ML061800263

Crack Growth Rates in a PWR Environment of Nickel-Base Alloys from Davis-Besse and V. C. Summer Plants

ML061800263
Person / Time
Site:	Davis Besse, Summer
Issue date:	09/18/2006
From:	Alexandreanu B, Chopra O, Cullen W, Shack W Argonne National Lab (ANL), NRC/RES/DFERR
To:
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ML061810190	List: ML061800263 ML061810182
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Download: ML061800263 (21)

Text

Crack growth rates in a PWR environment of nickel-base alloy welds from the Davis-Besse and V.C. Summer plants B. Alexandreanu1, O. K. Chopra1, W. H. Cullen Jr. 2 and W. J. Shack1 1Nuclear Engineering Division, Argonne National Laboratory 2U.S. Nuclear Regulatory Commission Fontevraud 6, September 18-22, 2006

Outline Objectives Experiment

- specimens

- testing conditions Results and discussion

- cyclic crack growth rates

- SCC crack growth rates

- fractography Summary 2

Objectives Obtain crack growth data under both cyclic and constant load conditions in PWR environment on field Alloy 182 welds Determine the effect of weld microstructure/orientation on SCC crack growth rates Compare results with existing CGR database to determine the relative susceptibility of these welds to environmentally assisted cracking.

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Field weld specimens tested Alloy 182 removed from the J-groove weld from Nozzle #11 from the Davis-Besse plant:

J11CC-1 (weld, Alloy 182)

J11CC-3 (weld, Alloy 182)

Alloys 182 and 82 from the reactor vessel nozzle-to-pipe from the V. C. Summer plant:

WCR-01 (weld, Alloy 82)

BCR-01 (butter, Alloy 182)

WLR-01 (weld, Alloy 82) 4

Location of specimens -

Davis-Besse J-groove weld of #11 nozzle Weld height at 180° location 45 mm L Orientation C Orientation C Orientation L Orientation 64 mm 128 mm Low-Alloy Steel Weld height at 30° Alloy 182 Weld location 29 mm Cladding 5

Location of specimens -

V.C. Summer reactor vessel nozzle-to-pipe weld 6

Experiment 1/2-T compact tension specimens fabricated from both welds Temp: 316°C (D-B) and 320°C (VCS)

PWR Water (<10 ppb DO, 1000 ppm B, 2 ppm Li, 2 ppm hydrogen Flow Rate: 55 mL/min Conductivity: 20 µS/cm Precracking carried out in the PWR environment to facilitate the transition from transgranular fatigue cracking to intergranular SCC cracking before conducting the constant load test Load Ratio R: 0.3-precrack; 0.5-0.7-sawtooth with up to 1000s rise time; 1.0-constant load Crack extension measured by DC potential drop method Final crack length confirmed/corrected by actual measurements.

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Davis-Besse weld alloys 8

Cyclic CGR data for Davis-Besse weld alloys 10-6 Alloy 182 J-Groove Weld Alloy 182 J-Groove Weld Davis Besse Nozzle #11 (Davis-Besse CRDM Nozzle #11) 316°C 316°C PWR Water 10-9 10-7 Experimental CGR (m/s) 10-8 Proposed Disposition Curve Alloy 182 Weld Metal 10-10 CGRenv. (m/s)

CGRair x 5 10-9 10-10 CGRenv. = CGRair + 0.018(CGR air)0.78 10-11 1/2-T CT 10-11 1/4-T CT Specimen #

J11CC-1 (1/4-T CT)

J11CC-3 (1/2-T CT) 10-12 10-12 10-12 10-11 10-10 10-9 10-8 10-7 10-6 CGRair for Ni-Alloy Welds (m/s) 10 15 20 25 30 35 40 45 50 Stress Intensity K (MPa*m1/2) 9

Fracture surface of specimen J11CC-1 10

V.C. Summer alloys 11

Cyclic and SCC CGRs for V.C. Summer weld alloys V.C. Summer Ni-Alloy Weld Metal 10-6 325°C Alloy 182 SMA Weld 10-9 Proposed Simulated PWR Water at 320°C CGR Curve 10-7 Alloy 182 Experimental CGR (m/s) 10-8 10-10 CGRenv (m/s) 10-9 10-10 10-11 10-11 WCR-01 WCR-01 BCR-01 BCR-01 WLR-01 WLR-01 10-12 A 82 weld, Jacko et al.

10-12 A 182 butter, Jacko et al.

10-12 10-11 10-10 10-9 10-8 10-7 10-6 CGRair for Ni-alloy Welds (m/s) 10 20 30 40 50 Stress Intensity K (MPa*m1/2) 12

Log-normal distribution of constant for several heats of Alloy 82 and 182.

1.0 Ni-Alloy Weld Metal 325°C 0.8 75th Percentile Cumulative Distribution F 0.6 Median 0.4 25th Percentile A 182 0.2 A 82 ANL BCR-01 ANL WCR-01 A 182 Jacko et al.

A 82 Jacko et al.

0.0 10-13 10-12 10-11 Constant in Scott Model at 325°C 13

Fracture surface of VCS specimen BCR-01 14

Fracture surface of specimen V.C. Summer BCR-01 15

Fracture surface of V.C. Summer specimen WLR-01 16

Fracture surface of V.C. Summer specimen WLR-01 17

Additional observations 18

Fracture surface of J11CC-1 and BCR-01 Cracks across the propagation front appear to impede crack advance 19

Fracture surfaces of Davis-Besse nozzle Alloy 600 specimens Fracture mode seems to depend on the location of the specimen 20

Summary The cyclic CGRs for Alloy 182 and Alloy 82 weld specimens showed minimal environmental enhancement except for one specimen For the Davis-Besse Alloy 182 weld specimens, the SCC CGRs under constant load are an order of magnitude lower than the disposition curve proposed for Alloy 182 weld metals For the V.C. Summer weld specimens, the CGR data under constant load were lower than data obtained by others on the same alloys and lower than the proposed disposition curve 21