Living Thermal Fatigue Management for Doel 1&2 and … · · 2017-11-0223-27/10/2017 Living Thermal Fatigue Management for Doel 1&2 and Tihange 1 NPPs 1 4th International IAEA Conference

XConfidential Restricted Public Internal

23-27/10/2017 Living Thermal Fatigue Management for Doel 1&2 and Tihange 1 NPPs 1

4th International IAEA Conference on Plant Life ManagementLyon, 23-27 October 2017

Living Thermal Fatigue Management for Doel 1&2 and Tihange 1 NPPs

INTRODUCTIONNuclear power in Belgium


Doel 1&2

Tihange 1

� 1st commercial operation of Doel 1&2 (2x433 MW) and Tihange 1 (962MW) in 1975

� Operating license unlimited in time

� Requirement to perform Period Safety Review (PSR) every 10 year

� 2003 – Nuclear phase out law – Shutdown after 40 years of operation

� Steam generator replacements (SGR) and power uprates (PU)

� Long Term Operation (10 years) granted to Tihange 1 in 2012, and to Doel 1&2 in 2015

INTRODUCTIONRegulatory context


1975 19851st PSR

19952nd PSR

20053rd PSR

20154th PSR

Nuclear phase out law √ LTO Tihange 1 √ LTO Doel 1&2

SGR+PU Tihange 1 SGR+PU Doel 2 SGR+PU Doel 1

� Fatigue due to Design Transients

� Thermal stratification PRZ surge line

� Thermal stratification FW lines/nozzles

THERMAL FATIGUE MANAGEMENTScope


� Swirl penetration cycling in non-isolable RCS branches

� Mixing zones

� Thermal striping (at cold/hot water interface of stratified flow)

Low-Cycle Fatigue (LCF) High-Cycle Fatigue (HCF)

Thermal Fatigue

Addressed through fatigue analyses(LTO > Time Limited Ageing Analysis)

Addressed through pragmatic approach: susceptibility analysis and inspections(LTO > Ageing Management Programme)

� DESIGN: fatigue analyses considered 30 years lifetime

� 1st PSR: equivalence demonstrated between design codes and ASME III Ed.1983

� SGR & PU: update design transients and fatigue analyses covering 40 years of operation

� OPERATING EXPERIENCE: USNRC Bulletins on stratification in PRZ surge lines and on cracking issues in FW systems >> numerous temperature measurement campaigns and fatigue analyses in Belgian plants

� 3rd PSR: review of fatigue analyses: Cl.1 analysis for Cl.2 regenerative heat exchangers

� LTO: revalidation of fatigue TLAA including Environmentally Assisted Fatigue (EAF)

� ASSESSMENTS: Development of THERMAXS and TEFen (EAF) software

LOW-CYCLE FATIGUELiving management


� Need for plant-specific stress & fatigue analyses of PRZ surge line and FW line components

� Thermal, stress & fatigue analysis of axisymmetric structures subjected to stratification transients• Piping• Nozzles• Reactor building penetrations

� Based on Green’s transfer function approach

� Developed in-house between 1991 and 2003

� Strong features• Designed to deal with measured transients (design transients can be included)• ASME III Cl.1 fatigue analysis in ‘cross-sections’, treated individually (peaks & valleys)• Contacts with pipe-whip restraints taken into account• Calculated pipe displacements can be used for validation purposes

LOW-CYCLE FATIGUETHERMAXS software


section G1

section G3section G4

T=f(t)

3 o'clock

2 o'clock

1 o'clock

12 o'clock

4 o'clock

5 o'clock

6 o'clock

Tbc

(t)Tle

(t)p(t) F&M(t)

Sections de mesures

Sections d'analyse

� Federal Agency for Nuclear Control (FANC) requested ENGIE to assess Ageing Management during LTO in line with US approach for License Renewal and with IAEA’s Safety Report SRS-57

� The LTO methodology requires review and revalidation of Time Limited Ageing Analyses, such as fatigue

� Fatigue TLAA revalidation considered:

— Extension of the intended period of operation from 40 to 50 years

— Potential environmental effects on fatigue life, according to the US approach, through environmental correction factors Fen

� Development of TEFen post-processor to Finite Element code to include EAF (Fen factors) in fatigue analysis

LOW-CYCLE FATIGUERevalidation of fatigue TLAA in view of LTO


� Selection based on• CUFair for 50 years of operation• Level of conservatism of existing TLAA• Expected value of Fen

• Cl.1 locations from NUREG/CR-6260

� Specificities• Many locations in PRZ (high temperature, high Fen)• SS cladding fatigue analyses (protecting CS from water)• SG FW nozzles are Safety Cl.2, but built according to Cl.1• No EAF for regenerative heat exchanger (ASME Cl.2)

� Summary

LOW-CYCLE FATIGUERevalidation of fatigue TLAA in view of LTO - Scope


Doel 1&2 Tihange 1

TLAA LCF + EAF 10 locations 10 locations

TLAA LCF Regenerative HEX; FW lines Regenerative HEX

Specific AMP FW baffle boxes -

� Acceptable CUF or CUFen for 50 years of operation, except for

— Weld between Doel 1&2 PRZ lower head and heater sleeves

— Locations subjected to Doel 1&2 PRZ spray transients

� Actions

— FAMOS (AREVA) temperature monitoring of PRZ bottom head & spray nozzle, periodic interpretation of measurements and update of stress reports (‘good performance’ 2017 SALTO review)

— Continuous follow-up of evolution of EAF investigations

• Assessment methods for EAF, regulatory and guidance documents

• Participation in EPRI’s Fen Benchmark

• ENGIE’s sponsorship of SCK•CEN’s (Nuclear Research Centre, Mol, Belgium) participation in INCEFA+ project, aiming at developing new guidelines for assessment of EAF for NPP components

LOW-CYCLE FATIGUERevalidation of fatigue TLAA in view of LTO – Results & Actions


� International OE on fatigue issues in FW systemsinitiated investigations in all Belgian NPPs

� Specific for Doel 1&2: FW baffle boxes

— To avoid water hammer in FW line

— Original SG had no J-tubes on FW torus

— Initial baffle boxes suffered from FAC

— Ferro-austenitic steel baffle boxes installed in 1986

� 2nd PSR:

— 1st temperature measurement campaign 1994-1996

— Baffle box acts as a trap for stratification

— ASME Cl.1 fatigue analysis for ASME Cl.2 component

LOW-CYCLE FATIGUEDoel 1&2 feed water line baffle boxes


� SGR:

— Replacement SG with J-tubes

— Nevertheless, baffle boxes maintained (to avoid convection flowof hot water into upstream FW line)

— VT and PT during SGR: baffle boxes in excellent condition

— 2nd temperature measurement campaign (2004-2007)

— Validation of ASME Cl.1 fatigue analysis

� LTO:

— Most appropriate way to manage fatigue of baffle boxes is through a Specific Ageing Management Programme• Flaw Tolerance Evaluation (App. L of ASME Code, Section XI)• ASME Fatigue Crack Growth curves for austenitic SS, corrected to account for

water environment• Periodic UT (no defects detected during 2015 inspections)

LOW-CYCLE FATIGUEDoel 1&2 feed water line baffle boxes


� OPERATING EXPERIENCE:

— 1988, Leakage in Tihange 1 ECCS (swirl penetration cycling + in-leakage) led to USNRC Bulletin 88-08>> resolved through design change and replacement of elbows

— 1998, Cracking in mixing zone in RHR system of Civaux NPP>> applicability to Belgian plants evaluated, and UT of similar locations (no cracks found)

� 3rd PSR:

— HCF (swirl penetration and mixing zones) addressed in comprehensive way for all Belgian NPPs

— Based on international OE, identification of potentially susceptible locations, determination of susceptibility level, and UT of most susceptible locations. No cracking found.

HIGH-CYCLE FATIGUELiving management


� LTO:

— Investigations performed during 3rd PSR on HCF have been integrated into the AMPs “One-time inspection of ASME Code Class 1 Small Bore Piping”

— LTO-Design part of LTO project

• LTO-Design looks into design aspects having an impact on nuclear safety, and evaluates which design issues require a design upgrade

• Evaluation of the vulnerability of the RHR system of Tihange 1 for common cause failures

• Preventive measures identified aiming at reducing the risk on non-isolable leakage>> preventive replacement of Tihange 1 RHR mixing tee in 2016(identified earlier as susceptible to fatigue cracking following the Civaux OE)

HIGH-CYCLE FATIGUELiving management


� No formal Ageing Management Programme existed when commissioning the Belgian units

� ENGIE soon started Ageing Management activities on specific degradation mechanisms, and gradually an Ageing Management methodology was developed

� AM activities are documented in Ageing Summaries since 1998

� Ageing Summaries address technical/economical risks, mitigative actions, surveillance methods, acceptance criteria, OE, R&R options, the actual condition in the Belgian NPPs, recommendations and actions for future ageing management

� Ageing Summaries are AMPs “avant la lettre”

� Ageing Summary on Thermal Fatigue: v0 1998, v7 2017

THERMAL FATIGUE MANAGEMENTAgeing Summary report


THERMAL FATIGUE MANAGEMENT in Doel 1&2, Tihange 1= Living PLAN-DO-CHECK-ACT cycle


- OPERATING EXPERIENCE- LCF

- Stratification in PRZ surge line- Stratification in FW lines

- HCF- Swirl penetration & mixing zones

- Benchmark EPRI & INCEFA+

- AGEING SUMMARY on Fatigue(v00 in 1998, v07 in 2017)

- Equivalent to IGALL AMPs on LCF, HCF

- TRANSIENT BOOKKEEPING- TEMPERATURE MEASUREMENTS

- PRZ surge line- PRZ bottom head & spray nozzle- FW lines- Regenerative heat exchanger

- INSPECTIONS- FW baffle boxes (Specific AMP)- HCF susceptible locations

- ASSESSMENTS- Updates in PSR, SGR & PU projects- THERMAXS & TEFen software- IGALL fatigue TLAAs for LTO

- PREVENTIVE REPLACEMENTmixing tee RHR Tihange 1

CHECK

ACT DO

PLAN

UNDERSTANDING

Thank you for your attention ! Any questions?


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Documents

Living Thermal Fatigue Management for Doel 1&2 and … · · 2017-11-0223-27/10/2017 Living Thermal Fatigue Management for Doel 1&2 and Tihange 1 NPPs 1 4th International IAEA Conference