On welding residual stresses in structural integrity analyses of NPP components

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientific

Abstract

It is typically assumed that weld residual stresses (WRSs) in the pipings of nuclear power plants (NPPs) are confined to the weld region and its immediate vicinity and have locally relatively high values, of the order of tensile yield stress in and near the inner surface. In many cases the welds have not been post weld heat treated, and thermal relaxation of the WRS levels is small due to the relatively modest operational temperatures. Therefore, the WRSs in NPPs can potentially affect the structural integrity through the risk of stress corrosion cracking (SCC). In this study the WRS assumptions of commonly used fitness-for-service procedures are compared for a set of representative NPP pipe sizes. Also, the behaviour of WRSs as a function of typical load transients, corresponding to several years of plant operation, is simulated with finite element analysis (FEA) for a nozzle connected to a safe-end and pipe. Finally, from the results of the computational analyses, conclusions and recommendations are given on the application of WRS assumptions.
Original languageEnglish
Title of host publicationBaltica VIII
Subtitle of host publicationLife Management and Maintenance for Power Plants
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Pages126-150
Volume1
ISBN (Electronic)978-951-38-7592-3
ISBN (Print)978-951-38-7591-6
Publication statusPublished - 2010
MoE publication typeB3 Non-refereed article in conference proceedings
EventBALTICA VIII - International Conference on Life Management and Maintenance for Power Plants - Helsinki-Stockholm, Finland
Duration: 18 May 201020 May 2010

Publication series

NameVTT Symposium
PublisherVTT
Number264
ISSN (Print)0357–9387
ISSN (Electronic)1455–0873

Conference

ConferenceBALTICA VIII - International Conference on Life Management and Maintenance for Power Plants
CountryFinland
CityHelsinki-Stockholm
Period18/05/1020/05/10

Fingerprint

Structural integrity
Nuclear power plants
Residual stresses
Welding
Welds
Pipe
Stress corrosion cracking
Yield stress
Loads (forces)
Nozzles
Finite element method

Cite this

Cronvall, O. (2010). On welding residual stresses in structural integrity analyses of NPP components. In Baltica VIII: Life Management and Maintenance for Power Plants (Vol. 1, pp. 126-150). Espoo: VTT Technical Research Centre of Finland. VTT Symposium, No. 264
Cronvall, Otso. / On welding residual stresses in structural integrity analyses of NPP components. Baltica VIII: Life Management and Maintenance for Power Plants. Vol. 1 Espoo : VTT Technical Research Centre of Finland, 2010. pp. 126-150 (VTT Symposium; No. 264).
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abstract = "It is typically assumed that weld residual stresses (WRSs) in the pipings of nuclear power plants (NPPs) are confined to the weld region and its immediate vicinity and have locally relatively high values, of the order of tensile yield stress in and near the inner surface. In many cases the welds have not been post weld heat treated, and thermal relaxation of the WRS levels is small due to the relatively modest operational temperatures. Therefore, the WRSs in NPPs can potentially affect the structural integrity through the risk of stress corrosion cracking (SCC). In this study the WRS assumptions of commonly used fitness-for-service procedures are compared for a set of representative NPP pipe sizes. Also, the behaviour of WRSs as a function of typical load transients, corresponding to several years of plant operation, is simulated with finite element analysis (FEA) for a nozzle connected to a safe-end and pipe. Finally, from the results of the computational analyses, conclusions and recommendations are given on the application of WRS assumptions.",
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Cronvall, O 2010, On welding residual stresses in structural integrity analyses of NPP components. in Baltica VIII: Life Management and Maintenance for Power Plants. vol. 1, VTT Technical Research Centre of Finland, Espoo, VTT Symposium, no. 264, pp. 126-150, BALTICA VIII - International Conference on Life Management and Maintenance for Power Plants, Helsinki-Stockholm, Finland, 18/05/10.

On welding residual stresses in structural integrity analyses of NPP components. / Cronvall, Otso.

Baltica VIII: Life Management and Maintenance for Power Plants. Vol. 1 Espoo : VTT Technical Research Centre of Finland, 2010. p. 126-150 (VTT Symposium; No. 264).

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientific

TY - GEN

T1 - On welding residual stresses in structural integrity analyses of NPP components

AU - Cronvall, Otso

PY - 2010

Y1 - 2010

N2 - It is typically assumed that weld residual stresses (WRSs) in the pipings of nuclear power plants (NPPs) are confined to the weld region and its immediate vicinity and have locally relatively high values, of the order of tensile yield stress in and near the inner surface. In many cases the welds have not been post weld heat treated, and thermal relaxation of the WRS levels is small due to the relatively modest operational temperatures. Therefore, the WRSs in NPPs can potentially affect the structural integrity through the risk of stress corrosion cracking (SCC). In this study the WRS assumptions of commonly used fitness-for-service procedures are compared for a set of representative NPP pipe sizes. Also, the behaviour of WRSs as a function of typical load transients, corresponding to several years of plant operation, is simulated with finite element analysis (FEA) for a nozzle connected to a safe-end and pipe. Finally, from the results of the computational analyses, conclusions and recommendations are given on the application of WRS assumptions.

AB - It is typically assumed that weld residual stresses (WRSs) in the pipings of nuclear power plants (NPPs) are confined to the weld region and its immediate vicinity and have locally relatively high values, of the order of tensile yield stress in and near the inner surface. In many cases the welds have not been post weld heat treated, and thermal relaxation of the WRS levels is small due to the relatively modest operational temperatures. Therefore, the WRSs in NPPs can potentially affect the structural integrity through the risk of stress corrosion cracking (SCC). In this study the WRS assumptions of commonly used fitness-for-service procedures are compared for a set of representative NPP pipe sizes. Also, the behaviour of WRSs as a function of typical load transients, corresponding to several years of plant operation, is simulated with finite element analysis (FEA) for a nozzle connected to a safe-end and pipe. Finally, from the results of the computational analyses, conclusions and recommendations are given on the application of WRS assumptions.

M3 - Conference article in proceedings

SN - 978-951-38-7591-6

VL - 1

T3 - VTT Symposium

SP - 126

EP - 150

BT - Baltica VIII

PB - VTT Technical Research Centre of Finland

CY - Espoo

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Cronvall O. On welding residual stresses in structural integrity analyses of NPP components. In Baltica VIII: Life Management and Maintenance for Power Plants. Vol. 1. Espoo: VTT Technical Research Centre of Finland. 2010. p. 126-150. (VTT Symposium; No. 264).