Acoustic Techniques for UF6 Density and Mass Flow Measurements

A key enabling capability for enrichment plant safeguards being considered by the International Atomic Energy Agency (IAEA) is high-accuracy, non-invasive, unattended measurement of UF6 gas density and mass flow rate. Acoustic techniques are currently used to non-invasively monitor gas flow in industrial applications; however, the operating pressures at gaseous centrifuge enrichment plants (GCEPs) are roughly two orders of magnitude below the capabilities of commercial instrumentation. Pacific Northwest National Laboratory is refining acoustic techniques for estimating density and mass flow rate of UF6 gas in scenarios typical of GCEPs, with the goal of achieving 1% measurement uncertainty. Proof-of-concept laboratory measurements using a surrogate gas for UF6 have demonstrated signature sensitivity to gas density at pressures equivalent to 10-50 Torr of UF6, typical pressures for GCEP unit header pipes. This sensitivity was clearly observable above background acoustic interference. Current efforts involve developing a test bed for conducting acoustic measurements on flowing surrogate gas, air, and SF6, at representative flow rates and pressures to ascertain the viability of conducting gas flow measurements under these conditions. Density and flow measurements will be conducted to support the evaluation. If successful, the approach could enable an unattended, non-invasive approach to measure UF6 mass flow and density in unit header pipes of GCEPs.