overview of the doel 3 and tihange 2 reactor pressure ... · reactor pressure vessel ......

Confidential Restricted Public Internal

22/02/2017 Overview of the Doel 3 & Tihange 2 RPV Safety Cases 1

R.Gérard, M. De Smet (Tractebel-ENGIE)

Overview of the Doel 3 and Tihange 2 Reactor Pressure Vessel Safety Cases

Technical Working Group on Life Management of NPPs – Vienna, 22-24/2/2017

Doel & Tihange NPPs (Belgium)7 PWR units operated by Electrabel (ENGIE)


1. Doel 1 - 433 MW (1975)2. Doel 2 - 433 MW (1975)3. Doel 3 - 1006 MW (1982)4. Doel 4 - 1046 MW (1985)

5. Tihange 1 - 962 MW (1975)6. Tihange 2 - 1008 MW (1983)7. Tihange 3 - 1046 MW (1985)

Westinghouse 3-loop PWR design

ASME Boiler & Pressure Vessel Code, Section III

Steel type SA-508 Class 3

RPV wall thickness 200 mm

Stainless steel cladding

Doel 3 & Tihange 2 Reactor Pressure Vessels


Starting point in 2012In-service inspection at Doel 3

422/02/2017 Overview of the Doel 3 & Tihange 2 RPV Safety Cases

Troubles started in June 2012…… when thousands of small quasi-laminar indications were found


1st UT

2012 2013 2014 2015

Operation

[Courtesy Intercontrôle]

Flake cartography3D boxes

Doel 3 Tihange 2

UCS 857 1931

LCS 7205 80

Safety Case was built and submitted before the end of 2012


1st UT

2012 2013 2014 2015

Operation

UT Validation

2012 SC

Structural Integrity Assessment

Embrittlement curves 2012

Root Cause AnalysisD3/T2 Hydrogen Flaking

Rejected VB395 shell

● Steam generator shell rejected in 2012 because of hydrogen flaking

● Size and material similar to RPV shells

● Hollow ingot



1st UT

2012 2013 2014 2015

Operation

UT Validation

2012 SC




Early diagnosis: hydrogen flakes

Generated duringmanufacturing

Inside remains of positive segregations

Quasi laminar



1st UT

2012 2013 2014 2015

Operation

UT Validation

2012 SC




D3H1 nozzle shell cut-out

Tested materials:

— VB395

— D3H1 nozzle shell cut-out

— D3 spare surveillance block

Focus on potential effect of:

— Segregations

— Specimen orientation

Effect of irradiation from literature

Tests on VB395 forging

Relevant material rejected for hydrogen flaking, representative of T2D3 flakes

Forging size and thickness comparable to RPV core shells (but hollow ingot vs. classical)

Properties of the zones free of flakes:

— Far from the flaked area

— Adjacent to the flaked area

Properties of the ligament between flakes

Fracture toughness measured on specimens with a real hydrogen flake as pre-crack

22/02/2017 9Overview of the Doel 3 & Tihange 2 RPV Safety Cases



1st UT

2012 2013 2014 2015

Operation

UT Validation

2012 SC






1st UT

2012 2013 2014 2015

Operation

UT Validation

2012 SC




Development of Flaw Acceptability Assessment methodology inspired on ASME Code Section XI

— Grouping rules (IWB-3300 Flaw Characterization)→ ASME Code Case N-848

— Flaw Screening Criterion (IWB-3500 Acceptance Standards)

— Refined Analysis Procedure (IWB-3600 Analytical Evaluation of Flaws)

Methodology tailored to

— The large numbers of flaws

— Their quasi-laminar orientation

UT Validation

11 Short-Term actions addressed in 2013 Safety Case Addenda…Allowing restart of both units


1st UT

2012 2013 2014 2015

Operation Operation

2nd UT

LT

2013 SC

X

2012 SC




LT : Load Test at a pressure slightly above design pressure

Followed by 2nd UT inspection: no evolution

Restart authorized 03/2013

UT Validation

5 Medium-Term actions to be addressed before next RFO


1st UT

2012 2013 2014 2015

Operation Operation

2nd UT

LT

2013 SC

X

2012 SC




UT Qualification

Testing of irradiated flaked specimens

Formal qualification with same equipment as for the RPVs:

● Practical trials on test block extracted from VB395

● Destructive examination of flakes (≈100 flakes)

● Simulations

Updated inspection procedure ensuring that all relevant flakes would be detected

UT Validation

5 Medium-Term actions to be addressed before next RFO


1st UT

2012 2013 2014 2015

Operation Operation

2nd UT

LT

2013 SC

X

2012 SC




UT Qualification


VB395 specimens irradiated in BR2

● with flakes as pre-crack

● between flakes

UT Validation

5 Medium-Term actions to be addressed before next RFO… unexpected results leading again to shutdown of both units


1st UT

2012 2013 2014 2015

Operation Operation

2nd UT

LT

2013 SC

X

2012 SC




UT Qualification


Atypical results of VB395

T0 shift for specimens between flakes = 167°C, 82°C above prediction

RTNDT shift = 120°C, 49°C above prediction

Irradiation hardening (yield stress increase) in agreement with predictions

Generally such results are indicative of non-hardening embrittlment (P segregation), but….

No intergranular fracture

Unexpected results of 1st irradiation campaign (VB395) …leading again to shutdown of both units

22/02/2017 16Overview of the Doel 3 & Tihange 2 RPV Safety Cases

UT Validation

5 medium-Term actions to be addressed before next RFO…leading to complementary material investigations and testing


1st UT

2012 2013 2014 2015

Operation Operation

2nd UT

LT

2013 SC

X

2012 SC




UT Qualification


3 additional irradiations in BR2:

● Doel 3 H1 cut-out material (inside and outside macro-segregation)

● Doel 3 upper core shell archive material (without flake)

● VB395 material out of the flaked area (far from it or adjacent to it)

● German KS02 material (rejected RPV flange with hydrogen flakes)

2015 Safety CasesSummary of VB395 irradiation results

In terms of fracture toughness, all VB395 materials from the zone affected by flaking have similar properties:

— Specimens with flakes as pre-crack

— Specimens from the ligament between flakes

— Specimens from the zone adjacent to the flaked area

Conclusion: the flakes themselves do not affect the material properties

22/02/2017 18Overview of the Doel 3 & Tihange 2 RPV Safety Cases 18

2015 Safety CasesKS02 irradiation results KS02 material taken in the

flaked area (in the same way as in VB395) behaves perfectly normally.

BR2 irradiation results consistent with “historical” results from German research program in the eighties

Confirmed by tests on remaining irradiated specimens from German program, reconstituted and re-tested (fracture toughness)


UT Validation

5 Medium-Term actions to be addressed before next RFO… leading to complementary material investigations and testing


1st UT

2012 2013 2014 2015

Operation Operation

2nd UT

LT

2013 SC

X

2012 SC




3rd UT

2015 SC

Structural Integrity AssessmentUPDATE

3 additional BR2 irradiations Embrittlement curves 2015

Root Cause AnalysisAtypical Embrittlement VB395

SID3

UT Qualification

2015 Safety CasesMaterials investigated - Results


2012 2013 2014 2015

Operation

3rd UT

2015 SC


3 additional BR2 irradiationsEmbrittlement curves 2015


SID3

UT Qualification

Rejected VB395 shell (Flaked material)

— Atypical embrittlement

Rejected KS02 RVH flange (flaked material)

— Embrittlement as predicted

D3H1 nozzle shell cut-out and D3 upper core shell archive

— Embrittlement as predicted

2015 Safety CasesEmbrittlement curves 2015


2012 2013 2014 2015

Operation

3rd UT

2015 SC




SID3

UT Qualification

Very unlikely that D3-T2 RPV would exhibit same atypical embrittlement as VB395

Additional VB395 embrittlement was nevertheless added to RSEM trend curve

2015 Safety CaseRTNDT trend curve used in Structural Integrity Analysis


2015 Safety CasesUT Qualification


2012 2013 2014 2015

Operation

3rd UT

2015 SC




SID3

UT Qualification

Upgraded inspection procedure

3rd UT inspection

Updated flake cartography

Doel 3 Tihange 2UCS 1440 3064

LCS 11607 85

2015 Safety CasesStructural Integrity Assessment Update


2012 2013 2014 2015

Operation

3rd UT

2015 SC




SID3

UT Qualification

Updated flake cartography

Updated RPV fluence distributions


Heating of SI water (Doel 3 only)

UT Validation

Doel 3 & Tihange 2 RPV Safety Cases


1st UT

2012 2013 2014 2015

Operation Operation

2nd UT

LT

2013 SC

X

2012 SC




3rd UT

2015 SC




SID3

www.fanc.fgov.be

UT Qualification

Restart authorized 11/2015

Thank you for your attention ! Any questions ?


More information: Proceedings of the 2016 ASME PVP conference (PVP2016-63878) Overview of the Doel 3 and Tihange 2 Reactor Pressure Vessel Safety CasesM.De Smet, J.Van Vyve

overview of the doel 3 and tihange 2 reactor pressure ... · reactor pressure vessel ......

Documents