原子炉容器内液面揺動防止方策の解析的検討,1; 流動抑制用リングプレートの検討

Investigation of prevention systems for free surface oscillations using numerical methods,1; Investigation on the effect of ring plates

松本 英一*; 村松 壽晴

not registered; not registered

定格負荷運転時の原子炉プレナム液面近傍では,炉容器壁から炉上部機構壁へ向かう液面流速が1m/sec程度となり,炉心上部機構壁近傍での下降流により冷却材中へのカバーガス巻き込みの発生が懸念される。このため,液面近傍の流速低減化方策の一つとしてリングプレート設備及び開放型炉心上部機構設備の有効性について検討した。検討には,自由液面モデルを組込んだAQUA‐VOFコードを開発し解析した。この結果,リングプレートを設置することにより,自由液面液位差及び液面勾配の最大値が50%以下に低減できることが明らかとなった。

In the case of thermohydraulic analysis including free surface, it is need to use a appropriate modeling for free surface motion. Therefore, the AQUA - VOF code was developed for the analysis of thermohydraulic phenomena with the free surface motions. In this study, analysis with the AQUA - VOF code was carried out for the upper plenum in reactor vessel to investigate efficiency of ring plates which are to eliminate the free surface oscillations. Through the analysis it is obtained that ring plates have a sufficiently high potential to eliminate the free surface oscillations due to the dispersion of axial momentum along the reactor vessel to both radial and circumferential directions. In the caluculations with the ring plates, maximum difference of the free surface level and maximum gradient of the free surface was reduced to about 50 percent compared to that for the case without the ring plates.