FATIGUE MANAGEMENT WITHIN EDF IN THE

FATIGUE MANAGEMENT

WITHIN EDF IN THE

FRAME OF LTO

Thomas METAIS1, Nicolas PROMPT2

Jean-Christophe LE ROUX3 et al.

1 : EDF R&D CHINA 2 : EDF DT 3 : EDF R&D

WNA Conference

SHANGHAI, May 2018

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| 2

SUMMARY

Fatigue management within EDF in the frame of LTO | WNA Shanghai - May 2018

1. FATIGUE MANAGEMENT ACCORDING TO FRENCH REGULATION

2. GENERIC THERMAL FATIGUE ASSESSMENT

PRACTICAL APPLICATION OF THE REGULATION

ENVIRONMENTAL FATIGUE CONSIDERATION IN THE SAFETY STUDIES

R&D SUPPORTING FRENCH POSITION ON EAF

3. LOCAL THERMAL FATIGUE ASSESSMENT : DEAD LEGS

ASSESSMENT OF LOCAL EFFECTS: DEAD LEGS

STRATIMÈTRES AND ORT, EDF SOLUTION FOR THERMAL LOADING ASSESSMENT

4. PREVENTION OF VIBRATION FAILURE IN EDF PLANTS

5. CONCLUSION AND PERSPECTIVES

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| 3

WHAT IS DONE IN EDF TO MANAGE FATIGUE?

LAW

Codes & Standards Practical requirements (Stress

Reports, ten-year visits, inspection, etc…)

R&D

OPEX

Numerical

simulation tools Tests Inspection

Safety demonstration

R&D

R&D

| 4

FATIGUE MANAGEMENT ACCORDING TO FRENCH REG.

Design rules : French law

Ministerial Decree 26/02/74 : transients and loads have to be defined at design stage

Ministerial Order 10/11/99 : 2 years after criticality, compare design and observed loadings

Reactor Coolant System In Service Inspection - French decree 10/11/99

Inspection plan during refueling outage and 10 years period visit:

• Zones sensitive to degradations ( fatigue, corrosion…)

• Zones exposed to complex thermal loadings ( dead legs, mixing zones)

• + Random inspection of non-sensitive zones

Periodic updates imposed by French law at least every 10 years:

Revise design transients, stress reports, inspection programs

Integrate operating experience, national & international R&D results


| 5


LAW



R&D

OPEX

Numerical



R&D

R&D

| 6

GENERIC THERMAL FATIGUE ASSESSMENT

Practical application of the regulation

Most of the revision and modification are realized during 10 years period outages

(“Visite Décennales”)

Periodic fatigue damage assessment outcome depends on UF value

UF < 0.5: NO action needed

0.5 < UF < 1: Locations are « concerned by fatigue »

• Random check inspections every 10 years;

1 < UF: Locations are « sensitive to fatigue »

• Crack growth assessment is mandatory

• Inspection at specific time steps determined by the crack growth analysis


| 7


LAW



R&D

OPEX

Numerical



R&D

R&D

| 8

ENVIRONMENTAL FATIGUE CONSIDERATION IN THE

STRESS REPORT Situation before 2015 = No EAF

2016 RCC-M evolution

RPP#2 modification of the design curve

• Mean air curve = NUREG/CR6909 mean air

curve

• Transfer coefficient on cycles (10)

• and strain amplitude (1,4)


French fatigue data tested with the

NUREG/CR6909 mean air model

| 9

ENVIRONMENTAL FATIGUE CONSIDERATION IN THE

STRESS REPORT 2016 RCC-M evolution

RPP#3 Environmental effects on fatigue life

• AREVA test results on austenitic stainless steels, representative of industrial conditions (ground

specimens tested in PWR environment) show that : – A part of the environmental effect is already covered by the fatigue design curve

– The global effect of the various parameters cannot be simply calculated by a multiplication of the effects of these

parameters taken individually

– Concept of Fen integrated :

• Assessment of Fen from NUREG/CR-6909

• Olkiluoto 3 approach (very close to this proposal) accepted by Finnish Safety Authority and

currently being reviewed by NRC

• Proposed as an ASME code-case


FUFen

FenFU REP )

intgrated;1(max

| 10

R&D SUPPORTING FRENCH POSITION ON EAF

National R&D

EDF R&D “FATCOR2” rigs

AREVA

CEA

INCEFA+ European Project (details on next slide)

July 2015-June 2020

€2.55M EC funding (€6.14M program)

16 European partners / 9 European countries

International collaborations

EPRI, Rolls-Royce, AMEC, VTT …


| 11 EDF APPROACH OF FATIGUE FAILURE PREVENTION | PLIM Lyon - October 2017

WP1: Project Management (AMEC)

COMPLETE

State of the art (AMEC)

WP2: Test Program (JRC)

WP2-1: Material procurement and

specimen design (EDF)

WP2-2: Fatigue tests in air environment

(INESCO)

WP2-3: Fatigue tests in LWR environment

(SCK)

WP2-4: Materials and specimen

examinations (VTT)

WP3: Development of a Fatigue Analysis

Procedure (EDF)

WP3-1: Fatigue standard data formats (JRC)

WP3-2: Fatigue assessment procedure (EDF)

Sc

op

e o

f

INC

EF

A+

WP4: Dissemination and Training (UC)

WP4-1: Development of INCEFA+ website,

training seminars and workshops (UC)

WP4-2: Provide a Reference Book (UC)

WP4-3: Organise special sessions in well-

known international conferences and

publish scientific papers (UC)

http://www.areva.com/

http://www.google.co.uk/url?sa=i&source=imgres&cd=&ved=0CAgQjRwwAA&url=http://www.preventicum.co.uk/clients/edf-energy-2/&ei=biCJVaqIIYuR7Abgz4HIBQ&psig=AFQjCNENua_ANPtISEODZ4p5o4MmoLs18A&ust=1435136494618154


http://www.inescoingenieros.com/en/index.php



http://www.ciemat.es/













| 12 Fatigue management within EDF in the frame of LTO | WNA Shanghai - May 2018

WP3

Assembly of a fatigue database accessible online MatDB (MHI has and NRC will soon contribute fatigue data in

exchange of fatigue results from the project)

WP4

Aim is to promote a method alternative to

NUREG/CR-6909

Conferences to be organized

| 13

ASSESSMENT OF LOCAL EFFECTS: DEAD LEGS Reminder about dead legs

Dead legs in stress reports

Dead legs detrimental effects discovered after plant commissioning !

Plant monitoring in the 1990’s addendum to transient file

New monitoring campaign based on stratimètres launched in 2013

Objective : confirm or revise the transient file of a few selected areas

Areas : SIS, RHR, surge line, U branch drain lines, EFW ; 900 & 1300 MWe plants

Data acquisition in 2 reactors for each line at least for 2 years

Measurement via stratimètres, internal wall temperature reconstruction via ORT


RCS

Vortex

Hot loop

Isolated circuit

To the RCS

vortex

Hot water

Cold water

Convection loop

Thermal

cycling Stratification

| 14

STRATIMÈTRES AND ORT, EDF SOLUTION FOR

THERMAL LOADING ASSESSMENT Stratimètres

Device that measures the temperature evolution and distribution vs time at the outer

surface of the pipe

Improvement of the precision

Qualification of the stratimètre


29/06/2011 29/06/2011 29/06/2011 29/06/2011 29/06/2011 30/06/2011 30/06/2011

216.5

217.0

217.5

218.0

218.5

1.5°C

Te

mp

era

ture

°C

TC1

TC2

TC3

TC4

TC5

TC6

TC7

TC8

TC9

TC10

TC11

TC12

TC13

TC14

TC15

TC16

TC17

TC18

TC19

TC20

1°C

| 15

STRATIMÈTRES AND ORT, EDF SOLUTION FOR

THERMAL LOADING ASSESSMENT ORT

Tool that calculates the temperature

evolution vs time at the inner surface of

the pipe from the experimental

measurements by the “stratimètres”

Tool based on direct fine heat transfer

simulations (F.E. with Code_Aster and

Salome_Meca) and inverse method

(data assimilation regularization)


reconstruction by ORT of the inner surface temperature

(top right) from the outer surface temperature (top left)

Comparison to the true value (bottom left)

| 16

Developped by EDF since 1989

Objectives for EDF:

An efficient software for engineering studies with quality assurance requirements

A numerical platform for software developments products of EDF’s research in various

computational mechanics fields

Distributed as a free software since 2001 downloadable from

www.code-aster.org with full documentation in English & French

Integrated as part of Salome Meca 3D Modeling platform

Continuous integration of EDF R&D results (ex.: POST_FATIGUE, B.M. Lei, V.X. Tran

et al., “Toward consistent fatigue crack initiation criteria for 304L austenitic stainless steel under multi-axial

loads,” International Journal of Fatigue, Elsevier, 10.1016/j.ijfatigue.2015.02.001, 2015)

16 PVP, Vancouver July 20th 2016 Evolutions of Fatigue Post-Processing in Code_Aster T. Métais

CODE_ASTER OVERVIEW

http://www.code-aster.org/



| 17

NUMERICAL TOOLS SERVING EDF GOALS


Fatigue operator - From old…

… to new

Main features of new POST-RCCM

Up-to-date methods for fatigue calculations

RCC-M compliant

New Fen and Fen-integrated (Fen-threshold) methodologies

Kept for Appendix ZD calculations &

Pm+Pb checks

AFCEN benchmark to be

organized on EAF calculations

– End of 2018

| 18

PREVENTION OF VIBRATION FAILURE IN EDF PLANTS

Cracking of SBPs (Small Bore Pipes , DN ≤ 50 mm) has been a concern for EDF

Caused by vibratory fatigue

429 cases since 1977 = 0.2 / reactor.year

Affected nuclear safety

Decreased NPP availability

Increased study & maintenance costs

A specific approach was developed


| 19

PREVENTION OF VIBRATION FAILURE IN EDF PLANTS:

METHODOLOGY


1. List sensitive SBPs (criterion : safety, availability) 70 000 SPs

2. Identify the most sensitive SBPs (2000 SBPs) Modify design/ excitation

3. Check remaining 68 000 SBPs

Focus on 10 000 SBPs, with a behaviour representative of 68 000 SBPs

Identify penalizing hydraulic configurations with accelerometers

Perform vibration measurement on 10 000 SBPs during penalizing configurations

Assess SBP’s sensitivity

1. Maximum speed < 12 mm/s No problem

2. Maximum speed >12 mm/s apply EDF criterion based on ASME-C fatigue curve + modeling. If not

respected, SBP classified at-risk (expert methods also possible)

4. Control at-risk SBPs (Dye Penetrant Testing) every outage (~42 / NPP today)

5. Cracked SBPs : replace and modify design or reduce hydraulic excitation

| 20

PREVENTION OF VIBRATION FAILURE IN EDF PLANTS:

THE RESULTS


Positive evolution since methodology was set up

EDF developed

a design guide aiming at suppressing SBPs vibratory fatigue cracking

an expert method so as to decrease analysis conservatism

| 21

CONCLUSION AND PERSPECTIVES

French regulation imposes an update of fatigue evaluation, at least every 10 years

Transient files, stress reports, inspection programs … are revised accordingly

R&D results and operational experience must also be integrated

In this context, progresses were made

Evolution of codification: EAF taken into account, with a less severe method than

NUREG/CR69-09

Monitoring and reconstruction of transient files in dead legs thanks to innovative and

qualified tools stratimètres and ORT

Development of an efficient preventive approach of vibratory fatigue failure

EDF approach mixing operational experience integration and R&D works is positive


Thank you!

FATIGUE MANAGEMENT WITHIN EDF IN THE

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