Materials Compatibility With Uranium Fluorides at High Temperatures PDF Download

Author: S. Anghaie
Publisher:
ISBN:
Category :
Languages : en
Pages : 162

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Book Description
The objective of an ongoing study being conducted by the Innovative Nuclear Space Power and Propulsion Institute (INSPI) at the University of Florida, is to find suitable materials for use in contact with uranium tetrafluoride from approximately 1200 to 3000 C. This temperature range encompasses both the liquid and gas phase of UF4. In this project ceramic materials were investigated which have been used in the fuel of nuclear reactors. These materials, if compatible with UF4, would be extremely valuable due to their very high melting temperatures, familiar chemistry, and well characterized nuclear properties. Experiments were conducted on thorium dioxide (ThO2) and uranium dioxide (UO2). Samples were exposed to liquid UF4 at 1100 C and to UF4 vaporized at above 1450 C. Exposures took place in a graphite crucible inside an evacuated quartz tube. An inductive heating system was used to heat the crucible and thereby the UF4. Use of the quartz tube allowed direct observation of the ongoing reactions. At the conclusion of each exposure samples of residual gases diluted with nitrogen were run through a gas chromatograph (GC) to determine which gases were released as corrosion products. Subsequent to each experiment remaining samples were weighed then photographed at 2.5x magnification. Power samples of the surface scales and the bulk samples were then prepared for x-ray diffraction analysis (XRD) to determine composition. Data from the GC and XRD were then correlated with equilibrium reaction product data obtained from F*A*C*T to determine the reactions present. Surface analysis of the samples was conducted using Scanning Electron Microscopy (SEM) to examine the scales formed at high magnification and Energy Dispersive X-Ray Spectroscopy (EDS), to qualitatively determine the elements present in various parts of the scales. Experiments with uranium dioxide showed that although UO2 does not react significantly with UF4, it does dissolve in liquid UF4 and apparently suffers from ablation when exposed to UF4 vapor. Thoria did react with UF4 in both the liquid and gas phase exposures, forming a mixture of uranium dioxide and uranium-thorium oxyfluorides.