ML071590121
| ML071590121 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 05/30/2007 |
| From: | Jacko R, Vaia A PWR Owners Group, Westinghouse |
| To: | Office of Nuclear Reactor Regulation |
| SAMANTHA CRANE, RES 301-415-6380 | |
| Shared Package | |
| ML071580602 | List: |
| References | |
| Download: ML071590121 (33) | |
Text
1 Industry Update PWROG Farley Zinc Program Rich Jacko -
Westinghouse Al Vaia -
2 PWROG Farley Zinc Program z Farley 2 Pilot Plant for Zinc Addition Laboratory and test reactor experiments indicated reduced general corrosion and PWSCC mitigation benefits of zinc addition EPRI sponsored demonstration plant Zinc injection began June 12, 1994 RCS zinc concentration 30 ppb Cycles 10, 12 -
14 15 ppb Cycles 15 -
17 (post SG replacement)
Integrated zinc exposure 1551 ppb-months at last inspection Integrated zinc exposure 1791 ppb-months at RV head replacement
3 PWROG Farley Zinc Program Heat M3935 at Farley
62 of 69 Farley 2 RV head penetrations were manufactured from Alloy 600 Heat M3935.
Heat M3935 have shown PWSCC in all other plants without Zn injection
Replacement of the RV head at Farley 2 during the Fall 2005 outage provided a unique opportunity to obtain Alloy 600 CRDM material that operated for an extended period with Zn additions to the primary coolant.
4 PWROG Farley Zinc Program Farley Heat 3935
Farley CRDM provided inservice exposed material to show the benefit of zinc as a PWSCC chemical mitigation
Plan to fabricate test specimens keeping as-is surface films intact
Divide specimens into two groups
Carefully remove zinc from the surface films of one group
Perform comparison crack initiation testing
EPRI and the PWR Owners Group (PWROG) have approved programs to study the effects of zinc addition on PWSCC
Ultimate Industry Goal -
Acceptance of Zinc as a chemical mitigation method to support inspection relief.
PWROG PA-MSC-0257 PWSCC Crack Initiation Testing of Farley Unit 2 Alloy 600 CRDM Material approved in February 2006 5 year program with 5 distinct phases including hold points.
Verify the enhanced PWSCC resistance of Ht M3935 at Farley is due to zinc Exposure of Alloy 600, Alloy 690, 82/182, and 52/152 materials to demonstrate that the benefits of soluble zinc extend to other primary side Alloy 600/Alloy 690 components and their associated welds.
Develop strategies to support utility technical evaluations.
6 PWROG Farley Zinc Program Task Description
Task 1 Development of the Industry Road Map and Creation of the Utility Core Team -
Completed
Task 2 -
Material Characterization and Validation of Accelerated PWSCC Testing Methods for Sub-sized Specimens in 752°F Steam -
Completed
Task 3 -
Baseline 680°F Autoclave Testing of Heat M3935 Material from the Davis-Besse and Farley 2 CRDM Penetrations (without zinc additions) -
underway
Task 4 -
680°F Autoclave Testing of Zn-Exposed Farley Unit 2 Heat M3935 Head Penetration Material (with zinc additions)
Task 5 -
Data Analysis and Comprehensive Final Report
7 PWROG Farley Zinc Program Task 2 - Overview
Test material and surface film characterization of Farley and Davis-Besse materials.
Design of sub-sized four point bent-beam specimens with convex and concave stressed surfaces.
Development of strain hardening method and verification of surface film integrity.
Crack initiation testing in 752°F steam using surrogate Alloy 600 and Davis-Besse material
Estimate time to crack initiation in primary water
8 PWROG Farley Zinc Program Task 2 - Test Materials
Davis Besse Penetration #2 from US-NRC Heat 3935 -
SCC test samples Material from above reactor head -
limited oxide on ID Air formed oxide on the OD
Farley Penetration #14 and #16 Heat 3935 Threaded end from inside head used for material characterization efforts
Surrogate Heat #1 -
B&W 91117 -
SCC test samples
Surrogate Heat #2 -
C2649 -
SCC test samples
9 PWROG Farley Zinc Program Task 2 - Heat 3935 Materials
Davis Besse Penetration #2 from US-NRC Heat 3935
Material from above reactor head
Air formed oxide on the OD and limited oxide on ID
Farley 2 material from Nozzles #14 &
- 16
Replicas taken from ID & OD
No obvious SCC initiation cracks detected
Surface generally in good condition
Some scratches to deal with -
generally axial so limited effect
10 PWROG Farley Zinc Program Task 2 - Heat 3935 Microstructure Davis-Besse #2 Farley #14
11 PWROG Farley Zinc Program Task 2 - Heat 3935 Microstructure Comparison
Heat M3935 from both Davis Besse and Farley 2 are similar
Same grain size and grain structure indicate similar processing and annealing treatments ASTM 2 grain size
Carbide structure similar in both materials Little evidence of intragranular carbides With 0.028% C, the Alloy 600 would need to have seen
~1800°F to fully solutionize all carbides Appears to be a distinct carbide free zone near the grain boundary in M3935 from both plants
12 PWROG Farley Zinc Program Material Characterization - Zinc Incorporation Farley 2 - CRDM 14-A1a As-Received 0
10 20 30 40 50 60 70 80 90 100 0
76 151 227 378 529 756 983 1210 1361 1512 1966 2419 2873 3326 3780 4234 4687 5141 Depth from Outer Surface (nm)
Normalized Wt% - Major Metals Ni Cr Fe Zn Ni Cr Fe Zn
After ~1800 ppb-mo of Zinc exposure, Zinc has fully penetrated the oxide film
Auger & EDS analysis indicates zinc represents about 10 wt% of the metals in the oxide film
Moderate thickness ID oxide/deposit visible
Porous metal layer visible below original oxide-metal interface; mostly on OD
Cr and Fe depleted from the base metal to form oxide
Average thicknesses Oxide/deposit = 3.2 m Porous A600 layer = 2.2 m Nickel Plate
13 Zinc incorporation 1996 Observations by comparison
14 PWROG Farley Zinc Program Specimen and Cyclic Hardening Process Finite element models were utilized to determine strain gradients across sub sized specimens as a function of specimen width and thickness Alloy 600 - RT Cyclic Stress-Strain Curve for 100 cycles & e < 0.006 (BAPL) y = 199.3x0.2502 0
10 20 30 40 50 60 70 80 0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 0.011 0.012 0.013 0.014 0.015 0.016 Total Strain Amplitude Cyclic Stress Amplitude (ksi)
Bettis increasing Bettis all W plan Power (Bettis all)
Cyclic hardening process developed to strain-harden the surfaces of the Alloy 600 to the level required to achieve the desired test results in reasonable times. Final strain: 0.7% to 0.8%
15 PWROG Farley Zinc Program Task 2 - SCC Initiation Test Matrix
80 specimens tested in high temperature steam at 752°F (400°C) -
44 small scale and 36 large scale
Combination of M3935 and two surrogate Alloy 600 heats size/heat=
large small large small small Stress (ksi)
M-3935 M-3935 91117 91117 C-2649 Strain 78°F 752°F (u-strain) 63.2 56.6 7
8 2000 56.9 51.0 5
5 6
8 4
1800 50.5 45.3 6
6 1600 45.8 41.1 5
5 7
8 1450 80 SCC specimen size Total number of specimens =
16 PWROG Farley Zinc Program Task 2 Results - Davis Besse Ht M3935
Results indicate similar characteristic lives for the two specimen sizes
Weibull slope or shape factor slightly lower for the small size specimens
90% Confidence bands are drawn on the failure distributions
Overlap indicates similar behavior (large / small)
17 PWROG Farley Zinc Program Task 2 Results - Surrogate Heat 91117
Results indicate similar characteristic lives for the two specimen sizes
Weibull slope or shape factor slightly lower for the small size specimens
Weibull slopes consistent with S/G experience
SCC in 54 of 56
18 PWROG Farley Zinc Program SCC in Davis Besse Heat M3935 Large-Scale Beams Small-Scale Beams
19 PWROG Farley Zinc Program Task 2 Conclusion
Farley CRDM: Zinc has incorporated deep into the oxide & deposits
Small scale test specimen design validated
Work hardening process validated
Weibull characteristic crack initiation times similar for conventional, large-scale bent beam specimens and the small-scale beams designed for use with the Farley material
Based on Westinghouse experience, the doped steam & hydrogen testing results would indicate that:
Baseline specimens of Ht M3935 would expect to initiate SCC in simulated 680°F primary water (no zinc) in ~3000 -
6000 hours0.0694 days <br />1.667 hours <br />0.00992 weeks <br />0.00228 months <br /> If SCC behavior meets expectations, should be able to demonstrate a significant zinc benefit when comparison tests run with Zinc
20 PWROG Farley Zinc Program Task 2 - Goals not met
Ability to remove zinc from Farley baseline specimens Additional decon studies planned for June
Demonstrate that the cyclic hardening operation does not introduce considerable damage to the oxide films Cyclic hardening of material removed from North Anna penetrations
21 Contingency Plan for Farley -
Davis Besse Comparisons
Plans are complete for OD material from Farley 2 and Davis Besse
FEM suggests that ID specimens may not be well suited for SCC studies
Comparisons can be made for fresh specimens removed below outer layer
22 PWROG Farley Zinc Program Task 3 and Task 4 Overview Task 3 preparation is underway for baseline crack initiation testing in 680°F primary water (with no zinc additions) scheduled to start July 07 Test specimens to include Davis-Besse, Farley 2 (zinc enriched surface film removed), surrogate Alloy 600, Alloy 82/182, Alloy 52/152, and Alloy 690.
Interim inspections after every 400 to 700 hours0.0081 days <br />0.194 hours <br />0.00116 weeks <br />2.6635e-4 months <br /> of testing until 8400 hours0.0972 days <br />2.333 hours <br />0.0139 weeks <br />0.0032 months <br /> total exposure (equivalent to ~19 EDY at 600°F using a Q = 50 kcal/mole).
Task 4 testing will consist of crack initiation testing in 680oF primary water (with 15 ppb zinc additions)
Test specimens to include Farley 2 M3935 with zinc enriched surface film, Davis-Besse M3935, Alloy 82/182 and 52/152 welds, and Alloy 690.
Interim inspections at approximately 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> intervals up to 18000 hours total (equivalent to ~ 41 EDY at 600°F).
23 Task 3 -
Baseline SCC performance of Heat M3935 & materials of interest Objective
Demonstrate that the excellent PWSCC performance observed by the Farley 2 M3935 material was due to Zinc addition
When Zinc is removed from the Farley Material, SCC performance is expected to be similar to the Davis Besse Material Complications may arise due to the presence porous layer below oxide Planning on removing some specimens below surface layer Baseline testing of 690/52/152/182/82 for surface characterization
24 Task 3 -
Baseline SCC performance of Heat M3935 and other Alloy 600
The deep Zinc penetration observed in the Farley 2 material may prove difficult to remove
Testing of 2nd layer specimens Farley & Davis Besse E at T (ksi)
E at T (ksi) 31.59 28.73 small Far#14 small Far#16 small DB#2 small Strain ksi ksi MPa M-3935 M-3935 M-3935 C-2649 (u-strain) 77°F 680°F 360°C 2100 66.3 60.3 416 5
5 10 7
1800 56.9 51.7 357 5
5 7
1800 56.9 51.7 357 5
5 10 1600 50.5 46.0 317 2
3 5
1450 45.8 41.7 287 Total No. of Alloy 600 Beams =
74 Lomi decon Flat beams
25 Task 3 -
Baseline SCC performance of Alloy 690 and weld metals
Alloy 690 and the associated weld metals will be tested as stressed beams
Regions on these specimens will be prepared for future surface film analysis (Auger / FEG SEM)
E at T (ksi)
E at T (ksi)
Flat beams 31.59 28.73 Alloy 690 cw 52M 152 182/82 large Strain ksi ksi MPa 7A21 archive archive VCSum (u-strain) 77°F 680°F 360°C 2100 66.3 60.3 416 5
5 4
9 1800 56.9 51.7 357 1800 56.9 51.7 357 1600 50.5 46.0 317 1450 45.8 41.7 287
26 Task 3 -
Baseline Testing
Original plan to test Alloy 690/52/152 as coupons
Only plan to examine similarity of Zn incorporation
Easier to examine these materials in the same test fixtures
There are technical reasons to examine stressed specimens; role of T and stress on Zn effects
Plan to test Alloy 690/52/152 as polished and electropolished stressed beams
27 Simulations of Task 3 Initiation Tests Expected Conservative
28 Task 3 Testing with Zinc Injection Current status
All Farley materials are cut into segments
Cutting of thin beam specimens has started
Hardening of surrogate Alloy 600 specimens complete
Starting to cut Alloy 690 specimens
Cyclic hardening of radioactive specimens planned for June
Testing scheduled for July 07 thru Aug 08
29 PWROG Farley Zinc Program US PWRs Cumulative Zinc Exposure PWRs Injecting Zinc in the US (2006) 0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 Farley 2R17 Diablo Cany 1R13 Diablo Cany 2R13 Palisades R18 Farley 1R20 Sequoyah 1R14 Sequoyah 2R13 Beaver Valley 1R17 Fort Calhoun R22 Callaway R14 Vogtle 1 R12*
Byron 2R12 Vogtle 2R11*
Ano 1R19*
Braidwood 2R12*
McGuire 1R18*
McGuire 2R17*
Salem 2R15*
TMI 1R17*
Cumulative Zinc Exposure (ppb-months) 2006 Cycle N + 1 Cycle N + 2 Cycle N + 3 Cycle
30 Task 4 -
Testing SCC performance of Heat M3935 and other Alloy 600 with Zn
Farley 2 OD specimens pre-exposure ~1800 ppb -
mo of zinc exposure
Davis-Besse OD specimen have 0 ppb -
mo pre-exposure
Selected flat beam specimens will be pre-exposed to either 200, 400 or 800 ppb-mo of zinc prior to the start of SCC testing E at T (ksi)
E at T (ksi) 31.59 28.73 small Far#14 small Far#16 small DB#2 small Strain ksi ksi MPa M-3935 M-3935 M-3935 C-2649 (u-strain) 77°F 680°F 360°C 2100 66.3 60.3 416 10 10 10 8
1800 56.9 51.7 357 8
8 1800 56.9 51.7 357 15 15 15 1600 50.5 46.0 317 1450 45.8 41.7 287 Total No. of Alloy 600 Beams =
99 Lomi decon Flat beams
31 Task 4 -
Testing SCC performance of Alloy 690/52/152 with Zn small Far#14 small Far#16 small DB#2 M-3935 M-3935 M-3935 Flat beams with no oxide preconditioned to:
5 5
5 200 ppb-mo =
50 ppb x 4 mo 5
5 5
400 ppb-mo =
100 ppb x 4 mo 5
5 5
800 ppb-mo =
200 ppb x 4 mo 15 15 15 E at T (ksi)
E at T (ksi)
Flat beams 31.59 28.73 Alloy 690 cw 52M 152 182/82 large Strain ksi ksi MPa 7A21 archive archive VCSum (u-strain) 77°F 680°F 360°C 2100 66.3 60.3 416 5
5 5
9 1800 56.9 51.7 357 Alloy 690 and the weld metals will be pre-exposed to Zinc containing primary water prior to the start of SCC testing
32 Task 4 -
Current plans are to initiate Zn testing in late 2008
If baseline Task 3 testing shows anticipated SCC initiation trends, would anticipate asking PWROG to move the start of Task 4 testing with zinc to 2008
18000 hours of crack initiation testing planned (equivalent to ~ 41 EDY at 600°F)
Approximately 2.5 years to complete after starting
33 Summary
Farley CRDM showed Zinc has incorporated deep into the oxide films & deposits
Small scale test specimen design validated
Work hardening process validated
Baseline testing of Farley & D-B material starting
Baseline testing of Alloy 690/52/152/182 also starting
Plans for Task 4 with zinc exposure will finalize after SCC initiation observed in baseline tests
Part of the Task 4 test matrix will be fresh specimens with different starting integrated ppb-mo of zinc exposure simulating conditions at various plants