scholarly journals SMILE: A European R&D Program for the Inclusion of Warm Pre-Stress in RPV Assessment

2005 ◽  
Author(s):  
Dominique Moinereau
Keyword(s):  
Beneficial Effect ◽  
Brittle Failure ◽  
Structural Integrity ◽  
Development Program ◽  
Experimental Results ◽  
Load History ◽  
Local Approach ◽  
Integrity Assessment ◽  
History Effects ◽  
Energy Community

The Reactor Pressure Vessel (RPV) is an essential component liable to limit the lifetime duration of PWR plants. The assessment of defects in RPV subjected to PTS transients made at an European level generally do not take necessary into account the beneficial effect of load history (warm pre-stress WPS). A 3-year Research & Development program — SMILE — has been started in January 2002 as part of the Fifth Framework of the European Atomic Energy Community (EURATOM). The SMILE project (“Structural Margin Improvements in aged-embrittled RPV with Load history Effects”) is one of a “cluster” of Fifth Framework projects in the area of Plant Life Management. It aims to give sufficient elements to demonstrate, to model and to validate the beneficial WPS effect in a RPV integrity assessment. Finally, this project aims to harmonize the different approaches in the European Codes and Standards regarding the inclusion of the WPS effect in a RPV structural integrity assessment. Within the framework of the project, an important experimental work has been conducted including WPS type experiments on CT specimens and also a PTS type transient experiment on a large component. The experimental results on CT specimens confirm the beneficial effect of warm pre-stress, with an effective significant increase of the material resistance regarding the risk of brittle failure. The WPS type experiment on the cylinder has been successfully conducted, with a final brittle failure during the reloading. The present paper describes the aims and objectives of the SMILE project, the main experimental results, and the corresponding analyses based on engineering methods, finite element elastic and elastic-plastic computations, and local approach to fracture.

NESC VII: A European Project for Application of WPS in RPV Assessment Including Biaxial Loading

2010 ◽  
Author(s):  
Dominique Moinereau ◽  
Ste´phane Chapuliot ◽  
Ste´phane Marie ◽  
Philippe Gilles
Keyword(s):  
Beneficial Effect ◽  
Brittle Failure ◽  
Large Scale ◽  
Biaxial Loading ◽  
Numerical Models ◽  
Development Program ◽  
Sufficient Evidence ◽  
Load History ◽  
Integrity Assessment ◽  
History Effects

The Reactor Pressure Vessel (RPV) is an essential component liable to limit the lifetime duration of PWR plants. The assessment of defects in RPV subjected to PTS transients made at a European level do not necessarily take into account the beneficial effect of load history (warm pre-stress WPS) on the resistance of RPV material regarding the risk of brittle failure. A 4-year European Research & Development program — SMILE — was successfully conducted between 2002 and 2005 as part of the 5th Framework of the European Atomic Energy Community (EURATOM). The objective of the SMILE project (‘Structural Margin Improvements in aged-embrittled RPV with Load history Effects’) was to provide sufficient evidence in order to demonstrate, to model and to validate the beneficial WPS effect in a RPV integrity assessment. Numerous experimental, analytical and numerical results have been obtained which confirm the beneficial effect of warm pre-stress on RPV steels, with an effective significant increase of the material resistance regarding the risk of brittle failure. In addition to SMILE, a new project dealing with WPS — NESC VII — has been launched in 2008 (linking with the European Network of Excellence NULIFE) with the participation of numerous international organizations (R&D, Utilities and Manufacturers). Based on experimental, analytical and numerical tasks, the project is focused on topics generally not covered by past experience on WPS: biaxiality of loading on large-scale specimens, effect of irradiation, applicability to intergranular fracture, modeling (including analytical and numerical models) … Among these tasks, some new novel WPS experiments are being conducted on large scale cruciform bend bar specimens in order to study the influence of biaxial loading on WPS effect, using a fully representative RPV steel (18MND5 steel similar to A533B steel). After a synthesis of main WPS results available from previous projects on representative RPV steels, a description of the NESC VII project is presented in this paper together with the corresponding organization, including the present status of the project.

scholarly journals SMILE: Interpretation of WP4 PTS Transient Type Experiment Performed on a Cracked Cylinder Involving Warm Pre-Stress

2005 ◽  
Author(s):  
Dominique Moinereau ◽  
Anna Dahl ◽  
Yves Wadier
Keyword(s):  
Brittle Failure ◽  
Development Program ◽  
Load History ◽  
Local Approach ◽  
Type Experiment ◽  
History Effect ◽  
Vessel Resistance ◽  
Energy Community ◽  
Reactor Pressure ◽  
Good Agreement

The Reactor Pressure Vessel (RPV) is an essential component liable to limit the lifetime duration of PWR plants. The assessment of defects in RPV subjected to PTS transients made at an European level generally not always account the beneficial effect of load history (warm pre-stress WPS) on vessel resistance regarding the risk of brittle failure. A 3-year Research & Development program — SMILE — has been started in January 2002 as part of the 5th Framework Program of the European Atomic Energy Community (EURATOM). The SMILE project — Structural Margin Improvements in aged embrittled RPV with Load history Effect — is one of a cluster of 5th framework projects in the area of Plant Life Management. It aims to give sufficient elements to demonstrate, to model and to validate the beneficial WPS effect in a RPV assessment. Within the framework of the project, an important experimental work has been conducted including WPS type experiments on CT specimens and one PTS type transient experiment on a large component. The WPS type experiment on the cylinder has been successfully conducted by MPA Stuttgart with a final brittle failure during the reloading. The present paper shortly describes the experiment and presents the corresponding analyses based on engineering methods, finite element elastic-plastic computations, and local approach to fracture. The results are in good agreement with the experimental observations. Very significant margins are underlined, with an effective important increase of the material resistance regarding the risk of brittle failure.

SMILE Project — The Effect of Warm Pre-Stress in RPV Assessment: Synthesis of Experimental Results and Analyses

2006 ◽  
Author(s):  
Dominique Moinereau ◽  
Anna Dahl ◽  
Ste´phane Chapuliot ◽  
David Lidbury
Keyword(s):  
Fracture Mechanics ◽  
Beneficial Effect ◽  
Experimental Work ◽  
Brittle Failure ◽  
Short Description ◽  
Experimental Results ◽  
Numerical Analyses ◽  
Local Approach ◽  
Model Following ◽  
Cracked Cylinder

Within framework of 5th EC European SMILE project, some R&D actions have been conducted to demonstrate, to model and to validate the beneficial warm pre-stress (WPS) effect regarding the risk of brittle failure in a RPV assessment. An important experimental work has been conducted including classical WPS type experiments on CT specimens on usual RPV steels, and one PTS type transient on a large cracked cylinder. All experimental results confirm the beneficial effect of warm pre-stress, with a significant increase of the materials resistance regarding the risk of brittle failure. The experiments have been analyzed using fracture mechanics, including both engineering methods (Chell, Haigh, Wallin) and more refined analyses based on local approach to fracture (‘modified Beremin’ model). Following a short description of WPS concept, the paper summarizes the main experimental results and presents a synthesis of mechanical analyses involving engineering approaches and numerical analyses.

Implications of Cleavage Fracture Criteria for Structural Integrity Assessment of RPV Steels

2010 ◽  
Author(s):  
S. J. Lewis ◽  
C. E. Truman ◽  
D. J. Smith
Keyword(s):  
Cleavage Fracture ◽  
Structural Integrity ◽  
Strain History ◽  
Assessment Procedure ◽  
Load History ◽  
Safe Operation ◽  
Local Approach ◽  
Integrity Assessment ◽  
Rpv Steel ◽  
Current Assessment

To accurately assess the safe operation of structures containing defects, it is necessary to consider the influences of previous load cycles on crack propagation. A number of current assessment codes contain advice to account for strain history and residual stress, but are generally known to be highly conservative which may potentially result in the unnecessary and expensive repair or replacement of infrastructure. This paper considers the results of previous investigations into cleavage fracture of an A533b RPV steel to determine the accuracy of the widely used R6 structural integrity assessment procedure for fracture following significant load history. The levels of conservatism associated with a number of assessment methods are discussed and compared with experimental data. The general trends suggested an improvement in assessment accuracy may be obtained by using local approach methods, compared to crack tip failure parameters. It is noted however that all the methods used produced some unsafe estimates of failure load, which is felt to be related to an over estimate of the characteristic material toughness.

scholarly journals Inclusion of Warm Pre-Stress Concept in French RPV Structural Integrity Assessment

2016 ◽  
Author(s):  
Dominique Moinereau ◽  
Malik Ait-Bachir ◽  
Stéphane Chapuliot ◽  
Stéphane Marie ◽  
Clémentine Jacquemoud ◽  
...  
Keyword(s):  
Brittle Fracture ◽  
Fracture Resistance ◽  
Large Scale ◽  
Structural Integrity ◽  
Stress Effect ◽  
Local Approach ◽  
Experimental Database ◽  
Term Operation ◽  
Integrity Assessment ◽  
Brittle Fracture Resistance

Evaluation of the fracture resistance of nuclear reactor pressure vessel (RPV) regarding the risk of brittle fracture is a key point in the structural integrity assessment of the component (RPV). Such approach is codified in French RSE-M code, based on a very conservative methodology. With respect to long term operation, an improvement of the present methodology is necessary and in progress to reduce this conservatism. One possible significant improvement is the inclusion of the warm pre-stress (WPS) concept in the assessment. After a short description of the WPS concept, the process engaged in France to allow inclusion of WPS in the integrity assessment is presented. In a first step, experimental and numerical studies have been conducted in France by EDF, CEA and AREVA (also including international collaborations and projects) to demonstrate and validate the beneficial effect of WPS on the brittle fracture resistance of RPV steels. A large panel of experimental results and data is now available obtained on small, medium and large scale specimens on representative RPV steels (including highly irradiated RPV materials). These data have been included in a specific WPS experimental database. Main experiments have been interpreted by refined computations, based on elastic plastic analyses and local approach to cleavage fracture. In a second step, a new criterion (ACE criterion) has been proposed by French organizations (AREVA, CEA and EDF) for an easy simplified evaluation of warm pre-stress effect on the brittle fracture resistance of RPV steels. Accuracy and conservatism of the criterion is verified by comparison to experimental data results and numerical analyses. Finally, implementation of the WPS effect in the French RSE-M code (for in service assessment) is in progress, based on the ACE criterion. The present paper summarizes all these steps leading to codification of WPS in RSE-M code.

Advanced Structural Integrity Assessment Tools for Safe Long Term Operation: ATLAS+ Project — Status of the Activities of the WP3 on Modelling

2019 ◽  
Author(s):  
Stéphane Marie ◽  
Arnaud Blouin ◽  
Tomas Nicak ◽  
Dominique Moinereau ◽  
Anna Dahl ◽  
...  
Keyword(s):  
Large Scale ◽  
Structural Integrity ◽  
Assessment Tools ◽  
Local Approach ◽  
Coupled Models ◽  
Large Defect ◽  
Ductile Tearing ◽  
Term Operation ◽  
Integrity Assessment

Abstract The main objective and mission of the ATLAS+ project is to develop advanced structural assessment tools to address the remaining technology gaps for the safe and long term operation of nuclear reactor pressure coolant boundary systems. ATLAS+ WP3 focuses mainly on ductile tearing prediction for large defect in components: Several approaches have been developed to accurately model the ductile tearing process and to take into account phenomena such as the triaxiality effect, or the ability to predict large tearing in industrial components. These advanced models include local approach coupled models or advanced energetic approaches. Unfortunately, the application of these tools is today rather limited to R&D expertise. However, because of the continuous progress in the performance of the calculation tools and accumulated knowledge, in particular by members of ATLAS+, these models can now be considered as relevant for application in the context of engineering assessments. WP3 will therefore: • Illustrate the implementation of these models for industrial applications through the interpretation of large scale mock-ups (with cracks in weld joints for some of them), • Make recommendations for the implementation of the advanced models in engineering assessments, • Correct data from the conventional engineering approach by developing a methodology to produce J-Δa curve suitable case by case, based on local approach models, • Improve the tools, guidance and procedures for undertaking leak-before-break (LBB) assessments of piping components, particularly in relation to representing structural representative fracture toughness J-Resistance curves and the influence of weld residual stresses. To achieve these goals, WP3 is divided into 4 sub-WPs and this paper presents the progress of the work performed in each sub-WP after 24 months of activities.

French R&D Program for RPV Aging Management

2004 ◽  
Author(s):  
H. Churier-Bossennec ◽  
D. Moinereau ◽  
P. Todeschini ◽  
C. Faidy ◽  
G. Bezdikian
Keyword(s):  
Structural Integrity ◽  
Probabilistic Approach ◽  
Development Program ◽  
Surveillance Program ◽  
Integrity Assessment ◽  
Large Program ◽  
Periodic Safety ◽  
Long Lifetime ◽  
Definition Of ◽  
Mitigation Methods

Until now French approach for RPV PTS assessment is based on at least 40 years lifetime. This lifetime has been taken into account at each step of the the RPV life: first early in the design, then at each periodic safety demonstration by including the surveillance program, the national and international feedback and R&D results. All of them confirm that all the 3-loop French RPV fulfill the existing criteria for at least 40 years of operation. In order to evaluate their capability to operate for 60 years, an Engineering and Research and Development program has been recently established and engaged by EDF. This large program of activities between all of divisions of EDF is focused on the different fields involved in the risk of fast rupture of the irradiated core vessel. The main purposes of this programme are: • the research of specific data corresponding to a long lifetime of about 60 years; • the studies of new methods to improve the demonstration including several themes such as fluence evaluation, determination of fracture toughness, structural integrity assessment including probabilistic approach, definition of transients; • the evaluation of mitigation methods. This paper contains first a description of what was done at each RPV PTS assessment and an overview of the present program.

Advanced Structural Integrity Assessment Tools for Safe Long Term Operation: ATLAS+ Project — Status of the Activities of the WP3 on Modelling in 2020

2020 ◽  
Author(s):  
Arnaud Blouin ◽  
Stéphane Marie ◽  
Tomas Nicak ◽  
Antti Timperi ◽  
Peter Gill
Keyword(s):  
Large Scale ◽  
Structural Integrity ◽  
Assessment Tools ◽  
Local Approach ◽  
Coupled Models ◽  
Large Defect ◽  
Ductile Tearing ◽  
Term Operation ◽  
Integrity Assessment

Abstract The main objective and mission of the ATLAS+ project is to develop advanced structural assessment tools to address the remaining technology gaps for the safe and long term operation of nuclear reactor pressure coolant boundary systems. ATLAS+ WP3 focuses mainly on ductile tearing prediction for large defect in piping and associated components: Several approaches have been developed to accurately model the ductile tearing process and to take into account phenomena such as triaxiality effects, or the ability to predict large tearing in industrial components. These advanced models include local approach coupled models or advanced energetic approaches. Unfortunately, the application of these tools is currently rather limited to R&D expertise. However, because of the continuous progress in the performance of calculation tools and accumulated knowledge, in particular by members of the ATLAS+ consortium, these models can now be considered as relevant for application in the context of engineering assessments. WP3 has been planned to: • Illustrate the implementation of these models for industrial applications through the interpretation of large scale mock-ups (with cracks in weld joints for some of them), • Make recommendations for the implementation of the advanced models in engineering assessments, • Correct data from the conventional engineering approach by developing a methodology to produce J-Δa curve suitable case by case, based on local approach models, • Improve the tools, guidance and procedures for undertaking leak-before-break (LBB) assessments of piping components, particularly in relation to representing structural representative fracture toughness J-Resistance curves and the influence of weld residual stresses. To achieve these goals, WP3 is divided into 4 sub-WPs and this paper presents the progress of the work performed in each sub-WP after 36 months of activities.

The Energy Approach of Elastic-Plastic Fracture Mechanics Applied to the Analysis of the Warm Pre-Stress Effect

2003 ◽  
Author(s):  
Yves Wadier ◽  
M. Bonnamy
Keyword(s):  
Release Rate ◽  
Energy Method ◽  
Ferritic Steel ◽  
Structural Integrity ◽  
Energy Approach ◽  
Experimental Results ◽  
Experimental Program ◽  
Stress Effect ◽  
Integrity Assessment ◽  
Good Agreement

An experimental program was recently carried out in the context of a MPA-EDF collaboration, in order to study the “Warm Pre-Stress” effect on CT25 side-grooved specimens made of 18MND5 (equivalent to A508) ferritic steel. At EDF, an energy approach has been developed and an energy release rate, called Gp, has been defined. Conversely to the J-approach, this energy approach is, in principle, valid in all situations, and can be used in particular to study the “Warm Pre-Stress” effect in RPV structural integrity assessment. For the WPS cycle called “LCF” (Loading + Cooling + Fracture), the comparison to the experimental results and to the results obtained with the Beremin model is very satisfactory, all the results being in a good agreement. For the WPS cycle called “LUCF” (Loading + Unloading + Cooling + Fracture) the results obtained with the energy method, compared to experimental results, show a conservatism which is not very important, anyway smaller than the conservatism obtained with the Beremin model.

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