Transferability of EAF Data and Models to Plant Applications

Tommi Seppänen; Jussi Solin

doi:10.1115/PVP2025-154611

Transferability of EAF Data and Models to Plant Applications

Research output: Chapter in Book/Report/Conference proceeding › Conference article in proceedings › Scientific › peer-review

Abstract

Environmental penalty factors (Fen) are used for assessment of Environmentally Assisted Fatigue (EAF) in NPP primary circuit components. The F_en factors are regression fitted based on reduced fatigue endurances of laboratory specimens tested in simulated reactor coolant environments and presented as functions of temperature and strain rate for relevant material types and water chemistries. The laboratory results are directly applied in fatigue management to adjust the allowable numbers of fatigue transients in reactor components. Plant operation experience and true ε-N data suggest that excessive conservatism is embedded in the environmental factors determined through stroke-controlled testing of stainless steels and/or transferability of the results (Fen per NUREG/CR-6909). Challenges in determining F_en factors and their transferability to plant operation are discussed in this paper. Possibilities for improvements by mechanism-based modelling of environmental effects are considered.

Original language	English
Title of host publication	Proceedings of ASME 2025 Pressure Vessels & Piping Conference (PVP2025)
Publisher	American Society of Mechanical Engineers (ASME)
Number of pages	10
Volume	Volume 1: Codes & Standards
ISBN (Electronic)	978-0-7918-8904-6
DOIs	https://doi.org/10.1115/PVP2025-154611
Publication status	Published - 2025
MoE publication type	A4 Article in a conference publication
Event	ASME 2025 Pressure Vessels and Piping Conference, PVP 2025 - Montreal, Canada Duration: 20 Jul 2025 → 25 Jul 2025

Conference

Conference	ASME 2025 Pressure Vessels and Piping Conference, PVP 2025
Country/Territory	Canada
City	Montreal
Period	20/07/25 → 25/07/25

Funding

This paper is prepared as part of the TOFFEE project, a sub-project of the Finnish Research Programme on Nuclear Power Plant Safety 2023-2028 (SAFER2028). Results and analyses in previous projects are revisited and discussed. The hypotheses, analyses and verification results related to the plastic strain based advanced EAF model are intellectual property of T. Seppänen.

Keywords

environment
fatigue
plastic strain
stainless steel
strain-controlled
thermodynamics

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10.1115/PVP2025-154611

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title = "Transferability of EAF Data and Models to Plant Applications",

abstract = "Environmental penalty factors (Fen) are used for assessment of Environmentally Assisted Fatigue (EAF) in NPP primary circuit components. The Fen factors are regression fitted based on reduced fatigue endurances of laboratory specimens tested in simulated reactor coolant environments and presented as functions of temperature and strain rate for relevant material types and water chemistries. The laboratory results are directly applied in fatigue management to adjust the allowable numbers of fatigue transients in reactor components. Plant operation experience and true ε-N data suggest that excessive conservatism is embedded in the environmental factors determined through stroke-controlled testing of stainless steels and/or transferability of the results (Fen per NUREG/CR-6909). Challenges in determining Fen factors and their transferability to plant operation are discussed in this paper. Possibilities for improvements by mechanism-based modelling of environmental effects are considered.",

keywords = "environment, fatigue, plastic strain, stainless steel, strain-controlled, thermodynamics",

author = "Tommi Sepp{\"a}nen and Jussi Solin",

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year = "2025",

doi = "10.1115/PVP2025-154611",

language = "English",

volume = "Volume 1: Codes \& Standards",

booktitle = "Proceedings of ASME 2025 Pressure Vessels \& Piping Conference (PVP2025)",

publisher = "American Society of Mechanical Engineers (ASME)",

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Seppänen, T & Solin, J 2025, Transferability of EAF Data and Models to Plant Applications. in Proceedings of ASME 2025 Pressure Vessels & Piping Conference (PVP2025). vol. Volume 1: Codes & Standards, PVP2025-154611, American Society of Mechanical Engineers (ASME), ASME 2025 Pressure Vessels and Piping Conference, PVP 2025, Montreal, Canada, 20/07/25. https://doi.org/10.1115/PVP2025-154611

Transferability of EAF Data and Models to Plant Applications. / Seppänen, Tommi; Solin, Jussi.
Proceedings of ASME 2025 Pressure Vessels & Piping Conference (PVP2025). Vol. Volume 1: Codes & Standards American Society of Mechanical Engineers (ASME), 2025. PVP2025-154611.

Research output: Chapter in Book/Report/Conference proceeding › Conference article in proceedings › Scientific › peer-review

TY - GEN

T1 - Transferability of EAF Data and Models to Plant Applications

AU - Seppänen, Tommi

AU - Solin, Jussi

PY - 2025

Y1 - 2025

N2 - Environmental penalty factors (Fen) are used for assessment of Environmentally Assisted Fatigue (EAF) in NPP primary circuit components. The Fen factors are regression fitted based on reduced fatigue endurances of laboratory specimens tested in simulated reactor coolant environments and presented as functions of temperature and strain rate for relevant material types and water chemistries. The laboratory results are directly applied in fatigue management to adjust the allowable numbers of fatigue transients in reactor components. Plant operation experience and true ε-N data suggest that excessive conservatism is embedded in the environmental factors determined through stroke-controlled testing of stainless steels and/or transferability of the results (Fen per NUREG/CR-6909). Challenges in determining Fen factors and their transferability to plant operation are discussed in this paper. Possibilities for improvements by mechanism-based modelling of environmental effects are considered.

AB - Environmental penalty factors (Fen) are used for assessment of Environmentally Assisted Fatigue (EAF) in NPP primary circuit components. The Fen factors are regression fitted based on reduced fatigue endurances of laboratory specimens tested in simulated reactor coolant environments and presented as functions of temperature and strain rate for relevant material types and water chemistries. The laboratory results are directly applied in fatigue management to adjust the allowable numbers of fatigue transients in reactor components. Plant operation experience and true ε-N data suggest that excessive conservatism is embedded in the environmental factors determined through stroke-controlled testing of stainless steels and/or transferability of the results (Fen per NUREG/CR-6909). Challenges in determining Fen factors and their transferability to plant operation are discussed in this paper. Possibilities for improvements by mechanism-based modelling of environmental effects are considered.

KW - environment

KW - fatigue

KW - plastic strain

KW - stainless steel

KW - strain-controlled

KW - thermodynamics

UR - https://www.scopus.com/pages/publications/105020663114

U2 - 10.1115/PVP2025-154611

DO - 10.1115/PVP2025-154611

M3 - Conference article in proceedings

AN - SCOPUS:105020663114

VL - Volume 1: Codes & Standards

BT - Proceedings of ASME 2025 Pressure Vessels & Piping Conference (PVP2025)

PB - American Society of Mechanical Engineers (ASME)

T2 - ASME 2025 Pressure Vessels and Piping Conference, PVP 2025

Y2 - 20 July 2025 through 25 July 2025

ER -

Transferability of EAF Data and Models to Plant Applications

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