MASS FLOW MEASUREMENT OF URANIUM HEXAFLUORIDE

Lorex Industries, Inc. developed its laminar flow meter (LFM) technology for unattended measurement and monitoring of uranium hexafluoride (UF6) gas mass flow rate at the blending point under the DOE Highly Enriched Uranium (HEU) Transparency Program. The LFM can provide stable and precise measurement of process gas mass flow rate of UF6 in the process lines of HEU, low enriched uranium (LEU) blend stock, and product LEU (P-LEU). The principle of measurement and method of application of the LFM is presented. In viscous flow taxonomy, laminar flow structure is characterized by smooth motion in laminae, or layers, as opposed to turbulent flow characterized by random, three-dimensional motion of fluid particles in addition to the mean motion. Based on the fluid dynamics principle that, when fluids of known thermal-dynamic properties, such as UF6, flow through a restricted region under fully developed laminar flow conditions, their volumetric flow rates can be precisely determined by measuring the pressure drop across the restricted region, or the laminar flow element (LFE). The calculated volumetric flow rates can then be converted to corresponding mass flow rates. The Lorex LFM consists of a measurement sensor module and a flow restrictor LFE. The LFE is designed to maintain fully developed laminar flow conditions inside and thus produce a pressure differential precisely related to the flow rate. The measurement module is comprised of a pair of precision pressure transducers and temperature sensors to measure the absolute pressure drop and temperature of the LFE. The mechanical and thermal-dynamic properties of the UF6 are calculated by a DSP using the real time measurements from the sensors and fluid dynamic equations are solved to determine the mass flow rate across the LFE. A direct weight loss method is used to precisely calibrate the physical properties of the LFE. When set up as a PC-based measurement station, the LFM system provides continuous, unattended accounting of the uranium flows through the blending point.