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大口径・高流速配管の流動励起振動試験

Flow-induced Vibration Tests of Large Diameter and High Velocity Piping

藤井 正; 近澤 佳隆  ; 此村 守; 山口 彰

Fujii, Tadashi; Chikazawa, Yoshitaka; Konomura, Mamoru; Yamaguchi, Akira

実用化戦略調査研究で検討しているナトリウム冷却炉では,建設コスト削減の観点から,冷却系ループ数を2ループに削減している。ループ数削減に伴い,従来設計と比較して,1次冷却系配管の口径が大型化し,かつ管内流速も増加する。このような大口径・高流速の配管系においては,エルボ(曲がり)部近傍での流動状況や,流体の乱れに起因する振動現象に関する知見が不足していた。そこで,大型炉の1次冷却系ホットレグ配管を1/3縮尺で模擬した水試験装置を用いて,エルボを含む配管系の流動励起振動特性を把握する試験を開始した。これまでに,アクリル製試験体を用いて流れの可視化を行うとともに,管内の流速分布等の流動特性を把握した。また,配管への振動源となる流体の圧力変動に関しては,エルボ部の剥離による乱れの程度に応じて配管内の圧力変動が4領域に区分できることを確認した。

The conceptual design study of sodium cooled reactor is in progress in the Feasibility Study on Commercialized Fast Reactor Cycle Systems. The cooling system is composed of two loops in order to reduce plant construction cost. With loop number reduction, large diameter pipings are adopted and mean velocity in the piping also increases in comparison with former design. As for these piping systems, knowledge concerning hydraulic behaviors around the elbow and vibration phenomenon which is caused by the turbulence of fluid was insufficient. Therefore, flow-induced vibration tests have been started using water test facility, which simulates a hot leg piping of primary cooling system of large-scale reactor at the 1/3 reduced scale. Until now, flow visualization was conducted using acryl model and hydraulic behaviors such as velocity distributions in the piping were clarified. Further, as for the pressure fluctuations of the fluid which become vibration sources to the piping, it confirmed that the pressure fluctuations in the piping could be divided into four sections according to the degree of the turbulence caused at flow separation in the elbow.

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