RTRTPTSPTS ReRe--evaluation of Korievaluation of Kori--1 RPV 1 RPV Beltline Weld by Master Curve TestsBeltline Weld by Master Curve Tests

Bong-Sang Lee1, Jun-Hwa Hong1, Dong-Hwan Lee2, Dong-Gwan Choi2

1KAERI (Korea Atomic Energy Research Institute)2KHNP (Korea Hydro & Nuclear Power Co. Ltd)

Second International Symposium on Nuclear Power Plant Life Management 15-18 October 2007, Shanghai, China

�Westinghouse Design (2-loop PWR) Bobcock & Wilcox RPV & Weld

�Base Metal: SA508-cl.2 steel forging�Beltline circumferential weld

Linde 80 flux weld (WF-233)Weld wire heat no.= T27944Flux lot no.= 8790

�Size: 600 MW capacityID 132 inch (3.35m) Thickness 6.5 inch (165 mm)

�Design/Operating Pressure: 2485 / 2235 psig (170 / 152 atm)

�Design Life : 30 yr (FSAR), 40 yr (Equipment Spec. WH-676413, 1969)

Kori-1 PWR (launched in 1978)KoriKori--1 PWR (launched in 1978)1 PWR (launched in 1978)

Surveillance tests summarySurveillance tests summarySurveillance tests summary

-200 -100 0 100 200 300 400 500 6000

20

40

60

80

100

Temperature (oF)

C V En

ergy (

ft-lb)

Unirr. V, f=0.54 (x1019n/cm2) T, f=1.12 (x1019n/cm2) S, f=1.22 (x1019n/cm2) R, f=2.99 (x1019n/cm2) P, f=3.88 (x1019n/cm2)

-100 -50 0 50 100 150 200 250 300

0

20

40

60

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100

120

2

( Jou

le)

(oC)

2

Linde 80 Weld (WF-233)Kori-1 RPV

-200 -100 0 100 200 300 400 500 600 7000

50

100

150

200

250

Temperature (oF)

C V En

ergy (

ft-lb)

Unirr. V, f=0.54 (x1019n/cm2) T, f=1.12 (x1019n/cm2) S, f=1.22 (x1019n/cm2) R, f=2.99 (x1019n/cm2) P, f=3.88 (x1019n/cm2)

-100 -50 0 50 100 150 200 250 300 350

0

50

100

150

200

250

300

( Jou

le)

(oC)

Base Metal (Tangential)Kori-1 RPV

2

Weld (Linde 80, WF-233) Base Forging (SA508-Cl.2)

High copper Linde 80 weld is the limiting material.- USE is lower than 50 ft-lb (after 6 EFPY)- RTPTS exceeds 300oF (after 27 EFPY)

Requires a plant-specific safety analysis based on F/M tests.

History of safety evaluation of irradiation embrittlement� 5th Surveillance tests (Charpy) (1980, 1984, 1986, 1990, 2000)

� Low upper-shelf evaluation (J-R tests by modified 1X-WOL specimens)• 1988, per NUREG-0744 • 1994 & 2005, per USNRC DG-1023 & USNRC RG-1.161

�Master curve fracture toughness tests (RTPTS re-evaluation)• Unirradiated archive weld (2000, ASTM E1921-97)• Irradiated tests by reconstituted specimens (2006, 3/4/5 capsules)• Additional unirradiated tests (2006, ASTM E1921-05)

� Plant-specific analysis of PTS, based on the probabilistic fracture mechanics, USNRC RG-1.154 (2003)

� P-T limit curve was revised by CC N-641 (circumferential flaw, 2004)

ASME KIC Curve:WRC Bulletin-175 (1972)Fracture toughness data were normalized by RTNDTparameter from Charpytests, conservatively.

Irradiated KIC curves :Those are shifted by the same amount of ∆T30ft-lbfrom Charpy tests.

ASME KIC Curve (lower bound) and its original database (1972)

C),mMPa(in)](036.0exp[*783.225.36 oNDTIC RTTK −+=

174 Data pointsEPRI NP-719-SR HSST-02 plate

A533B-1 steel

ASME KASME KICIC curve : CLB (Current Licensing Basis)curve : CLB (Current Licensing Basis)

assuming

How to get a fracture toughness data ?

� Large specimens should be used to get a valid fracture toughness.� Specimen size-dependence on the measured (cleavage) fracture

toughness can be compensated by a weakest-link theory.

� Cleavage fracture toughness data from the same (1 inch) size specimens show a single master curve shape for ferriticRPV steels.

� To (reference temperature) : at 100 MPa√m median value

Master Curve Test Method (ASTM E1921) Master Curve Test Method (ASTM E1921) KIC

KJC

T – To (oF)

Indexing Fracture Toughness For Many Different RPV Steels

(NUREG-1807, by Mark Kirk)Charpy-size specimens (PCVN) can be validfor direct indexing of fracture toughness.

Specimen reconstitution for MC testsSpecimen reconstitution for MC testsA broken half of Charpy specimensfrom surveillance programs

A new PCVN specimenfor the master curve testing

• 3/4/5th surveillance specimens (broken Charpy halves)

• Fluence: 1.2, 3.0 & 3.9 (x1019 n/cm2, E>1MeV)

• It is a well established procedure in the ASTM E1253 standard.

• Stud arc welding is good enough to make PCVN specimens for MC tests.(fast & simple, and no effects on the data)

• Best-estimation To (-106.7oC) value (E1921-05) envelopes the all data by the ASME code case N-629, RTTo curve.

• A conservative To (-83.3oC) value was calculated from a minimum property data set at a single temperature for the initial RTTo value determination .(Implicit margin of about 23.4oC was added to Kori-1 safety analysis.)

UnUn--irradiated material data (WFirradiated material data (WF--233)233)

-150 -120 -90 -60 -30 00

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100

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250

300

KIC Curve onRTTo without margin

K1W Pre-irradiationPCVN specimensTo,ASTM= -106.7 oC

K JC, 1

T-adju

sted (M

Pa-m

0.5)

Test Temperature (oC)

0.5 mm/min 0.15 mm/min 0.15 mm/min (recon.)

-150 -120 -90 -60 -30 0 300

50

100

150

200

250

300

KIC Curve onRTTo without margin

K1W Pre-irradiationPCVN specimensTo, conservative= -83.3 oC

K JC, 1

T-adju

sted (M

Pa-m

0.5)

Test Temperature (oC)

0.5 mm/min 0.15 mm/min 0.15 mm/min (recon.)

Standard To value from all data(E1921-05)

Conservative To value from a data setat a single temperature (E1921-97)

Irradiated test data (3/4/5Irradiated test data (3/4/5thth capsules)capsules)

-100 -50 0 50 100 1500

50

100

150

200

250

300capsule S

median 5%/95%

Kori-1 WeldPCVN 20%-SG(1.22x1019n/cm2)To = 13.4oC

K JC

, 1T-a

djuste

d (MP

a-m0.5

)

Temperature (oC)-100 -50 0 50 100 1500

50

100

150

200

250

300capsule R

median 5%/95%

Kori-1 WeldPCVN 20%-SG(2.99x1019n/cm2)To = 30.0oC

K JC, 1

T-adju

sted (M

Pa-m

0.5)

Temperature (oC)

-100 -50 0 50 100 1500

50

100

150

200

250

300capsule P

median 5%/95%

Kori-1 WeldPCVN 20%-SG(3.88x1019n/cm2)To = 31.5oC

K JC, 1

T-adju

sted (M

Pa-m

0.5)

Temperature (oC)

• Best-estimation To values were determined by the ASTM E1921-05.(13.4, 30.0, 31.5 oC)

0

50

100

150

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250

0 50 100 150 200 250

∆T 41J [oC]

∆To [oC]

Weld Fit (Slope=0.99)Plate Fit (Slope=1.10)Forging Fit (Slope=1.50)WeldPlateForgings

2

Kori-1 Weld

0

50

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250

0 50 100 150 200 250

∆T 41J [oC]

∆To [oC]

Weld Fit (Slope=0.99)Plate Fit (Slope=1.10)Forging Fit (Slope=1.50)WeldPlateForgings

2

Kori-1 Weld

(NUREG-1807 database)

<RPV steels & welds>

Transition temperature shifts after irradiationTransition temperature shifts after irradiation

(USNRC RG-1.99, Rev.2)

CF = 190.8oF (from Charpy, ∆T30ft-lb) CF = 191.6oF (Master Curve, ∆To)

0 10 20 30 40 500

50

100

150

200

250

300

∆RT N

DT or

∆T o

(o F)Fluence (x1018 n/cm2)

K1W Linde 80, WF-233 ∆To (by E1921-05) ∆RTNDT (by Charpy) RG-1.99 (CF=190.8) + 2σ (σ

∆=28oF)

Similar to the Charpy data for Kori-1 weld (Linde 80 / WF-233)

Comparison with US data for Comparison with US data for LindeLinde 80 welds80 welds

Kori-1 RPV weld showed a better property than the generic Linde 80 data.

• 2σ= 65.8oF• PCVN bias = 18oF• Explicit margin terms will be added for integrity evaluation.

Un-irradiated Irradiated

-200 -150 -100 -50 0 500

50

100

150

200

250

300

ASME KIC curve by RTTo without any marginbased on the generic value of -47.6oF

Linde 80 Unirradiated Data

BAW-2308 Kori-1 ('97) Kori-1 ('05)

K JC - a

djuste

d to 1

T (MP

a-m0.5 )

Test Temperature (oC)-50 0 50 100 1500

50

100

150

200

250Fracture Toughness Data of Irradiated Linde 80 Welds

Fluence (x1019 n/cm2)BAW-2308 : 0.8 ~ 2.0 Kori-1 weld : 1.1 ~ 3.9

KIC - RTTo curve without any marginbased on the 5th capsule fluence

K JC, 1

T-adju

sted (M

Pa-m

0.5)

Temperature (oC)

BAW-2308 Kori-1 (3rd) Kori-1 (4th) Kori-1 (5th)

304260.0RTPTS (oF) at 40 yr3.943.94Fluence at EOLE (40 yr)5665.8Margin (oF)

190.8191.6CF (oF)-10 (RTNDT)-65Initial RTTo (oF)

--53.9Initial RTTo (oC)-19.4RTTo correction (oC)-10PCVN Bias (oC)--83.3Initial (conservative) To (oC)--106.7Un-irradiated To,ASTM (oC)

Charpy basedMaster curve

RTRTPTSPTS rere--evaluation (from conservative initial data)evaluation (from conservative initial data)BAW-2308 approach

222.3 oFRTPTS (averaged)212.4 216.7 237.8 ARTTo,vessel

18 oFPCVN Bias factor65.8 oFMargin35 oFRTTo (= To + α)

93.6 97.9 119.0 To,vessel

253.7 258.0 279.0 △To,vessel (oF)3.938 (40 yr)Vessel Fluence at EOLE

3.883 2.989 1.222 Fluence (x1019n/cm2)248.9 241.9 214.2 △To,surveillance

88.9 81.9 54.1To,surveillance

-160 oFTo,unirradiated (PCVN)PRS

Kori-1 surveillance capsule

RTRTPTSPTS rere--evaluation (from irradiated data)evaluation (from irradiated data)

Kewauneeapproach

RTPTS evolution curve revised for Kori-1 weldRTRTPTSPTS evolution curve revised for Korievolution curve revised for Kori--1 weld1 weld

0 10 20 30 40 50100

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4000 10 20 30 40 50

Fracture toughness evaluationby the master curve testsincluding safety margin

Approximate Calendar Year of Kori-1

Surveillance Charpy dataincluding safety margin

Regulatory Reference

RTPT

S (o F)

Neutron Fluence (x1018n/cm2)

Master curve fracture toughness data (36 un-irradiated & 45 irradiated)showed a sufficient RTPTS margin for another 10 years and more operation.

Supplement 1: Low upperSupplement 1: Low upper--shelf energy => Jshelf energy => J--R dataR data•Elastic-plastic fracture mechanics methodology (J-R) :

J-T method, DPFAD, J-R CDF •USNRC RG-1.161 (1995) provides the safety criteria and J-R database.•Kori-1 produced its plant specific J-R data from irradiated WOL specimens.

J-R test data at 288oC demonstrated that the safety evaluation based on the USNRC RG-1.161 database was sufficiently conservative for Kori-1.

S2: PS2: P--T (pressureT (pressure--temperature) operation limit curvetemperature) operation limit curve•ASME Code Section XI, App.G assumes an axial surface crack of 1/4t depth.•The operating window was too narrow for Kori-1, which has no axial weld.•ASME Code Case N-641 permits a postulate flaw with a circumferential orientation, if there are only circumferential welds.=> This could reduce the stress intensity and the P-T curve constraint.

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0 50 100 150 200 250 300 350 400 450 500 550

Temperature (Deg. F)

Pres

sure

(psig

)

ASMEsec.XI,App. G.

Code caseN-641

150 oF

800p

sig

Operating window was increased by the code case N-641 application.

Master curve data is not applied to the P-T curve generation for Kori-1.

S3: ExS3: Ex--Vessel Vessel DosimetryDosimetry

DOSIMETRY CAPSULE (54)Fe, Ni, Cu, Ti, Co, Co-Cd, Nb, U & Np

DOSIMETRY CAPSULE (54)Fe, Ni, Cu, Ti, Co, Co-Cd, Nb, U & Np

BEAD CHAINS (156)Fe, Ni & Co

BEAD CHAINS (156)Fe, Ni & Co

Dosimetry Set

• Continuation of monitoring the intensity of neutron irradiation after removal the normal surveillance capsules.

• Enhancement of accuracy of dosimetry calculation.

SummarySummary�An application for a 10 year extension of the operating license for the first PWR in Korea, Kori-1, has been submitted to the government after a stable operation of its initial licensing period of 30 years. �Irradiation embrittlement of the beltline circumferential weld, Linde 80 WF-233, was the limiting issue of aging management.�Safety evaluation and aging management actions on irradiation embrittlement of Kori-1 RPV were successfully performed.• RTPTS was re-evaluated through the master curve test method using a total of 45 irradiated and 36 un-irradiated PCVN specimens for the limiting material, WF-233.• Low upper-shelf toughness issues were resolved by J-R testing of irradiated WOL specimens and USNRC RG-1.161 procedure.• P-T limit curve was revised by using the Code Case N-641.• An ex-vessel dosimetry system was installed for a continuous monitoring and improvement of calculation accuracy of neutron fluence during a continued operation of Kori-1.