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Molten salt reactors. --- Thorium.

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Thermodynamic equilibrium --- Molten salt reactors

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Molten salt reactors. --- Sodium cooled reactors.

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The investigation of the interfacial phase transitions in fluid systems with short-range intermetallic interactions are of great interest. The phenomena were studied in two systems exhibiting a liquid-liquid miscibility gap: at the fluid/wall interface in fluid KxKCl1-x and at the fluid/vacuum interface of the Ga1 xBix alloys. To characterize the interfacial changes of the ultra thin films (composition, thickness and their evolution with time) the spectroscopic ellipsometry was performed over a wide spectral range. Whereas in the experiments on KxKCl1-x an existing ellipsometer could be used, a completely new UHV-apparatus including the in-situ phase modulation ellipsometer had to be developed for Ga1 xBix alloys. For the KxKCl1-x system new results on complete wetting at solid-liquid coexistence as well as in the homogenous liquid phase (prewetting) are presented. The spectra show the typical F center absorption which indicates that the film is a salt-rich phase. The thickness strongly increases approaching the monotectic from 30 to 440 nm, which is in agreement with the tetra point wetting scenario. For this interpretation a quantitative description of the excess Gibbs energy has been developed. For the Ga1 xBix system the results on complete wetting, surface freezing and oscillatory interfacial instabilities are presented. The high-precision spectra have been recorded approaching the liquid-liquid miscibility. These spectra have been modeled using a Ga-Bi effective medium approximation for the substrate covered by a film of liquid Bi. The measurements give evidence of tetra point wetting in the Ga-Bi system. First ellipsometric study of the surface freezing in Ga-Bi has been performed. Within the miscibility gap a very interesting effect of surface and bulk oscillatory instability was observed. The details of this process at present are not well understood, but a qualitative description is given.

molten salt --- surface phase transition --- spectroscopic ellipsometry --- Ga-Bi alloys

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This master thesis aims to improve a numerical tool that simulates the heat transfers taking place on the Dynacor molten salt test loop built by John Cockerill. The purpose of this loop is to reproduce the conditions met in the receiver of a concentrated solar power plant using molten salt in order to analyze the corrosive effect of the salt in these conditions. We also wanted to establish test plans to experimentally assess parameters of the test section that cannot directly be measured and to analyze the data retrieved from the first circulations performed on the loop.
The thesis therefore contains an introduction developing the context in which the Dynacor loop was built and a state of the art on molten salt loops. The Dynacor loop is then presented in greater detail so the reader can understand the computations implemented in the heat balance assessment tool. This latter is described in a chapter including a description of the initial tool which was coded in Visual Basic for Applications followed by the development of the improved tool coded in Python. After that, a chapter is dedicated to the description of test plans to evaluate the coating resistivity and the heat transfer coefficient at the test section. A procedure to determine the uncertainty associated to these computed parameters is also given. The data from a first circulation on the test loop are then analyzed and compared to the python tool results in order to calibrate this latter before concluding the master thesis.
The developed Python tool behaves as expected qualitatively and could be further calibrated by performing more circulations on the Dynacor loop. A user friendly interface could also be added to this tool. Concerning the assessment of the parameters at the test section, no conclusion can be given for now since no test has already been performed.

molten salt --- corrosion test loop --- simulation --- Ingénierie, informatique & technologie > Energie