French RPV Assessment — Contribution of Expertises in Mechanical Analyses

2002 ◽  
Author(s):  
G. Bezdikian ◽  
Y. Rouillon ◽  
J. Bourgoin
Keyword(s):  
Brittle Fracture ◽  
Three Dimensional ◽  
Mechanical Analysis ◽  
Surveillance Program ◽  
Low Leakage ◽  
New Development ◽  
Safety Studies ◽  
Vessel Material ◽  
Vessel Integrity ◽  
Mechanical Studies

The process used by the French utility, concerning the Reactor Pressure Vessel assessment, applied on 54 PWR NPPs (3-loop and 4-loop Reactors), involves the verification of the integrity of the component by mechanical studies, in the most severe conditions of loading in relation with RTndt (Reference Nil Ductility Transition Temperature), and considering major parameters. This approach, is based on mechanical safety studies, to demonstrate the absence of risk of failure by brittle fracture. For these mechanical studies two major input data are necessary: 1 - the fluence distribution and the values during the lifetime in operation for each NPPs, 2 - the thermal-hydraulic evaluation and temperature distribution values in the downcomer. The main results must show significant margins against initiation of the brittle fracture. The flaws considered in this approach are shallow flaws beneath the cladding (subclad flaws) or in the first layer of cladding. The major tasks and expertises engaged by EDF are: • more precise assessment of the fluence and neutronic calculations, • better knowledge of the vessel material properties, including the effect of radiation, • the NDE inspection program based on the inspection of the vessel wall, with a special NDE tool to inspect the area in subcladding zone, • the evaluation of vessel integrity, the mechanical analysis of margins in major loading conditions. The principal actions conducted during recent years are: • the fuel management optimisation (low-leakage core design) and the new development to evaluate the fluence, • the data gathered from radiation specimen capsules, removed from the vessels (3 loop reactor), within the framework of the radiation surveillance program, and • the thermal-hydraulic-mechanical calculations based on finite element thermal-hydraulic computations and three dimensional elastic-plastic mechanical analyses.

French Four-Loop PWR 1300 MWe Reactor Pressure Vessel: First Results for Integrity Assessment and Life Manangement

2003 ◽  
Author(s):  
Georges Bezdikian ◽  
Franc¸oise Ternon-Morin ◽  
Henriette Churier-Bossennec ◽  
Dominique Moinereau ◽  
Alain Martin
Keyword(s):  
Brittle Fracture ◽  
Pressure Vessel ◽  
Three Dimensional ◽  
Pressure Vessels ◽  
Reactor Pressure Vessel ◽  
Surveillance Program ◽  
Integrity Assessment ◽  
First Results ◽  
Safety Studies ◽  
Reactor Pressure

The process used by the French utility, concerning the Reactor Pressure Vessel (RPV) integrity assessment, applied on 34 PWR NPPs 3-loop Reactors, involved the verification of the integrity of the component under the most severe conditions of situation, was engaged several years ago and the result obtained was the justification of the 900 MWe RPV life management for at least 40 years and to prepare the projection for beyond 40 years. Since 2000, in the continuity of this results, the studies was carried out on the 20 PWR NPPs 4-loop 1300 MWe Reactor Pressure Vessels, and the recent results obtained shows the demonstration of the integrity of the RPV, in the most severe conditions of loading in relation with RTNDT (Reference Nil Ductility Transition Temperature), and considering major parameters particularly the severity of the transient. This approach, is based on specific mechanical safety studies on the 1300 MWe RPV, to demonstrate the absence of risk of failure by brittle fracture. For these mechanical studies the major input data are necessary: 1 - the fluence distribution and the values of 4-loop RPV RTNDT during the lifetime in operation, 2 - the temperature distribution values in the downcomer and the PTS evaluation. The main results must show significant margins against initiation of the brittle fracture. The flaws considered in this approach are shallow flaws beneath the cladding (subclad flaws) or in the first layer of cladding. The major tasks and expertises engaged by EDF are: • better knowledge of the vessel material properties, including the effect of radiation, • more precise assessment of the fluence and neutronic calculations, • the NDE inspection program based on the inspection of the vessel wall, with a special NDE tool. The principal actions conducted during recent years are: • the optimisation of the fuel management and the new development for the fluence evaluation, • the data gathered from radiation specimen capsules, removed from the vessels (4loop reactor), within the framework of the radiation surveillance program, and the thermal-hydraulic-mechanical calculations based on finite element thermal-hydraulic computations and three dimensional elastic-plastic mechanical analyses.

RPV Integrity Assessment: Comparison Between 3 Loops and 4 Loops Studies

2004 ◽  
Author(s):  
Georges Bezdikian ◽  
Dominique Moinereau ◽  
Claude Faidy
Keyword(s):  
Brittle Fracture ◽  
Nuclear Power ◽  
Power Plants ◽  
Electric Energy ◽  
Pressure Vessels ◽  
Surveillance Program ◽  
Integrity Assessment ◽  
Safety Studies ◽  
Comparison Of The Results ◽  
Reactor Pressure

For the French utility (Electricite de France–EDF), Nuclear Energy represents 75% of generation of the total electric energy in France. Total nuclear electricity were generated mainly from Nuclear Power plants stations, 34 PWR NPPs 3-loop Reactors- 900 MWe, 20 PWR NPPs 4-loop Reactors- 1300 MWe and 4 PWR NPPs 4-loop Reactors- 1450 MWe. The 3-loop Reactor Pressure Vessel (RPV) integrity assessment, applied on 34 PWR NPPs Reactors, involved the verification of the integrity of the component under the most severe conditions of situation, and the result obtained was the justification of the 900 MWe RPV life management for at least 40 years and to prepare the projection beyond 40 years. Since 2000, in the continuity of these results, the studies were carried out on the 20 PWR NPPs 4-loop 1300 MWe Reactor Pressure Vessels, and the recent results obtained show the demonstration of the integrity of the RPV, in the most severe conditions of loading in relation with RTNDT (Reference Nil Ductility Transition Temperature), and other major parameters. This approach is based on specific mechanical safety studies on the RPV to demonstrate the absence of the risk of failure by brittle fracture. For these mechanical studies the major input data are necessary: 1 - the fluence distribution and the values of 3-loop and 4-loop RPV, 2 - RTNDT during the lifetime in operation, 3 - the temperature distribution values in the downcomer and the PTS evaluation. The main results must show significant margins against initiation of brittle fracture for all of 3-loop and 4-loop RPV. The flaws considered in this approach are shallow flaws beneath the cladding (subclad flaws) or in the first layer of cladding. The major tasks and expertises engaged by EDF are: • more precise assessment of the fluence calculations, • better knowledge of the vessel material properties, including the effect of radiation, • the NDE inspection program on the core zone. The comparison of the results are developed in this paper: • for the fluence evaluation and the optimisation of the fuel management, • the data gathered from radiation specimen capsules, removed from the vessels (radiation surveillance program), • and the thermal-hydraulic and mechanical calculations based on finite element thermal-hydraulic and 3D elastic-plastic mechanical computations.

Cleavage Planes of Icosahedral Quasicrystals: A Molecular Dynamics Study

2003 ◽  
Vol 805 ◽  
Author(s):  
Frohmut Rösch ◽  
Christoph Rudhart ◽  
Peter Gumbsch ◽  
Hans-Rainer Trebin
Keyword(s):  
Molecular Dynamics ◽  
Brittle Fracture ◽  
Crack Propagation ◽  
Three Dimensional ◽  
Propagation Direction ◽  
Mode I ◽  
Dynamic Crack ◽  
Fracture Surfaces ◽  
Icosahedral Quasicrystals ◽  
Crack Tip Plasticity

ABSTRACTThe propagation of mode I cracks in a three-dimensional icosahedral model quasicrystal has been studied by molecular dynamics techniques. In particular, the dependence on the plane structure and the influence of clusters have been investigated. Crack propagation was simulated in planes perpendicular to five-, two- and pseudo-twofold axes of the binary icosahedral model.Brittle fracture without any crack tip plasticity is observed. The fracture surfaces turn out to be rough on the scale of the clusters. These are not strictly circumvented, but to some extent cut by the dynamic crack. However, compared to the flat seed cracks the clusters are intersected less frequently. Thus the roughness of the crack surfaces can be attributed to the clusters, whereas the constant average heights of the fracture surfaces reflect the plane structure of the quasicrystal. Furthermore a distinct anisotropy with respect to the in-plane propagation direction is found.

scholarly journals Numerical aspects for efficient welding computational mechanics

2014 ◽  
Vol 18 (suppl.1) ◽  
pp. 139-148
Author(s):  
Tarek Aburuga ◽  
Aleksandar Sedmak ◽  
Zoran Radakovic
Keyword(s):  
Residual Stresses ◽  
Three Dimensional ◽  
Shell Element ◽  
Element Model ◽  
Mechanical Analysis ◽  
Tensile Test Specimen ◽  
Integrity Assessment ◽  
Mass Scaling ◽  
Three Dimensional Models ◽  
Thermal Mechanical Analysis

The effect of the residual stresses and strains is one of the most important parameter in the structure integrity assessment. A finite element model is constructed in order to simulate the multi passes mismatched submerged arc welding SAW which used in the welded tensile test specimen. Sequentially coupled thermal mechanical analysis is done by using ABAQUS software for calculating the residual stresses and distortion due to welding. In this work, three main issues were studied in order to reduce the time consuming during welding simulation which is the major problem in the computational welding mechanics (CWM). The first issue is dimensionality of the problem. Both two- and three-dimensional models are constructed for the same analysis type, shell element for two dimension simulation shows good performance comparing with brick element. The conventional method to calculate residual stress is by using implicit scheme that because of the welding and cooling time is relatively high. In this work, the author shows that it could use the explicit scheme with the mass scaling technique, and time consuming during the analysis will be reduced very efficiently. By using this new technique, it will be possible to simulate relatively large three dimensional structures.

Development and Application of Innovative Anti-Seismic Systems for the Protection of Cultural Heritage: New Achievements of ENEA

2002 ◽  
Author(s):  
M. Indirli ◽  
M. Forni ◽  
A. Martelli ◽  
B. Spadoni ◽  
A. Dusi ◽  
...  
Keyword(s):  
Cultural Heritage ◽  
Seismic Isolation ◽  
New Technology ◽  
Three Dimensional ◽  
Ambient Vibration ◽  
Civil Structures ◽  
Industrial Plants ◽  
Marche Region ◽  
Passive Devices ◽  
New Development

As described in detail at previous ASME-PVP Conferences and also reminded by separate papers presented this year, large efforts have been devoted by the Italian Agency for New Technology, Energy and the Environment (ENEA), with the cooperation of several further members of the Italian Working Group on Seismic Isolation (GLIS), to the development, validation and application of innovative anti-seismic (IAS) techniques since 1988. To date, considered have been base and floor seismic isolation (SI), energy dissipation through various types of passive devices, hydraulic coupling by means of innovative shock transmitters, systems formed by shape memory alloy devices and more recently, semi-active control of vibrations. New activities at ENEA, which are in progress in the framework of both international and national collaborations, concern the development of new IAS techniques of the aforesaid kinds to be applied to: • civil structures and industrial plants; • cultural heritage structures (CUHESs) to be restored or reconstructed, or masterpieces to be seismically protected. Progress of the work performed for civil and industrial structures has been separately presented at this Conference, while this paper deals with the new development, validation and application activities concerning the IAS techniques applicable to the seismic protection of CUHESs, to which particular attention has been devoted by ENEA for several years. The ongoing activities for CUHESs are being performed in the framework of: • PROSEESM, a national project which foresees pilot applications of the IAS techniques to the restoration of CUHESs damaged by the 1997–98 Marche and Umbria earthquakes; • a feasibilily study for the reconstruction in the original site, with SI and the original masonry materials, of Mevale di Visso, a village in the Marche Region destroyed by the aforesaid event; • a study for the design and application of an innovative three-dimensional SI system for seismic and ambient vibration protection of a roman ship excavated at Ercolano, near Naples.

Development and Mechanical Characterization of a Collagen/Hydroxyapatite Bilayered Scaffold for Ostechondral Defect Replacement

2011 ◽  
Vol 493-494 ◽  
pp. 890-895 ◽  
Author(s):  
Francesca Gervaso ◽  
Francesca Scalera ◽  
Sanosh Kunjalukkal Padmanabhan ◽  
Antonio Licciulli ◽  
Daniela Deponti ◽  
...  
Keyword(s):  
Mechanical Strength ◽  
Sol Gel ◽  
Three Dimensional ◽  
Collagen Scaffold ◽  
Mechanical Analysis ◽  
Design Parameters ◽  
Compression Tests ◽  
Templating Method ◽  
Organic Part ◽  
Hydroxyapatite Scaffold

In this work a novel three-dimensional ostechondral substitute is proposed that is made of an inorganic/organic hybrid material, namely collagen/hydroxyapatite. The two components of the substitute have been characterized separately. The inorganic part, a hydroxyapatite scaffold, was fabricated by a polymer sponge templating method using a reactive sub-micron powder synthesized in our laboratory by hydroxide precipitation sol-gel route. The organic part, a collagen scaffold, was fabricated by a freeze-dying technique varying design parameters. Both the parts were analysed by scanning electron microscopy and their mechanical properties assessed by compression tests. The hydroxyapatite scaffold showed a high and highly interconnected porosity and a mechanical strength equal to 0.55 MPa, higher than those reported in literature. The collagen scaffolds were seeded by chondrocytes, processed for histology analysis and tested in compression. The biological tests proved the ability of the scaffolds to be positively populated by chondrocytes and the mechanical analysis showed that the mechanical strength of the scaffolds significantly increased after 3 weeks of culture.

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