05/30/2007, MRP/PRWOG Mitigation Briefing, 'Effect Of .

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Effect of Primary WaterZinc Injection on PWSCC inNi-Based RCS ComponentsPeter AndresenGE Global ResearchMay 30, 2007MRP/PWROG Mitigation Briefing to NRC RES

History and Status of Zinc Injection BWRs started adding zinc for radiation field control in 1986 Farley 2 was the first US PWR plant to inject zinc in 1994 By Dec 2006, 39 PWR units world-wide were injecting zinc,including 18 International units Of the 21 US PWRs, 5 are injecting with the prime objectiveof PWSCC mitigation ( 15 ppb zinc), and the remainder forradiation field control, using lower zinc injection levels A further 10 PWRs have indicated definite plans toimplement zinc within the next year or two 2007 Electric Power Research Institute, Inc. All rights reserved.2

Plants Injecting ZincNumber of Units Injecting Zinc by Year454035Number of Units3025201510501994199519961997New US Units 2007 Electric Power Research Institute, Inc. All rights reserved.199819992000New International Units320012002200320042005Cumulative Units Injecting Zinc2006

Overall Correlation of Dose Rate to Zinc ExposurePositive Benefit with ZincCumulative Dose Rate Reduction Based on Zinc Exposure1.2Cumulative Dose Rate Reduction Fraction1Alloy 600 & 690 Plants w/Natural Zincy -0.1052Ln(x) 1.26762R 0.66430.80.60.4Alloy 800 Plants w/Depleted Zincy -0.1437Ln(x) 1.38952R 0.63220.2Alloy 600 & 690 w/Depleted Zincy -0.0777Ln(x) 1.0532R 0.53860020040060080010001200140016001800Cumulative Zinc Exposure, ppb-monthsAlloy 800 w/Depleted ZincLog Alloy 800 Plants w/Depleted Zinc 2007 Electric Power Research Institute, Inc. All rights reserved.Alloy 600 & 690 w/Depleted ZincLog Alloy 600 & 690 w/Depleted Zinc4Alloy 600 & 690 w/Natural ZincLog Alloy 600 & 690 w/Natural Zinc2000

Field SG Data Evaluation:PWSCC Zn Mitigation Five units injecting zinc primarily for PWSCC mitigation(15-40 ppb) Farley 1 and 2, Diablo Canyon 1 and 2, andBeaver Valley 1 Steam Generator data analyzed for PWSCC indications:– Numbers of cumulative PWSCC indications¾ Rate of increase in PWSCC observations (2 to 10X reduction)– Voltage growth rate data¾ Growth rate measurements (20% to 60% reduction) Comparisons performed of the results for periods ofoperation with and without zinc– Quantify the Benefit! 2007 Electric Power Research Institute, Inc. All rights reserved.5

Example of Smallest Zn Benefit Observed31% Decrease in Weibull Slope(It would take 1.9 times as long to go from 1% to 10% tubes affected)Weibull Fit (Least Squares)90%63%50%20%Cumulative Percentage of Tubes FailedNo zincIntermittant zincaddition betweengreen and redlines.(see Table 2-1for details)10%5 ppb zincPre-zinc slopeb 1.645%2%100% RPC Exam1%Shot-peened0.5%0.2%100% Pt ExamsCommenceto 0.00 EFPY0.1%0.05%Partial RPC Examb 1.130.02%Theta 856 EFPY0.01%123456810Service Time (EFPY)203040506080100Sequoyah 2 (5 ppb zinc) has experienced a 31% decrease in Weibull Slope 2007 Electric Power Research Institute, Inc. All rights reserved.6

Example of Largest Zn Benefit Observed79% Decrease in Weibull Slope(It would take 9.6 times as long to go from 0.8% to 10% tubes affected)Weibull Fit (Least Squares)No zinc90%63%50%Intermittant zincaddition betweengreen and redlines.(see Table 2-1for details)Cumulative Percentage of Tubes Failed20%10%35 ppb zinc5%Pre-zinc slopeb 4.352%1%100% Pt ExamsCommence0.5%0.2%to 0.00 EFPY0.1%100% RPC Exam0.05%b 0.900.02%Theta 3.49E 03 EFPY0.01%123456810203040506080100Service Time (EDY @ 607 F)Beaver Valley 1 (35 ppb zinc) has experienced a 79% decrease in Weibull Slope 2007 Electric Power Research Institute, Inc. All rights reserved.7

Fuel Materials Compatibility (Fuel)Zinc, by itself, is not expected to negatively affect fuelcladding integrity.– Early autoclave and in-reactor tests showed no impact.– Cladding corrosion measurements have shown zinc tohave little or no impact on clad performance. Assessments by vendors have determined that zinc doesnot interact with or exacerbate the degradation of leakingrod failure locations caused by other mechanisms. Zinc was shown to have no negative effect on other fuelcomponent materials during early autoclave testing, FRP and vendors are expanding the fuel surveillancedatabase as higher duty plants inject zinc. 2007 Electric Power Research Institute, Inc. All rights reserved.8

Fuel Materials Compatibility (Fuel)Experience: Fuel surveillances at Farley, Diablo Canyon and Palisadeshave shown zinc to be relatively benign at low duty units. In 2002, FRP sponsored detailed crud scrapes at DiabloCanyon-1 following Cycle 11 on the two highest-poweredassemblies in-core for later comparison with higher duty fuels– Surveillance performed for background information. Crud scrapes and cladding corrosion measurements atCallaway (first high-duty plant to add zinc) followingCycles 13 (2004) and 14 (2005) showed no acceleratedcladding corrosion. 2007 Electric Power Research Institute, Inc. All rights reserved.9

Fuel Materials Compatibility (Fuel) Vandellos II (Spain) demonstration in progress. Vandellosbounds most PWRs in U.S. with respect to fuel duty.––––Baseline oxide measurements taken during Refuel 14 (spring 2005)Zinc injection commenced half-way into Cycle 15 (June 2006)Refuel 15 planned May 2007 (oxide measurements & crud scrapesRefuel 16 planned fall 2008 (oxide measurements & crud scrapes) Expansion of the database to other high-duty units is beingpursued. FRP-sponsored autoclave experiments are underway todefine the limits under which zinc can be added.– This includes heated single-rod tests under bounding heat flux andsub-cooled nucleate boiling conditions and includes tests at highzinc concentrations and various levels of contaminants (e.g. silica)known to negatively affect crud deposits. 2007 Electric Power Research Institute, Inc. All rights reserved.10

Zinc Mitigation of PWSCC Initiation and GrowthThe inhibitive effect of zinc on PWSCC initiation is welldocumented Decrease in SG degradation rate (indications) by 2 to 10X Farley 2 head experienceHowever: Reduced crack growth benefit of zinc shown for A600 SGtubes does not necessarily transfer to thick-wall RCScomponents and to A82/182 welds 2007 Electric Power Research Institute, Inc. All rights reserved.11

Mitigation of PWSCC in RCSA600/182/82 by Zinc Injection MRP/PWROG objective is to supplement confirmed radiationfield control benefit from zinc injection with demonstratedreduction in rate of PWSCC initiation and growth in thick-wallRCS components to: Avoid or delay component repair/replacement by retarding PWSCCinitiation and growth of shallow (undetected) cracksObtain inspection relief for susceptible RCS locations bydemonstrating reduction in initiation and growth of existing cracks Parallel efforts underway by FRP and Chemistry to assure: Recommended levels do not effect fuel performance and claddingintegrityOrderly dissemination to utilities via Zn application guidelines Investigating synergistic PWSCC benefit of zinc and elevated H2 2007 Electric Power Research Institute, Inc. All rights reserved.12

Zn: Penetration to Crack TipLimited benefit of Zn inBWRs related to highcorrosion potential, whichdrives Zn2 from crack.But at low potential, Zndiffuses slowly and is initially“consumed” by incorporationinto crack oxides. 2007 Electric Power Research Institute, Inc. All rights reserved.13

GE Tests on SS at 20 ppb ZnNobleChem 20 ppb Zn2 Longer-term Effects of Zn on SCC0.511.6C237 - 0.5TCT of 316L / 20%RAStart 25 ksi in, 2 ppm O2, Pure Water0.10.311.211.11.62x10-7 mm/sOutlet conductivityBegin ZnO Injection at 1232 h.11.3Begin 6.18% H 2 in Ar at 679 h.Crack length (mm)0.10-0.1-0.2-0.3CT potential-0.40.08Crack Length Increment (mm)0.22.9x10-8 mm/s11.4-7da/dt 1.62x10 mm/sConductivity, μS/cm or Potential, Vshe8.3x10-9 mm/s11.5C237 - 0.5TCT of 316L / 20%RAStart 25 ksi in, 2 ppm O2, Pure Water2 ppm O2 Addition0.46.18% H2 in Ar AdditionInitial Zn2 Addition Period-8da/dt 1.1x10 mm/s-8da/dt 2.91x10 mm/s0.060.040.02112 Steady State Zn Addition-9da/dt 8.3x10 mm/s-0.5Pt potential10.9200-0.6700120017002200270000Test Time (hours)100200300400500600Test Time (hours)700Injection of Zn 2 at low potentials may mitigate crackingin highly irradiated materials. Zn is currently injected at5 – 7 ppb into reactor feed water for radiation control 2007 Electric Power Research Institute, Inc. All rights reserved.148009001000

Effects of Zn on SCC Growth RateTestLi, ppmB, ppmpH300C (1)Zn, ppbDurationhours12.26007.20 30500022.26007.20 10 30 0650030.312006.90 30 05000500 hrs for SCC transitioning 1500 hrs per test segmentEach test uses two 1TCT specimens; 325C, 30 cc/kg H2Spike Zn for several weeks to saturate system and crackTesting focused on Ni-metal stability high H2Testing now underway on Alloy 182 weld metal 2007 Electric Power Research Institute, Inc. All rights reserved.15

30 ppb Zn EffectSpiked to 150 ppb Zn injected for six weeksSCC#3 - c272 - Alloy 600, CRDM Tube, 9351011.450.411.311.25To 150 ppb Zn asacetate @ 1420h11.35To Constant K @ 913hCrack length, mm11.4-85 x 10mm/s0-0.21.8 x 10-8mm/s-0.4-0.63.1 x 10-8mm/sc272 - 0.5TCT of A600 CRDM, 325C25 ksi in, 20 cc/kg H2, 600 B / 2.2 Li11.2Pt potential11.1510000.214001800Conductivity, μS/cm or Potential, VsheTo 50 ppb Zn asacetate @ 2429hOutlet conductivity 100-0.8CT potential22002600-13000Test Time, hoursSpecimens run at 325C, 600 B / 2.2 Li, 30 cc/kg H2then 150 ppb Zn injected for six weeks. 2007 Electric Power Research Institute, Inc. All rights reserved.16

Test #2: 30 ppb Zn EffectSpiked to 150 ppb Zn injected for six weeks0.411.52Outlet conductivity 1000.211.5-911.4440 ppb @ 5698h1.7 x 10-8mm/s60 ppb @ 5531hZn reduced to100 ppb @ 5478hCrack length withoutRef.ProbeStart Zn injection150 ppb @ 4328h11.46To constant K@ 3033hCrack length, mm011.48-0.2-0.4-0.6c292 - 0.5TCT of A600 CRDM, 325C15 ksi in, 18 cc/kg H2, 600 B / 2.2 Li11.42-0.8Pt potential CT potential11.433003800430048005300-15800Test Time, hours325C, 600 B / 2.2 Li, 18 cc/kg H2Used 15 ksi in so growth rates are lower 2007 Electric Power Research Institute, Inc. All rights reserved.17Conductivity, S/cm or Potential, Vshe3 x 10 mm/s

Test #2: 30 ppb Zn EffectSpiked to 150 ppb Zn injected for six weeks11.50.4Outlet conductivity 1000.2c293 - 0.5TCT of A600 CRDM, 325C15 ksi in, 18 cc/kg H2, 600 B / 2.2 Li6 x 10-9 mm/sCrack length withoutRef.Probe11.440 ppb @ 5698h-0.4-0.6-0.8Pt potential11.38330060 ppb @ 5531h11.42Zn reduced to100 ppb @ 5478h1.7 x 10-8mm/s-0.2Start Zn injection150 ppb @ 4328h11.44To constant K@ 3033hCrack length, mm011.4638004300CT potential48005300-15800Test Time, hours325C, 600 B / 2.2 Li, 18 cc/kg H2Used 15 ksi in so growth rates are lower 2007 Electric Power Research Institute, Inc. All rights reserved.18Conductivity, μS/cm or Potential, Vshe11.48

Test #1: Zn Maps in CrackMicroprobe (WDS) very roughness/orientation sensitiveZn fracture surface 2007 Electric Power Research Institute, Inc. All rights reserved.19

Test #2: Zn Maps in CrackAuger Electron Spectroscopy in IG Area Near Fatigue Precrack 2007 Electric Power Research Institute, Inc. All rights reserved.20

Test #2: Zn Maps in CrackAuger Electron Spectroscopy in IG Area Near Crack Tip 2007 Electric Power Research Institute, Inc. All rights reserved.21

Test #3: 30 ppb Zn Effect 50 ppb Zn for 10 weeks – no effect observed yetSCC#4 - c315 - Alloy 600, CRDM Tube, 93510SCC#4 - c316 - Alloy 600, CRDM Tube, 9351011.230.411.280.4Outlet conductivity 100Outlet conductivity 10011.24-0.2-0.411.2311.22c315 - 0.5TCT of A600 CRDM, 325C15 ksi in, 18 cc/kg H2, 600B/2.2Li6.6 x 10-9mm/sPt potential40004500500011.19-0.2-0.45 x 10-9mm/sc316 - 0.5TCT of A600 CRDM, 325C15 ksi in, 18 cc/kg H2, 600 B / 2.2 LiPt potential11.1730005500Test Time, hours40004500325C, 600 B / 2.2 Li, 18 cc/kg H2At 15 ksi in growth rates are lower22CT potential-13500Test Time, hours 2007 Electric Power Research Institute, Inc. All rights reserved.-0.6-0.8CT 1Zn fluctuates during stabilizationperiod - analysis takes 1 week50005500Conductivity, μS/cm or Potential, Vshe11.2500.211.22Crack length, mmCrack length, mm11.26Zn fluctuates during stabilizationperiod - analysis takes 1 weekConductivity, μS/cm or Potential, VsheTo 50 ppb Zn @ 3994h0.2To 50 ppb Zn @ 3994h11.27

Conclusions on Zn EffectsSummary and Interpretation of Zn Results: Some benefit may occur at high Zn levels (150 ppb) Limited evidence of benefit at 30 ppb Zn, 25 ksi in Stronger evidence of benefit at 30 ppb Zn, 15 ksi in Follow-up, corroborative experiments essential Uncertain theoretical benefit of Zn in NiO structure– known benefit is from Zn incorporation into spinel Testing underway focuses on Alloy 182 2007 Electric Power Research Institute, Inc. All rights reserved.23

A600 PWSCC Summary ofTest Results and Ongoing WorkField and test data shows zinc inhibits PWSCC initiation in Alloy600/82/182; recently-initiated PWROG project will provide confirmation.Task-by-task results over the next few years.Some initial tests indicate zinc can reduce growth rate of undetected(shallow-low stress intensity) cracks in thick A600 components,confirmatory tests underway. Results in 2008.A600 tests to date have not shown zinc can reduce growth rate of deepcracks in high stress areas (high stress intensity cracks). It appears thatcrack-tip in a fast-growing crack out-runs zinc species that deposit oncrack flanks rather than on the tip. Further testing is underway. Resultsexpected in 2008.Ongoing testing will address crack growth in A182 material.Future MRP work will include evaluation of synergistic effects of elevatedhydrogen and zinc.SCC tests require thousand hours; results are slow to come. 2007 Electric Power Research Institute, Inc. All rights reserved.24

Present Schedule for Deliverable on ChemicalMitigation Technical basis document to be provided to NRC in 2008– Zinc– Hydrogen 2007 Electric Power Research Institute, Inc. All rights reserved.25

0.4 0.6 0.8 1 1.2 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Cumulative Zinc Exposure, ppb-months Cumulative Dose Rate Reduction Fraction Alloy 800 w/Depleted Zinc Alloy 600 & 690 w/Depleted Zinc Alloy 600 & 690 w/Natural Zinc Log Alloy 800 Plants w/Depleted Zinc Log Alloy 600 & 690 w/Depleted Zinc Log Alloy 600 & 690 w/Natural Zinc

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