Study on UF6 Gas Flow by Using Orifice and Needle Valve Under Medium Vacuum Condition and Investigation of Effective Parameters on It

In nuclear facility, the enrichment operation usually is carreid out under the medium and high vacuum conditions. Measurement of UF6 gas flow rate in the form of feed or product and tail is one of the principal parameters in operation and production. In this facility, several orifices were used to measure UF6 gas flow rate in the range of 10-80 gr/hr. Due to low pressure and mass flow range, measurement of flow rate should be made accurately. In this research, the method of flow rate measurement in tubes by using orifice and needle valve, and also effective parameters on it, has been studied. For the study of the gas flow rates, several orifices with different diameters were used. We observed that for a defined orifice diameter, an increase in the input pressure causes an increase in the flow rate and at a constant flow rate an increase in the input pressure causes a decrease in the orifice diameter. As the pressure difference between the upside and downside of the orifice increases, the flow rate will rise up to a certain limit. Since in all experiments of the needle valve, the ratio of outlet to the inlet pressure is less than 0.5926, the linearity of the mass flow change versus the inlet pressure at a constant cross sectional area shown to be consistant with the chock current equation. Also, the investigation of mass flow rates, when the valve is open, indicates that variations of the mass flow rate will increase against the inlet pressure and the pressure difference, intensively.