昭和62年度高速増殖大型炉の設計主要目に関する研究; 漏洩口想定の適正化

Key technology design study of large FBR; Study of crack opening area for LBB

渡士 克己; 吉田 博治*; 古橋 一郎*

not registered; not registered; Furuhashi, Ichiro*

本研究は、安全設計上想定する漏洩口面積を適正化する一手段であるクリープ疲労き裂進展挙動を測定する手法の高度化を非線形破壊力学に基づいて実施し、ホットレグ配管に適用することを目的とする。前年度開発したCANISコードにて、公称応力+-1.5Smの膜、曲げおよびこれらの組合せ応力を受ける種々の表面半楕円き裂を有する平板の疲労J積分およびクリープJ積分のデータを作成し、これを用いてエルボの最大応力発生場所のき裂進展計算を行った。結果:(1)板厚20.6mm、500におけるき裂進展データベースを作成した。(2)初期想定欠陥(長さ41.2mm、深さ4.12mm)の進展に伴う形状変化は疲労でもクリープ疲労でも殆ど同一である。(3)貫通繰返し数は疲労で6250(膜応力)30,520(曲げ応力)サイクル、クリープ疲労で3031534(同上)サイクルである。(4)開口面積は内圧(2atg)に対するものが1.5Sm相当の曲げモーメントに対するものより大きく、約0.5mm2である。(5)最大漏洩率は約23-/hrである。安定き裂進展のシミュレーション技術の高度化はほぼ終了した。今後曲率の影響調査及び実験による検証が必要である。

The present study includes the analytical work for of the stable crack growth of the finite plate with semi-elliptical surface defect by creep-fatigue loadings, and of the crack opening area for presumed leakage of cloolant to be considered in safety assessment. The objective of this study is to develop the basic inelastic fracture mechanics to the level in which the integrity of basic components, plate, vessel, piping, and so on, with crack would be able to be assessed analytically. CANIS code developed last year was used to analize the J integral for fatigue crack growth and J' integral for creep crack growth of SUS 304 plates with various shapes of semi-elliptical surface cracks at 500 C, then those distributions were arranged from the view point of crack growth assessment. An appricable range of these data is 1.5 Sm of fatigue cycle and hold time of 108,000 hr creep. 0nly secondary stress including membrane, bending and combination of these stresses were considered in the data base. Evaluation of elbow with 42 diameter and 20.6mm thickness considered in the design of large loop type FBR were achieved based on the data base. Then calculated through wall crack lengths were applied to the calculation of opening areas of 42 elbow subjected of internal pressure of 2 atg and in plane bending moment corresponding to stress level of 1.5Sm. The results are (1)A numbers of cycles at penetration are 6,250 for membrane stress and 30,520 for bending stress in the case of fatigue, and 303 for memberane and 1,534 for bending in the case of creep-fatigue. (2)opening area against internal pressure is larger than that against bending moment, and is about 0.5mm. (3)maximum leak rate from the opening area is about 23 /hr. The level up of analytical method for stable crack growth was almost accomplished. In the near future, the experimental study would be needed for validation of this method.