3次元有限要素法による沸騰水型原子炉のフルスケール地震応答解析

摘要

日本のような地震多発国において，原子力発電所を設置し安全に稼働させる上で，耐震設計は大変重要である。特にその重要性が再認識されたのが，2007年7月16日に発生したマグニチュード6.8の新潟県中越沖地震であった。この地震によって，震源から約16km地点にある東京電力柏崎刈羽原子力発電所では敷地内で震度7に相当する揺れが記録され,地震による被害が発生した。地震発生時，全7基のうち，3，4，7号隆の3基の原子炉は100％出力で運転中であった。この地震では，観測された最大応答加速度が設計基準地震動から予測された最大応答加速度を超え，また，観測記録の応答スペクトルが，すべての振動数範囲で設計基準地震動の応答スペクトルを大幅に上回った。%In this paper, we present the three-dimensional finite element seismic response analysis of the full-scale boiling water reactor BWR5 at the Kashiwazaki-Kariwa Nuclear Power Plant subjected to the Niigata-ken Chuetsu-Oki (NCO) earthquake that occurred on 16th July 2007. During the earthquake, the automatic shutdown of the reactors was performed successfully. Although the monitored seismic acceleration significantly exceeded the design level, it was found through in-depth investigation that there was no significant damage of the reactor cores or other important systems, structures and components (SSCs). In the seismic design commonly used in Japan, a lumped mass model is employed to evaluate the seismic response of SSCs. Although the lumped mass model has worked well so far for a seismic proof design, more precise methods should be developed to understand response behaviors visually. In the present study, we propose the three-dimensional finite element seismic response analysis of the full-scale and precise BWR model in order to directly visualize the dynamic behaviors of this model. Through the comparison of the analysis results, we discuss the characteristics of both models. The stress values were also found to be generally under the design value.