Transactions of the Korean Society of Mechanical Engineers A (대한기계학회논문집A)

The Korean Society of Mechanical Engineers (대한기계학회)
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Effects of Geometry of Reactor Pressure Vessel Upper Head Control Rod Drive Mechanism Penetration Nozzles on J-Groove Weld Residual Stress

원자로 상부헤드 제어봉구동장치 관통노즐 형상이 J-Groove 용접잔류응력에 미치는 영향

  • Received : 2011.05.25
  • Accepted : 2011.06.23
  • Published : 2011.10.01
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Abstract

In pressurized water reactors (PWRs), the reactor pressure vessel (RPV) upper head contains numerous control rod drive mechanism (CRDM) nozzles. In the last 10 years, the incidences of cracking in alloy 600 CRDM nozzles and their associated welds has increased significantly. Several axial and circumferential cracks have been found in CRDM nozzles in European PWRs and U.S. nuclear power plants. These cracks are caused by primary water stress corrosion cracking (PWSCC) and have been shown to be driven by welding residual stresses and operational stresses in the weld region. Therefore, detailed finite-element (FE) simulations for the Korea Nuclear Reactor Pressure Vessel have been conducted in order to predict the magnitudes of the weld residual stresses in the tube materials. In particular, the weld residual stress results are compared in terms for nozzle location, geometry factor$r_o$/t, geometry of fillet, and adjacent nozzle.

가압경수로형 원자로의 원자로압력용기 상부헤드에는 많은 제어봉구동장치(CRDM) 노즐이 분포한다. 최근 10 여 년 동안 제어봉구동장치 alloy 600 CRDM 노즐에서 균열 발생 사례가 증가하고 있으며, 이는 용접과 연관성이 매우 깊은 것으로 알려져 있다. CRDM 노즐에서 발생하는 축 및 원주방향 균열은 유럽과 미국의 원자력 발전소에서 발견되었으며, 사고의 원인은 용접 잔류응력 및 작용하중에 기인하는 일차수응력부식균열(PWSCC)임이 확인되었다. 이러한 이유로 본 연구에서는 유한요소해석을 통해 한국형 원자로의 CRDM 관통 노즐 용접부를 대상으로 용접 잔류응력을 예측하였으며, 특히, 관통노즐의 위치와 형상, 용접부 필렛 형상 및 인접노즐 용접에 의한 영향을 분석하였다.

Keywords

References

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  2. Effects of Repair Weld of Reactor Pressure Vessel Upper Head Control Rod Drive Mechanism Penetration Nozzle on J-Groove Weldment Using Finite Element Analysis vol.38, pp.6, 2014, https://doi.org/10.3795/KSME-A.2014.38.6.637
  3. Evaluation of J-groove weld residual stress and crack growth rate of PWSCC in reactor pressure vessel closure head vol.29, pp.3, 2015, https://doi.org/10.1007/s12206-015-0236-5
  4. PWSCC initiation and propagation in a CRDM penetration nozzle vol.31, pp.11, 2017, https://doi.org/10.1007/s12206-017-1033-0
  5. Sensitivity Analysis of Finite Element Parameters for Estimating Residual Stress of J-Groove Weld in RPV CRDM Penetration Nozzle vol.36, pp.10, 2012, https://doi.org/10.3795/KSME-A.2012.36.10.1115