Evolution of Microstructure and Mechanical Properties of Steam Generator Material After Long-Term Operation in Nuclear Power Plant

The microstructural evolution and mechanical properties of WWER 440 steam generator steel GOST 22K after long-term operation were thoroughly examined in this study. The samples were taken directly from a steam generator using the small punch test method. The uniqueness of these samples lies in the f...

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Main Authors: David Slnek, Mária Dománková, Marek Adamech, Jana Petzová, Katarína Bártová, Marek Kudláč, Matúš Gavalec
Format: Article
Language:English
Published: MDPI AG 2025-06-01
Series:Metals
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Online Access:https://www.mdpi.com/2075-4701/15/6/667
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author David Slnek
Mária Dománková
Marek Adamech
Jana Petzová
Katarína Bártová
Marek Kudláč
Matúš Gavalec
author_facet David Slnek
Mária Dománková
Marek Adamech
Jana Petzová
Katarína Bártová
Marek Kudláč
Matúš Gavalec
author_sort David Slnek
collection DOAJ
description The microstructural evolution and mechanical properties of WWER 440 steam generator steel GOST 22K after long-term operation were thoroughly examined in this study. The samples were taken directly from a steam generator using the small punch test method. The uniqueness of these samples lies in the fact that they were real operating materials used in a nuclear power plant with different years of operation. The microstructure was characterized using optical microscopy and transmission electron microscopy supplemented by selective electron diffraction and semi-quantitative chemical microanalysis. It was found that with the prolongation of the operation time of the steam generator, the density of carbides increased slightly, which was reflected in a decrease in the mean distance between particles, but these differences were very small, which indicates the microstructural stability of GOST 22K steel. The stability of this steel was also confirmed by measuring its mechanical properties, which changed only minimally depending on the years of operation. The tensile strength values were in the range of 508 to 579 MPa. In the case of the ductile-to-brittle transition temperature (DBTT), a slight increase was found after 6 years of operation. The DBTT did not change significantly with subsequent operation.
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issn 2075-4701
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spelling doaj-art-ca330df543de456d9684d6c7fd50336c2025-08-20T03:16:34ZengMDPI AGMetals2075-47012025-06-0115666710.3390/met15060667Evolution of Microstructure and Mechanical Properties of Steam Generator Material After Long-Term Operation in Nuclear Power PlantDavid Slnek0Mária Dománková1Marek Adamech2Jana Petzová3Katarína Bártová4Marek Kudláč5Matúš Gavalec6Faculty of Materials Science and Technology in Trnava, Slovak University of Technology in Bratislava, 811 07 Bratislava, SlovakiaFaculty of Materials Science and Technology in Trnava, Slovak University of Technology in Bratislava, 811 07 Bratislava, SlovakiaVUJE a.s., 918 64 Trnava, SlovakiaVUJE a.s., 918 64 Trnava, SlovakiaFaculty of Materials Science and Technology in Trnava, Slovak University of Technology in Bratislava, 811 07 Bratislava, SlovakiaFaculty of Materials Science and Technology in Trnava, Slovak University of Technology in Bratislava, 811 07 Bratislava, SlovakiaFaculty of Materials Science and Technology in Trnava, Slovak University of Technology in Bratislava, 811 07 Bratislava, SlovakiaThe microstructural evolution and mechanical properties of WWER 440 steam generator steel GOST 22K after long-term operation were thoroughly examined in this study. The samples were taken directly from a steam generator using the small punch test method. The uniqueness of these samples lies in the fact that they were real operating materials used in a nuclear power plant with different years of operation. The microstructure was characterized using optical microscopy and transmission electron microscopy supplemented by selective electron diffraction and semi-quantitative chemical microanalysis. It was found that with the prolongation of the operation time of the steam generator, the density of carbides increased slightly, which was reflected in a decrease in the mean distance between particles, but these differences were very small, which indicates the microstructural stability of GOST 22K steel. The stability of this steel was also confirmed by measuring its mechanical properties, which changed only minimally depending on the years of operation. The tensile strength values were in the range of 508 to 579 MPa. In the case of the ductile-to-brittle transition temperature (DBTT), a slight increase was found after 6 years of operation. The DBTT did not change significantly with subsequent operation.https://www.mdpi.com/2075-4701/15/6/667long-term operationthermal agingsmall punch testnuclear power plantwater-water energetics reactor
spellingShingle David Slnek
Mária Dománková
Marek Adamech
Jana Petzová
Katarína Bártová
Marek Kudláč
Matúš Gavalec
Evolution of Microstructure and Mechanical Properties of Steam Generator Material After Long-Term Operation in Nuclear Power Plant
Metals
long-term operation
thermal aging
small punch test
nuclear power plant
water-water energetics reactor
title Evolution of Microstructure and Mechanical Properties of Steam Generator Material After Long-Term Operation in Nuclear Power Plant
title_full Evolution of Microstructure and Mechanical Properties of Steam Generator Material After Long-Term Operation in Nuclear Power Plant
title_fullStr Evolution of Microstructure and Mechanical Properties of Steam Generator Material After Long-Term Operation in Nuclear Power Plant
title_full_unstemmed Evolution of Microstructure and Mechanical Properties of Steam Generator Material After Long-Term Operation in Nuclear Power Plant
title_short Evolution of Microstructure and Mechanical Properties of Steam Generator Material After Long-Term Operation in Nuclear Power Plant
title_sort evolution of microstructure and mechanical properties of steam generator material after long term operation in nuclear power plant
topic long-term operation
thermal aging
small punch test
nuclear power plant
water-water energetics reactor
url https://www.mdpi.com/2075-4701/15/6/667
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