Torsional Resonator System for the Simultaneous Measurement of Density and Viscosity at High Temperature

We propose to develop a robust, accurate multi-frequency torsional resonator system for the simultaneous measurement of density and viscosity of molten salts at high temperature. The goal of the project is to develop a stand-alone resonator system that is accurate, precise and robust, and therefore can be used as the basis for a laboratory instrument as well as an on-line process monitoring sensor. Molten salt systems are highly relevant to liquid fuel media and heat transfer fluids in advanced power generation and storage systems. Measurement and monitoring of the density and viscosity of molten salts is a critical yet unmet need for the engineering and operation of advanced nuclear reactors as well as concentrated solar power systems. Viscosity and density sensors for nuclear power applications must also be resistant to ionizing radiation, and our proposed design enables addressing this challenge. The proposed system excites a multi-lump cylindrical resonator at a frequency near the resonance frequency. The change in oscillation amplitude and phase when the resonator is immersed in the medium is measured, and for viscous materials such as molten salts, these parameters can be used to extract the viscosity and density of the surrounding medium at known temperature. Measurements made using a torsional resonator system are advantageous due to the small form factor and absence of motors or moving parts. Thus, the system may be configured for use as an in- line monitoring sensor with the electronics distanced from the sensor, in addition to being used as a sensitive laboratory instrument. Building upon research that was previously used to measure the viscoelastic properties of fluids at low temperature, we will design and demonstrate a minimum viable prototype of a robust, accurate torsional resonator viscosity and density measurement system. A commercially available high temperature viscometer and crucible will be used to control the temperature for the Phase I MVP development, which will allow us to focus efforts on the design and implementation of the resonator and signal processing. The measurement capabilities minimum viable prototype will be validated using standard molten salt systems where reference data are available (e.g., “Solar salt”). Customer needs for laboratory and clean power process monitoring applications will be established and integrated into the design process. We propose a new, customizable, high-precision torsional resonator system for the simultaneous measurement of density and viscosity of materials at high temperature. When used as an in-line molten salt process monitor, the system is directly applicable to advanced clean power generation and storage systems, including concentrated solar power (CSP) and next generation nuclear reactor designs, including molten salt reactors.