Feasibility Study on Ultrasonic Flow Meter for Sodium-cooled FBR

Hishida, Masahiko; Murakami, Tsutomu; Konomura, Mamoru

In the "Feasibility Study on Commercialized Fast Reactor Cycle Systems", 12-chromium steel which has the magnetic property is adopted to the primary and secondary system piping of sodium-cooled reactor. Hence the studies on ultrasonic flow-meter for primary and secondary cooling system have been conducted. In this study, elementary tests in the air and in water were performed in order to select ultrasonic transducer and couplant which suit high temperature and exchange by remote control operation and to verify the ultrasonic propagation characteristic of the transducer and couplant (mainly sensitivity) and the measurement performance in large-scale pipe (mainly influence of attenuation of ultrasonic). Furthermore, for conducing to the setup of set points like "primary flow rate low" reactor trip signal detected by the ultrasonic flow-meter, the ultrasonic transducers for normal temperature were attached at the downstream in the elbow of the test facility which has been used for the water fluid and oscillation test for large diameter piping and fluctuation data from the ultrasonic transducers were acquired. The results are as follows: (1)As a result of investigating high temperature couplant, gold was selected since it was the most stable on all the temperature range containing high temperature among solid metal couplants and force required for the stability of the characteristic is expected to be small. (2)Signal level of ultrasonic transducer with the surface pressure of 1.4510Pa (the force of 5kN) exceeds 50% of that with the couplant for normal temperature. In the transient temperature test, signal level of ultrasonic transducer became larger with a temperature rise and the fall of the signal level considered to originate in the fall of force was not appear. (3)S/N ratio of the signal exceeded 23dB in the elementaly test in water, and it was expected more than 18dB even if more attenuation of ultrasonic by the propagation longer distance ...