Identifi cation of nonregular indication according to change of grain size/surface geometry in nuclear power plant (NPP) reactor vessel (RV)-upper head alloy 690 penetration

• Published in: Nuclear engineering and technology pp. 1524 - 1536
• Main Authors: 김경조, 김창근, 김훈희, 김학준, 김진겸, 정명조
• Format: Journal Article
• Language: English
• Published: 한국원자력학회 01.10.2017
• Subjects: 원자력공학
• ISSN: 1738-5733; 2234-358X

During the fabrication process of reactor vessel head penetration (RVHP), the grain size of the tubematerial can be changed by hot or cold work and the inner side of the tube can also be shrunk due towelding outside of the tube. Several nonregular time-of-flight diffraction (TOFD) signals were foundbecause of deformed grains. In this paper, an investigation of nonregular TOFD indications acquired fromRVHP tubes using experiments and computer simulation was performed in order to identify anddistinguish 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 tubesand prediction of signals scattered from the grains using Finite Element Method (FEM) simulation wereperformed. Prediction of ultrasonic signals from the various sizes of side drilled holes to find equivalentflaws, determination of the size of the nonregular TOFD indications from the coarse grains, and experimentalinvestigation of TOFD signals from coarse grain and shrinkage geometry to identify PWSCCsignals were performed. From the computer simulation and experimental investigation results, it was possible to obtain thenonregular TOFD indications from the coarse grains in the alloy 690 penetration tube of RVHP; thesenonregular indications may be classified as PWSCC. By comparing the computer simulation and experimentalresults, we were able to confirm a clear difference between the coarse grain signal and thePWSCC signal. KCI Citation Count: 0