ML111101020

Brunswick Steam Electric Plant Unit 2 Reactor Pressure Vessel Flaw Evaluation

ML111101020
Person / Time
Site:	Brunswick
Issue date:	03/24/2011
From:	Sommerville D Structural Integrity Associates
To:	Office of Nuclear Reactor Regulation, Progress Energy Co
References
BSEP 11-0037 1100470.401, Rev 0
Download: ML111101020 (12)

Text

I Structural Integrity Associates, Inc.10731 E. Easter Avenue, Suite 100 FOR OWNER REVIEW SEE PAGE 12 Centennial, CO80112-3765 Phone: 303-792-0077 Fax: 303-792-2158 www.structint.com dsommerville@structint.com March 24, 2011 Report No. 1100470.401 Rev. 0 Quality Program: N Nuclear F] Commercial Mr. John Becker Progress Energy Brunswick Nuclear Plant 8470 River Road SE Southport, NC 28461-8869

Subject:

Brunswick Steam Electric Plant Unit 2 Reactor Pressure Vessel Flaw Evaluation

Dear Mr. Becker:

This letter report documents the results of a flaw evaluation of an indication detected in the Brunswick Steam Electric Plant Unit 2 (BSEP U2) reactor pressure vessel (RPV) circumferential weld joining the vessel closure flange to the adjacent shell.INTRODUCTION An indication was identified in the circumferential weld which joins the RPV closure flange forging to the adjacent shell, during in-service inspections (ISI). Progress Energy (PE)contracted Structural Integrity Associates, Inc. (SI), in PE Contract 66325, Work Authorization 170, to perform a flaw evaluation of the reportable indication using methods consistent with ASME XI, IWB-3600 [1].METHODOLOGY The evaluation documented in this report is performed using the methods of ASME XI, IWB-3600 and ASME XI, Non-mandatory Appendix A [1]. Since the methods are described in detail in Reference

[1] they are not repeated here.DESIGN INPUT The following design input and documentation was provided by PE in support of this evaluation:

1. Pre-operation inspection data [2], 2. B220R1 Inspection Data [3], 3. BSEP Main Closure Flange (MCF) stress analysis [4], 4. Evaluation Interval [5]a. End of current licensed life = December 27, 2034 b. End of original licensed life = December 27, 2014 Page 1 of 12 Mr. John Becker/PE March 24, 2011 Report No. 1100470.401 Rev. 0 Page 2 of 11 5. Main Closure Flange forging material initial RTNDT [10]EVALUATION This section documents the key assumptions and results of the flaw evaluation.

Attachment 1 contains a summary of the stresses extracted from the original stress report [4]. Attachment 2 contains the detailed calculations performed for this flaw evaluation.

Assumptions:

The following assumptions are made for this evaluation:

1. The reportable indication is assumed to be located at the location of highest stresses reported in the BSEP MCF stress report (at 41.5 inches below the upper surface of the vessel closure flange forging).2. A conservative load is defined as the bounding membrane, bending, and residual stresses for all load cases documented in the original stress report [4]. The load is considered conservative since it is a composite load formed from the highest individual membrane, bending, and residual stresses taken from all load cases.3. All load cycles are assumed to result in the bounding stress cycle range defined for this analysis.4. The stress cycles considered for the remainder of the plant licensed life are determined by scaling the number of cycles defined on the Thermal Cycle Diagram [6] by the following factor:# Cycles EOL -Year -Year .#Cycles 4 oe,.ars=-34-10

-458 = 275 40 40 5. A conservative R ratio of 1 is used to calculate anticipated fatigue crack growth (FCG)through the end of the evaluation interval.

This value is conservative since it maximizes the FCG calculated.

Since the flaw is subsurface no other crack growth mechanisms need to be considered in this evaluation.

6. An 8 ksi cosine distribution consistent with that considered in References

[7, 8] is assumed for the weld residual stress distribution.

7. All stresses, except for the weld residual stress, are conservatively scaled by a scaling factor defined as the largest ratio of power uprate to pre-power uprate pressures identified in the power uprate design specification

[9]. This is shown on page 1 of the calculation contained as Attachment

2. The scale factor is considered conservative since it is applied to both thermal and pressure stresses and it is calculated by taking the largest increase in pressure reported in the design specification

[9] for a single point in time for a single transient but applied uniformly for all load cases.Initial Flaw Size: The initial flaw size is taken from the inspection report [3] and is summarized below in the Results section. The pre-operational inspection data [2] shows that small reportable indications were identified during the pre-operational examinations.

Current inspection methods are Page 2 of 12 Mr. John Becker/PE Report No. 1100470.401 Rev. 0 March 24, 2011 Page 3 of 11 expected to result in more accurate sizing; therefore the original and current inspection results are not expected to match.Loads: Attachment 1 summarizes the results of the stress analysis contained in Reference

[4] taken at the bounding location in the vessel closure flange. The membrane, bending, and residual stresses selected for this flaw evaluation are taken as the bounding values from all load cases reported in Reference

[4]. The reference

[4] analysis considered all transients defined in the RPV thermal cycle diagram [6]. Residual stresses are taken from References

[7, 8].Flaw Evaluation Results: The results of the evaluation documented in Attachment 2 are summarized below for convenience:

a0o 10 n=AK=Aa=Al=af 0.225 in.6.4 in.275 cycles 15.8 ksi-in°'5 9.64x 10-4 in 3.86x10-3 in 0.226 in 6.40 in 23.4 ksi-in 0 5 63.2 ksi-in°'5 Initial flaw depth, total through-wall dimension is 2a 0 Initial flaw length Total load cycles through 60 years Range of stress intensity factor for each load cycle End of evaluation interval growth in flaw depth, total through-wall flaw growth is 2Aa End of evaluation interval growth in flaw length End of evaluation interval flaw depth, total through-wall dimension is 2 af End of evaluation interval flaw length Applied stress intensity factor at end of evaluation interval Allowable stress intensity factor if=KA =KI Allowable CONCLUSION The results of this evaluation support the following conclusions:

1. The indication reported in References

[2, 3] is likely a fabrication induced flaw;therefore, it is considered to have been present in this component for the life of the plant and is not the result of new crack initiation.

2. The reported indication is acceptable per the methods of ASME XI, IWB-3600 [1];therefore, it may be left as-is for operation through the end of the plant licensed life.Page 3 of 12 Mr. John Becker/PE March 24, 2011 Report No. 1100470.401 Rev. 0 Page 4 of 11 REFERENCES

1. ASME Boiler and Pressure Vessel Code,Section XI, 2001 Edition with Addenda through 2003.2. Preoperational Inspection Data attached to email from Damon Priestly (PE) to Daniel Sommerville (SI) dated 3/16/2011.

SI File No. 1100470.203.

3. Nuclear Generation Group UT Report UT-I 1-001, SI File No. 1100470.203.

4. Carolina Power and Light Company Calculation No. OB 11-0023, Rev. 0, RPV Stress Report, SI File No. 1100470.201.

5. Email containing BSEP Unit 2 license expiration date, sent from Larry Yemma (PE) to Daniel Sommerville (SI), SI File No. 1100470.204.

6. GE Dwg. 729E762, Rev. 0, "Reactor Thermal Cycles," SI File No. CPL-35Q-245.

7. White Paper on Reactor Vessel Integrity Requirements for Level A and B Conditions, EPRI TR-100251, January 1993.8. BWRVIP-60-A:

BWR Vessel and Internals Project, Evaluation of Stress Corrosion Crack Growth in Low Alloy Steel Vessel Materials in the BWR Environment, EPRI, Palo A lot, CA: 2003. 1008871.9. Reactor Vessel -Power Uprate, Design Specification 25A5062, Rev. 1, SI File No. CPL-61Q-205P.10. Stevens, Gary L., "Revised Brunswick Pressure-Temperature Curves," SIR-99-015, Rev. 0.Prepared by: Reviewed by: 3/24/2011 j#LJiI 3/24/2011 Daniel Sommerville, P.E. Date Hal Gustin, P.E. Date Associate Senior Associate Approved by:2~w/, 3/24/2011 Daniel Sommerville, P.E. Date Associate Page 4 of 12 Mr. John Becker/PE Report No. 1100470.401 Rev. 0 March 24, 2011 Page 5 of 11 Attachment 1: Stress Summary Page 5 of 12 Mr. John Becker/PE Report No. 1100470.401 Rev. 0 March 24, 2011 Page 6 of 11 Original Stress Report [4]r:s e Temperature I.D..een (I, m .. Refeen.e Event___ __ ts "X pi r psi. ksi§ ksi~ ,ksl Hydrotest 1250 150 -8367 33481 12.557 20.924 8 [4, 50-S1]Preload 0 70(2) -13274 14258 0.492 13.766 8 [4, 53-Si]Startup 1005 546w2) -26003 46347 10.172 36.175 8 [4, 57-Si]Shutdown 40 100 2) 2393 -1921 0.236 2.157 8 [4, 61-$1]Rapid Cooldown 40 100 (2) -10628 11798 0.585 11.213 8 [4, 65-51]Steady State 1005 546 -9476 29672 10.098 19.574 8 [4, 69-$1]Overload 1375 546 -7808 35404 13.798 21.606 8 [4,73-$1]Notes: 1. Assumed 8 ksi with cosine distribution as reported in [6, 7]2. Assumed value 3. Location is 41.5 inches below surface of RPV closure flange surface (near centerline of flange to shell circumferential weld)4. Membrane stress is calculated as (ID Stress + OD Stress) / 2, Using Hydrotest as an exampe, c=(-8367+33481)/2

= 12557 psi 5. Bending stress is calculated as OD Stress -a,,, Using Hydrotest as an exampe, Sb=3 3 4 8 1-1255 7 = 20924 psi Hydrotest

@ 1250 psi 130 Startup-Shutdown 120 I SCRAM 208 Hydrotest

@ 1563 psi ( 2 Notes: 1. Excluded from fatigue crack growth calculation since no shop hydrotest expected in remaining life.2. Taken from [4, 22-Fl4 Page 6 of 12 Mr. John Becker/PE Report No. 1100470.401 Rev. 0 March 24, 2011 Page 7 of 11 Attachment 2: Flaw Evaluation Page 7 of 12 Mr. John Becker/PE Report No. 1100470.401 Rev. 0 March 24, 2011 Page 8 of I I Input Data: 0.45 a .-2 1:= 6.4 S:= 0.35 t := 6.1 in Flaw half depth, See ASME XI, Appendix A, Fig. A-3300-1 (a).Rounded up from 0.43 inches reported from NDE.in Flaw length, See ASME Xl, Appendix A, Fig. A-3300-1 (a).in Distance between LAS surface and flaw tip, See ASME Xl, Appendix A, Fig. A-3300-1 (a). Rounded down from 0.367 reported from NDE.in Vessel shell thickness, excluding clad.t e:= --S- a 2 e = 2.475 in Flaw eccentricicty, See ASME XI, Appendix A, Fig. A-3300-1 (a)sys_70 := 50 ksi Yield strength of material at 70 F, for both SA-533, Gr. B, Cl. 1 and SA-508 to Code Case 1332 Par. 5 (Essentially yield strength consistent to SA-302 Gr. B)sys_550 := 42.6 ksi Yield strength of material at 550 F, see comment above for materials A bounding scaling factor is calculated using the largest increase in pressure defined in paragraph 4.4.1 of the Power Uprate Design Specification 700 SF6--5 665 SF = 1.053 sm:= SF. 13.8 + 8 sb := SF.2.2 RTNDT:= 10 ksi Bounding membrane stress taken for all events (Overload)

+8 ksi residual stress. Residual stress is assumed as a uniform stress over crack face. See bounding value identified in Attachment 1.ksi Bounding bending stress taken for all events (Shutdown).

Note that most load cases show compressive stress at ID.See bounding value identified in Attachment 1.F Highest initial RTNDT for closure flange materials.

See Reference

[10].Page 8 of 12 Mr. John Becker/PE Report No. 1100470.401 Rev. 0 March 24, 2011 Page 9 of 11 Determine M and Mb from Fig. A-3310-1 and Fig. A-3310-2 e 2- = 0.811 t Mm:= 1.1 Mb:=l 2a-2 = 0.074 t Conservatively taken as 1.1 since 2a/t and 2e/t not on Fig. A-3310-1 Conservatively taken as 1 since 2a/t and 2e/t not on Fig. A-3310-2 Proximity Check (See criterion on ASME Xl, Fig. IWA-3320-1):

0.4a = 0.09 S > 0.4a Therefore, flaw is subsurface Calculate plastic zone size correction (See ASME Xl, Appendix A. Eq. (4)): sm.Mm+ sbMb 2 550 sys 550 qy_55 :=6 6 sm-Mm + sb-Mb 2 qy_7 := sys70 6 6 qy_550 = 0.067 qy_70 = 0.049 Calculate Shape Factor (See ASME Xl, Appendix A, Eq. (3)):{a 1-65 Q_550:= I + 4.593.[/)

-qy_550 Q_70:= I + 4.593(a) -qy_70 Q_550 = 0.951 Q_70 = 0.969 Calculate K, for FCG (See ASME Xl, Appendix A, Eq. (2)): 7'ca K!:= [(sm -8).Mm + sb.Mb]- Q fýQ550 KI = 15.8 Smallest Q used in order to be bounding, residual stress removed from membrane term since it is a mean stress and does not affect the range of stress intensity factor considered for FCG.Page 9 of 12 Mr. John Becker/PE Report No. 1100470.401 Rev. 0 March 24, 2011 Page 10 of 1I Calculate K,, (See ASME Xl, Appendix A, Paragraph A-4200): KIC 70:= 33.2 + 2 0.7 3 4 e[0"02(7 0-RTNDT)]KIC_70= 94.7 KIC_550:=

33.2 + 2 0.7 3 4 e[002(550-RTNDT)]

KIC_550:=200 Calculate Kiallowable (See ASME Xl, IWB-3612):

KIC 550 KI Allowable LAB:= -KIC 70 KIAllowable LCD:= -_ _ 2 KIAllowableLAB

63.2 KIAllowableLCD

67 For Level A/B events and for pressure >20% design pressure For Level C/D events and for pressure <20% design pressure Since the bounding membrane, bending, and residual stress was selected from all load cases, the smalles K , calculated above will be used for all events (Level A, B, C, D).Calculate Fatigue Crack Growth (See ASME Xl, Appendix A, Paragraph A-4300, Eq. (1, 2): Let R conservatively equal 1.R:= I Then Co := 1.99. 10 .[25.72.(2.88-R)- 3.07]Co=7.37x l0 1 Assuming: 1. 24 years of additional operation and the cycles given in the orignial stress report, 2. All cycles result in a stress range given by the bounding stresses considered in this evaluation.

24.458 n:=- n = 275 40 DKI := KI DADN := Co.DKI 3 .07 DA := n-DADN Assume 25 years worth of cycles to get to end of 60 years.Assume rangeof stress intensity factor is given by zero load and the bounding conditions given here DADN = 3.508x 10 DA = 0.000964 Fatigue crack growth per load cycle, in/cycle Cumulative FCG for all considered cycles, in.Page 10 of 12 Mr. John Becker/PE Report No. 1100470.401 Rev. 0 March 24, 2011 Page 11 of 11 Since crack growth, Aa, is so small, the fatigue crack growth calculation is not performed by iterativley calculating a new K, then a new DA/DN then a new da, and so on.a-final := a + DA 1 final :=1 + 2-2-DA 2a final = 0.452 in 1 final = 6.404 in Final flaw depth, in Final flaw lengths, in Final check at end of evaluation interval to confirm that end of interval flaw size meets acceptance criteria: Proximity Check (See criterion on ASME XI. Fia. IWA-3320-1):

0.4aafinal

= 0.09 S final := S -DA S final = 0.349 S final > 0.4a final Therefore, flaw is subsurface Calculate Olastic zone size correction (See ASME XI. ADiendix A, Ea. (4)): C sm.Mms + sb .Mb q y _ 5 5 0 .-6 ( sm"Mm + sb*Mb 2 qy_70 = sys_70 6 qy_550 = 0.067 qy_70 = 0.049 Calculate Shape Factor (See ASME Xl, Appendix A, Eq. (3)): 4 ( a final I 1.65 Q_550:= I + 4.593- f ) -qy_550 Q_550= 0.951 (a final 1.6 5 Q_70 := I + 4.593-k f -qy_70 Q_70= 0.969 ( -ia Calculate K, (See ASME XI, Appendix A, Eq. (2)): iT-a final 1(-= (sm.Mm + sb.Mb) -KI = 23.4_Q550 Smallest Q used to be bounding Applied stress intensity factor remains less than allowable fracture toughness, see acceptance criteria in ASME XI, IWB-3612.Page 11 of 12 ATTACHMENT 2 Sheet 1 of 1 Record of Lead Review Document SI Report 11100470.401 Revision 0 Brunswick Steam Electric Plant U2 RPV Flaw Evaluation The signature below of the Lead Reviewer records that:-the review indicated below has been performed by the Lead Reviewer;-appropriate reviews were performed and errors/deficiencies (for all reviews performed) have been resolved and these records are included in the design package;-the review was performed in accordance with EGR-NGGC-0003.

Fl Design Verification Review-- Design Review Eli Alternate Calculation El Qualification Testing[1 Engineering Review 0 Owner's Review-- Special Engineering Review El YES nl N/A Other Records are attached.A. Borodotsky

.Lead Reviewer (print/sign)

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