원자로 CRDM 관통노즐 J-Groove 용접부 잔류응력 예측을 위한 유한요소 변수 민감도 해석

국문 초록 (Abstract)

최근 원자로 압력용기 상부헤드 관통노즐 J-groove 용접부 주변에서 균열로 인한 냉각수 누출사고가 발행하고 있다. 이러한 사고의 원인은 용접에 의한 인장잔류응력, 농축된 붕산수 및 응력부식에 민감한 재료로 인한 일차수응력부식균열(PWSCC : primary water stress corrosion cracking)인 것으로 판명되었다. PWSCC 평가는 원자로 건전성 평가의 주요 관심사로서 용접에 의해 발생되는 잔류응력을 정확하게 예측함으로써 가능하다. 본 연구에서는 유한요소해석을 이용하여 국내 원자로의 일반적인 J-groove 용접부의 해석절차를 소개하고, 용접해석 관련 변수의 민감도 해석을 통해 잔류응력 예측기법을 제시하고자 한다. 이를 위해 2차원 및 3차원 요한요소해석 방법을 바탕으로 변수 민감도 해석을 수행하였으며, 기존 연구결과와 비교를 통해 해석절차 및 방법의 유용성을 검정하였다.

다국어 초록 (Multilingual Abstract)

In nuclear power plants, the reactor pressure vessel (RPV) upper head control rod drive mechanism (CRDM) penetration nozzles are fabricated using J-groove weld geometry. Recently, the incidences of cracking in Alloy 600 CRDM nozzles and their associated welds have increased significantly. The cracking mechanism has been attributed to primary water stress corrosion cracking (PWSCC), and it has been shown to be driven by welding residual stresses and operational stresses in the weld region. The weld-induced residual stress is the main factor contributing to crack growth. Therefore, an exact estimation of the residual stress is important for ensuring reliable operation. This study presents the residual stress computation performed for an RPV CRDM penetration nozzle in Korea. Based on two and three dimensional finite element analyses, the effect of welding variables on the residual stress variation is estimated for sensitivity analysis.

목차 (Table of Contents)

• 1. 서론
• 2. J-groove 용접 형상 및 재료물성
• 3. J-groove 용접부 잔류응력 해석
• 4. J-groove 용접부에 대한 유한요소 변수 민감도 해석
• 5. 유한요소해석 타당성 검증
• 6. 결론
• 참고문헌

참고문헌 (Reference)

1 김윤재, "원전 이종 금속 다층 용접부 잔류응력 예측을 위한 유한요소 변수 민감도 해석" 대한기계학회 32 (32): 770-781, 2008

2 김주희, "원자로 상부헤드 제어봉구동장치 관통노즐 형상이 J-Groove 용접잔류응력에 미치는 영향" 대한기계학회 35 (35): 1337-1345, 2011

3 김종성, "용접 구조물의 사용중 적합성 평가를 위한 잔류응력 해석절차 개발" 대한기계학회 27 (27): 713-723, 2003

4 송태광, "동종금속용접이 이종금속용접부 잔류응력에 미치는 영향 평가 시 안전단 길이에 따른 효과" 대한기계학회 33 (33): 664-672, 2009

5 ASME, "Welding and Brazing Qualification, ASME Boiler and Pressure Vessel Code, Sec. IX"

6 Dong, P., "Welding Residual Stresses and Effects on Fracture in Pressure Vessel and Piping Components : A Millennium Review and Beyond" 122 : 329-338, 2000

7 Bate, S. K., "UK Research Programme on Residual Stresses – Progress to Date" 2007

8 Warren, A. P., "The Effect of Modeling Simplification on thePrediction of Residual Stresses in a Multi-pass PlateGroove Weld" 2007

9 Yaghi, A., "Residual Stress Simulation in Thin and Thick-walled Stainless Steel Pipe Welds Including Pipe Diameter Effects" 83 : 864-874, 2006

10 Dennis, R. J., "Optimisation of Weld Modeling Techniques : Beadon Plate Analysis" 2006

11 Leggatt, N. A., "Modeling the Fabrication of a Pressure VesselToroidal Seal" 2007

12 Kiyoshima, S., "Investigations on Welding Residual Stresses in Penetration Nozzles by Means of 3D thermal elastic plastic FEM and experiment" 45 : 1031-1042, 2009

13 Ogawa, K., "Influences of Heat Source Model on Welding Residual Stress and Distortion in a Multi- Pass J-Groove Joint" 46 : 987-995, 2009

14 Special metals, "Inconel alloy 600" 2008

15 Anderson, MT., "Final Report-Inspection Limit Confirmation for Upper Head Penetration Nozzle Cracking" U.S. Department of Energy 1-22, 2008

16 Cheng, W., "Effects Of Weld Geometry On Residual Stress and Crack Driving Force For Centerhole Control Rod Drive Mechanism Nozzles – Part I Weld Residual Stress" 1-6, 2005

17 Rudland, D., "Comparison of Welding Residual Stress Solutions for Control Rod Drive Mechanism Nozzles" 1-15, 2007

18 British Energy Generation Ltd., "Assessment of the Integrity of Structures Containing Defects, R6 Revision 4"

19 COMBUSTION ENGINEERING, INC., "Analytical Report for Korea Nuclear Unit No. 5 Reactor Vessel" CENC 1403-1488, 1981

20 ASME, "Alternate Examination Requirements for PWR Reactor Vessel Upper Heads With Nozzles Having Pressure-Retaining Partial-Penetration Welds, ASME Code Case N-729-1"

21 ASME B&PV Committee, "ASME B&PV Code Sec. Ⅱ, PART A, B, C"

22 ASME B&PV Committee, "ASME B&PV Code Sec. III, Appendices"

23 ASME B&PV Committee, "ASME B&PV Code Case Section XI Division 1, Nonmandatory Appendix O-3000"

24 ASME B&PV Committee, "ASME B&PV Code Case Section III Division 1 NB-4000"

25 ABAQUS, "ABAQUS Standard/User’s Manual, version 6.9"

26 Lee, S. G., "A Study for Mitigating Residual Stress in CRDM Penetration Nozzle Weld" 90-95, 2004

27 Brickstad, B., "A Parametric Study of Residual Stresses in Multi-Pass Butt-Welded Stainless Steel Pipes" 75 : 11-25, 1998