蒸氣發生器 傳熱管 外面 軸方向 균열의 定量的 平價에 관한 硏究

다국어 초록 (Multilingual Abstract)

Steam Generator (SG) tube, as a barrier isolating primary to the secondary coolant system of Nuclear Power Plants (NPP), shell maintain the structural integrity for the public safety and its efficient power generation capacity. And SG tubes bearing defects shell be timely detected and taken repair measures if needed.
For the accomplishment of these objectives, SG tubes have been periodically examined by Eddy Current Testing(ECT) on the basis of administrative notices and intensified SG Management Program (SGMP). Stress Corrosion Cracking(SCC) on the SG tubes is not easily detected and even missed since it has lower signal amplitude and other disturbing factors against its detection. However once SCC is developed, that can cause detrimental affects to the SG tubes due to its rapid propagation rate. Accordingly SCC is categorized as prime damage mechanism challenging the soundness of the SG tubes.
In this study, reproduced Electrical Discharge Machining(EDM) notch specimens are examined for the detectability and quantitative characterization of the axial Out Diameter SCC(ODSCC) by +Point MRPC probe, containing pancake, +Point and shielded pancake coils apart in a single plane around the circumference.

Through this study, the following is a summary of the results.

1. The defect depth 25% where the defect length is below 4mm ODSCC can not detect both +Point and Pancake coil. Meanwhile the defect of above depth 25% 6mm can detect and sizing. Also, Expansion specimen was more difficult than Non-expansion specimen caused by geometry noise signal.

2. The defect depth 50% or more detect possible from +Point coil and Pancake coil irrespective crack length. +Point coil is good detection ability but is evaluated short at the long length or deep crack.

3. The start point Look-ahead and Look-behind can calculate and confirmed a past theory.

4. The results of profile signal amplitude appear three type. This research presented each type of measurement method about axial crack length.

5. The form which has a minimum amplitude value in the middle of ECT signal pulse profiles measures the length between the right highest point and left highest point.

6. The form which has a maximum amplitude value in the middle of ECT signal pulse profiles measures the length including between rise and drop transition point. (this study names landing and take off point)

7. The form which has a saturated amplitude value of ECT signal pulse profiles measures a saturation point in the both sides.

8. The results of this study are assumed to be applicable for providing key information of engineering evaluation of SCC and improvement of confidence level of ECT on SG tubes.

목차 (Table of Contents)

• 제 1장 서론 1
• 1.1 연구 배경 1
• 1.2 연구 동향 3
• 1.2.1 국외 연구 동향 4
• 1.2.2 국내 연구 동향 5
• 1.3 연구 목적 6
• 제 2장 이론적 배경 7
• 2.1 와전류검사 7
• 2.1.1 와전류검사 이론 7
• 2.1.2 신호분석 방법 16
• 2.1.3 증기발생기 와전류검사 방법 20
• 2.2 증기발생기 개요 25
• 2.2.1 증기발생기 구조 25
• 2.2.2 증기발생기 전열관 재질 27
• 2.3 응력부식균열 31
• 2.3.1 응력부식균열 개요 31
• 2.2.2 증기발생기 전열관의 응력부식균열 32
• 제 3장 증기발생기 건전성평가와 균열크기 측정 34
• 3.1 성능기준 건전성평가 34
• 3.1.1 구조한계(SL) 36
• 3.1.2 상태감시평가 구조한계(CM) 36
• 3.1.3 운전평가 구조한계(OA) 38
• 3.2 균열크기 측정 41
• 제 4장 실험 재료 및 방법 45
• 4.1 시편 설계 및 제작 45
• 4.2 실험 장치 48
• 4.3 실험 방법 50
• 4.3.1 신호평가 변수 설정 50
• 4.3.2 실험 방법 50
• 제 5장 실험결과 및 고찰 53
• 5.1 EPRI 방전가공 Notch 보정시험편 분석 53
• 5.2 축방향 균열결함의 검출 57
• 5.3 축방향 균열결함의 위상각 측정 60
• 5.3.1 확관부 균열시편 신호 위상각 측정 60
• 5.3.2 비확관부 균열시편 신호 위상각 측정 62
• 5.4 축방향 균열결함의 진폭측정 65
• 5.4.1 확관부 균열시편 신호진폭 측정 65
• 5.4.2 비확관부 균열시편 신호진폭 측정 71
• 5.4.3 100% 관통결함 시편의 포화 진폭 74
• 5.3.4 결함의 길이와 신호진폭 75
• 5.5 결함 깊이별 결과 고찰 77
• 5.5.1 검출능(Detection Ability) 77
• 5.5.2 관두께 50% 및 75% 깊이 결함 83
• 5.5.3 관두께 100% 관통결함 (길이 8mm 이하) 87
• 5.5.4 관두께 100% 관통결함 (길이 10mm 이상) 90
• 5.6 미리보기(Look-Ahead) 및 뒤보기(Look-Behind) 신호 95
• 5.7 진폭 변화에 의한 결함의 길이 측정 결과 고찰 97
• 5.7.1 관두께 50% 및 75% 깊이 결함 97
• 5.7.2 관두께 100% 관통결함 98
• 5.7.3 결함 길이 측정 98
• 제 6장 결론 104
• References 108
• Abstract 114