- Volume 49 Issue 7
DOI QR Code
Identification of nonregular indication according to change of grain size/surface geometry in nuclear power plant (NPP) reactor vessel (RV)-upper head alloy 690 penetration
- Kim, Kyungcho (Korea Institute of Nuclear Safety) ;
- Kim, Changkuen (Doosan Heavy Industries and Construction) ;
- Kim, Hunhee (Doosan Heavy Industries and Construction) ;
- Kim, Hak-Joon (Sungkyunkwan University, School of Mechanical Engineering) ;
- Kim, Jin-Gyum (Korea Institute of Nuclear Safety) ;
- Jhung, Myungjo (Korea Institute of Nuclear Safety)
- Received : 2016.08.16
- Accepted : 2017.07.20
- Published : 2017.10.25
During the fabrication process of reactor vessel head penetration (RVHP), the grain size of the tube material can be changed by hot or cold work and the inner side of the tube can also be shrunk due to welding outside of the tube. Several nonregular time-of-flight diffraction (TOFD) signals were found because of deformed grains. In this paper, an investigation of nonregular TOFD indications acquired from RVHP tubes using experiments and computer simulation was performed in order to identify and distinguish TOFD signals by coarse grains from those by Primary Water Stress Corrosion Crack (PWSCC). For proper understanding of the nonregular TOFD indications, microstructural analysis of the RVHP tubes and prediction of signals scattered from the grains using Finite Element Method (FEM) simulation were performed. Prediction of ultrasonic signals from the various sizes of side drilled holes to find equivalent flaws, determination of the size of the nonregular TOFD indications from the coarse grains, and experimental investigation of TOFD signals from coarse grain and shrinkage geometry to identify PWSCC signals were performed. From the computer simulation and experimental investigation results, it was possible to obtain the nonregular TOFD indications from the coarse grains in the alloy 690 penetration tube of RVHP; these nonregular indications may be classified as PWSCC. By comparing the computer simulation and experimental results, we were able to confirm a clear difference between the coarse grain signal and the PWSCC signal.
Supported by : Korea Foundation of Nuclear Safety
- ASME B&PV Code Committee, Code Case N-729-1, Alternative Examination Requirements for PWR Reactor Vessel Upper Heads with Nozzles Having Pressure-Retaining Partial-Penetration Welds, ASME, 2006.
- S.S. Hwang, Review of PWSCC and mitigation management strategies of Alloy 600 materials of PWRs, J. Nucl. Mater. 443 (2013) 321-330. https://doi.org/10.1016/j.jnucmat.2013.07.032
- M. Nygards, P. Gudmundson, Three-dimensional periodic Voronoi grain models and micromechanical FE-simulations of a two-phase steel, Computat. Mater. Sci. 24 (2002) 513-519. https://doi.org/10.1016/S0927-0256(02)00156-8
- F. Zeng, S.R. Agnew, B. Raeisinia, G.R. Myneni, Ultrasonic attenuation due to grain boundary scattering in pure niobium, J. Nondestruct. Eval. 29 (2010) 93-103. https://doi.org/10.1007/s10921-010-0068-2
- S. Vernede, M. Rappaz, A simple and efficient model for mesoscale solidification simulation of globular grain structures,, Acta Mater. 55 (2007) 1703-1710. https://doi.org/10.1016/j.actamat.2006.10.031
- O. Ito, E.R. Fuller, Computer modelling of anisotropic grain microstructure in two dimensions, Acta Metall. Mater. 41 (1993) 191-198. https://doi.org/10.1016/0956-7151(93)90350-2
- L. Vergara-Dominguez, J.M. Paez-Borrallo, Backscattering grain noise modelling in ultrasonic non-destructive testing, Waves Random Media 1 (1991) 81-92. https://doi.org/10.1088/0959-7174/1/1/008
- F.J. Margetan, L. Yu, R.B. Thompson, Computation of grain-noise scattering coefficients for ultrasonic pitch/catch inspections of metals, Review of Progress in Quantitative Nondestructive Evaluation 760 (2005) 1300-1307.
- H.H. Kim, H.J. Kim, S.J. Song, B.S. Lim, K.C. Kim, Assessment of precipitates of isothermal aged austenitic stainless steel using measurement techniques of ultrasonic attenuation, J. Mech. Sci. Tech. 28 (2014) 3021-3026. https://doi.org/10.1007/s12206-014-0708-z