The Paton Welding Journal, 2026, №10

2026 №10 (01)

2026 №10 (03)

---

The Paton Welding Journal, 2026, #10, 12-29 pages

Analysis of the results of non-destructive testing of austenitic welded joints of power unit 3 of the Chornobyl NPP

V.M. Torop, Ye.O. Davydov, M.D. Rabkina

E.O. Paton Electric Welding Institute of the NASU. 11 Kazymyr Malevych Str., 03150, Kyiv, Ukraine. E-mail: v.torop@gmail.com

Abstract
To maintain the required level of safety and reliability of the 325 mm diameter (DN 300) piping with a wall thickness of 16 mm at the Chornobyl NPP, a special program of diagnostic, repair and restoration works was developed. According to this program, between 1997 and 2005, a significant amount of radiographic (RT), ultrasonic (UT), penetrant (PT), and visual (VT) testing of welded joints in DN 300 piping made of austenitic steel 08Kh18N10T was performed. Although more than 20 years have passed since then, non-destructive testing methods are still based on the same physical principles, and virtually the same methodological approaches to non-destructive testing (NDT) are used. Therefore, analyzing the results of a large volume of in-service testing data is very useful for understanding the reliability of the non-destructive testing methods used in modern everyday practice. It should be noted that the analysis of testing results was conducted as part of an independent task, rather than specifically for the purpose of evaluating and comparing NDT methods. Therefore, the article presents an unbiased, retrospective, and impartial analysis, which reflects a possible outcome rather than an expected one.
Keywords: reliability of non-destructive testing (NDT), austenitic welded joints, radiographic (RT ), ultrasonic (UT), penetrant (PT), visual (VT) testing, actual crack dimensions

Received: 23.03.2026
Received in revised form: 08.04.2026
Accepted: 29.10.2026

References

1. Torop, V.M., Rabkina, M.D., Davydov, Ye.O. (2025) Retrospective look at development of defects in austenitic steel welded joints of Chornobyl NPP. Welding and related technologies for reconstruction of Ukraine. In: Abstr. of Conf. Papers, 2025. Ed. by O.T. Zelnichenko. Kyiv, Paton Publishing House, 105–107 [in Ukrainian]. DOI: https://doi.org/10.37434/WRT2025.28
2. Angeliu, T.M., Andresen, P.L., Sutliff, J.A., Horn, R.M. (1999) Intergranular stress corrosion cracking of unsensitized stainless steel in BWR enviroments. In: Proc. of Ninth Inter. Symp. on Environmental Degradation of Materials in Nuclear Power Systems — Water reactors, AIME.
3. (1975): US NRC Pipe Crack Study Group. Investigation and Evaluation of Cracking in Austenitic Stainless Steel Piping of BWR Plants. NUREG–75/061.
4. GOST 7512‒82: Non-destructive testing. Welded joints. Radiography method (Cancelled in keeping with order of 25.12.2015, No 209. Cancellation deadline postponed according to order of 24.01.2018 No 15) [in Ukrainian].
5. PNAE G-7-017‒89: Unified procedure for control of the base materials (semi-finished products), welded joints and surfacing in NPP equipment and pipelines. Radiographic Testing. Moscow, USSR Gosatomenergonadzor [in Russian].
6. PK 1514-72: Rules of control of welded joints and surfacing of components and structures on nuclear power plants, test and research nuclear reactors and plants. Moscow, Energoatomizdat (SOU NAEK 160:2020. Ensuring engineering safety. Quality control of base metal, welded joints and surfacing in equipment and piping of nuclear power plants with WWER reactors. Technical requirements is in effect in Ukraine instead of PK 1514-72 and PNAE G-010-89. Equipment and piping of nuclear power plants. Rules of control) [in Russian].
7. PNAE G-010‒89: Equipment and piping of nuclear power plants. Welded joints and surfacing (SOU NAEK 160:2020. Ensuring engineering safety. Quality control of base metal, welded joints and surfacing in equipment and piping of nuclear power plants with WWER reactors. Technical requirements) [in Russian].
8. PNAE G-7-008‒89: Rules for the design and safe service of equipment and piping on nuclear power plants (SOU NAEK 158:2020. Ensuring engineering safety. Technical requirements for the design and safe operation of equipment and piping on nuclear power plants with WWER reactors and NP 306.2.227-2020. General safety requirements to the design and operation of equipment and piping of nuclear power plants instead of PNAE G-7-008-89, PNAE G-7-009-89 are in effect in Ukraine) [in Russian].
9. PNAE G-7-009‒89: Equipment and piping of nuclear power plants. Welding and surfacing. Main principles [in Russian].
10. MT-34-70-023-86: Procedure for ultrasonic testing of austenitic welded butt joints with wall thickness of 10–25 mm during nuclear power plant mounting and operation [in Russian].
11. DSTU ISO 17635:2018 (EN ISO 17635:2016, IDT; ISO 17635:2016, IDT) Non-destructive testing of welded joints. General rules for metallic materials [in Ukrainian].
12. Chassignole, B., Guerjouma, R.El., Ploix, M.-A., Fouquet, T. (2010) Ultrasonic and structural characterization of anisotropic austenitic stainless steel welds: Towards a higher reliability in ultrasonic non-destructive testing. NDT & E International, 43(4), 273–282. DOI: https://doi.org/10.1016/j.ndteint.2009.12.005
13. MTsU-7–97: Methods of ultrasonic control of austenitic welded joints Ø325×15 of nuclear power plants with RBMK reactors. Moscow, NGO TsNIITMASh [in Russian].
14. Razygraev, N.P., Razygraev, A.N. (2021) Ultrasonic head wave control of welded connections of Du-300 pipelines at Chornobyl nuclear power plant. Technical Diagnostics and Non-Destructive Testing, 1, 48–58 [in Russian].
15. Doctor, S., Jehenson, P. (1988) Description of the PISC III Round Robin Test on Cast Stainless Steel (CCSSRRT ) and evaluation of results. Inter. J. of Pressure Vessels and Piping, 35(1–4), 3–15 DOI: https://doi.org/10.1016/0308-0161(88)90087-7
16. Anderson, M.T., Diaz, A.A., Cinson, A.D. et al. (2011) An assessment of ultrasonic techniques for far-side examinations of austenitic stainless steel piping welds. NUREG/CR-7113, PNNL-19353, NRC Job Code N6398.
17. (2018) ASTM E2862 Standard Guide for Probability of Detection Analysis for Hit/Miss Data. ASTM International.
18. (2009) MIL-HDBK-1823A Nondestructive Evaluation System Reliability Assessment. Department of Defense. 19. ENIQ (2010): Recommended Practice 2 — Inspection qualification methodology.
20. Uzun, H., Gustiani, D. (2024) Review of phased array ultrasonic testing of weld joints. J. of Marine and Engineering Technology, 4(2), 77–92. DOI: https://doi.org/10.58771/joinmet.1525521
21. Kim, Y., Cho, S., Park, I.K. (2021) Analysis of flaw detection sensitivity of phased array ultrasonics in austenitic steel welds according to inspection conditions. Sensors, 21(1), 242. DOI: https://doi.org/10.3390/s21010242
22. Li, C., et al. (2025). Study on phased array ultrasonic testing techniques for austenitic stainless steel butt welds. J. of Fusion Energy, 44, 13. DOI: https://doi.org/10.1007/s10894-025-00475-6
23. Kumar, S., Menaka, M., Venkatraman, B. (2021) Performance comparison of phased array transducers for inspection of dissimilar welds on nuclear reactor components. Annals of Nuclear Energy, 162, 108482. DOI: https://doi.org/10.1016/j.anucene.2021.108482
24. Duan, J.X., et al. (2018) Hybrid ultrasonic TOFD imaging of weld flaws. J. of Nondestructive Evaluation, 37, 23. DOI: https://doi.org/10.1007/s10921-018-0476-2
25. Bürchner, T. et al. (2025) Quantitative comparison of the total focusing method, reverse time migration, and full waveform inversion for ultrasonic imaging. Ultrasonics, 155, 107705. DOI: https://doi.org/10.1016/j.ultras.2025.107705
26. ISO 9712 (2021) Non-destructive testing — Qualification and certification of NDT personnel.
27. EN ISO 17635 (2016) Non-destructive testing of welds — General rules. European Committee for Standardization.
28. RD EO 0488-03 (2003) Methodological recommendations for assessing the reliability of means and methods of non-destructive testing. Guidance document. Moscow [in Russian].

---

Suggested Citation

V.M. Torop, Ye.O. Davydov, M.D. Rabkina (2026) Analysis of the results of non-destructive testing of austenitic welded joints of power unit 3 of the Chornobyl NPP. The Paton Welding J., 10, 12-29.

---