Attn: Document Control Desk 11555 Rockville Pike · 2012. 12. 1. · The nozzle material is identified as SA336 Modified by Code Case 1236-1 [1]. This material is equivalent to SA

10 CFR 50.55a

RA-09-011March 9, 2009

U. S. Nuclear Regulatory CommissionAttn: Document Control Desk11555 Rockville PikeRockville, MD 20852

Oyster Creek Nuclear Generating StationFacility Operating License No. DPR-16NRC Docket No. 50-219

Subject: Submittal of Analytical Evaluation in Accordance with IWB-3134(b)

Reference: Letter from P. B. Cowan (Exelon Generation Company, LLC) to U. S. NuclearRegulatory Commission, "Submittal of Analytical Evaluation in Accordance withIWB-3134(b)," dated January 21,2009

In the referenced letter, Oyster Creek Nuclear Generating Station submitted in accordance withthe American Society of Mechanical Engineers (ASME) Code, Section XI, 1995 Edition through1996 Addenda, IWB-3134(b) ("Review by Authorities"), an analytical evaluation associated withthe recirculation suction (reactor pressure vessel outlet) nozzle-to-safe end weld (N1A). Thisanalytical evaluation is not considered a proprietary report by Structural Integrity Associates,Inc.

Attached is the analytical evaluation with all references to proprietary information deleted. Noother changes have been made to the evaluation. We request that the evaluation submittedwith the referenced letter be replaced with the attached document.

There are no new regulatory commitments contained in this letter.

®

U. S. Nuclear Regulatory CommissionMarch 9, 2009Page 2 of 2

If you have any questions or require additional information, please contact Tom Loomis(610-765-5510).

Respectfully,

Pamela B. CowanDirector - Licensing & Regulatory AffairsExelon Generation Company, LLC

cc: S. J. Collins, Administrator, USNRC, Region IM. S. Ferdas, USNRC Senior Resident Inspector, OCNGSG. E. Miller, USNRC Senior Project Manager

ATTACHMENT

Oyster Creek Nuclear Generating Station

Analytical Evaluation

"""" " I Associates, Inc. File No.: 0801457.301ViU ';118

CALCULATION PACKAGE Project No.: 0801457

Quality Program: r8J Nuclear D Commercial

PROJECT NAME:

Flaw Evaluation of Oyster Creek Nl Suction (RPV Outlet) Nozzle-to-Safe End Weld

CONTRACT NO.:

1002562 ReI. 44

CLIENT: PLANT:

Exelon Nuclear Oyster Creek Generating Station

CALCULATION TITLE:

Flaw Evaluation of Oyster Creek Nl Suction (RPV Outlet) Nozzle-to-Safe End Weld

Document Affected Project Manager Preparer(s) &

Revision Pages Revision Description Approval Checker(s)Signature & Date Signatures & Date

0 1 - 14 Initial Issue M. L. Herrera S. S. TangA-I - A-I 11/9/08 11/9/08

M. L. Herrera11/9/08

1 1 - 14 Incorporated Client M. L. Herrera S.S.TangA-I - A-I Comments 11/10/08 11/10/08

M.L. Herrera11110/08

2 1 - 14 Revised Operating Time M. L. Herrera S.S.TangA-I - A-I to 4 years and Include 11111/08 11/11/08

Reference to TODI M.L. Herrera11/11/08

3 1-14 Clarifications Added per M.L. Herrera S.S. Tang 11/12/08A-I - A-I Client Comments and 11/12/08 M.L. Herrera 11/12/08

Laminar IndicationEvaluation

4 1-14 Revised Number of~~~~ ~

A-I A-I Startup/Shutdown "\.7-<=

Cycles. Add SI File M.L. Herrera 12/18/08 S.S. Tang 12/18108Numbers for References

~~,~and Contract Number

M.L. Herrera 12/18/08

Page I of 14F0306-01RO

StrJ!Jctl.Jrallnt~'lJrlrr Associates, Inc.

1.0 INTRODUCTION

A flaw evaluation is performed to disposition an indication associated with the Recirculation Suction(RPV Outlet) nozzle-to-safe end weld (NlA). The indication is circumferential, approximately 12.1inches long with a through-wall depth of 0.20 inches taken from the clad base metal interface, [1]. Theindication is located 0.6 inches upstream of the weld centerline (nozzle side) which would place it in thelow alloy steel. The nozzle-to-safe end weld is a dissimilar metal weld joining the low alloy steel nozzleto Alloy 182 weld, Figure 1 [1]. This location was stress mitigated using Mechanical StressImprovement (MSIP) in 1994 [1].

EPRI performed an independent evaluation of the examination results, which is documented inReference 2. EPRI concluded that this indication was present during examinations that date back to1991. The report also concludes that the indication is embedded at the interface between the stainlesssteel clad and the ferritic base metal. EPRI also states that the indication appears to be related to thefabrication process or localized repairs. Based on evidence available, EPRI states this is not a serviceinduced flaw.

Even though the indication is considered fabrication related, this analysis conservatively assumes thatthe indication is an active flaw. The flaw evaluation was performed using Appendix H of Section XI ofthe ASME Boiler & Pressure Vessel Code (B&PV) [3].

In addition, an evaluation was performed assuming the indication to be oriented such that it would beconsidered and analyzed as a laminar flaw.

2.0 TECHNICAL APPROACH

The evaluation consists of:

1. Allowable flaw size evaluation based on the guidelines of ASME B&PV Code, Section XI, IWB3600 and Appendix H [3]. The allowable flaw size was determined using the tabular solutions asallowed by Article H-6300.

2. Evaluation of the stress intensity factor, stress corrosion and fatigue crack growth analyses tocompare end of evaluation period flaw size to the allowable flaw size. The evaluation period is 2operating cycles for a total of 4 years.

3. Evaluation of indication as a laminar indication.

3.0 DESIGN INPUTS

The inside diameter of the recirculation suction nozzle is 24.312 inches [1]. The nominal thickness ofthe nozzle is 1.375 inches [1]. The clad thickness is 7/32 inches [1].

File No.: 0801457.301Revision: 4

Page 2 of 14

F0306-01

Strd'lctl.JrR.llntffl1rtty Associates, Inc.

The nozzle material is identified as SA336 Modified by Code Case 1236-1 [1]. This material isequivalent to SA 508 Class 2 in composition as discussed in Code Case 1236-1. The weld material isAlloy 182 [1].

The loading on the nozzle is shown in Table 1 [1].

The pressure and temperature conditions used in this analysis were [1]:

1. Design limiting temperature = 550°F2. Design limiting pressure 1200 psi.

The yield and tensile strength ofSA508 Class 2 is 57.55 ksi and 80 ksi at 550 of, respectively [4]. Theallowable stress intensity, Sm is 26.7 ksi at 550 of [4].

4.0 ASSUMPTIONS

The following assumptions are used in the flaw evaluation:

1. The residual stress is assumed to have a through-wail cosine distribution based on the test datapresented in Reference 5. It is also assumed that the through-wall residual stress distribution inthe low alloy steel at the flaw location is similar in shape to that for stainless steel [5].

2. The residual stress at the inside surface is at the material yield strength of low alloy steeL3. Alloy 182 is assumed to have the same material properties as Alloy 600. Alloy 182 is the

corresponding SMAW wire for Alloy 600 and the composition elosely matches. Use of Alloy600 properties for the Alloy 182 material is consistent with general industry practice.

4. The load from OBE is 0.8 times the load from SSE.5. The indication is in the low alloy materiaL6. The flaw is an active stress corrosion flaw.7. No credit is taken for the MSIP treatment.

Note that since the weld has been treated with MSIP, using a residual stress for the as-welded conditionwith a maximum stress equivalent to the low alloy steel yield strength is conservative. It is likely thatthe MSIP process significantly improved the residual stress with regards to intergranular stress corrosioncracking. Using the cosine shape for the residual stress in the low alloy steel does not significantlyimpact the results since the driving force for crack extension is the stress distribution from the insidesurface to the crack tip. The distribution shape between the crack tip and the outer surface does notimpact the results. Even if a linear (bending) distribution was assumed for the residual stressdistribution, the stress between the inside surface and crack tip does not differ enough to have asignificant impact on the results. Again note that the maximum stress is being assumed to be the yieldstrength of the low alloy steel even though the weld was subjected to MSIP.


Page 3 of 14

F0306-01

smtlCfLifBllnlt,'l/fliryAssociates, Inc.

5.0 CALCULATIONS

5.1 Allowable Flaw Size

The resulting forces and moments due to Dead Weight (DW), SSE and thermal are obtained fromReference 1 and shown in Table 2. The resultant forces and moments due to OBE are calculatedassuming the OBE loads are 80% of the SSE loads.

The nozzle area and moment of inertia is calculated as:

A ~ trR' =3.1416' ( (24.312 + 2 '1.~75)' - 24.312') llO.96in' (I)

S=~(d4-d4)= Jr ((24.312+2*1.375)4 -24.3124)= 678.29in 4 (2)32d I 32*(24.312+2*1.375)

The primary stresses for normal operating conditions are:

<Jm= PR/(2t)+F/A 1200*13.53/(2*1.375)+(2860+7115)1110.96 = 5904+90 =5994 psi (3)<Jb = M/S (25217+49678)*12/678.29 1323 psi (4)<Je F/A+M/S=25089I1l0.96+138777*12/678.29 226+2455=2681 psi (5)

For faulted conditions, <Jm 6.01ksi, <Jb = 1.55 ksi and <Je = 2.68 ksi.

For screening criteria as stated in H-4221.1 [3], SC is calculated using the following equations:

sc= K~S;K; =(IO~OKi )0,5

E J/c

S; = ~J + Pc for (<Jb+<Je)::::<Jm(Jb

Kl=Klm+KlbK1m = <Jm-V(na)FmK1b ==<Jb -V(na)Fb

[ ( B10.855 ( B))F m= 1.1 + x 0.15241 + 16.772 .: ) -14.944 .:

[ (B)' 0.565 ( B)JF b=1.1+x -0.09967+5.0057 xJr -2.8329 .:

x aft


(6)

(7)

(8)

(9)(10)(11)

(12)

(13)

(14)

Page 4 of 14

F0306-01

for (9+f3):'Sn

for (9+f3»n

Strj1JctL"allntf~lIr1i'VAssociates, Inc.

a = crack deptht wall thickness91n ratio of crack length to pipe inner circumference

2()y ['"' . fJ a. LlJ()h ---;;- LSIn -[SInU

fJ=~[1C-aB-1C. Pm ]2 t 2.4Sm

2()" [( aJ ]()h ---;;- .2 [sinfJ

t 2.4SmfJ = 1C-'------'--2- a

t

(15)(16)(17)

(18)

(19)

(20)

(21)

Using a lIe of 350 in-lb/in2 for ferritic steel base metal (Table H-4211.1 from [3]), Young's Modulus25.45x106 psi, crack size a 0.2", and 1= 12.1", and the above equations, SC is calculated to be 1.55.As shown in Figure H-4220-l, for 0.2:'SSC:'S1.8, the failure mode is EPFM.

For the EPFM failure mode, the stress ratio is calculated as

for test, normal and upset conditions

for emergency and faulted

(22)

(23)

For conservatism, Z is calculated as material category 2 from Table H-6310-1 [3]. The stress ratio fornormal operating conditions is:

SR = 1.82(5.994 ksi +1.323 ksi+2.681 ksi/2.77)/26.7 = 0.56

For II(nD) 12.1I(n*24.3l2) 0.1584, the allowable flaw size for normal operating conditions, TableH-5310-1 is 75% of the wall thickness (I flaw length = 12.1 in).

For faulted conditions, SFb is taken as 1.39, the stress ratio is

SR = 1.82(6.01 ksi+ 1.55 ksi+ 2.68 ksi/1.39)/26.7 0.65

For lienD) 12.1/(n*24.312) = 0.1584, the allowable size for faulted conditions from Table H-531 0-2 is75% of the wall thickness.

Based on these the allowable flaw size is 75% of the wall thickness for all cases.


Page 5 of 14

F0306-01

Stnllcttlral Jnt~~!Jrij'Y Associates, Inc.

5.2 Stress Intensity Factor

A linear elastic fracture mechanics analysis is performed for the observed indication to obtain the crackgrowth due to stress corrosion crack growth and fatigue crack growth.

The fracture mechanics model is a full 360° circumferential crack in a cylinder.

In additional to the applied stresses calculated in Section 5.1, the stress intensity factor due to residualstress is also obtained. The residual stress is a cosine through-wall distribution with the residual stress atthe inside surface equal to the yield strength of the low alloy steel (57.55 ksi). The residual stress iscurve-fit to a 3rd order polynomial for the stress intensity factor calculation, Figure 2.

Also, the ()b and ()e are combined and treated as a bending load case since the axial stress in ()e is verysmall.

The stress intensity factor is calculated using pc-CRACK [6].

The stress intensity factors for membrane ()m, bending and residual stress are shown in Figure 3.

5.3 Stress Corrosion Crack Growth Analysis

A stress corrosion crack growth (SCCG) analysis is performed to determine the crack growth for 2operating cycles (4 years).

Since the indication is 0.6 inches from the weld center line, it is assumed that the indication is in the lowalloy base metal. Therefore, BWRVIP-60A [7] provides the stress corrosion crack growth in low alloysteel in the BWR environment. The stress corrosion crack growth law is

da/drda/dr

6.82xlO- I2K4 (in/hr)2.83xl0-6 in/hr

for K > 50 ksiv'infor K::: 50 ksiv'in

(24)(25)

From Figure 3, for an initial crack size of 0.2 inch, the total K is less than 50 ksiv'in. Recall that theresidual stress being used is considered very conservative since this location has been treated with MSIP.Therefore, Equation (25) can be used for SCCG. the total SCCG for 4 years is

da 2.83x 10-6 in/hr *4 * 365*24 0.0992 in.

The final flaw size is 0.2" + 0.0992" 0.2992", corresponding to alt = 0.2992/1.375 0.2176, less thanthe allowable flaw size.

Since the crack is in the vicinity of the Alloy 182 weld metal, the potential for growth into the Alloy 182cannot be ruled out and therefore the stress corrosion crack growth rate in the Inconel 182 is alsoevaluated. BWRVIP-59 [8] provides stress corrosion crack growth for high nickel bases austenitic


Page 6 of 14

F0306-01

strjiJct""allntffgrlty Associates, Inc.

alloys for different reactor pressure vessel water chemistry conditions. The see growth law for normalwater chemistry is:

da/dT 1.6xlO-8K2.s (in/hr)

da/dT =5.0xI0-S in/hrfor K:::: 25 ksi-Vinfor K > 25 ksi-Vin

(26)(27)

From Figure 3, it is shown that when the crack size is larger than 0.6 inches and in the Alloy 182, thetotal K is less than 25 ksi-Vin. Therefore, for conservatism, the initial crack size is assumed to be 0.6inch and in the Alloy 182 weld metal allowing the use of Equation (4). The crack depth after 4 years ofoperation is 0.736 inches for this conservatively assumed initial flaw. The resulting aft 0.54 which isless than the allowable of75%.

5.4 Fatigue Crack Growth

Fatigue crack growth for 2 operating cycles is not significant due to a limited number of cycles thatresult in significant stress. For the purpose ofthis evaluation, 5 startup/shutdown cycles per year will beassumed (20 cycles total over 4 years) which conservatively bounds actual plant experience. Even witha L1K of 50 ksi-Vin, the total fatigue crack growth in the low alloy steel exposed to the water environmentis estimated to be 4.15xlO-3 inches using Figure A~4300-2 of Reference 3 and an R ratio:::; 0.25. This isconservative since no credit is taken for the beneficial compressive residual stress caused by MSIP.Thus, fatigue crack growth, even with the conservative assumption on the number of significant cycles,is small.

5.5 Laminar Flaw Evaluation

In Reference 2, it was mentioned that there is a presence of a laminar indication that directly correlateswith the planar indication. No other detailed information was provided regarding this potential laminarindication.

Per IWA-3360 of Reference 3, planar indications oriented within 10 degrees of a plane parallel to thesurface of the component shall be considered laminar flaw. For the purpose of this calculation, the entireplanar flaw will be assumed as laminar.

Per IWB-351 0.2 of Reference 3, the allowable laminar flaw shall not exceed the limits specified in TableIWB-35 10-2. For component with a thickness ofless than 2 inches, the allowable area is 7.5 inches.The area of the postulated laminar indication is 0.2 x 12.1 = 2.42 in2

. Even with the conservativeassumption that the indication is oriented purely as a laminar indication the area of the indication is wellbelow the limit specified in Table IWB-35 10-2.


Page 7 of 14

F0306-0J

StrlJ'ctul'8llnteQnfty A:r:;so(':lat6's, Inc.

6.0 CONCLUSIONS

A flaw evaluation has been performed conservatively assuming that the fabrication related flaw at nozzleNIA is an active stress corrosion flaw for an operating period of 4 years. Fatigue crack growth was alsoevaluated and was determined to be smalL Results of this evaluation demonstrate that growth of theobserved flaw, whether assumed in the nozzle or Alloy 182, will remain less than the allowable flaw sizeof75% of the pipe wall. Therefore, the required safety factors will be maintained during operation withthis flaw over the next 2 operating cycles.

In addition, the flaw was assumed to be oriented such that it would be considered and analyzed as alaminar flaw. Results of this evaluation showed that even with the conservative assumption that theindication is oriented purely as a laminar indication, the area of the indication is well below the limitspecified in Table IWB-351O-2 and therefore acceptable.

7.0 REFERENCES

1. Exelon TODI 00842492-02, November 10,2008, SI File 0801457.210.2. EPRI Report IR-2008-340, "Evaluation of Dissimilar Metal Weld Examinations Performed at Oyster

Creek during Refueling Outage 22 (R22) November 2008.3. ASME, Boiler and Pressure Vessel Code, Section XI, 1995 Edition with 1996 Addenda.4. ASME, Boiler and Pressure Vessel Code, Section II, Part D, 1995 Edition with 1996 Addenda.5. NUREG-0313, Rev. 2, 'Technical Report on Material Selection and Processing Guidelines for BWR

Coolant Pressure Boundary Piping.'6. pc-CRACK, Version 3.1-98348, December 1998.7. BWRVIP-60A: BWR Vessel and Internals Project Evaluation of Stress Corrosion Crack Growth in

Low Alloy Steel Vessel Materials in the BWR Environment.8. BWRVIP-59A, BWR Vessel and Internals Project, Evaluation of Crack Growth in BWR Nickel

Base Austenitic Alloy in RPV Internals,' EPRI Report TR-108710, Palo Alto, CA 1998.


Page 8 of 14

F0306-01

Strj'Jctt"allntf~Orltv Associates, Inc.

Table 1: Recirculation Suction Nozzle Load

Calculation No.c~ I:102·2.23·E540-0J4

CAl.CUl.ATION SHEETiRef. Ep·0061

A

Calculated nozzle [oreM and moments are listed In Table C·S Absen! loads and IOIlO comblnatiuns, such as OBED±SSE, are not limiting. 'TIle maximum resultants In Table COS life used In the Nozzle Evaluation in Seetion C·7 4A~

~uNUCLEAR

Tuble (;·8 Forces lll1d Moments on the Nozzles

Mz 1l.eSllltlillt(ft-lll) (fNb)

Nates:I. in the Au!oPIPEmodel the positive X direction north, the positive Y direction is vertical, and the posi!!ve Z direction

eas!2. Maximum vailles are hold~

Revision: 4Page 9 of 14

F0306-01

Stn!Jctl"allntf~flnlryAssocjates, Inc.

Table 2: Loads due to Thermal and SSE

Resultant Foree (lb) Resultant Moment (ft-Ib)DW 2860 25217SSE 8894 62098Thermal 25089 138777aBE 7115 49678

Note: Thermal loads were ealculated usmg the dIfference between the load case D andload case D+T3 resultants.


Page 10 of 14

F0306-0J

StrjrJctt"allnlf~!JnryAssociates, Inc.

_mu~MlEIl" ,.tlKOIFml!lllTAMltATtllll..·..·_~I __ ..

"WtII OIl STllffO tlIClIll1llrUl1llSIW If TllL1MIItU.IIU lJIl!tll$llIlIS II I_I.

._~24M. D

H1I1 TM'U IWE IlIIl _WIt Plllll tof1ll1l. lW:lIllU)lG

23 11/11.

I~,

(II ~i::Tt"t:=.1l1:..... IlL IX-OW. mUI

tl' lIlllU" (Wille melftCArtlllIWI." m ••• f1RO'UM:TA IlltiiOllATllll '.'1110 IIl$TlUJIlIet, Mil I!!. AmI '/Esm. fltt:Tm: lllnll 1I:l/n. ftlllK n '" SlfiT HTlltfll 'IlIIl "U fV 2. IKlI flUlliWIS.'

(1) 115m nEB IlUAllIl'lIllCflllRf IlL II. ID. I, mUll '1l10"W AlllllIlNlIl Of WE: OiH.'

(41 1ft tA\.t'!IUllOl DAnII 'nm. UJ10 'III111IlII1111lRSS !ItWE tlll Al 'IfI. ClllIIIm,llIl' I'f L. t. I£INII,

(I) I'I'I! CII.ClJl.ATIOl .m tlJlll. IIJ10 '1Illl1U1 lIlCIlllH !ItWI III Al MOUt.l _nor ,f I.. t. If,..,

tIl !II'll ~tulJl _nil IlJi7l&"-, tlTlEO • Illlllllllll TlItt_H filiilIlUI.t II' $11ft m ~lOiI" U L. t. UltM.

m tllI!IIl!lSflllll_lIWllllQ tl.:'~lIQ•• m·m. m. ,.,UllO,~ flll!l. Mtlllllllll,'

OYSTER CREEK REACTOR vesselREciRCUlAT10N SYSTEM SAFE END DETAILS

FIGURE 1

IilPft AlI80CIAntlp-la-nl-,

1OITI.,

11»' CUll

suer!. 1m omn) 24.112 • I.M':!1I1SQI\W 1m 11l\.U} M 1/1 .••".. -I -0 f~

t>i""\'l-t,·~-'J \,

Figure 1. Oyster Creek Reactor Vessel Recirculation System Safe End Details


Page 11 of 14

F0306·01

smrJCflltal mlf~l1nrvAssociates, Inc.

100

80

60

40

....20g::l~

~o

-20

-40

-60

-80

0 0<2 0.4 0<6

Crack

0<8 1.4

Stress)

Figure 2. Residual Stress Distribution in Low Alloy Steel


Page 12 of 14

F0306-01

40

-20

-40

-60

StrlJctlJrrallntfrfl"ty Associates, Inc.

~Bending

Residual

o 0.2 0.4 0.8 1.2


Figure 3: Stress Intensity Factor

Page 13 of 14

F0306-01

StrJiJctttrallnlf1.0rllV Associates, Inc.

0.76

0.74

0.72

0.7

gJ:;

Q.0.68'"c

"'"~Q

0.66

0.64

0.62

0.6

... , ;....

~d

MPMAff....AP«

r",+..r,r

/./1

I

I'o 5000 10000 15000 20000

Tome (hrs)

25000 30000 35000 40000

Figure 4 Crack Growth Assuming in Inconel


Page 140f14

170306-01

StnfJcttrrallnlftonrvAssociates, Inc.

APPENDIX A

COMPUTER FILES


F0306·0JRO

Page A-I of A- I

Documents

Attn: Document Control Desk 11555 Rockville Pike · 2012. 12. 1. · The nozzle material is identified as SA336 Modified by Code Case 1236-1 [1]. This material is equivalent to SA