Na冷却FBR向け超音波流量計の検討

Feasibility Study on Ultrasonic Flow Meter for Sodium-cooled FBR

菱田 正彦; 村上 勤; 此村 守

Hishida, Masahiko; Murakami, Tsutomu; Konomura, Mamoru

実用化戦略調査研究ではナトリウム冷却炉の主配管に磁性体である12Cr鋼を採用しており、電磁流量計が使用できないため、適用可能な主冷却系流量計として超音波流量計(伝播時間差方式)を選定して検討を行っている。本作業では、高温、遠隔交換に適合する送受信子、カプラントの選定及びそれらの超音波伝播特性(主に感度)の確認、大口径配管での計測性(超音波の減衰の影響)の確認を目的に、気中基礎試験及び水基礎試験を実施した。次に、超音波流量計を用いた「1次主冷却系流量低」などの原子炉トリップ信号の作動設定値設定に資するため、大口径配管向け水流動・振動試験装置のエルボ下流に常温用の超音波送受信子を設置してゆらぎデータを取得し、取得した試験データの確認及び整理を行った。

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 ...