The Paton Welding Journal, 2023, №01



2023 №01 (07)

DOI of Article 10.37434/tpwj2023.01.08

2023 №01 (01)

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The Paton Welding Journal, 2023, #1, 55-59 pages

Influence of residual process stresses on brittle fracture resistance of WWER-1000 reactor baffle in case of an emergency

O.V. Makhnenko, S.M. Kandala

E.O. Paton Electric Welding Institute of the NAS of Ukraine 11 Kazymyr Malevych Str., 03150, Kyiv, Ukraine. E-mail: office@paton.kiev.ua

Abstract
At present, the majority of WWER-1000 reactors in Ukrainian NPPs are going through the procedure of extension of their service life. Reactor internals (RI) are one of the key elements of the structure, which limit the NPP beyond design life. Physical control of RI condition is rather difficult, and even impossible for some areas, so that mathematical modeling is the main method of prediction and analysis of the technical condition. Note that most of the studies in this area are limited to modeling the normal operation mode, but the project also envisages emergency situations (ES), characterized by a rather abrupt change of boundary conditions and loads that promotes formation of quite high stresses. The work analyzes how the residual process stresses generated during RI baffle manufacture, can affect the values of stress intensity factor on the contour of postulated cracks during ES. A significant influence of RPS on the baffle brittle fracture resistance during ES was revealed that should be taken into account at calculation-based substantiation of extension of service life of WWER-1000 type power units. 8 Ref., 2 Tabl., 7 Fig.
Keywords: WWER-1000, reactor internals, baffle, residual process stresses, emergency situation, crack-like defect, stress intensity factor

Received: 09.09.2022
Accepted: 28.02.2023

References

1. Pištora, V., Švrček, M., Ferko, P., Mirzov, I. (2018) Fracture Mechanical Assessment of VVER Reactor Internals. ASME 2018 Pressure Vessels and Piping Conference (July 15-20 2018, Prague, Czech Republic). https://doi.org/10.1115/PVP2018-84589
2. Orynyak, A.I. (2021) Methods of stress intensity factor calculation allowing for geometrical nonlinearity and arbitrary shape of the crack. In: Syn. of Thesis for Cand. of Tekh. Sci. Degree, 05.02.09, Kyiv [in Ukrainian].
3. Makhnenko, O.V., Kandala, S.M. (2022) Evaluation of brittle fracture resistance of WWER-1000 reactor baffle during long-term service, taking into account the residual technological stresses. Tekh. Diahnost. ta Neruiniv. Kontrol, 3, 3-11 [in Ukrainian]. https://doi.org/10.37434/tdnk2022.03.01
4. Makhnenko, O., Kandala, S., Basistyuk, N. (2021) Influence of the heat transfer coefficient on the level of residual stress after heat treatment of the VVER-1000 reactor baffle. Mechanics and Advanced Technologies, 5(2), 254-259. https://doi.org/10.20535/2521-1943.2021.5.2.245074
5. PМ-Т.0.03.333-15. Typical program on evaluation of the technical condition and extension of service life of WWER- 1000 reactor internals [in Russian].
6. Chirkov, A.Yu. (2020) On correctness of the known mathematical model of radiation swelling allowing for the effect of stresses in the problems of elastoplastic deformation mechanics. Problemy Mitsnosti, 2, 5-22 [in Russian]. https://doi.org/10.1007/s11223-020-00165-y
7. (2012) Guide on strength analysis of equipment and piping of RBMK, WWER and EGP reactor units at the stage of operation including operation beyond the design life. RD EO 1.1.2.05.0330-2012 [in Russian].
8. (2013) Guidelines for Integrity and Lifetime Assessment of Components and Piping in WWER Nuclear Power Plants (VERLIFE). Vienna, Int. At. Energy Agency.

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