Abstract: The methodology of high-precision measurement of main feedwater flow is proposed based on Hualong No.1 and other nuclear power plants(NPP) to achieve measurement uncertainty recapture power uprates(MUR).The components of uncertainty measured by ultrasonic flowmeter such as calibration coefficient and medium density are quantified.Under the conditions with defining the structure and measurement principle of ultrasonic flowmeter and the complex operating conditions of high pressure and high temperature(HPHT),the uncertainty evaluation methodology of channel geometric factor and pipe cross-sectional area has been given respectively.By analyzing the influence of the operating conditions on the flow measurement,the uncertainty introduced by the flow field velocity has been evaluated.The analysis results indicate that the metrological traceability method which based on the combination of several uncertainty evaluation methods is feasible.

Key words: Ultrasonic flowmeter, Main feedwater, Uncertainty, Traceability methodology, Metrology