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.

French Nuclear Reactor Pressure Vessel Integrity Assessment and Life Management Strategy

2011 ◽  
Author(s):  
H. Churier ◽  
G. Balard ◽  
E. Meister ◽  
F. Clemendot ◽  
P. Todeschini ◽  
...  
Keyword(s):  
Structural Integrity ◽  
Probabilistic Approach ◽  
Operating Experience ◽  
Crack Arrest ◽  
Design Stage ◽  
Surveillance Program ◽  
Stress Effect ◽  
Deterministic Approach ◽  
Integrity Assessment ◽  
The Future

The structural integrity of the RPV is an essential issue for the plant safety. At the design stage, the demonstration is required with material properties at end of life, to ensure the adequacy of the design with the expected operating transients in all conditions. During operation, the integrity assessment is updated every ten years with new existing knowledge and feedback of operating experience, in particular in service aged material data coming from Irradiation Surveillance Program ISP, fluence evaluations taking into account the effective in service core arrangements in each vessel, in service detected flaws plus a postulated subclad crack whose detection cannot be guaranteed by the qualified ISI program. The final assessment showed that the regulatory criteria are met until the fourth decennial outage for 900 MW RPV. The analysis is performed in accordance with French regulations (use of safety coefficients) and follows a deterministic approach in which the input parameters and uncertainties are taken into account conservatively. For the future demonstration beyond 40 years, a multidisciplinary effort is committed to improving knowledge in order to reduce uncertainties in data and in methods. This extensive program involves in particular: - Thermohydraulic analysis and description of transients: temperatures and heat exchange coefficients; - Mechanical analysis: warm pre-stress effect and crack arrest. In addition, a complementary study using a probabilistic approach to rationalize the level of conservatism of input data is launched. In this report, the French deterministic approach and the main results for 40 years duration are presented and the new developments for the future.

Estimation of Through-Wall Cracking Frequency of RPV Under PTS Events Using PFM Analysis Method for Identifying Conservatism Included in Current Japanese Code

2014 ◽  
Author(s):  
Kazuya Osakabe ◽  
Koichi Masaki ◽  
Jinya Katsuyama ◽  
Genshichiro Katsumata ◽  
Kunio Onizawa
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Crack Initiation ◽  
Structural Integrity ◽  
Probabilistic Approach ◽  
Pressure Vessels ◽  
Assessment Procedure ◽  
Analysis Method ◽  
Integrity Assessment ◽  
The U.S

To assess the structural integrity of reactor pressure vessels (RPVs) during pressurized thermal shock (PTS) events, the deterministic fracture mechanics approach prescribed in Japanese code JEAC 4206-2007 [1] has been used in Japan. The structural integrity is judged to be maintained if the stress intensity factor (SIF) at the crack tip during PTS events is smaller than fracture toughness KIc. On the other hand, the application of a probabilistic fracture mechanics (PFM) analysis method for the structural reliability assessment of pressure components has become attractive recently because uncertainties related to influence parameters can be incorporated rationally. A probabilistic approach has already been adopted as the regulation on fracture toughness requirements against PTS events in the U.S. According to the PFM analysis method in the U.S., through-wall cracking frequencies (TWCFs) are estimated taking frequencies of event occurrence and crack arrest after crack initiation into consideration. In this study, in order to identify the conservatism in the current RPV integrity assessment procedure in the code, probabilistic analyses on TWCF have been performed for certain model of RPVs. The result shows that the current assumption in JEAC 4206-2007, that a semi-elliptic axial crack is postulated on the inside surface of RPV wall, is conservative as compared with realistic conditions. Effects of variation of PTS transients on crack initiation frequency and TWCF have been also discussed.

Probabilistic Leak Before Break

2018 ◽  
Author(s):  
L. Stefanini ◽  
F. J. Blom
Keyword(s):  
Fracture Toughness ◽  
Yield Stress ◽  
Master Curve ◽  
Structural Integrity ◽  
Probabilistic Approach ◽  
Leakage Rate ◽  
Critical Crack ◽  
Critical Crack Length ◽  
Integrity Assessment ◽  
Leak Before Break

In this study a probabilistic Leak-Before-Break (LBB) analysis was carried out based on the R6 FAD Option 1 assessment method. The method uses the material fracture toughness and yield stress in order to determine, deterministically, a Critical Crack Length (CCL) and a Leakage Rate (LR) through a crack. In order to define the fracture toughness of the material, the Master Curve approach was used accordingly to BS7910:2013 Annex J. Initially, deterministic analyses were carried out and the fracture toughness and yield stress were set to 190 MPa√m and 158 MPa, respectively. In order to implement a probabilistic approach, the yield stress and fracture toughness were introduced as stochastic parameter. The Fracture toughness was generated using a Weibull distribution to match the Master Curve. The distribution was built such that 190 MPa√m represents the 5% probability fracture toughness. The Yield stress (0.2% proof strength) was generated using a normal distribution with standard deviation 10.35 MPa such that the average value was 175 MPa and the lower bound (5% of probability of occurrence) was 158 MPa. The choice of building the distribution as above mentioned was justified by the fact that in structural integrity assessment the lower 5% is generally used for material parameters. Thus, once a Detectable Leakage Rate (DLR) was determined, it was possible to assign an implicit probability of failure to the deterministic case. The calculations were then extended by using several LR formulas. The calculations were carried out making use of the probabilistic software RAP++ coupled to MATLAB. The probabilities of failure were calculated with regard to a postulated DLR and a DLRSF corrected with a safety factor of 10. The probabilities of failure for the DLRSF were proved to be 9 to 15 times higher than for the postulated DLR case, which leads to the opportunity of conservatism reduction.

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.

Study on Application of PFM Analysis Method to Japanese Code for RPV Integrity Assessment Under PTS Events

2015 ◽  
Author(s):  
Kazuya Osakabe ◽  
Koichi Masaki ◽  
Jinya Katsuyama ◽  
Genshichiro Katsumata ◽  
Kunio Onizawa ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Input Data ◽  
Structural Integrity ◽  
Probabilistic Approach ◽  
Pressure Vessels ◽  
Analysis Method ◽  
Integrity Assessment ◽  
Analysis Models ◽  
Reactor Pressure ◽  
The U.S

A probabilistic fracture mechanics (PFM) analysis method for pressure boundary components is useful to evaluate the structural integrity in a quantitative way. This is because the uncertainties related to influence parameters can be rationally incorporated in PFM analysis. From this viewpoint, the probabilistic approach evaluating through-wall cracking frequencies (TWCFs) of reactor pressure vessels (RPVs) has already been adopted as the regulation on fracture toughness requirements against PTS events in the U.S. As a study of applying PFM analysis to the integrity assessment of domestic RPVs, JAEA has been preparing input data and analysis models to calculate TWCFs using PFM analysis code PASCAL3. In this paper, activities have been introduced such as preparing input data and models for domestic RPVs, verification of PASCAL3, and formulating guideline on general procedures of PFM analysis for the purpose of utilizing PASCAL3. In addition, TWCFs for a model RPV evaluated by PASCAL3 are presented.

Structural Integrity Assessment of a Pipeline Subjected to an Underwater Explosion

2011 ◽  
Author(s):  
Paolo Monti ◽  
Caterina Molinari ◽  
Massimiliano Bocciarelli ◽  
Alberto Corigliano ◽  
Stefano Mariani
Keyword(s):  
Structural Integrity ◽  
Underwater Explosion ◽  
Structural Response ◽  
Potential Hazard ◽  
Limit States ◽  
Integrity Assessment ◽  
Definition Of ◽  
Bubble Pulsation ◽  
Numerical Approaches

Several trunklines cross either areas which in the recent past were war theatre or dumping areas used for burying weapons after the last war. The presence of unexploded mines, bombs or torpedoes on the seabed constitutes a potential hazard for the structural integrity of submarine pipelines. Before laying, it is therefore necessary to remove the unexploded charges within a corridor including the route. Risk still remains during the pipeline life, since annual surveys can show evidences of unexploded mines or torpedoes dragged by fishing gears till the protruding pipeline. Consequently, the structural integrity assessment of a submarine pipeline subjected to underwater explosions is of the utmost importance. The aforementioned assessment involves several aspects: the characterization of shock wave and gas bubble pulsation in water; the definition of loading conditions on the pipeline; the characterisation of the strain-rate properties of the steel; the local and global structural analysis; the pipe verification criteria. Aim of this study is to describe how the aforementioned aspects can be managed. Analytical and numerical approaches concerning the assessment of the structural response of the pipeline are presented, and criteria for Serviceability and Accidental Limit States are proposed.

scholarly journals Remote Monitoring of Floating Covers Using UAV Photogrammetry

2020 ◽  
Vol 12 (7) ◽  
pp. 1118 ◽  
Author(s):  
Leslie Wong ◽  
Benjamin Steven Vien ◽  
Yue Ma ◽  
Thomas Kuen ◽  
Frank Courtney ◽  
...  
Keyword(s):  
Structural Integrity ◽  
Wastewater Treatment Plants ◽  
Health Assessment ◽  
Treatment Plant ◽  
Renewable Resource ◽  
The State ◽  
Integrity Assessment ◽  
Structural Health Assessment ◽  
Aerial Vehicle ◽  
Definition Of

High-density polyethylene (HDPE) is commonly the material of choice for covered anaerobic lagoons (CAL) at wastewater treatment plants. The membrane floats on the wastewater, and hence is called a “floating cover”, and is used for odour control and to harvest the methane-rich biogas as a renewable resource to generate electricity. The floating cover is an expensive and high-value asset that demands an efficient methodology for the determination of a set of engineering quantities for structural integrity assessment. Given the dynamics of the anaerobic activities under the floating cover, the state of deformation of the floating cover is an engineering measurand that is useful for its structural health assessment. A non-contact measurement strategy is preferred as it offers practical and safety-related benefits over other methods. In collaboration with Melbourne Water Corporation (MWC), an unmanned aerial vehicle (UAV) assisted photogrammetry approach was developed to address this need. Following the definition of the appropriate flight parameters required to quantify the state of deformation of the cover, a series of periodic flights were operated over the very large floating covers at MWC’s Western Treatment Plant (WTP) at Werribee, Victoria, Australia. This paper aims to demonstrate the effectiveness and practicality of this inspection technique to determine the state of deformation of the floating covers measured over a ten-month period.

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