The Paton Welding Journal, 2025, №03

2025 №03 (05)

DOI of Article 10.37434/tpwj2025.03.06

2025 №03 (01)

---

The Paton Welding Journal, 2025, #3, 41-48 pages

Study of intergranular corrosion cracking in welded joints of Chornobyl NPP pipelines. Materials science aspect

V.M. Torop¹, V.B. Hutsaylyuk², M.D. Rabkina¹, E.O. Davydov¹

¹E.O. Paton Electric Welding Institute of the NASU. 11 Kazymyr Malevych Str., 03150, Kyiv, Ukraine. E-mail: v.torop@gmail.com
²Military University of Technology gen. Sylwestra Kaliskiego str. 2, 00-908, Warsaw, Poland

Abstract
Stress corrosion cracking, similar to intergranular corrosion in austenitic steel welds, primarily affects grain boundaries in the heat-affected zone when exposed to a corrosive environment, leading to sensitization, i.e. reduction in structural integrity, which causes cracking and grain loss. The object of studies were specimens cut out of rings from the pipelines of Power Unit 3 of the Chernobyl NPP in the areas of damaged welded joints. Based on radiographic and ultrasonic testing of pipeline welds, as well as determination of the content of alloying elements in the tested specimens, mechanical properties, metallographic, fractographic and micro-X-ray spectral studies, including investigation of fracture surfaces of specimens that were cyclically loaded taking into account fatigue grooves, and with regard to solution of the problem of corrosion cracking of austenitic steels in boiling water reactors, a set of measures was developed, including long-term measures: replacement of steels with others, that are not prone to corrosion cracking; short-term measures: deposition of external weld coating, repair of defective areas, relieving residual stresses; temporary measures: justification of the admissibility of the defective weld for operation.
Keywords: radiographic and ultrasonic testing of welded joints, intergranular corrosion, stress corrosion cracking, corrosion-resistant steel, pipelines, alloying elements, chromium carbides, fatigue grooves

Received: 17.10.2024
Received in revised form: 27.11.2024
Accepted: 17.04.2025

References

1. IAEA. Report of a regional workshop on environmentally assisted cracking of NPP austenitic piping. Slavutych, Ukraine, 22-26 June 1998. Introduction, 7-38.
2. Krasovsky, A.Ya., Makovetskaya, I.A., Torop, V.M., Chugunov, V.A. (2000) Examination of causes of stress corrosion cracking in 1st pipeline circuit of NPP. In: Proc. of Conf. on Assessment and Substantiation of Extension of the Service Life of Structural Elements, Kyiv, 6-9 June, 2000, IPS, Vol. 1, 27-34 [in Russian].
3. Yasniy, P.V., Hlado, V.B., Hutsaylyuk, V.B., Vuherer, T. (2005) Microcrack initiation and growth in heat-resistant 15Kh2MFA steel under cyclic deformation. Fatigue & Fracture of Engineering Materials & Structures, 28(4), 391-397. https://doi.org/10.1111/j.1460-2695.2005.00870.x
4. Lai, J.K., Shek, C.H., Lo, K.H. (2015) Stainless steels: An introduction and their recent development. Hong Kong, Bentham Books.
5. Lawrynowicz, Z. (2018) Diagnostics of the effect of prior cold deformation and aging time on intergranular corrosion resistance in case of austenitic stainless steel. In: Proc. of . 17th Inter. Conf. on Diagnostics of Machines and Vehicles. MATEC Web of Conf., 182, 2018. 01011. https://doi.org/10.1051/matecconf/201818201011
6. (1975) US NRC pipe crack study group. Investigation and evaluation of cracking in austenitic strainless steel piping of BVR plants. NUREG-75/061.
7. (1986) Pressure vessel and piping codes. Evaluation of flaws in austenitic steel piping. Transact. of ASME. J. of Pressure Vessels Technology, 3, 357.
8. (1988) Instruction on investigation of state of metal of NPP pipelines using cut-out samples after 100 thou h of operation (AI-35-17-86). Moscow, VNIIAES. Introd. 30.04.88 [in Russian]. 9. (1990) GOST 6032-89: Corrosion-resistant steels and alloys. Moscow, Izd-vo Standartov [in Russian].
10. (2002) IAEA-EBP-IGSCC Mitigation of intergranular stress corrosion cracking in RBMK reactors. Final Report of the Programme's Steering Committee. IAEA-EBP-IGSCC. A publication of the extrabudgetary programme on mitigation of intergranular stress corrosion cracking in RBMK reactor.

---

Suggested Citation

V.M. Torop, V.B. Hutsaylyuk, M.D. Rabkina, E.O. Davydov (2025) Study of intergranular corrosion cracking in welded joints of Chornobyl NPP pipelines. Materials science aspect. The Paton Welding J., 03, 41-48.

---