3D RFEC simulations for the in-service inspection of steam generator tubes in fast breeder reactors

高速炉の蒸気発生器伝熱管における供用期間中検査のための3次元リモートフィールド渦電流探傷解析

Mihalache, O. ; 山口 智彦 ; 上田 雅司 ; 宮原 信哉  

Mihalache, O.; Yamaguchi, Toshihiko; Ueda, Masashi; Miyahara, Shinya

高速増殖原型炉「もんじゅ」の蒸気発生器伝熱管は、140本の伝熱管がヘリカル形状に密接に配置され、蒸気発生器の中に格納されている。伝熱管の検査には、渦電流探傷試験(ECT)を適用する。このように伝熱管が密集した環境では、渦電流が隣の管にも流れることから検出感度に影響を与えることが懸念される。著者らは、複数の伝熱管が存在した場合や伝熱管サポート部での影響について3次元の電磁場解析で定量的に明らかにした。

In FBR, one of the techniques used in the ISI of magnetic steam generator (SG) tubes is the remote field eddy current technique (RF-ECT). The SG tubes, made of 2.25Cr-1Mo alloy, are very long, including several parts with helical, bent and straight shape. The longer parts of these tubes are fixed in a helical shape-structure using multiple support plates (SP) which are also ferromagnetic. The complicated shape of the SP and multiple connections of several tubes to the SP can be quantitatively analyzed only by a 3-dimensional analysis, in order to evaluate the influences in the ECT signal due to the close proximity of the SG tubes. Also, the tube curvature and additionally the presence of sodium on the outer tube surface induces supplementary effects. The paper presents 3D finite element simulations of the SG inspection using RF-ECT. It is evaluated the influences of the SG tubes curvature on the eddy current sensor signal.