ML072060138

07/17/2007 Slides from Meeting Between NRC Staff and Wolf Creek Panel Enclosures 2 to 3, Advanced Fea Crack Growth Calculations for Evaluation of PWR Pressurizer Nozzle Dissimilar Metal Weld Circumferential Pwscc.

ML072060138
Person / Time
Site:	Wolf Creek
Issue date:	07/17/2007
From:	Broussard J, Collin J, Klug M, White G Dominion Engineering
To:	Office of Nuclear Reactor Regulation
References
Download: ML072060138 (45)

Text

11730 Plaza America Dr. #310Reston, VA 20190703.437.1155 www.domeng.com Advanced FEA Crack Growth Calculations for Evaluation of PWR Pressurizer Nozzle Dissimilar Metal Weld Circumferential PWSCC Sponsored by: EPRI Materials Reliability Program Presented To:Expert Review Panel for Advanc ed FEA Crack Growth Calculations Presented By:

Glenn White John Broussard Jean Collin Matthew Klug Dominion Engineering, Inc.

Tuesday, July 17, 2007 Meeting on Implications of Wolf Creek Dissimilar Metal Weld Inspections DEI Offices, Reston, Vi rginia and via Webcast Project Review Meeting:Advanced FEA Crack Growth Evaluations 2July 17, 2007, Reston, VA, and via Webcast AgendaIntroductions / Opening RemarksResults Missing from Draft A ReportNew Case S9b to Further Address Effect of Multiple FlawsValidationEvaluation CriteriaFinal Industry ReportJuly 12 NRC CommentsRemaining WorkMeeting Summary and Conclusions Project Review Meeting:Advanced FEA Crack Growth Evaluations 3July 17, 2007, Reston, VA, and via Webcast Principal Meeting ParticipantsEPRI Project Management / Support

- Craig Harrington, EPRI

- Christine King, EPRI

- Tim Gilman, Structural Integrity AssociatesProject Team

- Glenn White, DEI

- John Broussard, DEI

- Jean Collin, DEI

- Matthew Klug, DEIExpert Review Panel

- Ted Anderson, Quest Reliability, LLC

- Warren Bamford, Westinghouse

- David Harris, Structural Integrity Associates

- Doug Killian, AREVA

- Pete Riccardella, Structural Integrity Associates

- Ken Yoon, AREVANRC Participants

- Al Csontos, NRC Research

- Tim Lupold, NRC NRR

- Dave Rudland, EMC2

- Simon Sheng, NRC NRR

- Ted Sullivan, NRC NRR Project Review Meeting:Advanced FEA Crack Growth Evaluations 4July 17, 2007, Reston, VA, and via Webcast Results Missing from Draft A Report SummaryStable arrest was still be confirmed for 6 matrix cases

- Now confirmed using FEACrackFive matrix cases were still in progress

- Case 23c multiple repair case: Results on next two slides

- Case 28b surge nozzle case: Results on next slide

- Case 36c stress "redistribution" case: Results expected July 17

- Cases 52 and 53 with nozzle-to-safe-end geometry: Results expected ~July 23Leak rate was still to be reported in Table 7-6 for Case 48b at time load margin factor reaches 1.2

- Missing leak rate is 70.1 gpmLeak rate and stability time plots were requested for all cases with a load margin factor of ~1.7 or lower when leak rate is 1 gpm

- Results not in Draft A are provided below for all cases with factor 1.75 Project Review Meeting:Advanced FEA Crack Growth Evaluations 5July 17, 2007, Reston, VA, and via Webcast Results Missing from Draft A Report Case 23c and 28b ResultsNozzleTypeGeometryConfiguration R i(in)t (in)Timeto TW(yrs)FractionXsectionCrackedCrackFaceF (kips)Max totFaxial(kips)Max PmBased onCF (ksi)StabilityMarginFactorSupport.Pm(ksi)Support.Pb (thick)(ksi)23cS&RConfig 2a/2b2.8101.0650.50.29814.9175.333.373.5512.027.128bsurgebounding5.9201.5803.40.51877.12331.234.971.256.212.5Geometry CaseWRS SubcaseCase#Surface Crack Stability Results (Press + DW + NT loads and Z-factor for Critical Size)Case and StepFractionXsectionCrackedCrackFaceForce (kips)Max totFaxial(kips)Max PmBased on CF (ksi)Support.Pm(ksi)Support.Pb (thick)(ksi)StabilityMarginFactorTime since TW(hrs)Time since TW (days)Leak Rate(gpm @ 70°F)C23cS160.36918.4478.873.5310.5322.762.991799751.003C28bS000.35552.84306.964.618.4915.471.84002.426Case and StepFractionXsectionCrackedCrackFaceForce (kips)Max totFaxial(kips)Max PmBasedon CF (ksi)Support.Pm(ksi)Support.Pb (thick)(ksi)StabilityMarginFactorTime since TW (hrs)Time since TW(days)Time since 1 gpm (hrs)Time since 1 gpm (days)Leak Rate(gpm @ 70°F)C23cS200.38719.3479.763.5710.0821.572.83229696497>>211.272C28bS300.42463.08317.204.765.7112.001.20655276552728.752 Project Review Meeting:Advanced FEA Crack Growth Evaluations 6July 17, 2007, Reston, VA, and via Webcast Results Missing from Draft A Report Case 23c Crack Mesh for TW Step 20 Project Review Meeting:Advanced FEA Crack Growth Evaluations 7July 17, 2007, Reston, VA, and via Webcast Results Missing from Draft A Report Leak Rate and Load Margin Factor vs. Time-Case 17b 0.020.040.060.080.0100.0 120.0140.0160.00102030405060708090100110120130140150160170180Time after Initial Through-Wall Crack (days)Leak Rate (gpm @ 70°F)0.00.20.40.60.8 1.01.21.4 1.6 1.82.02.2 2.42.62.83.0Stability Margin on LoadC17b LeakageC17b Stability MarginLoad Factor = 1.2 Project Review Meeting:Advanced FEA Crack Growth Evaluations 8July 17, 2007, Reston, VA, and via Webcast Results Missing from Draft A Report Leak Rate and Load Margin Factor vs. Time-Case 27b0.020.040.060.080.0100.0 120.0140.0160.00102030405060708090100110120130140150160170180Time after Initial Through-Wall Crack (days)Leak Rate (gpm @ 70°F)0.00.20.40.60.8 1.01.21.4 1.6 1.82.02.2 2.42.62.83.0Stability Margin on LoadC27b LeakageC27b Stability MarginLoad Factor = 1.2 Project Review Meeting:Advanced FEA Crack Growth Evaluations 9July 17, 2007, Reston, VA, and via Webcast Results Missing from Draft A Report Leak Rate and Load Margin Factor vs. Time-Case 44c0.01.02.03.04.05.06.07.08.09.010.00102030405060708090100110120130140150160170180Time after Initial Through-Wall Crack (days)Leak Rate (gpm @ 70°F)0.00.20.40.6 0.8 1.01.21.41.61.82.02.2 2.4 2.62.83.0Stability Margin on LoadC44c LeakageC44c Stability MarginLoad Factor = 1.2Time at 1 gp m

Project Review Meeting:Advanced FEA Crack Growth Evaluations 10July 17, 2007, Reston, VA, and via Webcast Results Missing from Draft A Report Leak Rate and Load Margin Factor vs. Time-Case 46b0.020.040.060.080.0100.0 120.0140.0160.00102030405060708090100110120130140150160170180Time after Initial Through-Wall Crack (days)Leak Rate (gpm @ 70°F)0.00.20.40.60.8 1.01.21.4 1.6 1.82.02.2 2.42.62.83.0Stability Margin on LoadC46b LeakageC46b Stability MarginLoad Factor = 1.2 Project Review Meeting:Advanced FEA Crack Growth Evaluations 11July 17, 2007, Reston, VA, and via Webcast Results Missing from Draft A Report Leak Rate and Load Margin Factor vs. Time-Case 48b0.020.040.060.080.0100.0120.0140.0160.00102030405060708090100110120130140150160170180Time after Initial Through-Wall Crack (days)Leak Rate (gpm @ 70°F)0.00.20.40.6 0.8 1.01.21.41.61.82.02.2 2.4 2.62.83.0Stability Margin on LoadC48b LeakageC48b Stability MarginLoad Factor = 1.2 Project Review Meeting:Advanced FEA Crack Growth Evaluations 12July 17, 2007, Reston, VA, and via Webcast Results Missing from Draft A Report Leak Rate and Load Margin Factor vs. Time-Case S1b0.020.040.060.080.0100.0120.0140.0160.00102030405060708090100110120130140150160170180Time after Initial Through-Wall Crack (days)Leak Rate (gpm @ 70°F)0.00.20.40.6 0.8 1.01.21.41.61.82.02.2 2.4 2.62.83.0Stability Margin on LoadS1b LeakageS1b Stability MarginLoad Factor = 1.2 Project Review Meeting:Advanced FEA Crack Growth Evaluations 13July 17, 2007, Reston, VA, and via Webcast Results Missing from Draft A Report Leak Rate and Load Margin Factor vs. Time-Case S2b0.020.040.060.080.0100.0 120.0140.0160.00102030405060708090100110120130140150160170180Time after Initial Through-Wall Crack (days)Leak Rate (gpm @ 70°F)0.00.20.40.60.8 1.01.21.4 1.6 1.82.02.2 2.42.62.83.0Stability Margin on LoadS2b LeakageS2b Stability MarginLoad Factor = 1.2 Project Review Meeting:Advanced FEA Crack Growth Evaluations 14July 17, 2007, Reston, VA, and via Webcast Evaluation Case Matrix Effect of Multiple Crack Initiation SitesSensitivity cases investigate the effect of multiple crack initiation (e.g., Wolf Creek surge nozzle NDE results)

- Enveloping of multiple initia l flaws with one modeled flaw

- Modeling of a part-depth 360° flaw

- Growing multiple individual flaws and then combining on a single weld cross section for stability calculation Project Review Meeting:Advanced FEA Crack Growth Evaluations 15July 17, 2007, Reston, VA, and via Webcast New Case S9b Further Addresses Effect of Multiple FlawsCase S9b added to further address this concern for limiting surge nozzles

- Case 9b is based on Case 17b, but with 21:

1 26%tw initial flaw placed at top and bottom of weld cross section

- Crack interaction effects are insignifi cant for this case based on distance between flaws and Quest Reliability, LLC experience with interaction effects

- Thus, leak rate and stability margin tr ends can be based on separate growth of flaws and then combination of flaws in crack stability calculation

- Two 21:1 26%tw initial flaws represent 46% (167°) of the ID circumferenceResults vs. Case 17b

- 1.22 years to go through-wall is unaffected

- Leak rate trend with time of Case 17b is unaffected

- Stability margin factor trend is lowered by between 0.10 and 0.12

- Time from 1 gpm to load margin factor of 1.2 is reduced from 35 to 29 days Project Review Meeting:Advanced FEA Crack Growth Evaluations 16July 17, 2007, Reston, VA, and via Webcast New Case S9b Crack Profiles vs. Time: Cartesian Coordinates-8.0-6.0-4.0-2.0 0.0 2.04.06.08.0-8.0-6.0-4.0-2.00.0Case S9b after breaking through-wallCase S9b 7 days after through-wallCase S9b 12 days after through-wallCase S9b 25 days after through-wallCase S9b 35 days after through-wallCase S9b 42 days after through-wall Project Review Meeting:Advanced FEA Crack Growth Evaluations 17July 17, 2007, Reston, VA, and via Webcast New Case S9b Crack Profiles vs. Time: Polar Coordinates0.00.10.20.30.40.50.60.70.80.91.00306090120150180Circumferential Position, (deg)Nondimensional Crack Depth, y/tCase S9b after breaking through-wallCase S9b 7 days after through-wallCase S9b 12 days after through-wallCase S9b 25 days after through-wallCase S9b 35 days after through-wallCase S9b 42 days after through-wall Project Review Meeting:Advanced FEA Crack Growth Evaluations 18July 17, 2007, Reston, VA, and via Webcast New Case S9b Leak Rate and Load Margin Factor vs. Time42, 1.0042, 1.0042, 1.0042, 1.0042, 1.0025, 1.2842, 0.9042, 0.9042, 0.9042, 0.9042, 0.900, 1.7325, 1.4012, 1.6035, 1.200, 1.7135, 1.090, 1.607, 1.5212, 1.480.020.040.060.080.0100.0120.0140.0160.00102030405060708090100110120130140150160170180Time after Initial Through-Wall Crack (days)Leak Rate (gpm @ 70°F)0.00.20.40.6 0.81.01.2 1.41.61.8 2.02.22.4 2.62.83.0Stability Margin on LoadCase 17b and Case S9b LeakageCase 17b Stability MarginCase S9b Stability MarginLoad Factor = 1.2 Project Review Meeting:Advanced FEA Crack Growth Evaluations 19July 17, 2007, Reston, VA, and via Webcast Validation TopicsDuane ArnoldEU MockupMRP-107 Project Review Meeting:Advanced FEA Crack Growth Evaluations 20July 17, 2007, Reston, VA, and via Webcast Validation Duane Arnold Circumferential CrackThe Duane Arnold crack was applied as a validation caseFrom MRP-113:Crack initiation and growth were attributedto the presence of a fully circumferential crevice that led to development of an acidic environment because of the oxygenin the normal BWR water chemistry, combined with highresidual and applied stresses as a result of the geometry andnearby welds. The water chemistr y conditions th at contributedto cracking at Duane Arnold do not exist for the case of Alloy82/182 butt welds in PWR plants.

Project Review Meeting:Advanced FEA Crack Growth Evaluations 21July 17, 2007, Reston, VA, and via Webcast Validation Duane Arnold Circumferential Crack (cont'd)Duane Arnold WRS (ksi) Profile Fity = 2091.284192x 4 - 4024.030339x 3 + 2171.322441x 2 - 279.638139x + 4.697888-50-40-30-20-10 0 10 20 30 40 50 60 70 800.00.20.40.60.81.0Dist from Thermal Sleeve ID (in.)Axial WRS (ksi)Tip of CreviceThermal SleeveSafe-EndFrom 30% TW 360° Surface Flaw Actual Crack ProfileSimulated Crack Profile Project Review Meeting:Advanced FEA Crack Growth Evaluations 22July 17, 2007, Reston, VA, and via Webcast Validation EU Mockup-DEI Hoop Stress Project Review Meeting:Advanced FEA Crack Growth Evaluations 23July 17, 2007, Reston, VA, and via Webcast Validation EU Mockup-DEI Axial Stress Project Review Meeting:Advanced FEA Crack Growth Evaluations 24July 17, 2007, Reston, VA, and via Webcast Validation EU Mockup-DEI Butter Hoop Stress Project Review Meeting:Advanced FEA Crack Growth Evaluations 25July 17, 2007, Reston, VA, and via Webcast Validation EU Mockup-DEI Butter Axial Stress Project Review Meeting:Advanced FEA Crack Growth Evaluations 26July 17, 2007, Reston, VA, and via Webcast Validation MRP-107 Lab Study of PWSCC in Alloy 182The report summary for MRP-107 (EPRI 1009399, 2004) includes the following:

- "Abstract: Detailed examinations of Al loy 182 capsule samples containing PWSCC established the relationship between crack in itiation sites and the microstructure of the weld metal. These examinations also identified microstructural features that facilitate or arrest PWSCC propagation. Cr ack initiation only occurred at high angle, high energy, dendrite packet grain boundaries, and growth apparently arrested at

low energy boundaries due to low angular misorientation or coincidence of lattice

sites. The work also revealed important fi ndings with regard to crack geometries, in particular what aspect ratios may develop during PWSCC of nickel-base (Ni-base) weld metals.

"- "The cracks exhibited an unusual aspect ra tio in that they never showed a large lateral surface extent, even when they extended through the wall thickness. This is a very different feature compared to PWSCC in Ni-base alloys such as Alloy 600. The aspect ratio is thought to relate to indica tions of crack arrest observed at low energy grain boundaries in Alloy 182."

Project Review Meeting:Advanced FEA Crack Growth Evaluations 27July 17, 2007, Reston, VA, and via Webcast Evaluation Criteria Figure 7-1 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.00102030405060708090Time after Initial Through-Wall Crack (days)Leak Rate (gpm at 70°F) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0Stability Margin on Load 7 da y s4 on 0.25 gpm leak ratestabilit y mar g inleak ratebegin timeload factor of 1.2Does this point fall below the stability mar gin line?Illustration of Approach f or Hypothetical Leak Rate and Crack Stability Results Project Review Meeting:Advanced FEA Crack Growth Evaluations 28July 17, 2007, Reston, VA, and via Webcast Final Industry Report TopicsPreliminary ResultsPreliminary ConclusionsSchedule- Draft B- Industry and NRC Review

• Main report

• Appendix A on probabilistic assessments

- Schedule for Release of Rev. 0Missing items

- EPRI report summary, abstract, and full list of acronyms

- EU Mockup WRS simulation

- Discussion of Implications of MRP-107

- Duane Arnold crack growth case

- Missing matrix results and discussion, including new Case S9b

- Move references to Section 9 Project Review Meeting:Advanced FEA Crack Growth Evaluations 29July 17, 2007, Reston, VA, and via Webcast Final Industry Report Preliminary ResultsAll 105 completed cases in the main sensitivity matrix showed either

- stable crack arrest (59 cases), or

- crack leakage and crack stability results sati sfying the evaluation criteria (46 cases)

- generally considerable margins beyond evaluation criteria10 supplemental cases further investigated effect of multiple

flaws on limiting surge nozzle cases

- Conservative application of the three indications found in the Wolf Creek surge nozzle weld to limiting surge nozzles (fill-in weld a nd relatively high moment load) gives results meeting the evaluation criteria with additional margin

- Multiple flaw case based on Case 17b with two 21:1 26%tw initial flaws at opposite sides of model shows modest effect on crack stabil ity, with reduction of only 6 days in time interval from 1 gpm leak rate to 1.2 load margin factor (35 to 29 days)

- On this basis, it is concluded that the c oncern for multiple flaws in the limiting surge nozzles is adequately addressed by cases th at satisfy the evaluation criteria with additional margin Project Review Meeting:Advanced FEA Crack Growth Evaluations 30July 17, 2007, Reston, VA, and via Webcast Final Industry Report Preliminary ConclusionsAssumption of semi-elliptical flaw shape shown to result in large unnecessary overconservatismAll 51 subject welds are adequately covered by crack growth

sensitivity cases that satisfy the evaluation criteria Results show tendency of circumferential surface cracks to show stable arrest

- Axisymmetric welding residual stress profile must self-balance

- Consistent with Wolf Creek experience given unlikeliness that four indications found in narrow depth band were growing rapidly at that timeSensitivity cases indicate a large beneficial effect of relaxation of secondary loads upon through-wall penetration

- Detailed evaluations tend to su pport such a relaxation effect

- Not credited in main cases Project Review Meeting:Advanced FEA Crack Growth Evaluations 31July 17, 2007, Reston, VA, and via Webcast July 12 NRC Comments Welding Residual Stress UncertaintyThe WRS profile applied in Case 17b is conservative with respect to:

- DEI WRS FEA result for Type 8 surge nozzle, including SS weld simulation

- EMC2 WRS FEA result for Type 8 surge nozzle, including SS weld simulation

- ASME profile as modified by EMC2Because the WRS profile applied in Case 17b is shifted

significantly in the conservative direction versus all three of these profiles, it appropriately addresses the effect of WRS uncertaintyConsistent with the most likely Wolf Creek behavior, the EMC2 WRS FEA result for Type 8 surge nozzle (including SS weld simulation) leads to crack arrest in the growth model Project Review Meeting:Advanced FEA Crack Growth Evaluations 32July 17, 2007, Reston, VA, and via Webcast July 12 NRC Comments Surge Nozzle Axial WRS at NOT-80,000-60,000-40,000-20,000 020,00040,00060,000 80,0000.00.10.20.30.40.50.60.70.80.91.0Nondimensional Distance from ID, x/tAxial Stress (psi)Type 8-1 (base case)ASME Modified per EMC2EMC2 NoRepair-WithSS (Left-Right)Poly. (Type 8-3 (no SS Weld))

Project Review Meeting:Advanced FEA Crack Growth Evaluations 33July 17, 2007, Reston, VA, and via Webcast July 12 NRC Comments Effect of Multiple Through-Wall Crack SegmentsBill Shack of ACRS inquired on July 11 regarding the effect of multiple through-wall flaw segments on the leak rateThe effect of multiple through-wall flaw segments to reduce

the leak rate (in comparison to a single through-wall flaw) is mitigated by the increased resistance to rupture provided by the ligaments between the flaw segments

- Significant axial offsets between crack s egments are perhaps likely because of the relatively long axial region of susceptible materialThe effect of the tight intergranular SCC type morphology is generally addressed by the leak rate prediction methodology Project Review Meeting:Advanced FEA Crack Growth Evaluations 34July 17, 2007, Reston, VA, and via Webcast July 12 NRC Comments Effect of Multiple Through-Wall Crack Segments (cont'd)Substantial margin beyond the evaluation criteria exists for nearly all cases in main matrix

- Applying a leak rate margin factor of 10 rather than 4 on the 0.25 gpm detectability limit results in all 14 of the most limiting cases* in the main matrix satisfying the evaluation criteria with one exception (Case 44c)

- A leak rate margin factor of about 9 does satisfy the evaluation criteria for Case 44c- All other cases in the main matrix very li kely satisfy the evaluation criteria with a

leak rate margin factor of 10 based on the compiled leak rate and stability data

- A leak rate margin factor of 10 has historically been applied in long-term regulatory LBB assessments

- The most limiting surge nozzle case (Cas e 17b) is predicted to have an initial through-wall leak rate of 2.6 gpm, with the leak rate increasing to 69 gpm when

the load margin factor decreases to 1.2, indicating robustness with respect to the value of the leak rate margin factor*The 14 most limiting cases are defined here as those cases for which the load margin factor is 1.75 or less at the time the leak rate is calculated to be 1 gpm.

Project Review Meeting:Advanced FEA Crack Growth Evaluations 35July 17, 2007, Reston, VA, and via Webcast July 12 NRC Comments Effect of Multiple Through-Wall Crack Segments (cont'd)Given the above points, the matrix results show sufficient margin to address modeling uncertainties such as those associated with the potential for multiple through-wall crack

segmentsMore detailed evaluation of the effect of multiple through-

wall crack segments may be considered in the context of

longer-term evaluations

- More detailed evaluations will require significant additional developmental effort

- Current study has had benefit of significant ly refining crack growth evaluation tools, but explicit evaluation of multiple flaws is an emerging area Project Review Meeting:Advanced FEA Crack Growth Evaluations 36July 17, 2007, Reston, VA, and via Webcast Remaining WorkRemaining DEI Work

- Nozzle-to-safe end geometry crack growth casesFinal Industry ReportAugust 9 Meeting at North Bethesda MarriottNRC Safety Assessment Project Review Meeting:Advanced FEA Crack Growth Evaluations 37July 17, 2007, Reston, VA, and via Webcast Nozzle-to-safe-end Geometry Cases Example Cracked Model Project Review Meeting:Advanced FEA Crack Growth Evaluations 38July 17, 2007, Reston, VA, and via Webcast Meeting Summary and ConclusionsIndustryNRC NRC Questions and Comments on the NRC Questions and Comments on the Industry Advanced FEA Draft Report Industry Advanced FEA Draft Report Ted Sullivan & Al Csontos July 17, 2007 2U.S. Nuclear Regulatory Commission General Comments General Comments

• NRC staff has reviewed the industry draft report and will provide our comments and questions today

• NRC recognizes the significant effort to develop, benchmark, verify, and evaluate the advanced FEA

program and the validation of weld residual stresses

• Overall, the industry developed a groundbreaking

and technically sound research program

• The products from this research program will be

essential in resolving the regulatory issues at hand 3U.S. Nuclear Regulatory Commission General Comments General Comments

• NRC comments are for clarification & completeness

• For many, the industry's advanced FEA report will be sole source of information on this issue

• Report needs some additional information provided

in the industry's presentations at public meetings

• Interested parties outside the project deliberations

may need the additional information for clarity

• NRC needs to review the references, supporting sections, and appendices as soon as they become available 4U.S. Nuclear Regulatory Commission General Questions General Questions

• When will the supplementary analyses discussed in the draft industry report be available to the NRC?

- EU validation writeup?

- Westinghouse fabrication writeups?

- David Harris leak rate writeup?

- References?

• What, if any, additional cases will the industry run?

• Will the industry respond to Bill Shack's comments

related to leak rate modeling with multiple TWCs?

• What are industry's plans for a peer review?

Page #Line #

NRC1-227-29 The group of nine PWRs should be planning to accelerate outages or take mid-cycle outages based on commitments made.

Revise to read...the group of nine PWRs planning to accelerate outages or take mid-cycle outages based on commitments made. Should this study

demonstrate flaw stability via sufficient time from initial detectable leakage

until pipe rupture, as demonstrated to the NRC, these plants could then

resume plans to perform PDI inspection or mitigation during the spring 2008

outage season.

NRC1-66-7 The ima g es of each example pressurizer nozzle should contain identification markers for all major fabrication components Add identification markers NRC1-71 The image of the CE pressurizer nozzle should contain identification markers for all major fabrication components Add identification markers NRC 2-General In general, this section needs to be augmented with the information provided in previous public meetings to include more figures detailing the

nozzle geometries, dimensions, and typical fabrication procedures for the

three types of plants; CE, W, W with CE-like fabrication procedures Augment this section to include information previously provided in public meetings by DEI (Glenn White) and Westinghouse (Cameron Martin)

NRC2-214 It would be helpful to explain why the definition of Pm is given as PDo/4t in this section, but the pressure is used differently in the crack growth portion

of the work Add explanation NRC2-39 With regards to the back welding, this should clearly state that certain amounts of the ID material are removed and weld material is reapplied to

the ID. Revise, make similar to Type 8 Surge Nozzle description on pate 3-5, lines 23-31.NRC2-316 In addition to no fill-in welds, include no back chipping/backwelding completed Make revision NRC2-53 In this table labels such as land thickness and fill-in weld are a bit confusin g. It is su gg ested that fi g ures in the WRS section be placed here to help better explain these geometric details.

Provide figures with the major fabrication details of the nozzles identified.

NRC2-6-Question for Plant H spray line PDI results.Recheck Plant H results.

NRC3-116-30 Some dimensions are needed for completeness of the report, i.e., SS weld location, fill-in dimensions, etc. (see general comment)

Add dimensions, figures, or references as needed.

NRC3-26Note that the 5/16 inch repair simulates the back chipping and weld buildupMake revision NRC3-222How long is the repair?Add length of repair to explanation NRC3-224this line notes that minor simplifications are madeList the minor simplifications NRC3-226 In the WRS analyses long slender weld beads were used. Since these beads differ from actual weld beads, please explain how the approximation

resulting from this approach was assessed and reflected in the study.

Add explanation NRC3-235 How was piping system compliance treated in the WRS analysis? How long was the stainless steel pipe in the analysis?

Add explanation NRC3-316-31 Why was the elastic limit defined as the yield strength for the base metal but the flow strength for the weld material? The base metal near the weld

may also melt and solidify as would the weld.

Add explanation NRC3-334 The stainless steel yield strength of 28.9 ksi at 600F seems to be a high value; in looking at 550F tensile data from Vol. 8 of Degraded Piping semi-

annual reports, the yield strengths for 5 stainless steel pipes ranged from

20.1 ksi to 26.1 ksi with an average value of 22.7 ksi. How would this affect

the WRS modeling and critical crack size calculations?

Add explanation NRC3-44Different than what, the base material?Add explanation NRC3-54-10 The stress improvement observed from a hydrotest will be limited for low R/t pipes such as on the pressurizer None NRC3-58hydrostatic testing referred to as a form of mechanical stress improvementDelete mechanical and just refer to as a form of stre ss improvement NRC3-513 Why was 653F listed as the operating temperature when the surge line will be at a temperature closer to 644F?

Add explanation NRC3-534Refers to an amount of the ID that was "ground out"Was this ground or machined? If machined, revise.

NRC3-536 Statement that the inside surface is 0.25 inch smaller should read, "the inside diameter is 0.25 inches smaller replace surface with diameter NRC3-61"removed back"Replace with machined, if actually machined NRC3-65States the welds were v-weld-. Should be U-grooveVerify this is suppose to be U-groove NRC3-65v-weldRefer to as v-groove weld NRC3-636 Was it verified that a stress path perpendicular to the axial direction represents the maximum stress path for PWSCC growth?

Add explanation NRC3-73-16 Was the path changed for the case with the SS weld since the path of maximum stress may shift location??

Add explanation NRC3-810Section 3.3 should be referred to as Validation and BenchmarkingAdd title Cmt #Comments and Proposed Changes:

Due Date: July 20, 2007 Advanced FEA Evaluation of Growth of Postulated Circ PWSCC Flaws in PZR Nozzle DM Welds - Rev. A Comment Resolution Comment LocationCommentProposed Change Reviewer's Organization Page #Line #

Cmt #Comments and Proposed Changes:

Due Date: July 20, 2007 Advanced FEA Evaluation of Growth of Postulated Circ PWSCC Flaws in PZR Nozzle DM Welds - Rev. A Comment Resolution Comment LocationCommentProposed Change Reviewer's Organization NRC3-814-17 Based on the available WRS validation and benchmarking activities to the EU report, this section should assess uncertainties related to WRS and how

they will be addressed in the overall advanced FEA Phase II sensitivity

matrix.Add section NRC3-155Identify what is meant by 'backweld'Add clarification in text.

NRC4-120 U-groove weld geometry stated here vs. V-groove geometry sated in section 3, page 6 and in the figures Revise to make consistent between sections NRC4-127 What the rationale for using 8-noded brick elements in a computational fracture mechanics analysis? The crack tip singularity ahead of simulated

sharp crack is approximated by collapsed 20-noded elements with the

midpoint nodes moved to the quarter point location. If 8-noded elements are

used, they must be of sufficient small size.

Explain and provide mesh sensitivity results for using the 8-noded elements NRC4-216 Since ANSYS does not calculate fracture parameters, please explain the process on how it was done in this study Add explanation NRC4-539What is meant by '- remain self- similar-'?Add correction NRC4-614 Why was the time between leakage and rupture not reported for the Phase I study?Add Phase I leakage and margin results NRC4-75 When you provide Duane Arnold crack validation, please provide what parameters were modified to obtain the final validation results.

Add explanation NRC5-128Explain CMTRAdd explanation NRC5-27 The study conducted by Riccardella and Anderson should be discussed in more detail since the report refers to the results several times. It would be

nice if they could be included in detail as part of this report or in an appendix Add work from Riccardella and Anderson to report NRC5-215 Along with radial differential thermal expansion, WRS are also not included in the stability calculations Modify sentence NRC5-318 The DPZP may not be greater than unity for the cases of a complex crack where the apparent toughness is greatly reduced as compared to the C(T)

toughness remove this sentence or modify NRC5-48 It should be noted that in this study the DPZP was calculated using the C(T) toughness and not the apparent toughness for complex cracks This should be noted in this sentence NRC6-114Spell out CODSpell out as crack open displacement (COD)

NRC6-125Explain what (albeit over a longer length) meansAdd explanation NRC6-229List what the summary is provided in List Table 6-2 (?) as containing the summary of inputs NRC6-310-11Explain what is meant by the potentially important effect of moment bendingAdd explanation NRC 7-2 6-7 Further explain how the conversion is a conservative assumption given the complex crack envelopes the TW crack Add explanation NRC7-215-16 Why were different axial stresses used in the stability and crack growth calculations?

Modify sentence NRC7-235 Rather than state the acceptability involves licensing and regulatory issues, state the acceptability is dependent upon uncertainty of input parameters

and the accuracy of the modeling methodology Revise as noted NRC7-325 Recommend listing either six or seven days as being conservative.

Change to state "six days is conservatively required for the plant to shut down-.NRC7-35What is the basis for the 7 day criteria?Provide the basis NRC7-326-27 Would like to see discussion of where 0.25 gpm comes from, i.e. RCS leak rate monitoring committed to by licensees. Some mention of the baseline

and that the margin factor of 4.0 also addresses leak rate changes that may

occur that could affect the baseline but have not been incorporated in the

baseline, i.e. a high baseline may have been measured in 1st seven days of

operation that decreases over time or leaks may have been identified and

repaired that effectively reduce the baseline. It would also be worthwhile to

list the range of values used as baseline at the nine plants assessed in this

evaluation.

Indicate where the 0.25 g pm is from. Include discussion of the baseline and how the margin factor of 4 encompasses baseline changes that may not

have resulted in a baseline revision. Include range of baseline values being

used.NRC7-43New readers may not understand the stability margin factor.Provide a definition of the stability margin factor NRC7-45Expand the explanation for why the factor of 1.2 is considered appropriateexpand explanation NRC7-412 The statement that there is no clear evidence that a purely limit load based approach is insufficient should be worded differently since there is no clear

evidence that the purely limit load based approach is sufficient for cracks in

A82/182 Modify the statement to say- there is no experimental data on circumferential cracks in A82/182 that verify that limit load or elastic-plastic

fracture conditions control.

NRC7-619 Here the operating temperature is given as 650F. Table 6-1 and Page 3-5 give the operating temperature as 653F Correct temperature NRC7-735 Were the stresses from Fi g ure 3-19 used in the repair anal y ses?? Were the values interpolated from what's shown in Fi g ure 3-19 to each circumferential position in the crack growth analyses?

Add explanation Page #Line #

Cmt #Comments and Proposed Changes:

Due Date: July 20, 2007 Advanced FEA Evaluation of Growth of Postulated Circ PWSCC Flaws in PZR Nozzle DM Welds - Rev. A Comment Resolution Comment LocationCommentProposed Change Reviewer's Organization NRC7-1028 This write-up always assumes that the dominate crack initiates on top of the pipe. What if it does not initiate on the top of the pipe?

Add explanation NRC7-1233Same as previousAdd explanation NRC7-1420-21 Under what conditions would the thermal loads be reduced during surface crack growth in such a way that the reduction would cause arrest?? If the

surface crack is near critical, and much rotation occurs, some of the

displacement-controlled loads may be reduced, but during subcritical crack

growth, I'm not sure when the displacement controlled loads would be

relieved Add explanation NRC7-1430-31 It is stated that using 360 deg flaws in surge nozzle analyses is not appropriate. However, 360 de g cracks were assumed in Case 18,26,29 and

30. Please clarify?

Add explanation NRC7-151-2Same comment as 7-10 line 28Add explanation NRC7-1516 It may be helpful to have a table that shows the how the parameters varied in the sensitivity matrix affected the margin, i.e., 10% decrease in as built

wall thickness can decrease margin by 30%

Add table if possible NRC7-1516 In addition, it may be worthwhile to comment on how the changes in margin due to the sensitivity parameters may be combined. For instance, a 10 %

decrease in wall thickness and the high growth rate can decrease the

margin by more than 50% - Are these cases probable?

Add explanation NRC7-1524 Why was the 21:1 aspect ratio only used for the large bending moment cases?Add explanation NRC7-1535Same comment as 7-10 line 28Add explanation NRC7-167 Earlier it was stated that only two of the wolf creek surge flaws were enveloped with the 21:1 surge nozzle flaw. How are the three wolf creek

flaws applied in the crack growth analyses?

Add explanation NRC7-1617 The wolf creek flaws may not have been growing rapidly in the depth direction, but may have been growing rapidly in the length direction, as

indicated by the Phase 1 results.

Please modify sentence NRC 8 The same comments given above apply to the conclusion section NRC8-231-33 Cases CS1b (SMF = 1.03 at TW leakage) and CS2b (3 days to SMF=1.2) do not support the statement that the results met the evaluation criteria with

additional margin Revise to reflect actual results.

NRCA1-7Table 2-1 There are some numbers in Table 2-1 of the probabilistic study in Appendix A that we believe are not correct. Calvert 2 had indications in the CL drain

and the HL drain. Table 2-1has the CL drain listed as a circ indication, when

it was actually an axial indication, as documented in LER 2005-001-00. The

HL drain had 2 axial flaws attributed to PWSCC and a circumferential that

was attributed to original construction once the original radiographs were

digitized (this fact was not listed in the LER, but we have first hand

information on this item). Also, the depths and lengths were not measured

for these flaws, as the procedure used was not qualified for length or depth

measurement for this size nozzle. It is unclear where the numbers for the

flaw information come from.

We also checked Calvert 1 in Table 2-1 with the information Constellation sent to us in their flaw evaluation. The HL Drain thickness is 0.54, not 0.375;

the surge nozzle thickness is 1.6", not 1.3, and the relief indication length

was 0.6" not 0.000".

This is a high number of inaccuracies in 5 indications. It calls into question the accurac y of the remainin g information in this table. We recommend that all the data in the table be verified for accuracy and a portion of section 2.1

be devoted to data accuracy and verification.

NRCGeneral-Supplementary analyses need to be provided for NRC review.

Provide supplementary analyses as soon as possible to expedite NRC's review.NRCReferences-References are needed to expedite NRC's review.Provide references as soon as possible to expedite NRC's review.