Abstract

Molten salts are of high interest for use in nuclear reactors, though their thermophysical properties are notoriously hard to measure due to the extreme conditions created by them. Significant gaps remain in thermal conductivity and heat capacity data, which this work seeks to fill by improving the Needle Probe-a modified transient hot wire probe originally used by Merritt et al to measure the thermal conductivity of FLiNaK- measuring two new salts, and exploring new materials for use with molten salts. Improvements made to the Needle Probe include automation to reduce human error, more accurate heat generation modeling, a more thorough uncertainty quantification, and the added capability to concurrently measure heat capacity which will be applied to future studies. New thermal conductivity measurements have been taken for eutectic NaCl-KCl (51-49 mol%) between 660-736°C, (0.399 and 0.5126 [W/(m*K)], 17.5-22.45% uncertainty), and of eutectic LiCl-NaCl (72-28 mol%) between 567-737°C (0.437 and 0.668 [W/(m*K)], 16.2-20.9% uncertainty). Measurements for NaCl-KCl agree well with existing models, which gives further confidence for our novel measurements of LiCl-NaCl. As the current Needle Probe design is limited to a max temperature of 750°C and cannot be used for all salts, potential redesigns using different materials are explored to help overcome these limitations. Materials would need high thermal conductivity, high electrical resistivity, chemical stability in molten salts, and be reasonably manufacturable. This work explores other technical ceramics that meet these requirements and has found that aluminum nitride offers the best combination of material properties. SEM analysis was used to verify its chemical stability in molten salts. This work has reached new milestones in the thermal characterization of molten salts, having provided new thermal conductivity measurements for NaCl-KCl and LiCl-NaCl, and has laid the groundwork for future studies by identifying new materials suitable for use with molten salts.

Degree

College and Department

Ira A. Fulton College of Engineering; Mechanical Engineering

Rights

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