Transactions of the Korean Society of Pressure Vessels and Piping (한국압력기기공학회 논문집)

Korean Society of Pressure Vessels and Piping (한국압력기기공학회)
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Susceptibility of Stress Corrosion Crack Initiation of Type 304 SS in Simulated Primary Water Environment of PWR

원전 1차 계통수 모사환경에서 Type 304 스테인리스강의 응력부식균열개시 민감도

  • Sung-Hwan Cho ;
  • Sung-Woo Kim ;
  • Jong-Yeon Lee
  • 조성환 (한국원자력연구원 재료안전기술연구부) ;
  • 김성우 (한국원자력연구원 재료안전기술연구부) ;
  • 이종연 (한국원자력연구원 재료안전기술연구부)
  • Received : 2024.05.21
  • Accepted : 2024.06.18
  • Published : 2024.06.30
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Abstract

The core shroud of rector vessel internals (RVI) of OPR1000 and ARP1400 is made of Type 304 stainless steel (SS) by bending and welding process that may induce high deformation and residual stress in manufacturing. This work aims to evaluate the susceptibility of stress corrosion crack (SCC) initiation of bent parts of RVI in high temperature primary water environment. For SCC initiation test, tensile specimens were fabricated from the 90 degree bent plate of Type 304 SS (DT specimen), that is an archived part of a Korean APR1400. After the SCC initiation test, the specimen surface was thoroughly examined by optical and scanning electron microscopy, and compared to the specimen fabricated from the as-received plate of Type 304 SS (AR specimen). The surface observation revealed that SCC initiated on the AR specimen surface in typical intergranular (IG) mode, while SCC on the DT specimen occurred in transgrannular mode as well as IG mode. It was also found that the size and number of SCC on the DT specimen were larger than that on the AR specimen. This was attributable to a strain-hardening during the bending process. To compare the susceptibility of SCC initiation, total crack density (TCD) was calculated from the total crack length divided by the measured area of AR and DT specimens. TCD of DT specimen was 4.6 times higher than AR specimen in average, indicating that higher possibility of degradation of bent parts of RVI for a long-term operation.

Keywords

Acknowledgement

본 연구는 한국연구재단을 통해 과기부 원자력연구개발사업(2021M2E4A1037979, RS-2022-00143718)의 지원을 받아 수행되었다.

References

  1. Kim, S. W., Kim, D. J., and Jin, Y. G., 2015, "Benchmarking of Recent Technology for IASCC Evaluation of Neutron-irradiated Materials," Korea Atomic Energy Research Institute, Daejeon, KAERI/AR/1078. 
  2. Hong, J. H., 2013, chapter 4.3 Structural Materials, Nuclear Materials, 2nd ed, Hans House, Seoul. 
  3. Kim, S. W., Kim, H. P., Choi, M. J., Cho, S. H., Lee, J. Y., Lim, Y. S., and Kim, D. J., 2023, "Technical Report on Corrosion Resistance of Stainless Steel for Welded Reactor Vessel Internals," Korea Atomic Energy Research Institute, Daejeon, KAERI/TR-10038/2023. 
  4. Kim, S. W., Hwang, S. S., Lim, Y. S., Kim, D. J., Choi, M. J., Kwon, J. H., Jin, H. H., and Lee, S. R., 2016, "Technical Report on IASCC models of PWR reactor internals," Korea Atomic Energy Research Institute, Daejeon, KAERI/TR-6404/2016. 
  5. Lim, Y. S., Kim, D. J., Kim, S. W., Jin, H. H., Kim, H. P., Choi, M. J., Cho, S. H., Lee, J. Y., and Lee, S. R., 2022, "Microstructural analyses of the core structural components and their welds in domestic nuclear power plants," Korea Atomic Energy Research Institute, Daejeon, KAERI/TR-9552/2022. 
  6. Fukuya, K., Fujii, K., and Kitsunai, Y., 2005, "DEFORMATION STRUCTURE IN 316 STAINLESS STEEL IRRADIATED IN A PWR," Proc. of the 12th International Conference on Environmental Degradation of Materials in Nuclear Power System-Water Reactors, TMS, pp. 389-393. 
  7. Cho, S. H., Kim, S. W., and Hwang, S. S., "Study of Stainless Steel 304 using IASCC Test Facility(ITF) Mock-up," The Korean Institute of Surface Engineering, Jeju, 2023 May 17-19, pp. 170. 
  8. Kim, S. W., Hwang, S. S., and Lee, J. M., 2015, "Effect of Local Strain Distribution on Stress Corrosion Cracking of Cold-Rolled Alloy 690 With Inhomogeneous Microstructure," Corrosion Science Section, Vol. 71, No. 9, doi:http://dx.doi.org/10.5006/1652. 
  9. Kim, H. P., Lee, J. Y., Cho, S. H., Choi, M. J., Kim, S. W., Kim, D. J., Hwang, S. S., and Lim, Y. S., 2021, "Analysis on relationship between delta ferrite and cracking in austenitic stainless steels," Korea Atomic Energy Research Institute, Daejeon, KAERI/AR1336/2021.