High Cycle Thermal Fatigue in French PWR

2002 ◽  
Author(s):  
Eric Blondet ◽  
Claude Faidy
Keyword(s):  
Thermal Fatigue ◽  
Nuclear Power ◽  
Power Plants ◽  
Load History ◽  
Power Stations ◽  
The World ◽  
Potential Damage ◽  
High Cycle Thermal Fatigue ◽  
Coolant System ◽  
Reactor Pressure

Different fatigue-related incidents which occurred in the world on the auxiliary lines of the reactor coolant system (SIS, RHR, CVC) have led EDF to search solutions in order to avoid or to limit consequences of thermodynamic phenomenal (Farley-Tihange, free convection loop and stratification, independent thermal cycling). Studies are performed on mock-up and compared with instrumentation on nuclear power stations. At the present time, studies allow EDF to carry out pipe modifications and to prepare specifications and recommendations for next generation of nuclear power plants. In 1998, a new phenomenal appeared on RHR system in Civaux. A crack was discovered in an area where hot and cold fluids (temperature difference of 140°C) were mixed. Metallurgic studies concluded that this crack was caused by high cycle thermal fatigue. Since 1998, EDF is making an inventory of all mixing areas in French PWR on basis of criteria. For all identified areas, a method was developed to improve the first classifying and to keep back only potential damage pipes. Presently, studies are performing on the charging line nozzle connected to the reactor pressure vessel. In order to evaluate the load history, a mock-up has been developed and mechanical calculations are realised on this nozzle. The paper will make an overview of EDF conclusions on these different points: • dead legs and vortex in a no flow connected line; • stratification; • mixing tees with high ΔT.

Nuclear Reactor Pressure Vessel Integrity Assessment: Enhancement Provided by 3D Modeling Flaw Stability Calculations

2013 ◽  
Author(s):  
Adolfo Arrieta-Ruiz ◽  
Eric Meister ◽  
Henriette Churier
Keyword(s):  
Pressure Vessel ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Reactor ◽  
Structural Integrity ◽  
Reactor Pressure Vessel ◽  
Integrity Assessment ◽  
Potential Damage ◽  
Vessel Integrity ◽  
Reactor Pressure

Structural integrity of the Reactor Pressure Vessel (RPV) is one of the main considerations regarding safety and lifetime of Nuclear Power Plants (NPP) since this component is considered as not reasonably replaceable. Brittle fracture risk associated with the embrittlement of RPV steel in irradiated areas is the main potential damage. In France, deterministic integrity assessment for RPV is based on the crack initiation stage. The stability of an under-clad postulated flaw in the core area is currently evaluated under a Pressurized Thermal Shock (PTS) through a fracture mechanics simplified method. One of the axes of EDF’s implemented strategy for NPP lifetime extension is the improvement of the deterministic approach with regards to the input data and methods so as to reduce conservatisms. In this context, 3D finite element elastic-plastic calculations with flaw modelling have been carried out recently in order to quantify the enhancement provided by a more realistic approach in the most severe events. The aim of this paper is to present both simplified and 3D modelling flaw stability evaluation methods and the results obtained by running a small break LOCA event.

French PWR Nuclear Power Plants Steam Generators and Reactor Pressure Vessel Heads Aging Management Criteria and Replacement Strategy

2004 ◽  
Author(s):  
Georges Bezdikian
Keyword(s):  
Pressure Vessel ◽  
Nuclear Power ◽  
Power Plants ◽  
Life Time ◽  
Reactor Pressure Vessel ◽  
Steam Generators ◽  
Life Management ◽  
Power Stations ◽  
Reactor Pressure

The approach used by the French utility, concerning the Aging Management system of the Steam Generators (SG) and Reactor Pressure Vessel Heads, applied on 58 PWR NPPs, involves the verification of the integrity of the component and the Life Management of each plant to guarantee in the first step the design life management and in the second step to prepare long term life time in operation, taking into account the degradation of Alloy 600 material and the replacement of these materials by components made with Alloy 690. The financial stakes associated with maintaining the lifetime of nuclear power stations are very high; thus, if their lifetime is shortened by about ten years, dismantling and renewal would be brought forward which would increase their costs by several tens of billions of Euros. The main objectives are: • to maintain current operating performances (safety, availability, costs, security, environment) in the long term, and possibly improve on some aspects; • wherever possible, to operate the units throughout their design lifetime, 40 years, and even more if possible. This paper shows the program to follow the aging evaluation with application of specific criteria for SG and for Vessel Heads, and the replacement of the Steam Generators and Vessel Heads at the best period. The strategy of Steam Generators Replacement are developed and Vessel Head program of monitoring and replacement are detailed.

Analysis of the Thermal Fatigue Cracking of 316L Model Pipe Components at Fast Reactor Temperatures

2011 ◽  
Author(s):  
Elena Paffumi ◽  
Karl-Fredrik Nilsson
Keyword(s):  
Fatigue Damage ◽  
Thermal Fatigue ◽  
Nuclear Power ◽  
Power Plants ◽  
Tensile Load ◽  
Fatigue Cracking ◽  
Experimental Conditions ◽  
Additional Constant ◽  
Maximum Temperatures ◽  
High Cycle Thermal Fatigue

In order to assess the high-cycle thermal fatigue damage risk of the nuclear power plants mixing zones, the knowledge of the temperature fluctuations effect on the structure surface is necessary. To advance the accuracy and reliability of thermal fatigue load determination, a combined experimental and numerical investigation has been conducted on cylindrical components of 316L stainless steel subject to cyclic thermal shocks of varying intensity. Slightly different experimental conditions were applied in each test to explore the effect of ΔTmax values of increasing severity, addressing also higher temperatures typical for fast reactors, the effect of a superimposed static axial load to study the effect of a constant pressure on the thermal fatigue damage and a reduced test piece wall thickness. A comparison between thermal down-shock tests with and without additional constant tensile load and with different maximum temperatures are analysed in details here below.

High cycle thermal fatigue Issues in PWR nuclear power plants, life time improvement of some austenitic stainless steel components

2007 ◽  
Vol 104 (3) ◽  
pp. 156-162 ◽  
Author(s):  
J. -A. Le Duff ◽  
A. Lefrançois ◽  
Y. Meyzaud ◽  
J.-Ph. Vernot ◽  
D. Martin ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Thermal Fatigue ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Life Time ◽  
High Cycle Thermal Fatigue

Analysis of the FATHER Experiment With an Engineering Method Devoted to High Cycle Thermal Fatigue

2011 ◽  
Author(s):  
Romain Beaufils ◽  
Stephan Courtin
Keyword(s):  
Fatigue Damage ◽  
Thermal Fatigue ◽  
Turbulent Mixing ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Nuclear Industry ◽  
Engineering Method ◽  
Different Temperatures ◽  
High Cycle Thermal Fatigue

Nuclear power plants necessarily include connections of branches conveying fluids at different temperatures. Thermo-hydraulic fluctuations arising from the turbulent mixing of the flows may affect the inner wall of the pipes and lead to fatigue damage. The FATHER experiment was carried out in order to better understand this phenomenon of High Cycle Thermal Fatigue (HCTF). The aim of this paper is to present an analysis of the FATHER experiment with a simplified engineering method which is used in French nuclear industry to identify and classify zones presenting a HCTF risk.

PREREQUISITES FOR THE DEVELOPMENT OF NUCLEAR ENERGY IN THE GLOBAL ECONOMY

2020 ◽  
Vol 2 (3) ◽  
pp. 153-158
Author(s):  
E. V. YANUSIK ◽  
Keyword(s):  
Energy Consumption ◽  
Economic Efficiency ◽  
Global Economy ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Energy ◽  
World Market ◽  
Global Energy ◽  
The World ◽  
Global Energy Consumption

The article discusses the main prerequisites for the development of nuclear energy in the global econo-my, also defines nuclear energy and discusses the structure of global energy consumption. The article proves that the crucial prerequisite for the development of nuclear energy in the world market is the economic efficiency of nuclear power plants.

The method for calculating the probability of brittle destruction of NPP equipment in different operating modes with postulated defectiveness

2021 ◽  
Vol 14 (1) ◽  
pp. 34-39
Author(s):  
D. A. Kuzmin ◽  
A. Yu. Kuz’michevskiy
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Nuclear Power ◽  
Power Plants ◽  
Reactor Pressure Vessel ◽  
Practical Significance ◽  
Reactor Unit ◽  
Operating Modes ◽  
Brittle Destruction ◽  
Reactor Pressure

The destruction of equipment metal by a brittle fracture mechanism is a probabilistic event at nuclear power plants (NPP). The calculation for resistance to brittle destruction is performed for NPP equipment exposed to neutron irradiation; for example, for a reactor plant such as a water-water energetic reactor (WWER), this is a reactor pressure vessel. The destruction of the reactor pressure vessel leads to a beyond design-basis accident, therefore, the determination of the probability of brittle destruction is an important task. The research method is probabilistic analysis of brittle destruction, which takes into account statistical data on residual defectiveness of equipment, experimental results of equipment fracture toughness and load for the main operating modes of NPP equipment. Residual defectiveness (a set of remaining defects in the equipment material that were not detected by non-destructive testing methods after manufacturing (operation), control and repair of the detected defects) is the most important characteristic of the equipment material that affects its strength and service life. A missed defect of a considerable size admitted into operation can reduce the bearing capacity and reduce the time of safe operation from the nominal design value down to zero; therefore, any forecast of the structure reliability without taking into account residual defectiveness will be incorrect. The application of the developed method is demonstrated on the example of an NPP reactor pressure vessel with a WWER-1000 reactor unit when using the maximum allowable operating loads, in the absence of load dispersion in different operating modes, and taking into account the actual values of the distributions of fracture toughness and residual defectiveness. The practical significance of the developed method lies in the possibility of obtaining values of the actual probability of destruction of NPP equipment in order to determine the reliability of equipment operation, as well as possible reliability margins for their subsequent optimization.

scholarly journals Improvement of turbogenerators as a technical basis for ensuring the energy independence of Ukraine

2021 ◽  
pp. 19-30
Author(s):  
V. V. Shevchenko ◽  
A. N. Minko ◽  
M. Dimov
Keyword(s):  
Renewable Energy ◽  
Electric Power ◽  
Energy Security ◽  
Nuclear Power ◽  
Power Plants ◽  
Renewable Energy Sources ◽  
Electric Power Industry ◽  
Energy Sources ◽  
The World ◽  
Energy Independence

The paper defines the directions of improving turbogenerators as the basis for ensuring the energy independence of Ukraine. The analysis of the state, problems and prospects for the development of modern electric power industry. Goal of the work is to identify promising directions for sustainable development of the national electric power industry in order to ensure energy security of Ukraine, to conduct a comparative analysis of electricity sources, to confirm the need to improve the main sources – turbogenerators. Methodology. During the research, an analytical analysis of the electricity sources, which are installed at power plants in Ukraine and the world, was carried out, taking into account the growth of the planet's population and its energy activity. Cyclic theory was chosen as the theoretical basis for forecasting. On the basis of this theory, global development trends, advantages and disadvantages of currently used sources of electricity - thermal (including nuclear) power plants and stations that operate from renewable energy sources - have been established. A review of literary sources on the methods of the energy sector forecasting the development, including the development of the energy sector in Ukraine, has been carried out. Originality. It has been established that due to the active growth of the planet's population, with the increase in its energy activity, obtaining electricity from renewable energy sources is not enough, that for the next 20-30 years nuclear power plants will be the main sources of electricity. The internal and external threats to the energy security of Ukraine, directions of development of turbogenerator construction, ways to improve turbogenerators, to increase their energy efficiency, power per unit of performance, to increase the readiness and maneuverability factors, and overload capacity have been identified. Practical significance. The need to continue the modernization and improvement of the turbogenerators of nuclear power plant units, as the main sources of electricity, has been proved. The directions of their improvement are established: increasing the power in the established sizes, making changes to the design of the turbogenerators inactive elements, replacing the cooling agent to keep Ukrainian turbogenerators at the world level, improving auxiliary systems, improving and increasing the reliability of the excitation system, introduction of automatic systems for monitoring the state turbogenerators. Possible limits of use, advantages, disadvantages and problems of using renewable energy sources for Ukraine have been established.

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