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
Industry Update PWROG Farley Zinc Program Rich Jacko - Westinghouse Al Vaia - Westinghouse 1
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
- 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 2
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.
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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 4
PWROG Farley Zinc Program 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.
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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 6
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 7
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 8
PWROG Farley Zinc Program Task 2 - Heat 3935 Materials Davis Besse Penetration #2 from US- Farley 2 material from Nozzles #14 &
- 16 NRC Heat 3935 Replicas taken from ID & OD Material from above reactor head No obvious SCC initiation cracks Air formed oxide on the OD and detected limited oxide on ID Surface generally in good condition Some scratches to deal with -
generally axial so limited effect 9
PWROG Farley Zinc Program Task 2 - Heat 3935 Microstructure Davis-Besse #2 arley #14 10
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 11
PWROG Farley Zinc Program Material Characterization - Zinc Incorporation Farley 2 - CRDM 14-A1a As-Received 100 90 Zn Normalized Wt% - Major Metals 80 Fe 70 60 50 Cr 40 30 Ni 20 10 0
0 76 151 227 378 529 756 983 1210 1361 1512 1966 2419 2873 3326 3780 4234 4687 5141 Depth from Outer Surface (nm) Nickel Plate Ni Cr Fe Zn Moderate thickness ID oxide/deposit After ~1800 ppb-mo of Zinc exposure, visible Zinc has fully penetrated the oxide film Porous metal layer visible below original Auger & EDS analysis indicates zinc oxide-metal interface; mostly on OD represents about 10 wt% of the metals in Cr and Fe depleted from the base metal to the oxide film form oxide Average thicknesses
- Oxide/deposit = 3.2 m
- Porous A600 layer = 2.2 m 12
Zinc incorporation 1996 Observations by comparison 13
PWROG Farley Zinc Program Specimen and Cyclic Hardening Process Alloy 600 - RT Cyclic Stress-Strain Curve for 100 cycles & e < 0.006 (BAPL) 80 70 0.2502 y = 199.3x 60 Cyclic Stress Amplitude (ksi) 50 Bettis increasing Bettis all 40 W plan Power (Bettis all) 30 20 10 0
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 Finite element models were utilized to Cyclic hardening process developed to determine strain gradients across sub strain-harden the surfaces of the Alloy 600 sized specimens as a function of to the level required to achieve the desired specimen width and thickness test results in reasonable times. Final strain: 0.7% to 0.8%
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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 SCC specimen size 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 Total number of specimens = 80 15
PWROG Farley Zinc Program Task 2 Results - Davis Besse Ht M3935 esults indicate similar haracteristic lives for the wo specimen sizes eibull slope or shape actor slightly lower for he small size specimens 0% Confidence bands re drawn on the failure istributions verlap indicates similar ehavior (large / small) 16
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 17
PWROG Farley Zinc Program SCC in Davis Besse Heat M3935 Large-Small-Scale Scale Beams Beams 18
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 19
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 20
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 21
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).
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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 23
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 24
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
-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 -- -- -- --
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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 26
Simulations of Task 3 Initiation Tests Conservative Expected 27
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 28
PWROG Farley Zinc Program US PWRs - Cumulative Zinc Exposure PWRs Injecting Zinc in the US (2006) 2006 Cycle N + 1 Cycle N + 2 Cycle N + 3 Cycle TMI 1R17*
Salem 2R15*
McGuire 2R17*
McGuire 1R18*
Braidwood 2R12*
Ano 1R19*
Vogtle 2R11*
Byron 2R12 Vogtle 1 R12*
Callaway R14 Fort Calhoun R22 Beaver Valley 1R17 Sequoyah 2R13 Sequoyah 1R14 Farley 1R20 Palisades R18 Diablo Cany 2R13 Diablo Cany 1R13 Farley 2R17 0
200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 Cumulative Zinc Exposure (ppb-months) 29
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 30
Task 4 - Testing SCC performance of Alloy 690/52/152 with Zn oy 690 and the weld metals will be pre-exposed to Zinc containing primary ter prior to the start of SCC testing 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 ain ksi ksi MPa 7A21 archive archive VCSum ain) 77°F 680°F 360°C 00 66.3 60.3 416 5 5 5 9 00 56.9 51.7 357 -- -- -- --
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Task 4 - SCC Testing with Zinc 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 32
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 33