Evaluation on double-wall-tube residual stress distribution of sodium-heated steam generator by neutron diffraction and numerical analysis

中性子ビーム回折測定と数値解析によるナトリウム加熱型蒸気発生器の2重伝熱管の残留応力分布評価

木曽原 直之 ; 鈴木 裕士  ; 秋田 貢一; 笠原 直人*

Kisohara, Naoyuki; Suzuki, Hiroshi; Akita, Koichi; Kasahara, Naoto*

A double-wall-tube is the steam generator heat transfer tube of future sodium fast reactors in Japan. An inner tube and an outer tube are contacted to keep the heat transfer performance. The contact stress falls down due to relaxation, and this phenomenon might degrade the heat transfer performance. Although the relaxation can be predicted by numerical analysis, the analysis requires the data of the initial stress distributions. However, unclear initial stress distributions prevent precious relaxation evaluation. To resolve this issue, a neutron diffraction method was employed to reveal the initial stress distributions. The measurement results were also analyzed using a structural computer code to determine the initial stress distributions. Based on the stress distributions, the computer code has predicted the transition of the contact stress, and showed that the inner and outer tubes are contacted with sufficient stresses during the plant life time.