Experimental study on gas entrainment at free surface in reactor vessel for a compact sodium cooled fast reactor

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上出 英樹 ; 小林 順 ; 飛田 昭; 林 謙二; 木村 暢之

Kamide, Hideki; Kobayashi, Jun; Tobita, Akira; Hayashi, Kenji; Kimura, Nobuyuki

コンパクト化した原子炉容器内の自由液面でのガス巻き込み現象について、1/10スケールの全周炉容器モデルと1/1.8スケールセクター部分モデルを用いて実験研究を行った。その結果、ガス巻き込みが設計している体系で生じる可能性が少ないことを明らかにした。また、ホットレグ配管の周りで下降流、旋回流れが見られ、この領域でのガス巻き込みの発生に留意する必要があることを明らかにした。

In order to realize a fast reactor with advanced economical efficiency, various typed fast reactors have been studied for a several years. As for sodium cooled fast reactor, adoption of a simplified and compact reactor vessel (R/V) with free surface is investigated. The compact R/V may cause gas entrainment phenomena due to increase of velocity in the R/V. Two types of water experiments have been performed in order to prevent the gas entrainment. One is an 1/10th scaled upper plenum model of the R/V. This model is used to optimize flow in whole upper plenum, and the other one is an 1/1.8th scaled partial model of the upper plenum. The partial model experiment evaluates a scale effect on the gas entrainment and mechanism of phenomena. The boundary condition of the partial model is extrapolated from the measured results of the 1/10th scaled full sector model, where flow velocity toward the free surface was reduced by dipped plates. No gas entrainment was observed in the 1/1.8th partial model under the velocity similarity condition as in the designed reactor. Every vortex did not evolve into the gas entrainment though some vortices were found at free surface and in submerged region. It is possible to suppress gas entrainment in this design of the compact R/V.