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Development of an auto-welding system for CRD nozzle repair welds using a 3D laser vision sensor

  • K. Park
  • Y. Kim
  • J. Byeon
  • K. Sung
  • C. Yeom
  • S. Rhee
Article

Abstract

A control rod device (CRD) nozzle attaches to the hemispherical surface of a reactor head with J-groove welding. Primary water stress corrosion cracking (PWSCC) causes degradation in these welds, which requires that these defect areas be repaired. To perform this repair welding automatically on a complicated weld groove shape, an auto-welding system was developed incorporating a laser vision sensor that measures the 3-dimensional (3D) shape of the groove and a weld-path creation program that calculates the weld-path parameters. Welding trials with a J-groove workpiece were performed to establish a basis for developing this auto-welding system. Because the reactor head is placed on a lay down support, the outer-most region of the CRD nozzle has restricted access. Due to this tight space, several parameters of the design, such as size, weight and movement of the auto-welding system, had to be carefully considered. The cross section of the J-groove weld is basically an oval shape where the included angle of the J-groove ranges from 0 to 57 degrees. To measure the complex shape, we used double lasers coupled to a single charge coupled device (CCD) camera. We then developed a program to generate the weld-path parameters using the measured 3D shape as a basis. The program has the ability to determine the first and final welding positions and to calculate all weld-path parameters. An optimized image-processing algorithm was applied to resolve noise interference and diffused reflection of the joint surfaces. The auto-welding system is composed of a 4-axis manipulator, gas tungsten arc welding (GTAW) power supply, an optimized designed and manufactured GTAW torch and a 3D laser vision sensor. Through welding trials with 0 and 38-degree included-angle workpieces with both J-groove and U-groove weld, the performance of this auto-welding system was qualified for field application.

Keywords

Laser vision sensor Welding path creation CRD nozzle 

References

  1. [1]
    Charles R. Frye, Melvin L. Arey, Jr. Evaluation and repair of primary water stress corrosion cracking in alloy 600/182 control rod drive mechanism nozzles, 10th Int. Con. Nuclear Engineering. (2002) No. 22653.Google Scholar
  2. [2]
    S.W. Glass, D.M. Schlader, Inspection and repair techniques and strategies for alloy 600 PWSCC in reactor vessel head CRD nozzles and welds, 10th Int. Con. Nuclear Engineering, (2002) No.22743.Google Scholar
  3. [3]
    D. Waskey, R. Payne, D. Schlader, Emergent development and application of reactor vessel head penetration inspections and repairs in the United States, Welding and Repair Technology for Power Plants. (2002) N 1.1-N1. 13.Google Scholar
  4. [4]
    J.G. Byeon, K.S. Park and Y.J. Kim, Development of repair system for alloy 600 PWSCC in reactor vessel head CRDM nozzle and welds, 6th Int. Con. the Integrity of Nuclear Components, (2006) 184–188.Google Scholar
  5. [5]
    J.E. Agapakis, Approaches for recognition and interpretation of workpiece surface features using structured lighting,Int. J. Robotics Research. 9 (1990)3–16.CrossRefGoogle Scholar
  6. [6]
    Y. Suga and A. Ishii, Trends of image processing application to welding process control and inspection of weld,J. JSNDI 48 (1999) 729–737.Google Scholar
  7. [7]
    J. Boillot and J. Noruk, The benefits of laser vision in robotic arc welding,Welding Journal. 81(2002) 32–34.Google Scholar
  8. [8]
    M.R. Robinson, Cracking of RV head penetrations due to primary water stress corrosion cracking (PWSCC), Duke Power Company, (2001).Google Scholar

Copyright information

© The Korean Society of Mechanical Engineers (KSME) 2007

Authors and Affiliations

  • K. Park
    • 1
  • Y. Kim
    • 1
  • J. Byeon
    • 1
  • K. Sung
    • 2
  • C. Yeom
    • 2
  • S. Rhee
    • 2
  1. 1.Corporate R&D InstituteDoosan Heavy Industries & Construction Co., LtdChangwonKorea
  2. 2.Precision Mechanical EngineeringHanyang UniversitySeoulKorea

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