VGB PowerTech 5 (2012) - Areva

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Advanced cycle based fatigue VGB PowerTech 5 l 2012

Kurzfassung

Fortschrittliche zyklenbasierte Ermüdungs- analyse – Eine Synthese aus Temperaturprofil und Spannungsverlauf

Die zyklenbasierte Ermüdungsanalyse (Cycle Based Fatigue, CBF) ist eines der internatio-nal etablierten und angewendeten Verfahren, um die Materialermüdung von Komponenten in Kernkraftwerken zu bewerten. Sie basiert auf einem Katalog von thermischen Transien-ten, der entweder aus den Design-Transienten (zusammengestellt in der Planungsphase des Kraftwerks) und den zugehörigen Betriebswei-sen abgeleitet wird, oder, für realistischere Er-gebnisse, aus Temperaturmessungen im Betrieb gebildet wird. Ein weiteres anerkanntes Verfah-ren ist die spannungsbasierte Ermüdungsana-lyse (Stress Based Fatigue, SBF), die eine diffe-renzierte Bewertung des Ermüdungszustandes zulässt.Das Areva Fatigue Concept (AFC) enthält einen dreistufigen Ansatz für die Ermüdungsbewer-tung, der sowohl CBF- als auch SBF-Verfahren enthält. Als ein neues Modul wurde zuletzt das Verfahren „Advanced Cycle Based Fatigue“ (A-CBF) entwickelt. Dieses ermöglicht eine Erstel-lung von thermischen Transienten für den Tran-sientenkatalog durch eine Kombination der zu-vor genannten Ansätze. Der vorliegende Beitrag beschreibt das neue A-CBF-Verfahren, das nicht nur die ermittelten Temperaturprofile, sondern auch die Spannungsverläufe, die vorher im dreistufigen Ansatz berechnet wurden, nutzt. l

Advanced cycle based fatigue – a stress and temperature based synthesis of existing basic approachesChristian Heinze, Jürgen Rudolph, Steffen Bergholz, Benoît Jouan and Martin Reithinger

Introduction

The aging management in nuclear power plants gains importance, as many coun-tries aim at a prolonged operation beyond the originally designed lifetime of those plants. The consideration and evaluation of possible and present aging mechanisms are integrated parts of these lifetime exten-sion measures. Aging effects due to cyclic loading of components, e.g. fatigue phe-nomena, play a central role in this context. The correct determination of a realistic cu-mulative fatigue usage factor and an asso-ciated prospect for the additional lifetime is the central task of fatigue assessment of a real plant.Two different approaches – the so-called “Cycle Based Fatigue” (CBF) and “Stress Based Fatigue” (SBF) – constitute estab-lished methods and tools for the follow-up of the real fatigue usage. In the framework of this methodology, on the one hand the CBF based approach focuses on the regis-tration and allocation of fatigue relevant cyclic loads as well as the counting in ma-trices of frequencies of occurrence. On the other hand, the SBF based approach focus-es on the determination of component spe-cific load-time (respectively stress-time) series.

In addition to the lifetime extending meas-ures tighter requirements on the fatigue checks are defined in nuclear design codes (ASME, KTA, etc.). These are particularly due to new research results concerning the influence of the medium on the fatigue process (Environmentally Assisted Fatigue, EAF). This paper aims at describing an improve-ment with respect to the quantification of the fatigue usage factor compared to the classical CBF procedure by introducing a new A-CBF (advanced CBF) approach.

Areva fatigue concept

Areva develops its own integrated fatigue concept (AFC) [1]. This concept provides for a multiple step and multidisciplinary process (process engineering, fatigue monitoring, fatigue analyses etc.) against fatigue before and during the entire opera-tion of nuclear power plants. The structure and the modules of the AFC are shown in F i g u r e 1. Compared to previous sche-matical representations, the new module A-CBF is added.The modules are described in more detail in [1] and [2]. Figure 1 underlines the central position of the fatigue monitor-ing module. Areva now offers Famosi (“i”

AuthorsChristian HeinzeJürgen RudolphSteffen BergholzBenoît JouanMartin Reithinger Corresponding authorJürgen RudolphAreva NP GmbHErlangen/Germany

Design data

Linear-elastic stress information

AnalyseApproval ofdocuments

Aging and lifetimemanagement

Long-term operation

• Optimisation

• Availability

• Detection of failure

Temperature Cycle countingmethods

Simplified fatigueestimation (SFE)

Fast fatigueevaluation (FFE)

Detailed fatiguecalculation (DFC)Transients catalogue

Adv

ance

d cy

cle

base

d fa

tigue

(A-C

BF) Famos

measurement

R & D Methods Tools Surface Sequence Size Environment

Further effects from code requirementSupporting function +

Ope

ratio

nEr

ectio

n

Licensedstatus

Figure 1. Areva Fatigue Concept (AFC).

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>>> VGB DIGITAL <<<VGB PowerTech - Autorenexemplar - © 2012

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VGB PowerTech 5 l 2012 Advanced cycle based fatigue

stands for integrated) as a modern central data logging system (for further descrip-tion and explanation see [2] and [3]).

FamosThe Fatigue Monitoring System (Famos) was developed by then Siemens KWU at the end of the 1980s and systematically installed in German nuclear power plants. The associated development efforts were both triggered by thermal fatigue issues and authority requests. The monitoring systems allowed thermal load histories to be available for those fatigue relevant com-ponents equipped with the appropriate measurement sections. In terms of a data logging system the installation of Famos is carried out as a clamped measurement strap on the outer wall surface of the pipe nearby the fatigue relevant location as it is shown in F i g u r e 2 .Nowadays, the measurement system is based on a modern data management ap-proach (data bus structure, SQL database, live network data stream) and is very flex-ible in installation and application. The modern system design ensures an easy sys-tem installation and relatively low costs. The actual data logging frequency is 1 Hz, respectively 1s. Any further processing of measured (temperature) data has to take into account the capacitive effect of the applied measurement sections. This effect is appropriately considered by correction

factors specific to the respective measure-ment section.Famos gathers measurement sections, which are mostly located on the:

– primary loops, – surge line, – spray lines, – volume control system, – feedwater system and further positions.

The different Famos measurement sections (see e.g. Figure 2) can be composed of seven or more thermocouples if some ther-mal events like stratification are suspected (horizontally installed pipes). However, in case of plug flow the application of only two thermocouples is sufficient (vertically installed pipes).For a more detailed description of the tech-nical bases of the Famos system, see e.g. [1] and [2].

Fast fatigue evaluationAs described above, Famos measurements deliver temperature-time histories for the measurement sections at outer wall posi-tions. The derivation of component stress and fatigue data requires two intermedi-ate transfer steps: 1) outer wall to inner wall position and 2) inner wall and other fatigue relevant component positions in terms of temperature and stress tensor. The “Fast Fatigue Evaluation” (FFE) tech-nology relies on the elementary transients (Green’s function) approach for both trans-fer steps. The according flowchart for the determi-nation of the inner wall temperature based on the outer wall temperature within step 1) is shown in F i g u r e 3 . The difficulties associated with the description of the heat transfer from the bulk fluid to the inner wall (left branch in Figure 3) are to some extent avoided by application of the FFE method to the determination of the time history of the inner wall temperature by solving the inverse problem of conduction of heat (right branch in Figure 3). Note that the knowledge of the transient tem-

perature distribution throughout the wall is sufficient to perform the required struc-tural analyses. Solving the inverse conduction equation of heat is done by application of poten-tial functions (elementary transients). An elementary transient is applied at the in-ner surface of the pipe (boundary condi-tion), the equation of conduction of heat is solved, the resulting time history of tem-perature at the outer wall is observed. The equation of heat can be resolved by means of an analytical method or with the help of a finite element program (Ansys®). In that case, a two-dimensional model of the section of the pipe is generated. The benefit of this last choice is the opportu-nity to integrate the thermal influences of the thermocouple installation at the outer surface of the pipe in the solution. The de-termined temperature response calculated in the thermocouple (outer wall) will be considered as a reference. Its evolution is characteristic by the applied unit transient at the inside surface of the pipe (characterised by a temperature rate of changes and a thermal amplitude ΔTref). Thus the Famos measured outside tem-perature will be scanned step by step (typi-cally every second). The temperature dif-ference at the outer wall between two time steps is compared with the simulated outer wall temperature (reference). The factor resulting from this comparison is through linearity properties also available at the in-ner side of the structure. Thus, step by step the inside temperature of the pipe can be restituted. For a more in-depth description of the process, see [2].The application of the FFE technology for step 2) is described below in the chapter “Elementary transient”.

Detailed fatigue calculationThe detailed code based fatigue calcula-tion is usually carried out after a certain time period of plant operation (e.g. 10 years), preferably in the framework of the periodic safety inspection. Loading data

Figure 2. Exemplary local measurement section.

T_fluid(t)

Pressure(t)

Flow(t)

Geometry

Temperatureinner wall (t + ∆t1)

Temepratureouter wall (t + ∆t2)

Newton‘s law

Equation of conduction of heat

Inverse solve of the equation of heat

Figure 3. Determination of inner wall temperature.

Tem

pera

ture

in °C

Time in s

Maximumgradient

Temperaturedifference

Original temperaure profileSubstitution transient

Figure 4. Substitution transient.

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of the operational period as well as antici-pated loads of future operation are used as essential input parameters. In a broader sense, these loading data may be delivered by the new method described in this arti-cle. In this way FFE may be directly com-bined with “Detailed Fatigue Calculation” (DFC). Fatigue usage factors are calculated for the current state of the plant and until the end of life (e.g. 40 or 60 years). The fatigue analysis for primary circuit com-ponents is based on design codes such as the ASME code [4], the German KTA rules [5] or the French RCC-M code [6]. Fatigue calculations are usually carried out as sim-plified elasto-plastic or elasto-plastic anal-yses. The simplified elasto-plastic fatigue analysis based on elastic FEA and plasticity correction (fatigue penalty or strain con-centration factors Ke) is known to yield fre-quently conservative results. In the prac-tical application this will often yield high calculated usage factors. As a consequence, the branch of elasto-plastic fatigue analysis methodology based on non-linear FEA will often be used. This is associated with an increased calculation effort. Computing times for complex 3D geometries and numerous transients (cou-pling of transient thermal and mechanical analyses) are significant. Under these cir-cumstances the specified model transients have to be rearranged in a small set (often 7 to 10) of covering transients for calcula-tion purposes in the sense of manageabil-ity. These model transients have to cover conservatively the real temperature versus time functions measured in the plant pref-erably based on the local monitoring strat-egy described above. Now, these model transients can be equally delivered by the A-CBF approach to be described below.

Cycle based fatigue

The accurate knowledge of the real load-ings is crucial as fatigue is a direct function of the resulting component stresses and strains. Generally, the (thermal) loads are defined in so-called transient catalogues. In turn, those transient catalogues con-

stitute the input for component checks. These catalogues include the typical loads (pressure, temperature, etc.) as a function of time and the associated frequency of oc-currence. The component fatigue check is based on the information of the catalogue and determines the expected fatigue usage of the component. Additionally, it has to be shown that the occurring operational loads correspond in character and frequency of occurrence to those specified in the catalogue. For this purpose, so-called load case counting lists are recorded and compared to the specified loads. As long as the frequency of occur-rence of the existing (and measured) loads remains below the specified loads (used for the design fatigue check based on design transients) the safety margin against the aging mechanism of fatigue is assumed to be given. Internationally, this procedure is called CBF. Nevertheless, compared to the SBF approach the existing CBF models only constitute a rough assessment method of fatigue considerations. In the case of SBF, the stress-time histories occurring in the component as a consequence of the tran-sient loading constitute the basis for the determination of the damage contribution. By application of the usual counting pro-cedures (e.g. the rain flow counting algo-rithm) stress-time series are transformed to component fatigue usages.For further information refer to [7].

Advanced cycle based fatigueOverviewThe A-CBF offers an improvement over the methodology of the “Detailed Fatigue Cal-culation” (DFC) and can be applied anal-ogously to the classical CBF. The DFC is based on a covering substitution transient for the temperature, which is determined only from the temperature profile on the inner wall of the measurement section or specified in terms of bulk temperature in connection with appropriate heat transfer coefficients. The covering transient is char-

acterized by the extreme values of the tem-perature profile as well as the maximum gradients between those extreme values ( F i g u r e 4 ).

The A-CBF uses additional information available from the FFE technology. In or-der to perform the FFE the elementary transient for the stress tensors needs to be known for every fatigue relevant loca-tion of a given component. That informa-tion enables the calculation of the stress resulting from any arbitrary temperature profile for those locations. Therefore, the gradients of the substitution transient can be selected based on maximum equivalent stresses instead of the maximum gradients in the measured temperature profile. The resulting substitution transient is more re-alistic and leads to lower but still covering usage factors.

Resulting maximum stress for linear temperature change The substitution transient is composed of parts with constant temperature and parts with linear temperature change. Therefore, preliminary considerations on the result-ing maximum stress of a linear tempera-ture change with a limited duration (a tem-perature ramp) on the inside of a wall are required. The following investigations will be conformed on axially symmetric pipe geometry with temperature-independent material properties, linear-elastic material behaviour and adiabatic conditions on the outside wall.

F i g u r e 5 shows a temperature ramp on the inside wall. It is fully defined by the temperature difference and the duration of the ramp Δt. The temperature change rate (TCR) of the ramp is defined by T = ΔT/Δt. Furthermore the resulting tempera-ture on the outside as well as the resulting equivalent stress at an arbitrary location is shown qualitatively. The equivalent stress is any function that reduces the stress ten-sor σ= to a one-dimensional stress value.

σeqv = ƒeqv (σ=)� (1)

In te

mpe

ratu

re/s

tress

In time

Temperature inside

Temperaure outside

Equivalent stress

Figure 5. Temperature ramp with resulting equivalent stress.

In st

ress

/TCR

Duration of the ramp

Reference stress profile

TCR

Resulting maximum stress

smax

Dt

Figure 6. Resulting maximum stress over ramp duration for a given temperature difference.

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Based on the diagram and the character-istics of a pipe geometry two assumptions can be made: firstly, the maximum stress is reached at the end of the temperature ramp. This is conclusive, since the maxi-mum temperature difference is reached at this time. Secondly, the stress is pro-portional to the TCR because of the linear dependency between TCR, temperature profile in the component and the resulting stress.

Those assumptions allow the calculation of the maximum stress induced by a tempera-ture ramp with a given temperature differ-ence ΔT for any location in a component, if the reference stress profile σeqv (Δt) is known for a reference ramp, characterised by its TCR Tref.

ΔT σref (Δt)σmax (Δt) = –– –––––––– (2) Δt Tref

This equation only holds true, if there is no pre-existing stress in the component, caused by pressure or previous tempera-ture ramps. Otherwise the pre-existing stress σ=0 has to be accounted for with all its stress components.

ΔT σ=ref (Δt)σmax (Δt) = ƒeqv ∙σ=0+ –– ––––––––∙ (3) Δt Tref

With the equation (2) and (3), respec-tively, a maximum stress over ramp dura-tion graph can be calculated for any given temperature difference, pre-existing stress, and reference stress profile. The results are shown qualitatively in F i g u r e 6 . With this graph the necessary ramp duration for a stress peak can be found easily.

In summary, it is possible to calculate the maximum equivalent stress resulting from a temperature ramp and any pre-existing stress under the following conditions:

– stress is proportional to TCR, – maximum stress occurs at the end of

temperature ramps.

Elementary transientThe thermal stress determination is based on an elementary transients approach within the FFE technology described above. Depending on the monitored component, a two-dimensional or three-dimensional finite element model is generated and pre-pared for thermal transient and linearly elastic structural analysis.

The inside temperature is scanned step by step and transferred to the component in-ner wall position. Between two time steps, the temperature difference is interpreted as an elementary transient the amplitude of which is compared to the reference elementary transient of a range ΔTref. In the subsequent step, two elementary tran-sients of ±100K are used to scan the origi-nal temperature time history at each time step. The calculated stress components are the response to a reference load character-

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ised by a temperature rate of change and a thermal range ΔTref. Because of linearity in the thermal stress calculation, the com-parison between the measured amplitude and the reference gives a coefficient to be applied to the reference stress matrix in or-der to obtain the stress contribution result-ing from the thermal load at the calculated time. The time-dependent stress compo-nents are then obtained by the summation of all these single contributions. The stress matrix references have to be calculated previously. The results are then added to the database of FFE: it is the pre-processing work. Subsequently, the calculation at the selected locations can be processed.

It is obvious and straight forward that the stress responses to the temperature ramps required for the A-CBF approach to be de-veloped here are advantageously calcu-lated by means of the FFE technology de-scribed above.

Determining a covering substitution transientWhen determining a covering substitution transient regarding the stresses, it has to be considered that the stresses caused by the temperature changes are different at every location. Therefore, the fatigue lead-ing locations have to be identified and a substitution transient has to be found for all of those locations. Finally all substitu-tion transients have to be compared and merged into a covering substitution tran-sient. This chapter will describe how the substitution transients can be found and how they are merged.

The overall process is depicted in F i g - u r e 7. At first, during the data prepara-tion, the actual stress profile as well as the reference stress profile for a temperature ramp is calculated. This is done via the

method of elementary transients. The re-quired input is the measured temperature profile and the elementary transient for the stress at the location. The next step is the determination of the substitution transient for the current location. After the substitu-tion transients for all locations are identi-fied, they are compared and merged into a covering substitution transient.

In F i g u r e 8 a flowchart is shown for the determination of a substitution transient at a single location. The measured tempera-ture profile, the actual stress profile as well as the reference stress profile for a temper-ature ramp need to be available from the data preparation.

The first temperature value of the substitu-tion transient is identical to the first value of the measured temperature profile. The resulting stress is calculated via the meth-od of elementary transients.

The measured temperature is then consec-utively scanned for temperature extremes. For each pair of extremes it is checked whether there is a local stress maximum in between. If so, the end of the ramp for the substitution transient is set to be at the same time as the stress maximum. Then the duration of the ramp is chosen using equation (2) and (3), respectively. The pre-existing stress is here the stress that results

from the ramps that are already written in the substitution transient at the time of the designated end of the current ramp. If the calculated beginning of the ramp is before the end of the previous ramp, the desig-nated end of the current ramp is moved forward and the calculation for the ramp duration is redone. In addition the limit for the duration of the ramps is the time be-tween the two temperature extremes.

If a ramp is found, that does not overlap with the previous ramp, it is written in the substitution transient. If there is no local stress maximum between two tempera-ture extremes to begin with, the ramp is chosen as a connection between those two extremes and also saved in the substitution transient. This process is repeated, until the last temperature extremism has been found and is accounted for by a tempera-ture ramp.

In addition to the actions in Figure 8 a smoothing of the temperature profile can be performed to avoid numerous, very small ramps. An easy approach is the band-width method. When applying this method only temperature differences that exceed a certain value are considered. Smaller dif-ferences are ignored.

When the substitution transients are deter-mined for every fatigue leading location in the component, they are compared regard-ing the TCR of the ramps. For every ramp, the highest TCR of all substitution tran-sients is chosen for the covering substitu-tion transient. This transient can now be used as a highly qualified basis for further analysis of the cycle based fatigue.

A more general approach to calculate a substitution transient based on stresses omits the specific stress information and el-ementary transients, respectively, and uses

Start

End

Save first temperaturevalue in substitution

transient

Calculate stress profile from substitutiontransient

via method of elementary transients

no

no

no

yes

yes

yes

End of ramp at time ofmaximum stress

Calculate ramp duration

Move end of rampIs begin of ramp beforeend of previous ramp?

Begin of ramp: =End of ramp -Ramp duration

Is there a local stressmaximum?

Does next temperatureextremum exist?

Ramp is connection of lasttwo temperature extrema

Save ramp in substitutiontransient

Figure 8. Flowchart for the determination of the substitution transient at a single location.

123

Figure 9. FEA model of the nozzle.

Start

End

Location: = 1

Location: = Location +1 Determination of the

substitution transient

Data preparation

Location < numberof locations?

Comparison of thesubstitution transients

Covering substitutiontransient

Temperatur profile;elementary transient

no

yes

Figure 7. Flowchart for determination of a covering substitution transient.

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only a general elementary transient from the inner wall of a cylinder. This allows the application of the method for components that have not been analysed with FFE. The simplification is viable since the described method results in very similar substitution transients for arbitrary locations in an ac-tual component as well as for the general substitution transient.

ExampleThe exemplary calculation is performed on a FEA model of a nozzle with an actual measured temperature profile. The axially symmetric nozzle geometry is shown in F i g u r e 9 .

It is made of austenitic steel (turquoise) at the thermal sleeve and the pipe and ferritic steel (purple) at the spherical area, model-ling a main coolant line. The water (red) in the annular gap of the thermal sleeve is also modelled with solid elements and adapted

material parameters to account for the free convection. The nozzle was chosen because of its elaborate geometry, its mix of materi-als and its relevance in fatigue analysis. The fatigue leading locations are known from a previous FEA and are shown in Figure 9.

180

160

140

120

100

80

60

40

Tem

pera

ture

in °C

Time in s0 2,000 4,000 6,000 8,000

Figure 10. Temperature profile. Tem

prea

ture

in °C

Stre

ss in

MPa

Time in s

200

160

120

80

40

0

-40

Temperature

Stress (actual)

Substitution transient

Stress (substitution)

300

250

200

150

100

50

02,000 3,000 4,000 5,000

Figure 11. Covering substitution transient and stresses at location 1.

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The temperature profile used originates from a measurement section at a heat ex-changer in the secondary circuit of a nu-clear power plant. It can be seen in F i g - u r e 10 . The profile contains fast con-secutive temperature changes. Therefore, an interference of stresses induced by the temperature ramps can be expected and the influence on the results of the method can be examined.

F i g u r e 11 shows a section of the cover-ing substitution transient calculated for the fatigue leading locations as well as the stress resulting from the original tempera-ture profile and the substitution transient at location 1. All temperature differences of the original profile are adequately mapped by the temperature ramps. The stress re-sulting from the covering substitution transient emulates the original stress pro-file, especially the stress maxima and the amplitudes, very well. At the same time the substitution transient is conservative since the resulting stress maxima and stress amplitudes are bigger then in the original stress profile.

Ta b l e 1 contains the relative error of the stress maxima for the described method (based on temperature profile and elemen-tary stress transient) and the old method (based solely on the temperature profile, as described in the chapter overview) for the three fatigue leading locations of the exam-

ple. The new method obviously gives more realistic results. The relative error is in the range of 4 % to 11% for the new method. The old method results in errors of 30 % to 35%. To illustrate the improvement for on an actual fatigue analysis the impact on the resulting life expectancy of a com-ponent is calculated under the assumption of a power function for the S-N curve. The parameters for the power function are ob-tained from an S-N curve for ferritic steel. The results are shown in Ta b l e 2 .

With the new method the life expectancy for the example is underestimated by 15% to 30%. With the old method the error is about 60%. In conclusion there is still a considerable margin of error with the new method but a significant improvement over the old method.

Conclusion

Within the three-stage approach of the AFC, the A-CBF is an obvious addition to utilise the stresses previously calculated by FFE as a highly qualified basis for cycle counting. The obtained substitution tran-sients are realistic but still conservative regarding the stresses.

Even without the specific stress informa-tion at the fatigue relevant component the methodology enables the determination of

a more reasonable substitution transient by using a general elementary transient for stress calculation.

Either way the conservatism concerning the resulting usage factors are reduced sig-nificantly compared to the methodology solely using the temperature profile.

References[1] Abib, E., Bergholz, S., Pöckl, C., Rudolph, J.,

and Wirtz, N.: Areva Fatigue Concept (AFC) – an integrated and multi-disciplinary ap-proach to the fatigue assessment of NPP components. Proceedings of ICAPP 2011, Nice, France, May 2-5, 2011, Paper 11027.

[2] Rudolph, J., Bergholz, S., Heinz, B., and Jouan, B.: Areva Fatigue Concept – A Three Stage Approach to the Fatigue Assessment of Power Plant Components, In “Nuclear Power Plants”, edited by Dr. Soon Heung Chang, KAIST Department of Nuclear & Quantum Engineering, Korea, South http://www.intechopen.com/books/nucle-ar-power-plants.

[3] Abib, E., Bergholz, S., and Rudolph, J.: Ger-man Experiences in Local Fatigue Monitor-ing. Proceedings of ICAPP ’12, Chicago, USA, June 24-28, 2012, Paper 12150.

[4] 2010 ASME Boiler & Pressure Vessel Code Section III Division 1 - Subsection NB: Class 1 Components. Rules for Construction of Nuclear Power Plant Components.

[5] KTA 3201.2 (06/96). 1996. Components of the Reactor Coolant Pressure Boundary of Light Water Reactors. Part 2: Design and Analysis.

[6] RCC-M, Edition 2007: Design and Construc-tion Rules for Mechanical Components of PWR Nuclear Islands. Section I, Subsection B: Class 1 components.

[7] Woods, K., and Thomash, K.: Fatigue Cycle Monitoring, Proceedings of PVP 2011, Bal-timore, Maryland, USA, July 17-21, 2011, Paper 58036. l

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Table 2. Impact of the relative error on life expectancy.

Position New Method Old Method

1 –23.53 % –61.71 %

2 –28.71 % –59.60 %

3 –13.48 % –60.86 %

Table 1. Relative error of the stress maxima.

Position New Method Old Method

1 +8.67 % +34.66 %

2 +11.06 % +32.44 %

3 +4.59 % +33.75 %

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Cancellation: This order may be cancelled within 14 days. A notice must be sent to to VGB PowerTech Service GmbH within this period. The deadline will be observed by due mailing. I agree to the terms with my 2nd signature.

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Vo lu me 89/2009 · ISSN 1435-3199

K 43600

In ter na tio nal Edi ti on

Focus: Power Plants in Competiton

New Power Plant Projects of EskomQuality Assurance for New Power PlantsAdvantages of Flexible Thermal Generation

Market Overview for Imported Coal

In ter na tio nal Jour nalfor Elec tri ci ty and Heat Ge ne ra ti on

Pub li ca ti on ofVGB Po wer Tech e.V.www.vgb.org

Vo lu me 89/2009 · ISSN 1435-3199

K 43600


Focus: VGB Congress

Power Plants 2009

Report on the Activities

of VGB PowerTech

2008/2009

EDF Group Reduces

its Carbon Footprint

Optimising Wind Farm

Maintenance

Concept for Solar

Hybrid Power Plants

Qualifying Power Plant Operators

In ter na tio nal Jour nal

for Elec tri ci ty and Heat Ge ne ra ti on

Pub li ca ti on of

VGB Po wer Tech e.V.

www.vgb.org

Con gress Is sue

Vo lu me 89/2009 · ISSN 1435-3199

K 43600


Focus: Furnaces, Steam Generators and Steam TurbinesUSC 700 °C Power Technology

Ultra-low NOx Combustion

Replacement Strategy of a Superheater StageEconomic Post-combustion Carbon Capture Processes

In ter na tio nal Jour nalfor Elec tri ci ty and Heat Ge ne ra ti onPub li ca ti on ofVGB Po wer Tech e.V.www.vgb.org

Vo lu me 90/2010 · ISSN 1435-3199

K 43600


Fo cus: Pro Quality

The Pro-quality

Approach

Quality in the

Construction

of New Power Plants

Quality Monitoring of

Steam Turbine Sets

Supply of Technical

Documentations



Pub li ca ti on of


www.vgb.org

V

00634 K

9913-5341 NSSI · 5002/58 emulo

International Edition

Schwerpunktthema:

Erneuerbare Energien

Hydrogen Pathways

and Scenarios

Kopswerk II –

Prevailing Conditions

and Design

Arklow Bank

Offshore Wind Park

The EU-Water

Framework Directive

International Journal

for Electricity and Heat Generation

Publication of

VGB PowerTech e.V.

www.vgb.org

Vo lu me 89/2009 · ISSN 1435-3199

K 43600


Focus: Maintenance

of Power Plants

Concepts of

IGCC Power Plants

Assessment of

Generators for

Wind Power Plants

Technical Data for

Power Plants

Oxidation Properties

of Turbine Oils



Pub li ca ti on of


www.vgb.org

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(incl. se arch func ti on for all do cu ments)

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(pho ne: +49 201 8128-200).* Plus VAT.Annual update 1 Euro 150.–; 2 Euro 350.– The update has to be ordered annually.

Re turn by fax or in business envelope with window to VGB Po wer Tech Ser vice GmbHFax No. +49 201 8128-329In fo Ex pert

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Can cel la ti on: This or der may be can cel led wi thin 14 days. A no ti ce must be sent to to VGB Po wer Tech Ser vice GmbH wi thin this pe ri od. The deadline will be observed by due mailing. I ag ree to the terms with my 2nd sig na tu re.

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VGB PowerTech 5 (2012) - Areva

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Transcript of VGB PowerTech 5 (2012) - Areva