ML13317A072

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Attachment 2 - Flaw Fracture Mechanics Evaluation to Support Restart, Calculation 32-9212942-001, Palo Verde Unit .3 Bmi Nozzle Repair - Section XI Analysis for Restart
ML13317A072
Person / Time
Site: Palo Verde Arizona Public Service icon.png
Issue date: 11/08/2013
From:
Arizona Public Service Co
To:
Office of Nuclear Reactor Regulation
References
102-06794-JJC/RKR/DCE 32-9212942-001
Download: ML13317A072 (39)
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Text

Enclosure - Flaw Fracture Mechanics Evaluation to Support Restart

Attachment 2 -

Flaw Fracture Mechanics Evaluation To Support Restart 0402-01-FOl (Rev. 017, 11/19/12)

A CALCULATION

SUMMARY

SHEET (CSS)

AREVA Document No. 32 - 9212942 - 001 Safety Related: H Yes 0 No Title Palo Verde Unit 3 BMI Nozzle Repair - Section Xl Analysis for Restart PURPOSE AND

SUMMARY

OF RESULTS:

Purpose The purpose of the present fracture mechanics analysis is to determine the suitability of leaving degraded J-groove weld and butter material in the Palo Verde Nuclear Generation Station, Unit 3 (PVNGS3) reactor vessel bottom head (RVBH) following the repair of bottom mounted instrument (BMI) nozzle #3. It is postulated that a small flaw in the head could combine with a large stress corrosion crack in the weld and butter to form a radial corner flaw that could only propagate into the low alloy steel head by fatigue crack growth under cyclic loading conditions.

The purpose of revision 001 is to incorporate customer comments and address the removal of "boat" sample from remnant J-groove weld.

Summary of Results Based on a combination of linear elastic and elastic-plastic fracture mechanics analysis of a postulated remaining flaw in the original Alloy 182 J-groove weld and butter material, bottom mounted instrument (BMI) nozzle #3 in the Palo Verde Nuclear Generation Station, Unit 3 reactor vessel bottom head is considered to be acceptable for one fuel cycle. Using EPFM analysis with safety factors of 3 on primary loads and 1.5 on secondary loads, it has been shown that the applied tearing modulus (17.508) is less than the material tearing modulus at instability (26.580).

Furthermore, with safety factors of 1.5 on primary loads and 1.0 on secondary loads the applied J-integral (0.953 kips/in) is less than the J-integral of the low alloy steel head material (2.701 kips/in) at a crack extension of 0.1 inch.

THE DOCUMENT CONTAINS ASSUMPTIONS THAT SHALL BE THE FOLLOWING COMPUTER CODES HAVE BEEN USED IN THIS DOCUMENT: VERIFIED PRIOR TO USE CODE/VERSION/REV CODEN.ERSION/REV l YES ANSYS 14.0 Z NO Page 1 of 38

Attachment 2 -

Flaw Fracture Mechanics Evaluation To Support Restart 0402-01-FO01 (Rev. 017, 11/19/12)

P.. 1!: W..

.Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair- Section Xl Analysis for Restart Review Method: j[^ Design Review (Detailed Check)

D Alternate Calculation Signature Block P/RIA Name and Title and Pages/Sections (printed or typed) Signature LPILR Date Prepared/Reviewed/Approved Samer Mahmoud Principal Enginee, LP .1-2oI3 All Except Appendix A Silvesler Noronha LR 11 1OI3 All Except Appendix A Principal Engineer Jasmine Cooo 2-o 1; Principal Engineer Appendix A Martin Kolar , .*N GO,, j Engineer IV R Appendix A Tim Wiger " A 6)* All Unit Manager A Note: P/R/A designates Preparer (P), Reviewer (R), Approver (A);

LP/LR designates Lead Preparer (LP), Lead Reviewer (LR)

Project Manager Approval of Customer References (N/A if not applicable)

Name Title (printed or typed) (printed or typed) Signature Date Maya Chaid rashekhar Project Manager

(

Mentoring Information (not required per 0402-01)

Page 2

Attachment 2 -

Flaw Fracture Mechanics Evaluation To Support Restart A 0402-01-FO1 (Rev. 017, 11/19/12)

AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section Xl Analysis for Restart Record of Revision Revision Pages/Sections/Paragraphs No. Changed Brief Description / Change'Authorization 000 All Original Release 001 Page 1 Added purpose for revision and updated results (minor change to results)

Section 1.0 Page 8 Added discussion of "boat" sample removal Section 3.2/Page 15 Corrected typo (butte to butter)

Section 5.2/Page 21 Updated computer files Page 26 Corrected (2150 to 2235) and updated fonts for all equations Page 27-28 Updated results (only minor change to the results)

Section 8 / Page 31 Updated Reference 1 and added reference to Boat sample drawing Appendix A Changed Page numbering to be sequential with the rest of the document t t Page 3

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Flaw Fracture Mechanics Evaluation To Support Restart A

ARE VA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart Table of Contents Page SIG NATURE BLO CK ............................................................................................................................. 2 RECO RD O F REVISIO N ....................................................................................................................... 3 LIST O F TABLES ................................................................................................................................ 6 LIST O F FIG URES ................................................................................................................................ 7 1.0 INTRO DUCTIO N ......................................................................................................................... 8 2.0 ANALYTICAL METHO DO LOGY .............................................................................................. 9 2.1 Stress Intensity Factor Solution ................................................................................................. 10 2.2 Plastic Zone Correction .................................................................................................................. 11 2.3 Linear Elastic Fracture Mechanics ............................................................................................. 12 2.4 Elastic-Plastic Fracture Mechanics ........................................................................................... 12 2.4.1 Screening Criteria ....................................................................................................... 12 2.4.2 Flaw Stability and Crack Driving Force ........................................................................ 13 2.5 Sources of Stresses ....................................................................................................................... 14 3.0 ASSUM PTIO NS ....................................................................................................................... 15 3.1 Unverified Assumptions .................................................................................................................. 15 3.2 Justified Assumptions ..................... ........ ............ ......... 15 3.3 Modeling Simplifications ............................................................................................................ 15 4.0 DESIG N INPUTS ...................................................................................................................... 16 4 .1 Ma te ria ls ......................................................................................................................................... 16 4.1.1 Yield Strength .................................................................................................................. 16 4.1.2 Reference Temperature .............................................................................................. 16 4.1.3 Fracture Toughness ..................................................................................................... 16 4.1.4 J-integral Resistance Curve ......................................................................................... 17 4.2 Basic Geometry .............................................................................................................................. 19 4.3 Operating Conditions ...................................................................................................................... 20 4.4 Applied Stresses ............................................................................................................................ 20 5.0 CO MPUTER USAG E ............................................................................................................... 21 Page 4

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Flaw Fracture Mechanics Evaluation To Support Restart A

AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section Xl Analysis for Restart Table of Contents (continued)

Page 5.1 Hardware/Software ......................................................................................................................... 21 5.2 C o m p ute r F ile s ............................................................................................................................... 21 6.0 FLAW EVALUATIO N................................................................................................................ 22 6.1 LE F M E va lu a tio n ............................................................................................................................ 22 6.2 EPFM Evaluation ............................................................................................................................ 26 6.3 Primary Stress Check ..................................................................................................................... 29 7.0

SUMMARY

OF RESULTS AND CONCLUSIONS ................................................................ 29 7.1 Summary of Results ....................................................................................................................... 29 7 .2 C o n c lu s io n ...................................................................................................................................... 30

8.0 REFERENCES

......................................................................................................................... 31 APPENDIX A : COOLDOW N STRESS ANALYSIS ...................................................................................... 32 Page 5

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Flaw Fracture Mechanics Evaluation To Support Restart A

AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section Xl Analysis for Restart List of Tables Page Table 1-1: Safety Factors for Flaw Acceptance ............................................................................... 9 Table 4-1: Material Designation ...................................................................................................... 16 Ta ble 4 -2 : Ge o m etry ........................................................................................................................... 19 Table 4-3: Applied T ransients ........................................................................................................ 21 Table 6-1: LEFM Evaluation of BMI Nozzle Corner Crack for Heatup/Cooldown ............................. 23 Table 6-2: EPFM Evaluation of BMI Nozzle Corner Crack for Heatup/Cooldown ........................... 27 Table A-I: Material Properties ........................................................................................................ 33 Table A-2: Reactor Coolant Temperature during Cooldown Transient ............................................ 33 Table A-3: Maximum Thermal Stresses in Lower Head during Cooldown Transient ....................... 35 T able A-4 : C om puter F iles .................................................................................................................. 37 Page 6

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Flaw Fracture Mechanics Evaluation To Support Restart A

AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart List of Figures Page Figure 2-1: Postulated Flaw in the J-groove Weld ........................................................................... 10 Figure 2-2: Schematics of Nozzle Corner Flaw Used in SIF Solution ............................................. 11 Figure 4-1: Correlation of Coefficient, C, of Power Law with Charpy V-Notch Upper Shelf Energy ...... 18 Figure 4-2: Correlation of Exponent, m, of Power Law with Coefficient, C, and Flow Stress, Yo..... 18 Figure 4-3: Sketch showing the geometric parameters .................................................................... 19 Figure 6-1: J-T Dia g ra m ...................................................................................................................... 28 Figure A-1: Finite Element Model, Boundary Condition (Left) and Temperature field (Right) ........... 34 Figure A-2: Temperature vs. Time (Left) and Temperature Difference vs. Time (Right) .................. 34 Figure A-3: Thermal Stress in Radial (Left) and Hoop (Right) Directions ......................................... 35 Figure A-4: Thermal Stress in Radial (Left) and Hoop (Right) Directions vs. Depth from ID to OD ...... 36 Figure A-5: Temperature vs. Depth from ID to OD ........................................................................... 36 Page 7

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Flaw Fracture Mechanics Evaluation To Support Restart A

AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart

1.0 INTRODUCTION

In 2013, inspection of the Alloy 600 Bottom Mounted Instrument (BMI) nozzles on the outside surface of the reactor vessel bottom head (RVBH) at Palo Verde Nuclear Generation Station, Unit 3 (PVNGS3), identified areas of potential reactor coolant (RC) leakage between the interface of the RVBH penetration(s) and the BMI nozzle(s). Arizona Public Service (APS) Company (Owner) has contracted AREVA to develop and implement a modification for the BMI nozzle penetration(s) at PVNGS3.

The repair activity as described in Reference [1] will consist of removing the existing in-core instrument (ICI) guide tube to BMI weld, removing a portion of the existing BMI nozzle below the RVBH, the machine application of an Alloy 52M/52MSS temper bead weld pad on the outer surface of the RVBH around the penetration, replacing the portion of BMI nozzle removed with an Alloy 690 nozzle, attaching it to the weld pad with a J-groove partial penetration weld, and attaching the ICI guide tube with a socket weld using Alloy 52M/52MSS weld filler metal.

The present concem is that a flaw in the remnant J-groove weld could impact the structural integrity of the vessel.

A flaw in the weld metal may propagate into the low alloy steel by fatigue. Since the hoop stress in the J-groove weld is greater than the axial stress at the same location, the preferential direction for cracking is radial relative to the nozzle. It is postulated that a radial crack in the Alloy 82/182 weld metal could propagate by PWSCC, through the weld and butter, to the interface with the low alloy steel head material, where it is fully expected that such a crack would then blunt, or arrest, as discussed in Reference [2]. Although primary water stress corrosion cracking would not extend into the head, it is further postulated that a small fatigue initiated flaw forms in the low alloy steel head and combines with the stress corrosion crack in the weld to form a large radial comer flaw that could propagate into the head by fatigue crack growth under cyclic loading conditions. Linear-elastic (LEFM) and elastic-plastic (EPFM) fracture mechanics procedures are utilized to evaluate this worst case flaw in the original J-groove weld and butter. Since the current analysis considers one fuel cycle, fatigue crack growth will be minimal.

The boat sample removed from the BMI nozzle and J-groove weld, which is described in Reference [3], has no adverse impact on the flaw evaluation conducted in this document. Obtaining the boat sample involves removing a portion of the degraded J-groove weld and nozzle. From a fracture mechanics perspective, removing a portion of the degraded J-groove weld could have a twofold impact on the structural integrity of the RVBH. From a flaw size view point, the postulated flaw size in the vicinity of the boat sample would be smaller and therefore beneficial. On the other hand, removing the boat sample would lead to a slight redistribution of residual and operating stresses. The impact of any residual stress redistribution on the flaw evaluation is expected to be very minimal from flaw growth consideration during one fuel cycle. Also, any impact on operational stresses will be insignificant. In summary, removal of the boat sample from the BMI nozzle and J-groove weld will not alter the results and conclusions of the current flaw evaluation.

The flaw evaluation of the as-left J-groove weld postulates a large planar flaw at the inside comer of the head, at the location of the partial penetration weld between the nozzle and the head. The comer flaw model used to generate the crack tip stress intensity factor is based on free surfaces along each "leg" of the comer, along the inside surface of the head as well as along the interface with the nozzle. These free surfaces maximize the crack opening displacement of the postulated flaw. Consideration of the nozzle would only serve to restrict the crack opening displacement of the comer flaw in the head, and thereby reduce the calculated stress intensity factors.

Furthermore, even if there was any partial through-wall cracking of the nozzle, the uncracked volume of the nozzle would still provide some degree of restraint for the postulated flaw. It is therefore appropriate to use the postulated comer flaw model to calculate stress intensity factors for the as-left J-groove weld flaw evaluation The purpose of this calculation is to provide a Section XI [9] analysis for restart of PVNGS3.

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Flaw Fracture Mechanics Evaluation To Support Restart A

AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section Xl Analysis for Restart Key features of the fracture mechanics analysis are:

" This analysis applies specifically to BMI nozzle penetration #3 in the PVNGS3 RVBH.

  • Flaw acceptance is based on linear elastic fracture mechanics (LEFM) acceptance criteria of IWB-3612 of Section XI of the ASME Code [9] considering the safety factors listed in Table 1-1.
  • In the event that LEFM margins based on IWB-3612 of Section XI of the ASME Code [9] are not met, final flaw acceptance is based on elastic plastic fracture mechanics (EPFM) methodology considering the ductile tearing resistance of the reactor vessel bottom head material and the safety factors listed in Table 1-1. Table 1-1 lists the EPFM safety factors that were used in the current evaluation. In addition, Table 1-1 lists the safety factors that are recommended in ASME Code Case N-749 [4]. Note that for the EPFM flaw evaluation, the current analysis used safety factors that are higher than the safety factors recommend by the ASME Code Case N-749 [4], which provides a significant degree of conservatism to the analysis.

Table 1-1: Safety Factors for Flaw Acceptance Linear-Elastic Fracture Mechanics Operating Condition Evaluation Method Fracture Toughness / K, Normal/Upset Kia fracture toughness 410 = 3.16 Elastic-Plastic Fracture Mechanics Operating Condition Evaluation Method Primary Secondary Normal/Upset J/T based flaw stability 3.0 (2.14+) 1.5 (1.0')

Normal/Upset J0.1 limited flaw extension 1.5 (1.5#) 1.0 (1.0+)

ý Safety factors based on ASME Code Case N-749 [4]. These safety factors are listed here for information only. The higher safety factors were used in the EPFM flaw evaluation analysis.

2.0 ANALYTICAL METHODOLOGY A radial flaw at the inside comer of the nozzle penetration is evaluated based on linear elastic fracture mechanics (LEFM) and elastic-plastic fracture mechanics (EPFM), as outlined below.

1. Postulate a flaw in the J-groove weld, radial with respect to nozzle axis extending from the inside comer of the penetration to the interface between the J-groove weld and reactor vessel shell, as shown in Figure 2-1 for flaw propagation in axial and meridional directions. The postulated flaw is shown Figure 2-1.
2. Obtain operating and residual stresses need for evaluating the stress intensity factor (SIF).
3. Calculate SIF based on the closed form solution provided in Reference [5] for a nozzle comer flaw.
4. Utilize the screening criteria of ASME Code Section XI, Appendix C to determine the failure mode and appropriate method of analysis (LEFM, EPFM, or limit load) for flaws in ferritic materials, considering Page 9

Attachment 2 -

Flaw Fracture Mechanics Evaluation To Support Restart A

AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart the applied stress, temperature, and material toughness. For LEFM flaw evaluations, compare the stress intensity factor at the final flaw size to the available fracture toughness, with appropriate safety factors.

When the material is more ductile and EPFM is the appropriate analysis method, evaluate flaw stability and crack driving force.

Nozzle RVBH U-I Figure 2-1: Postulated Flaw in the J-groove Weld 2.1 Stress Intensity Factor Solution Section G of Reference [5], summarizes the stress intensity factor (SIF) solution that is applicable for a surface flaw in the blend radius of a nozzle, see Figure 2-2 for illustration of flaw model. Section G-2.2 of Reference [5]

provides the stress intensity factor for a polynomial stress distribution for a circular crack. For a stress distribution of the form a(x) = A0 + A1 x +A 2 x2 + A 3 X where x is the distance from the inside comer (Figure 2-2), the stress intensity factor is given by Equation (G-2.2) of Reference [5] (corrected). The stress intensity factor solution for the nozzle comer flaw model is:

K, = x--na2x 0.706xA +0.537x2xaxA,+0.448xa xA2+0.393x4xa K1 57 rxOOrA+ 2 2 3 37r.

7 xA 3 Page 10

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Flaw Fracture Mechanics Evaluation To Support Restart A

AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart where a is the crack depth measured from the nozzle comer.

For any arbitrary stress distribution, it is necessary to .determine the constants A0 , A,, A 2. A 3 by fitting a cubic polynomial to the stress. Knowing the coefficients, the K value for a crack depth, a, can be determined from the above equation. The above equation can be modified to included crack face pressure as:

I2xa KI = 1- xa x [0.706 x (AD + AP) + 0.537 x 2 L2 x A, + 0.448 x a2

- x A 2 + 0.393 x 4 3ir 3 x x a---

xA I33r 3

where Ap is the applied pressure.

Figure 2-2: Schematics of Nozzle Corner Flaw Used in SIF Solution 2.2 Plastic Zone Correction The Irwin plasticity correction is used to account for a moderate amount of yielding at the crack tip. The formulation of Irwin plasticity correction is given in Reference [6]. For plane strain conditions, this correction is given by 2

ry= 6 KI(a) J Page 11

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Flaw Fracture Mechanics Evaluation To Support Restart A

AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart where KI(a)= stress intensity factor based on the actual crack size, a Ty= material yield strength.

A stress intensity factor, Kx(aj), is then calculated for an effective crack size, a,= a + ry, 2.3 Linear Elastic Fracture MechanicsSection XI, Article IWB-3612 [9] requires that the applied stress intensity factor, K, at the final flaw size be less than the available fracture toughness at the crack tip temperature, with appropriate safety factors, as outlined below.

Normal Conditions: K, < Kia / '/10 where KI, is the fracture toughness based on crack arrest.

Faulted Conditions: K, < Kic / 4I2 where K1 c is the fracture toughness based on crack initiation.

2.4 Elastic-Plastic Fracture Mechanics Elastic-plastic fracture mechanics (EPFM) will be used as alternative acceptance criteria when the flaw related failure mechanism is unstable ductile tearing. This type of failure falls between rapid, non-ductile crack extension and plastic collapse. Linear elastic fracture mechanics (LEFM) would be used to assess the potential for non-ductile failure.

2.4.1 Screening Criteria Screening criteria for determining failure modes in ferritic materials may be found in Appendix C of Section XI.

Although Appendix C, Article C-4221 [9] contains specific rules for evaluating flaws in Class 1 ferritic piping, its screening criteria may be adapted to other ferritic components, such as the reactor vessel, as follows:

Let, Kr' =Klpp / Kic Sr' = Umax / a'f Then the appropriate method of analysis is determined by the following limits:

LEFM Regime: K,' / Sr' > 1.8 EPFM Regime: 1.8 > Kr' / Sr' >0.2 Page 12

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Flaw Fracture Mechanics Evaluation To Support Restart A

ARE VA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart Limit Load Regime: 0.2 > Kr' / Sr' 2.4.2 Flaw Stability and Crack Driving Force Elastic-plastic fracture mechanics analysis will be performed using a J-integral/tearing modulus (J-T) diagram to evaluate flaw stability under ductile tearing, where J is either the applied (Japp) or the material (Jmat) J-integral, and T is the tearing modulus, defined as (E/yf2) (dJ/da). The crack driving force, as measured by Jpp, is also checked against the J-R curve at a crack extension of 0.1 inch (JO 1). Consistent with industry practice for the evaluation of flaws in partial penetration welds used to attach nozzles to vessels, different safety factors will be utilized for primary and secondary loads. Flaw stability assessments for normal and upset conditions will consider a safety factor of 3 on the stress intensity factor due to primary (pressure) stresses and a safety factor of 1.5 for secondary (residual plus thermal) stresses. The crack driving force will be calculated using safety factors of 1.5 and I for primary and secondary stresses, respectively.

The general methodology for performing an EPFM analyses is outlined below.

Let E' = E/(1-v 2)

Final flaw depth = a Total applied K1 = KIapp K, due to pressure (primary) = Kip K, due to residual plus thermal (secondary) = Kis = Kjapp- Kip Safety factor on primary loads = SFp Safety factor on secondary loads = SF, For small scale yielding at the crack tip, a plastic zone correction is used to calculate an effective flaw depth based on a,=a + [1/(67r)] [ (Kip+ K1 ,) / ay]2, which is used to update the stress intensity factors based on K'Ip = K1p(ae) and K'1 s= Kis(a,).

The applied J-integral is then calculated using the relationship Japp = (SFp*K'lp + SF,*K' S2/E'.

The final parameter needed to construct the J-T diagram is the tearing modulus. The applied tearing modulus, T~pp, is calculated by numerical differentiation for small increments of crack size (da) about the final crack size (a), according to Page 13

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Flaw Fracture Mechanics Evaluation To Support Restart A

AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section Xl Analysis for Restart SJapp(a + da)

Tapp = 2KO -

)

2 daJapp(a - da))

Using the power law expression for the J-R curve, JR = C(Aa)m, the material tearing modulus, Tm,, can be expressed as Tmat = (E/oy) Cm(Aa)m-i.

Constructing the J-T diagram, J

Unstable Region Tapp a Tmat Applied Instability

/- Point Material Stable Region Tapp -Tmat T

flaw stability is demonstrated at an applied J-integral when the applied tearing modulus is less than the material tearing modulus. Alternately, the applied J-integral is less than the J-integral at the point of instability.

To complete the EPFM analysis, it must be shown that the applied J-integral is less than J0.1, demonstrating that the crack driving force falls below the J-R curve at a crack extension of 0.1 inch.

2.5 Sources of Stresses Pertinent stresses that contribute to the crack driving force are attributed to pressure, thermal, and residual stresses. Reference [7] performed a finite element analysis specific to PVNGS3 RVBH that simulated the J-groove weld fabrication and operating stress. The stresses in Reference [7] are attributed to welding residual stress Page 14

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ARE VA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart plus stress due to operating pressure and temperature. The stresses reported in Reference [71 can be used to determine the stress intensity factor at steady state conditions. From flaw stability perspective, it is also desirable to obtain the stresses during cooldown conditions since cooldown produces additional tensile stress. A simplified finite element analysis is provided in Appendix A to estimate thermal stresses during cooldown conditions. These stresses are conservatively combined with the stresses from Reference [7] to provide a source of stress for evaluating cooldown.

3.0 ASSUMPTIONS This section discusses assumptions and modeling simplifications applicable to the present evaluation of the PVNGS3 BMI nozzle remnant J-groove weld flaw.

3.1 Unverified Assumptions There are no assumptions that must be verified before the present analysis can be used to support the instrumentation nozzle repair at PVNGS3.

3.2 Justified Assumptions

" The size of the J-groove weld prep is based on the dimensions depicted in Reference [11]. Since within the RVBH shell, only the J-groove weld and butter are susceptible to SCC, it is assumed that the postulated flaw extends through the entire J-groove weld and butter.

  • A crack extension of 0.04" is conservatively assumed to account for crack extension during one fuel cycle. This assumption is based on the calculation provided in Reference [12] for South Texas Project Unit 1 (STP-1) RVBH following a half-nozzle repair of a bottom mounted instrumentation (BMI) nozzle.

The crack growth for 50 years of operation calculated in Reference [12] is 0.305". Based on the results from Reference [12] crack growth for one fuel cycle is calculated as 0.009". The current analysis conservatively used 0.04" of crack extension for one fuel cycle.

3.3 Modeling Simplifications The operating plus residual stresses extracted from Reference [7] do not include the repair modification. This is deemed to be an appropriate modeling simplification since the repair weld (at the OD of the RVBH) is sufficiently separated from the region of interest that is adjacent to the degraded J-groove weld, which is located near the ID of the RVBH.

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section Xl Analysis for Restart 4.0 DESIGN INPUTS This section provides basic input data needed to perform flaw evaluation of the postulated flaw in the remnant J-groove weld.

4.1 Materials Material designations for the PVNGS3 RVBH from References [1, 11] are listed Table 4-1.

Table 4-1: Material Designation Item Material RVBH material SA-533 Gr. B C1.1 [11]

Cladding mat. Stainless Steel [11 ]

Original nozzle SB-166, Alloy 600 [11]

Original J-groove weld and Alloy 182 [1]

buttering I 4.1.1 Yield Strength From the ASME Code [8] the specified minimum yield strength for the head material is 50.0 ksi at 100 'F and 42.0 ksi at 600 'F. The yield strength value at the operating temperature (565 'F) is interpolated from Reference

[8] to be 42.4 ksi.

4.1.2 Reference Temperature The RTNDT value for the PVNGS3 RVBH is reported in Reference [1] to be -60 'F. The Charpy V-notch upper-shelf energy correlation for the J-integral resistance curve with a Charpy V-notch upper-shelf energy of 119 ft-lbs

[1].

4.1.3 Fracture Toughness From Article A-4200 of Section XI [9], the lower bound Kla fracture toughness for crack arrest can be expressed as Kla = 26.8 + 12.445 exp [0.0 145 (T - RTNDT)],

where T is the crack tip temperature, RTNDT is the reference nil-ductility temperature of the material, KI, is in units of ksi'iin, and T and RTNDT are in units of 'F. In the present flaw evaluations, KIa is limited to a maximum value of 200 ksix/in (upper-shelf fracture toughness). The crack arrest Kia upper shelf toughness of 200 ksi/in is achieved at T-RTNDT > 182 'F.

A higher measure of fracture toughness is provided by the Kjc fracture toughness for crack initiation, approximated in Article A-4200 of Section XI [9] by KIc = 33.2 + 20.734 exp [0.02 (T - RTNDT)],

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section Xl Analysis for Restart 4.2 Basic Geometry The dimensions used in this document are taken from References [11]. Pertinent dimensions for the reactor pressure vessel and the instrumentation nozzle are described in Table 4-2.

Table 4-2: Geometry Item Uphill Side Downhill Side Reference

. ..... .. ._(inches) (inches)

RVBH inside radius (to base metal) 93.35 93.35 [11]

RVBH thickness 6.5 (min.) 6.5 in. (min.) [11]

Cladding thickness 0.22 0.22 [11]

J-groove Depth 1.22 1.37 [11]

Nozzle Bore diameter 3.002 3.002 [11]

Horizontal distance of nozzle axis from sphere center 8.180 8.180 [11]

Figure 4-3: Sketch showing the geometric parameters The initial flaw is postulated to extend from the inner surface of the nozzle to the interface between the butter and the low alloy steel. The depth of the butter from the point where the toe of the weld fillet intersects the nozzle 2.033" as modeled in Reference [7].

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart 15 10 C

5 0.0 0.4 0.8 1.2 1.6 2.0 CVN/I00 Figure 4-1: Correlation of Coefficient, C, of Power Law with Charpy V-Notch Upper Shelf Energy 0.7 I I I 0.6 0

0.5 0.4 m TESTED AT 0.3 CT IT-CT (OC) 0 120 I I W 130 0.2 o 150 170 0.1 o 200 0 . .. . .....

II, I

l 0 2 4 6 8 10 12 14 16 x= C+ 1.5( -)

Figure 4-2: Correlation of Exponent, m, of Power Law with Coefficient, C, and Flow Stress, a.

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Flaw Fracture Mechanics Evaluation To Support Restart A

AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart 4.2 Basic Geometry The dimensions used in this document are taken from References [11]. Pertinent dimensions for the reactor pressure vessel and the instrumentation nozzle are described in Table 4-2.

Table 4-2: Geometry Item Uphill Side Downhill Side Reference

_______________________________ (nches) (inches)______

RVBH inside radius (to base metal) 93.35 93.35 [11]

RVBH thickness 6.5 (min.) 6.5 in. (min.) [11]

Cladding thickness 0.22 0.22 [11]

J-groove Depth 1.22 1.37 [11]

Nozzle Bore diameter 3.002 3.002 [11]

Horizontal distance of nozzle axis from sphere center 8.180 8.180 [11]

1.37 Figure 4-3: Sketch showing the geometric parameters The initial flaw is postulated to extend from the inner surface of the nozzle to the interface between the butter and the low alloy steel. The depth of the butter from the point where the toe of the weld fillet intersects the nozzle 2.033" as modeled in Reference [7].

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart Crack Propagation Consideration The only credible mechanism for flaw growth in the low alloy steel in PWR environment is by fatigue. Because the intent of this document is to demonstrate acceptance of a postulated flaw in the existing J-groove weld for one fuel cycle, crack growth due to fatigue in one fuel cycle is marginal. To conservatively account for any potential fatigue crack growth during one fuel cycle, an additional 0.04" of crack extension will be added to the depth of the postulated flaw, which is the depth of the existing J-groove weld and butter. Thus the total flaw depth after one fuel cycle of operation is assumed to be 2.037" (2.033+0.04"). The 0.04" crack extension is conservatively used based on the crack growth estimation provided in Reference [12] for South Texas Project Unit 1 (STP-1)

RVBH following a half-nozzle repair of a bottom mounted instrumentation (BMI) nozzle (See Section 3.0 for additional details).

4.3 Operating Conditions Per Reference [1] the design pressure and temperature are 2500 psia and 650 'F, respectively. The operating pressure and inlet temperature are 2250 psia and 564.5 'F [11] (565 'F was used).

4.4 Applied Stresses Two sources of stress are considered for the present flaw evaluations, stresses that occur during normal operation, and residual stresses from welding.

Residual plus operating stresses are obtained from Reference [7], which performed a three-dimensional elastic-plastic finite element stress analysis that simulates the attachment of the original nozzle to RVBH. The analysis in Reference [7] includes the simulation of steady state operating conditions at operating temperature and pressure of 5657F and 2,235 psig.

As stated earlier, it is important to demonstrate flaw stability at cooldown conditions. A simplified finite element analysis (provided in Appendix A) was performed to estimate the thermal stresses during cooldown conditions.

These stresses are conservatively combined with the stresses from Reference [7] to provide a source of stress to be used for evaluating the crack driving force during cooldown conditions.

The stresses used in the flaw evaluation are listed in Table 4-3 for several positions (x) along crack depth.

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart Table 4-3: Applied Transients Position SS CD SS+CD x Hoop Stress (in.) (ksi) (ksi) (ksi) 0.0000 50.014 7.485 57.499 0.2980 61.709 6.461 68.170 0.5950 73.123 5.493 78.616 0.8920 71.136 4.576 75.712 1.1890 74.007 3.710 77.717 1.4860 57.094 2.895 59.989 1.7830 24.199 2.130 26.329 2.0330 3.862 1.526 5.388 2.2460 40.983 1.039 42.022 SS = Steady State CD = Cooldown 5.0 COMPUTER USAGE This section describes computer resources and stored computer files.

5.1 Hardware/Software The following computer resources were used in the present analysis.

1. Computer: Dell Precision Workstation - Tag#5VJV5SI
2. Computer processor: Intel CoreTM i7-2640M CPU @ 2.80 GHz
3. Computer memory: 8.00 GB RAM
4. Computer operating system: Microsoft Windows 7 Enterprise 2009 Service Pack 1 5.2 Computer Files The computer files listed below are stored in the AREVA ColdStor repository in the directory \cold\General-Access\32\32-9000000\32-9212942-00 \official\EXCELFiles".

File Name Time and Date File ColdStor Storage Date File Size Checksum Modified and Time PV3 BMN HUCD EPFM.xlsx Oct 31 2013 15:00:28 Oct 31 2013 15:02:55 43660 46282 PV3 BMN HUCD EPFM.xlsx Oct 30 2013 10:03:13 Oct 31 2013 15:02:56 248832 21664 Page 21

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart 6.0 FLAW EVALUATION 6.1 LEFM Evaluation Table 6-1 presents a fracture mechanics analysis wherein stress intensity factors are calculated for comparison with the fracture toughness requirements of Section XI. Article IWB-3612 [9] requires that a safety factor of 4I10 be used when comparing the applied stress intensity factor to the fracture toughness for crack arrest. Calculations are performed for a postulated radial comer crack in BMI nozzle head penetration.

Since the calculated fracture toughness margins are less than the Code required minimums, EPFM flaw evaluations were performed in Section 6.2 to account for the ductile behavior of the low alloy steel under stable crack propagation.

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart Table 6-1: LEFM Evaluation of BMI Nozzle Corner Crack for Heatup/Cooldown INPUT DATA Initial Flaw Size: Distance to base metal: 2.033 in.

Allowance for crack growth: 0.040 in.

Total depth, a= 2.073 in.

Material Data: Reference temp., RTndt = -60 OF Upper shelf toughness = 200 ksi'!in Transition temperature = 121.6 OF Kia = 26.8 + 12.445 exp[ 0.0145 (T - RTndt )

Stresses:

Loading Conditions SS CD SS+CD Temperature (°F) 565 565 565 Yield Strength (ksi) 42.4 42.4 42.4 Pressure (ksi) 2.235 2.235 2.235 Kia (ksi'lin)

Position 200 200.0 200.0 x Hoop Stress (in.) (ksi) (ksi) (ksi)

Toe of the fillet 0.0000 50.014 7.485 57.499 0.2980 61.709 6.461 68.170 0.5950 73.123 5.493 78.616 0.8920 71.136 4.576 75.712 1.1890 74.007 3.710 77.717 1.4860 57.094 2.895 59.989 1.7830 24.199 2.130 26.329 Butter/Head Interface 2.0330 3.862 1.526 5.388 2.2460 40.983 1.039 42.022 SS = Steady State CD = Cooldown Page 23

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart Table 6-1: LEFM Evaluation of BMI Nozzle Corner Crack for Heatup/Cooldown (Continued)

STRESS INTENSITY FACTOR Kl(a) = [0.706(Ao+A,) + 0.537(2a/7t)A 1 + 0.448(a 2/2)A2 + 0.393(4a 3/37r)A 3 ]

where the through-wall stress distribution is described by the third order polynomial, S(x) = A0 + Ajx + A2x 2 + A3x3, defined by:

Loading Stress Conditions Coeff. SS CD SS+CD (ksi) (ksi) (ksi)

A3 30.808 -0.002 30.806 A2 -127.324 0.296 -127.027 A1 122.528 -3.525 119.003 A0 43.826 7.485 51.311 Effective crack size:

2 ae = a + 1/(6rc)*[Kl(a)/Sv]

Effective stress intensity factor:

KI(ae) = [ 0.706(Ao+Ap) + 0.537(2aeli)Aj + 0.448(ae 2/2)A 2 + 0.393(4ae3/37t)A 3 ]

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section Xl Analysis for Restart Table 6-1: LEFM Evaluation of BMI Nozzle Corner Crack for Heatup/Cooldown (Continued)

FRACTURE TOUGHNESS MARGINS Final Flaw Size: a = 2.0730 in.

Margin = Kia / Ki(ae)

Loading Conditions SS CD SS+CD Fracture Toughness, 200 200.0 200.0 Kia ksiin KI(a) 108.63 11.86 116.46 ksi'in ae 2.4212 2.0771 2.4733 in KI(ae) 109.44 11.86 117.37 ksi'in Actual Margin 1.83 16.86 1.70 Required Margin 3.16 3.16 3.16 Page 25

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section Xl Analysis for Restart 6.2 EPFM Evaluation Because the EPFM methodology applies different safety factors to the primary (pressure) and secondary contributions of the total stress intensity factor, is necessary to separate the total stress intensity factor to its primary and secondary contributions. The pressure stress intensity factor (KIp) is calculated using the closed form solution used in this document as

_=J x [o.7o6x(A 0 +A)]

Where a is the crack depth, A0 is the hoop stress with stress concentration due to the hole, Ap is the term used to account for crack face pressure (pressure value is used). A0 is evaluated using the equation below.

= Rm AD = SCFxP x-2xt Where SCF is stress concentration factor (a value of 2 is used for a hole in a flat plate under biaxial stress filed), P is the applied pressure, Rm is the mean radius, and t is the thickness. Substituting into the above equation 96.6 A0 = 2 x 2235 9 = 33215-5 psi 2 x 6.5 Substituting into Kip equation Kip = ýrx 2073 x [0.706x (33215.5 + 2235)] = 63870-8 psi Fm Once Kip is known then the secondary stress intensity factor (Kis) can be evaluated as KIS = KI p where K, is the total stress intensity factor.

Table 6-2 contains the EPFM evaluation. The J-T diagram is shown in Figure 6-1.

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section Xl Analysis for Restart Table 6-2: EPFM Evaluation of BMI Nozzle Corner Crack for Heatup/Cooldown EPFM Equations: Jrmt = CA~ C= 7.68 2 m=

Tt= (E/a )-CM(Aa)r"l 0.45 Japp = [Kl'(ae)] 2/E' Tapp = (E/cyf 2)*(dJappda)

Ductile Crack Growth Stability Criterion: Tap < Tret At instability: Tapp --- Tmat Safety Factors Kl*p KI s Kl*(a) ae Kl'(ae) Japp Tapp Stable?

Primary Secondary (ksiqin) (ksiin) (ksi'in) (in.) (ksi'in) (kips/in) 1.00 1.00 63.870 52.592 116.462 2.4733 127.209 0.533 1.897 Yes 2.00 1.00 127.740 52.592 180.332 3.0326 218.114 1.568 5.576 Yes 3.00 1.50 191.610 78.887 270.497 4.2322 386.498 4.924 17.508 Yes 5.00 1.00 319.350 52.592 371.942 6.1554 640.920 13.539 48.146 No 7.00 1.00 447.090 52.592 499.682 9.4411 1066.361 37.479 133.278 No Iterate on safety factor until Tapp = Tt to determine Jinstbiy:

Jmnstability Tapp Trt 2.6589 2.6589 169.824 139.836 309.660 4.9027 476.213 7.475 26.580 26.580 at Jnt = 4.924 kips/in, Tra,= 43.915 ( Tapp - Tat = 0.000 Applied J-Integral Criterion: Japp J0.1 where, J0.1 = Jrt at a = 0.1 in.

Safety Factors Kl*p KIls Kl*(a) a, Kl'(a.) Japp JO. 1 OK?

Primary Secondary (ksi'/in) (ksi'/in) (ksi'in) (in.) (ksi',in) (kips/in) (kips/in) 1.50 1.00 95.805 52.592 148.397 2.7229 170.073 0.953 2.701 Yes

  • Note that the value of the Young's Modulus (E) at 565 TF from Reference [8] is 27610 ksi.

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section Xl Analysis for Restart Figure 6-1: J-T Diagram 10 9

8 7

6 0~

5 0) 0 5 10 15 20 25 30 35 40 45 50 Tearing Modulus Page 28

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI -Nozzle Repair - Section Xl Analysis for Restart 6.3 Primary Stress Check The flaw acceptable criterion of IWB-3610(d)(2) requires that a the primary stress limits of NB-3000 be satisfied assuming a local area reduction of the pressure retaining membrane that is equal to the area of the flawed material.

This primary stress check can be met by satisfying the reinforcement requirements of NB-3332 for openings in shells and formed heads since these requirements provide for adequate compensation for material removed from the pressure boundary, in a similar fashion to the area of degraded material associated with a postulated or detected flaw.

The Section III based justification for continued operation [13] provides a reinforcement calculation for the PVNGS3 lower head considering the enlarged opening at penetration #3. Per NB-3335 both the original J-groove and repair weld may be counted for the area of reinforcement. NB-3336 requires the area of the reinforcement be multiplied by the ratio of the design stress intensity (Sm) of the reinforcement material to the design stress intensity of the removed material. The repair weld material Sm is equal to the Sm for the original J-groove weld and the area of the repair J-groove weld and weld pad is obviously greater than the area of the original J-groove weld and butter. Since the repair weld and weld pad were not considered in satisfying the reinforcement requirements of NB-3332, the additional reinforcement provided by the repair weld and weld pad may be used to implicitly satisfy the primary stress check of JWB-3610(d)(2).

7.0

SUMMARY

OF RESULTS AND CONCLUSIONS Linear-elastic and elastic-plastic fracture mechanics has been used to evaluate a postulated radial flaw in the remnant J-groove weld and butter of a BMI nozzle reactor vessel bottom head penetration after repair. It is determined that the flaw size would remain acceptable after one fuel cycle, as summarized below.

7.1 Summary of Results Flaw Sizes Initial flaw size, ai = 2.033 in Assumed Flaw Extension, Aa = 0.040 in Final flaw size, af = 2.073 in Operating Conditions Temperature, T =565 'F Material tearing modulus, Tmat = 26.580 Material J-integral at 0. 1" crack extension, Jo1 = 2.701 kips/in Safety factors (primary/secondary), SF = 3 / 1.5 Applied tearing modulus (.<.Treat) Tapp = 17.508 Safety factors (primary/secondary), SF= 1.5/1 Applied J-integral (< J0 1. ) Japp = 0.953 kips/in Page 29

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section Xl Analysis for Restart 7.2 Conclusion Based on a combination of linear elastic and elastic-plastic fracture mechanics analysis of a postulated flaw in the original Alloy 182 J-groove weld and butter material, the Palo Verde Nuclear Generation Station, Unit 3 (PVNGS3) reactor vessel bottom head (RVBH) is considered to be acceptable for one fuel cycle following the proposed repair.

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ARE VA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart

8.0 REFERENCES

References identified with an (*) are maintained within [PVNGS3] Records System and are not retrievable from AREVA Records Management. These are acceptable references per AREVA Administrative Procedure 0402-01, . See page [2] for Project Manager Approval of customer references.

1. AREVA Document 08-9212780-001, "Palo Verde Unit 3 Reactor Vessel Bottom Mounted Instrument Nozzle Modification."
2. AREVA Document 51-5012047-00, "Stress Corrosion Cracking of Low Alloy Steel."
3. *Document N001-0301-00633, Revision 0, "Boat Sample Extraction General Layout Drawing.". OEM Doc No. BBE-2205, Rev. 0.
4. Cases of ASME Boiler and Pressure Vessel Code, Code Case N-749, "Alternative Acceptance Criteria for Flaw in Ferritic Steel Components Operating in the Upper Shelf Temperature Range,"Section XI, Division 1, Approval Date: March 16, 2012.
5. Marston, T.U., "Flaw Evaluation Procedures- Background and Application of ASME Section XI, Appendix A," EPRI Report NP-719-SR, August 1978.
6. T.L. Anderson, Fracture Mechanics: Fundamentals and Applications, CRC Press, 1991.
7. *Dominion Engineering, Inc., Calculation No. C-7789-00-2, Revision No. I "Palo Verde Bottom Head Instrumentation Nozzle Stress Analysis."
8. ASME Boiler and Pressure Vessel Code,Section III, Subsection NB, 1971 Edition, through Summer 1973 Addenda.
9. ASME B&PV Code Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components",

2001 Edition, including Addenda through 2003."

10. NUREG-0744, Vol. 2, Rev. 1, "Resolution of the Task A-Il Reactor Vessel Materials Toughness Safety Issue," Appendix D, Materials Toughness Properties, Division of Safety Technology, Office of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, D.C. 20555, October 1982.
11. *Report N001-0301-00214, Revision 007, "Reactor Vessel, Unit 3, Analytical Report, V-CE-30869, 30AU84."

12 AREVA Document 32-5027942-002, "STP-1 BMI Nozzle Original J-Groove Weld Flaw Evaluation."

13. AREVA Document 32-9212915-001, "Palo Verde Unit 3 - Instrument Nozzle Repair Section III One Cycle Justification."

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart APPENDIX A: COOLDOWN STRESS ANALYSIS A.1 Purpose The purpose of the analysis in this appendix is to determine the maximum hoop thermal stress in the Palo Verde reactor vessel lower head developed during cooldown transient.

A.2 Methodology

1. Generate a 2D axisymmetric finite element model to simulate a simplified reactor vessel lower head with an inner radius of 93.3 inches and a thickness of 6.5 inches (Reference [A. ]);
2. Perform thermal transient analysis for cooldown condition to determine the temperature field of the reactor vessel lower head,
3. Get temperature field and thermal gradients for each time point;
4. Identify maximum thermal gradient across thickness and the time point of its occurrence;
5. Perform structural analysis, using temperature field identified in Step 4, to determine the thermal stress distribution through the thickness of the head.

A.3 Assumptions

1. The finite element model represents a perfect hemisphere. Any feature other than the sphere portion of the base metal of the lower head, such as cladding, weld, and penetration elements are not included;
2. The fluid temperature data during cooldown transient are taken from Figure 2 of Reference [A.2]. It has an approximately 100 °F/hr temperature drop rate;
3. The initial condition of the lower head is assumed to be a uniformly distributed temperature of 565 'F.

A.4 Material Properties Per Reference [A.l], the material of the reactor vessel lower head is SA-533 Gr. B Class 1 (C-Mn-Mo-0.4-0.7Ni).

The material properties are taken from Reference [A.3] except the material densities are taken from Reference

[A.5].

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart Table A-i: Material Properties Modulus of Thermal Thermal Specific Heat Density Temp. Elasticity Expansion Conductivity (k) (C) (p)

Coefficient (u)(C()

OF x 106, psi x10-6, 1/-F Btu/hr-in-0 F Btu/lb-0 F lb/in3 100 29.80 6.13 2.5833 0.1147 0.2839 200 29.50 6.38 2.5000 0.1169 0.2831 300 29.00 6.60 2.4250 0.1210 0.2823 400 28.60 6.82 2.3417 0.1251 0.2817 500 28.00 7.02 2.2667 0.1292 0.2809 600 27.40 7.23 2.1833 0.1333 0.2802 700 26.60 7.44 2.1083 0.1393 0.2794 Reference [A.3] [A.3] [A.3] Calculated" [A.5]

Note: *C= K/(p" Td), where Tais thermal diffusivity from the same source as thermal conductivity (k in the table).

A.5 Finite Element Model and Boundary Conditions and Results Definition of the reactor coolant temperature history for cooldown transient is listed in Table A-2 (Reference

[A.2]). The temperature data is input as bulk temperatures of the inner surface of the head in the thermal transient analysis.

Table A-2: Reactor Coolant Temperature during Cooldown Transient Time (hr) 0 4.8 8.0 Reactor Coolant Temperature (F) 565 70 70 A convection coefficient of 1000 Btu/hr-ft2-°F is applied on the inner surface of the base metal of the head. This value is based on experiences from similar projects performed in the past. The convection coefficient on the outer surface of the lower head is assumed to be 0.150 Btu/hr-ft2-'F and the ambient air temperature is assumed to be 70'F during cooldown. The lower head is assumed to be initially under uniformly distributed temperature of 565 0F.

Figure A-I shows Finite element model boundary conditions and the temperature field. Figure A-2 shows the history of temperature vs. time and the history of temperature gradient between inside and outside surface of the head vs. time. Note that curves identified with TEMPI, TEMP_2 and TEMP_3 in the left graph of this figure are temperature histories for node located on inner surface, at depth of 1.5 inches from inner surface, and on outer surface. Figure A-3 shows radial and hoop thermal stresses in the lower head at the maximum temperature difference time point during cooldown transient (at time of 1.31343 hours). Table A-3 lists radial and hoop thermal stresses in a path across the thickness of the lower head (path is shown in Figure A-1). Figure A-4 provides graphs for the thermal stresses vs. depth from ID to OD of the lower head. Figure A-5 shows the temperature vs. depth from ID to OD.

It is seen that the maximum hoop thermal stress on the inner surface of the lower head during Cooldown transient is about 7.5 ksi.

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart Figure A-i: Finite Element Model, Boundary Condition (Left) and Temperature field (Right)

AN AN

%%WJ VAm Tim TIM Figure A-2: Temperature vs. Time (Left) and Temperature Difference vs. Time (Right)

Note: TEMPI, TEMP_2, and TEMP 3 represents locations at inner surface, 1.5 inches from the inner surface, and the outer surface of the lower head, respectively.

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart XB0 14.0 NV0 14.0 CCT28 2013 =rY28 2013 11:48: 13 11:48.21 6129 MD. 1 PLOWND. 1 0UPAL06WrEclO N29L SOUMMl 926-1 T0B-1 RSS-1 OW :28237

-. ICK -. 260237 SN6 -. 004827 5W -3521.6 SN--3521.6 OW -190.635 5N4 -7485.09 SXB-090 635 566-7485 08

-3521 6

  • 211859
  • 2298663 42 367 -1075.67 63.5481 147.297 847292- 1370 26 105 91 2593 22 19 127.091 3816.

50m* 15 148 272 169 454 6M6212 190 635 7485.08 I pn ture Ogy onl L Mtue odyI Figure A-3: Thermal Stress in Radial (Left) and Hoop (Right) Directions Note: Thermal stresses are calculated based on temperature field at the time point, during cooldown transient, with maximum temperature difference between ID and OD of the lower head.

Table A-3: Maximum Thermal Stresses in Lower Head during Cooldown Transient Palo Verde (Ri-93.35", Thk*-6.5") .....

Depth from IDto OD Temperatur (F) SX'* (psi) SY*(psi), SZ* (psi) 0.0 433.26 2 7485 0.5 438.58 72 5797 1.0 443.46 124 4255 1.5 447.90 160 2858 2.0 451.90 182 1604 2.5 455.46 191 491 3.0 458.59 189 -482 3.5 461.29 177 -1317 4.0 463.57 158 -2015 4.5 465.42 133 -2579 5.0 466.85 103 -3009 5.5 467.86 70 -3309 6.0 468.46 35 -3479 6.5 468.66 0 -3522 Note:

  • The stresses are under spherical coordinate system. SX represents the stress in radial direction, and SY and SZ represent the stresses in the hoop directions.

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart Radial and Hoop Stresses vs. Depth from IDto OD

-40.m-Palo Verde (Ri=9335", Thk=6.5") SK 250 SX (Radial Stress) --- Palo Verde (Ri=93.35', Thk=6.S5) SY 201)0 r,-4160D0j ri 1so 00 o -6oo 42000

_ _ _ _ _6000 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 Depthfrom IDt OD (In)

Figure A-4: Thermal Stress in Radial (Left) and Hoop (Right) Directions vs. Depth from ID to OD Note: Thermal stresses are calculated based on temperature field at the time point, during cooldown transient, with maximum temperature difference between ID and OD of the lower head.

Temperature vs. Depth from IDto OD 475.00 470.00 _

465.0_

460.00 ___ ___ ___

  • 455.00 450100 /

-w- Palo Verde (Ri=93.35", Thk=6.5S) Temp. (F) 445.00 ___le 440.00 /

435.00f _

430.00 0.0 0.S 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 Ditance fhmn ID to OD (In)

Figure A-5: Temperature vs. Depth from ID to OD Page 36

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AREVA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section Xl Analysis for Restart A.6 Hardware, Software and Computer Files A.6.1 Hardware and software The EASI listed computer program ANSYS Release 14.0 (Reference [A.4]) is used in this calculation.

Verification tests of similar applications are listed as follows:

" Error notices for ANSYS Release 14.0 are reviewed and none apply for this analysis.

" Computer hardware used:

o Dell Precision (Computer Name: MOCAO2, Service Tag #: 5VKT5S1) with Intel CoreTM i7-2640M CPU @ 2.80GHz, 2.80 GHz, 8.00 GB of RAM and Operating System is Microsoft Windows 7 Enterprise Version 2009 Service Pack 1.

o Name of person running tests: Jasmine Cao

  • Date of tests:

o October 27, 2013 on computer "MOCAO2" (Service Tag #: 5VKT5S1)

  • Acceptability: Results shown in files vm5.out and vm28.out show that the test runs are acceptable.

A.6.2 Computer Files The computer files for this evaluation are stored in the ColdStor under /cold/General-Access/32/32-9000000/32-9212942-000/official directory. The computer files are listed below:

Table A-4: Computer Files File Name Time and Date File ColdStor Storage Date File Size Checksum Modified and Time CD tr.inp Oct 21 2013.17:05:53 Oct 30 2013 15:18:01 1299 25823 SA533_TypeB_Class2_ASME_1971.mp Oct 28 2013 11:20:45 Oct 30 2013 15:18:04 1773 50847 postjpv.out Oct 28 2013 11:45:14 Oct 30 2013 15:18:01 13978 34722 poststress.inp Oct 27 2013 12:47:46 Oct 30 2013 15:18:02 800 11532 pv st studydiff Ri.inp Oct 28 2013 09:39:24 Oct 30 2013 15:18:02 2864 05548 rpv_pv.out Oct 28 2013 11:45:08 Oct 30 2013 15:18:03 1076520 31094 vm28.out Oct 27 2013 12:17:36 Oct 30 2013 15:18:04 18528 26608 vm5.out Oct 27 2013 12:17:39 Oct 30 2013 15:18:05 40368 37793 Page 37

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ARE VA Document No. 32-9212942-001 Palo Verde Unit 3 BMI Nozzle Repair - Section XI Analysis for Restart A.6.3 References for Appendix A References identified with an (*) are maintained within [PVNGS3] Records System and are not retrievable from AREVA Records Management. These are acceptable references per AREVA Administrative Procedure 0402-01, Attachment 8. See page [2] for Project Manager Approval of customer references.

[A.1 ]. *Report NOO1-0301-00214, Revision 007, "Reactor Vessel, Unit 3, Analytical Report, V-CE-30869, 30AU84."

[A.2]. *Customer Document, N001-0301-00006, OEM Document No. 00000-PE-1 10, Rev. 05, B3, OEM Title "General Specification for Reactor Vessel Assembly."

[A.3]. ASME Boiler and Pressure Vessel Code,Section III, Subsection NB, 1971 Edition, through Summer 1973 Addenda.

[A.4]. ANSYS Finite Element Computer Code, Version 14.0, ANSYS Inc., Canonsburg, PA.

[A.5]. AREVA Document NPGD-TM-500 Rev. D, "NPGMAT, NPGD Material Properties Program, User's Manual (03/1985)"

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