nuclear reactor designs use molten salts as both coolants and fuel media. Advanced reprocessing technologies, such as the pyrochemical reprocessing of used nuclear fuel, rely on molten chloride melts as the electrolyte during electrochemical processing of used nuclear fuel. Before any of these technologies can reach the industrial scale, techniques for the monitoring of nuclear material in a nondestructive and in situ manner must be further developed for molten salt systems. Real-time monitoring of nuclear material allows for process optimization, along with addressing nuclear security concerns associated with the diversion of actinide materials. In this study, we explore the use of Raman spectroscopy, employed using a fiber-coupled system, as a method for the in situ analysis of molten salt. We present the development of an automated, in situ Raman system for analysis of electroactive species in molten LiCl-KCl. The Raman modes of lanthanide chlorides, serving as actinide surrogates, were investigated in LiCl-KCl eutectic at 500°C and compared with the available literature. This work was performed under the auspices of the US Department of Energy (DOE) under contracts DE-NE0008262, DE-NE0008236 and DE-NE0008572, and the US Nuclear Regulatory Commission (NRC) under contract NRC-HQ-13-G-38-0027. Dr. Kenny Osborne serves as the program manager for the DOE awards and Ms. Nancy Hebron-Isreal serves as the grants program officer for the NRC award.
In order to maximize uranium resources and minimize the need to store radioactive material in geologic repositories, it is necessary to reprocess used nuclear fuel (UNF) to recycle the fissile material and transuranic isotopes that remain. The pyroprocessing operation developed by Argonne National Laboratory as part of the integral fast reactor project was designed to accomplish this goal while minimizing the risk of proliferation (1). Inclusion of oxide based UNF from the current light water reactor fleet into the metallic fuel based fast reactor cycle will require electrolytic oxide reduction in a LiCl-Li2O electrolyte (2). As a side reaction during the electroreduction of U, Li is codeposited on the cathode surface and subsequently dissolves, forming a ternary LiCl-Li2O-Li electrolyte (3, 4). The presence of metallic Li in the electrolyte negates the possibility of using the reference electrodes typically used for molten salt electrochemistry. The Li-Bi couple has been used as a reference electrode previously but has not yet been well characterized (5, 6). This work investigates the stability of the Li-Bi reference couple in varying solution chemistries typical of those found during electrolytic reduction of UO2. Acknowledgements: This work was performed under the auspices of the Department of Energy (DOE) under contracts DE-NE0008262 and DE-NE0008236, and the US Nuclear Regulatory Commission (NRC) under contracts NRCHQ-11-G-38-0039, NRC-HQ-10-G-38-0027, NRC-HQ-13-G-38-0027. W.P. and A.M acknowledge the Fellowship Award from the USNRC. Dr. Kenny Osborne serves as the program manager for the DOE award and Ms. Nancy Hebron-Isreal serves as the grants program officer for the NRC awards. References: 1. J. J. Laidler, J. E. Battles, W. E. Miller, J. P. Ackerman, E. L. Carls, Development of Pyroprocessing Technology. Progress in Nuclear Energy 31, 131-140 (1997). 2. S. D. Herrmann, S. X. Li, M. F. Simpson, S. Phongikaroon, Electrolytic Reduction of Spent Nuclear Oxide Fuel as Part of an Integral Process to Separate and Recover Actinides from Fission Products. Separation Science and Technology 41, 1965-1983 (2006). 3. T. Takenaka, K. Shigeta, H. Masuhama, K. Kubota, Influence of Some Factors upon Electrodeposition of Liquid Li and Mg. ECS Transactions 49, 441-448 (2009). 4. A. S. Dworkin, H. R. Bronstein, M. A. Bredig, Miscibility of Metals with Salts. VI. Lithium-Lithium Halide Systems. The Journal of Physical Chemistry 66, 572-573 (1962). 5. M. Iizuka, Y. Sakamura, T. Inoue, Electrochemical reduction of (U-40Pu-5Np)O2 in molten LiCl electrolyte. Journal of Nuclear Materials 359, 102-113 (2006). 6. X. Ning et al., Self-healing Li-Bi liquid metal battery for grid-scale energy storage. Journal of Power Sciences 275, 370-376 (2015).
Cyclic voltammetry (CV) was used to investigate the electrochemical behavior of SmCl3 when it is solvated in the molten LiCl-KCl eutectic at 773 K. An experimental method obtained from the literature was adjusted to produce repeatable current responses attributed to the Sm3+/Sm2+ reaction couple and to determine working electrode surface area. The effect of solvating SmCl3 at high concentration was investigated as it relates to electrochemical reversibility and diffusion coefficient analysis. An electrochemically reversible region was identified using correlations between the current response and the scan rate along with peak current ratio measurements. In these, the reversibility was unaffected by increasing concentration. The correlation between current response and concentration was less linear than expected, suggesting the effects of additional modes of diffusion, solution resistance, and charge transfer kinetics may be contributing more at high concentrations. The measurement errors associated with peak current response, working electrode surface area, and melt temperature were used to estimate the associated uncertainties of the reported diffusion coefficients of Sm3+ in the molten LiCl-KCl eutectic. These diffusion coefficient values were found to be relatively consistent with values for Sm3+ reported in the literature for lower concentrations.
The mass transport behavior of samarium was investigated in molten eutectic LiCl-KCl in order to develop real-time concentration monitoring capabilities for the pyrochemical reprocessing of used nuclear fuel. Pyrochemical reprocessing relies on electrolysis in molten LiCl-KCl to recycle fissile material from used nuclear fuel. Without the capabilities to monitor concentrations of various actinides and fission products, pyrochemical reprocessing cannot be commercialized due to strict material accountability requirements set by the International Atomic Energy Agency (IAEA) [1]. Therefore, physical electrochemical properties of these species in molten salts is extremely important. Cyclic voltammetry was utilized to investigate electrochemical behavior of samarium in LiCl-KCl. By establishing valid relationships between these parameters and the peak current, the diffusion coefficient of samarium in our system can be reported with confidence [2]. Experiments were conducted in a high-purity argon atmosphere glove box using a three-electrode cell contained in an alumina crucible inside a resistive furnace. A high-resolution translation stage equipped with ceramic electrode mounts was used to accurately control electrode positions inside the melt. Tungsten was used as the counter and working electrodes, and a silver wire was used as a quasi-reference (Ag|AgCl2). The variation in peak current that resulted from changing the concentration, scan rate and electrode surface area will be reported, along with calculated diffusion coefficient values for samarium in molten LiCl-KCl at 500°C. The effects of using molybdenum as a working electrode will also be reported and compared to results obtained using tungsten. A comparison between reported diffusion coefficient values obtained by separate research organizations and results obtained in these studies will also be discussed. Acknowledgements: This work was performed under the auspices of the Department of Energy (DOE) under contracts DE-NE0008262 and DE-NE0008236 as well as the US Nuclear Regulatory Commission (USNRC) under contracts NRCHQ-11-G-38-0039. Dr. Kenny Osborne serves as the program manager for the DOE award and Ms. Nancy Hebron-Isreal serves as the grants program officer for the NRC awards. References 1. Iizuka, M., et al., Application of normal pulse voltammetry to on-line monitoring of actinide concentrations in molten salt electrolyte. Journal of Nuclear Materials, 2001. 297(1): p. 43-51. 2. Tylka, M.M., et al., Method Development for Quantitative Analysis of Actinides in Molten Salts. Journal of The Electrochemical Society, 2015. 162(9): p. H625-H633.
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