ML101400406
| ML101400406 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 05/11/2010 |
| From: | Killian D, Noronha S, Wiger T AREVA NP |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| L-10-143, TAC ME3703 32-9136508-002 | |
| Download: ML101400406 (60) | |
Text
ENCLOSURE B DB-1 CRDM NOZZLE J-GROOVE WELD FLAW EVALUATION FOR IDTB REPAIR (NONPROPRIETARY VERSION)
AREVA CALCULATION 32-9136508-002 Fifty-Nine Pages Follow
Controlled Document 0402-01-FOl (20697) (Rev. 014;,04/13/2009)
A CALCULATION
SUMMARY
SHEET (CSS)
AREVA Document No.
32 9136508 002 Safety Related: [
Yes []No Title DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair PURPOSE AND
SUMMARY
OF RESULTS:
Purpose This document is a non-proprietary version of AREVA NP Document 32-9134664-003. The AREVA NP proprietary information removed from 32-9134664-003 is indicated by a pair of braces "{
}".
The purpose of the present analysis is to determine from a fracture mechanics viewpoint the suitability of leaving degraded J-groove weld and butter material in the Davis Besse Unit 1 reactor vessel head following the repair of a Control Rod Drive Mechanism (CRDM) nozzle by the ID temper bead weld procedure. It is postulated that a small flaw in the head would combine with a large stress corrosion crack in the weld and butter to form a radial corner flaw that would propagate into the low alloy steel head by fatigue crack growth under cyclic loading conditions.
The purpose of Revision 2 is to change the full load core exit temperature to {
} OF.
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, a Davis Besse Unit 1 CRDM nozzle is considered to be acceptable for at least 4 years of operation following an IDTB weld repair. The controlling loading condition was determined to be the rod withdrawal transient, for which it was shown that with safety factors of 3 on primary loads and 1.5 on secondary loads that the applied tearing modulus (11.63) was still less than the tearing modulus of the low alloy steel head material (12.88).
- This document consists of pages 1 - 46, A-i, B B-3, C C-4, D D-3, and E E-2.
THE DOCUMENT CONTAINS ASSUMPTIONS THAT SHALL BE THE FOLLOWING COMPUTER CODES HAVE BEEN USED IN THIS DOCUMENT:
VERIFIED PRIOR TO USE CODENERSION/REV CODENERSION/REV YES ANSYS/10/0 NO AREVA NP Inc., an AREVA and Siemens company Page 1 of 59.*
A AREVA AREVA NP fnc.,
an AREVA and Siemens company Controlled Document 0402-01-FOl (20697) (Rev. 014, 04/13/2009)
Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Review Method: P\\] Design Review (Detailed Check)
I-Alternate Calculation Signature Block PIR/A Name and Title and Pages/Sections (printed or typed)
Signature LP/LR Date Prepared/ReviewedlApproved D. E. Killian P
.All Technical Consultant S. J. Noronha R
All Engineer IV T. M. Wiger A
All Unit Manager 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)
Sig t e Date R. J. Baker, Jr.
Project Manager L 4 44:
Mentoring Information (not required per 0402-01)
Name Title Mentor to:
(printed or typed)
(printed or typed)
(PIR)
Signature Date N/R Page 2
Controlled Document A,
AREVA AREVA NP Inc..
en AREVA abd Siemensicom!panY 0402-01-F01 (20697) (Rev. 014,. 04/13/2009)
Document No. 32-90 36508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Record of RevisiOn Revision PageslSectionsl NO.
PWe Paragraphs, Changed Brief Description i
Change Authorization 000 04/2010 All Originalc release 001 04/2010 Throughout Changed indicator for proprietary information from square brackets (
])to braces({
}"
002 05/2010 Pages 25-26, 30, 32-Calculations modified to reflect a full load core exit 46, B-I - B-3, D-2, D-3, temperature of O F E-1 Page 3
Controlled Document A
AR VA Document No. 32-9136508-002 AREVA NP Inc.,
an AREVA and Siemens company DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Table of Contents Page SIGNATURE BLOCK................................................................................................................................
2 RECORD OF REVISION..........................................................................................................................
3 LIST OF TABLES.....................................................................................................................................
6 LIST OF FIGURES...................................................................................................................................
7
1.0 INTRODUCTION
...... I...8...........................8 2.0 ANALYTICAL METHODOLOGY.............................................................................................
11 2.1 Stress Intensity Factor Solution...................................................................................
13 2.1.1 Finite Element Crack Model........................................................................................
13 2.1.2 Stress Mapping............................................................................................................
13 2.1.3 Crack Growth Considerations......................................................................................
15 2.1.4 Plastic Zone Correction...............................................................................................
15 2.2 Linear-Elastic Facture Mechanics.............................................................................................
16 2.3 Elastic-Plastic Facture Mechanics.............. w..............................................................................
16 2.3.1 Screening Criteria.......................................................
16 2.3.2 Flaw Stability and Crack Driving Force...........................................................................
16.
3.0 ASSUM PTIONS..................................
- ........................................................................................ 19 3.1 Unverified Assumptions....................................
.................... t........................................................
19 3.2 Justified Assumptions......................
19 3.3 Modeling Simplifications............................................................................................................
19 4.0 DESIGN INPUTS........................................................................................................................
20 4.1 Materials.........................................................................................................................................
20 4.1.1 Mechanical and Thermal Properties............................................................................
20 4.1.2 Reference Temperature..............................................................................................
22 4.1.3 Fracture Toughness...................................................
22 4.1.4 J-integral Resistance Curve................
22......................
22 4.1.5 Fatigue Crack Growth Rate.......................................
- ..................................................... 24 4.2 Basic Geometry...........................
25 4.3 Operating Transients..................
25 4.4 Applied Stresses............................................................................................................................
26 Page 4
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Table of Contents (continued)
Page 4.4.1 Residual Stresses......................................................................................................
26 4.4.2 Operational Stresses...............................................................................
26 5.0 CALCULATIONS............................................................
,........................................................... 31 5.1 Fatigue C rack G row th....................................................................................................................
31 5.2 LE FM Flaw Evaluations..................................................................................................................
35 5.3 EPFM Flaw Evaluations.................................................................................................................
36 6.0
SUMMARY
OF RESULTS AND CONCLUSIONS...................................................................
44 6.1 Summary of Results 4......................
6.2 C o nclusio n............................................................................................................................
.......... 44
7.0 REFERENCES
45 APPENDIXA: ' VERIFICATION OF COMPUTER CODE ANSYS.....................................
............................ A-1 APPENDIX B:
COMPUTER FILES IN COLDSTOR.................... !.................................................................... B-1 APPENDIX C:
FINITE ELEMENT CRACK MODEL........................................
C-1 APPENDIX D:
FINITE ELEMENT STRESS MODEL...............................................................................
D-1 APPENDIX E:
STRESS INTENSITY FACTOR DUE TO PRESSURE............................................................
E-1 Page 5
Controlled Document A
AREVA AREVA NP Inc.,,
an AREVA and Siemens _company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Table 1-1:
Table 4-1:
Table 4-2:
Table 4-3" Table 4-4:
Table 5-1:
Table 5-2:
Table 5-3:
Table 5-4:
List of Tables Page Safety Factors for Flaw Acceptance..................................................................................
9 M aterial Properties for Head............................................................................................
20 Material Properties for Weld Metal...............................................
21 Material Properties for Cladding.........................................
21, Transient Analysis Time Points for Operational Stresses.................................................
30 Flaw Growth and LEFM Evaluation.......................................
32 EPFM Evaluation for Shutdown Conditions....................................................................
38 EPFM Evaluation for Heatup/Cooldown with Reactor Trip.......................
39 EPFM Evaluation for Rod Withdrawal Accident..............................................................
40 Page 6
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Figure 1-1:
Figure 2-1:
Figure 2-2:
Figure 4-1:
Figure 4-2:
Figure 4-3:
Figure 4-4:
Figure 4-5:
Figure 5-1:
Figure 5-2:
Figure 5-3:
List of Figures Page ID Temper Bead Weld Repair........................................................................................
10 Postulated Radial Flaw on Uphill Side...........................................................................
12 Finite Element Crack Model................................................
...................................... 14 Correlation of Coefficient, C, of Power Law with Charpy V-Notch Upper Shelf Energy...... 23 Correlation of Exponent, m, of Power Law with Coefficient, C, and Flow Stress, a0..... 23 DEI Finite Element Stress Model....................................................................................
27 DEI Finite Element Stress Model - Weld Region...........................................................
28 Finite Element Stress Model for Operational Stresses...................................................
29 J-T Diagram for Shutdown Conditions...........................................................................
41 J-T Diagram for Heatup/Cooldown with Reactor Trip.....................................................
42 J-T Diagram for Rod Withdrawal Accident....................................................................
43 Page 7
Controlled Document A
ARE VA Document No. 32-9136508-002 AREVA NP Inc.,
an AREVA and Siemens company DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair
1.0 INTRODUCTION
A March 2010 inspection of Alloy 600 control rod drive mechanism (CRDM) nozzles in the reactor vessel closure, head (RVCH) at Davis Besse Unit 1 revealed defects in several nozzles and nozzle-to-RVCH partial penetration welds, along with evidence of leakage as manifested by deposits of boric acid crystals on the outer surface of the head. The original RVCH at Davis Besse Unit 1 (DB-1) was replaced in 2002 with the closure head from a suspended Midland plant owned by Consumers Power Company. It is currently believed that the leakage in the DB-1 RVCH was caused by primary water stress corrosion cracking (PWSCC) of the susceptible Alloy 600 nozzles and Alloy 182 welds.
Degraded nozzles at DB-1 are to be repaired using an inside diameter temper bead (IDTB) welding procedure wherein the lower portion of a nozzle is removed by a boring procedure and the remaining portion of the nozzle is welded to the low alloy steel reactor vessel head above the original Alloy 182 J-groove attachment weld, as shown in Figure 1-1. The repair is more fully described by the design drawing [1] and the design specification [2]. Although the remnant J-groove weld would no longer be associated with the primary pressure boundary, a defect in the weld could grow into the low allow steel RVCH and thereby impact the structural integrity of the remaining pressure boundary. Since a potential, or even detected, flaw in the J-groove weld can not be sized by currently available non-destructive examination techniques, it is assumed that the "as-left" condition of the remnant J-groove weld includes degraded or cracked weld material extending through the entire J-groove weld and Alloy 182 butter material.
Since it is known from analysis of the original Davis Besse Unit 1 CRDM reactor vessel head nozzle penetrations [3] that the hoop stress in the J-groove weld is greater than the axial stress at the same location, the preferential direction for cracking would be axial, or radial relative to the nozzle. Reference 3 also demonstrates that stresses tend to be higher on the uphill side of the nozzles than on the downhill side. It is postulated that a radial crack in the Alloy 182 weld metal would propagate by PWSCC, through the weld and butter, to the interface with the head material, where it is fully expected that such a crack would then blunt, or arrest, as discussed in Reference 4 for interfaces with low alloy steels. Since the height of the weld and butter along the bored surface is about 2" on the uphill side of the outermost CRDM nozzle, a radial crack depth extending from the corner of the weld to the low alloy steel head would be very deep. 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 flaw that would 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.
Key features of the fracture mechanics analysis are:
This analysis applies specifically to the CRDM nozzle penetrations in the Davis Besse Unit 1 reactor vessel closure head. A Ji-integral resistance curve is developed based on estimates of the Charpy V-notch upper-shelf energy for the DB-1 head plate material.
Flaw growth is calculated for a 4 year period of operation, corresponding to 2 fuel cycles.
Flaw acceptance is based on the available fracture toughness and ductile tearing resistance of the RVCH material considering the safety factors listed inTable 1-1.
Page 8
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Table 1-1: Safety Factors for Flaw Acceptance Linear-Elastic Fracture Mechanics Operating Condition Evaluation Method Fracture Toughness / K, Normal/Upset Kla fracture toughness 10= 3.16 Emergency/Faulted Kic fracture toughness 42 = 1.41 Elastic-Plastic Fracture Mechanics Operating Condition Evaluation Method Primary Secondary Normal/Upset J/T based flaw stability 3.0 1.5 Normal/Upset J 0.1 limited flaw extension 1.5 1.0 Emergency/Faulted J/T based flaw stability 1.5 1.0 Emergency/Faulted J0.1 limited flaw extension 1.5 1.0 Page 9
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company.
Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair GR. B-CL. 1 ERNiCrFe-7A ALLOY 52M-STAINLESS STEEL
-CLADDING Figure 1-1: ID Temper Bead Weld Repair Page 10
Controlled Document A
AR EVA Document No. 32-9136508-002 AREVA NP Inc.,
an AREVA and Siemens company DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair 2.0 ANALYTICAL METHODOLOGY A radial flaw at the inside corner of non-radial head penetration is evaluated based on a combination of linear-elastic fracture mechanics (LEFM) and elastic-plastic fracture mechanics (EPFM), as outlined below.
- 1. Postulate a radial flaw in the J-groove weld, extending from the inside corner of the penetration to the interface between the butter and head, as shown in Figure 2-1 for the uphill side of the penetration. Previous analysis [5] has shown that even for large downhill welds, the controlling location is the uphill side of the penetration, due to higher stresses and the additional constraint provided by the acute angle between the material borders along the cladding and bore.
- 2. Develop a three-dimensional finite element crack model of the reactor vessel head in the vicinity of the outermost nozzle penetration, with crack tip elements along the interface between the Alloy 182 butter and the low alloy steel base metal. This crack model will be used to obtain stress intensity factors at various positions along the crack front for combined stresses due to J-groove welding, hydrostatic testing, nozzle removal, and transient loading conditions.
- 3. Develop a mapping procedure to transfer stresses from uncracked finite element stress analysis models (for residual and operational stresses) to the crack face of the crack model. This will enable stress intensity factors to be calculated for arbitrary stress distributions over the crack face utilizing the principle of superposition.
- 4. Calculate fatigue crack growth for cyclic loading conditions using combined residual and operational stresses from pressure and thermal loads. It is noted that the only effect of residual stress on fatigue crack growth is in the calculation of the R ratio, or Kmin/Kmax, which is the ratio of the minimum and maximum stress intensity factors for a pair of stress states. Starting from the stress intensity factor calculated by the finite element crack model for the initial flaw size, stress intensity factors are updated for each increment of crack growth by the square root of the ratio of the flaw sizes over the increment.
- 5. Utilize the screening criteria of ASME Code Section XI, Appendix H to determine the failure mode and appropriate method of analysis (LEFM or EPFM) for flaws in ferritic materials, considering 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, as discussed in Section 2.2. When the material is more ductile and EPFM is the appropriate analysis method, evaluate flaw stability and crack driving force as described in Section 2.3.
Page 11
Controlled Document A
AREVA AREVA NP Inc.,
an AREMVA and 81wmna cranwny Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Figure 2-1: Postulated Radial Flaw on Uphill Side Page 12
Controlled Document A
AR VA Document No. 32-9136508-002 AREVA NP Inc.,
an AREVA and Siemens company DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair 2.1 Stress Intensity Factor Solution Stress intensity factors for corner flaws at a non-radial nozzle penetration are best determined by finite element analysis using three-dimensional models with crack tip elements along the crack front.
Although loads can be applied to finite element crack models like any other structural model, the crack model was developed to serve as-a flaw evaluation tool that could accept stresses from separate stress analyses. This strategy makes it possible, for example, to obtain pressure and thermal stresses from an independent thermal/structural analysis and then transfer these stresses to a crack model for flaw evaluations. Using the principle of superposition common to fracture mechanics analysis, the only stresses that need be considered for these flaw evaluations are the stresses on the crack face. A mapping procedure is developed to transfer stresses from a separate stress analysis to the crack face of the crack model.
2.1.1 Finite Element Crack Model A three-dimensional finite element model is developed for the reactor vessel head in the vicinity of the outermost nozzle penetration, by modeling a portion of the head, cladding, and butter with the ANSYS finite element computer program [6]. Since stresses increase with penetration angle, it is conservative to base the model on the outermost nozzle penetration. Details of the finite element crack models are presented in Appendix A.
The three-dimensional finite element model is first constructed to represent an unflawed non-radial nozzle penetration in the reactor vessel head using the ANSYS SOLID95 20-node structural element.
Elements along the crack front are then replaced by a sub-model of crack tip elements along the interface between the Alloy 182 butter and the low alloy steel base metal. These elements consist of 20-node isoparametric elements that are collapsed to form a wedge with the appropriate mid-side nodes shifted to quarter-point locations to simulate a singularity at the crack tip. The final crack model is shown in Figure 2-2.
Stress intensity factors are obtained using the ANSYS KCALC routine at 10 positions along each crack front, as indicated in Figure 2-2. Position 1 in located on the cladding surface, Position 2 at the cladding/base metal interface, and Position 10 is at the bored surface in the head.
2.1.2 Stress Mapping Residual and operational stresses, obtained from separate finite element models, are mapped onto the crack face of the finite element crack model shown in Figure 2-2 to calculate the individual contributions to the stress intensity factors. A set of ANSYS parametric design language instructions (macro) has been written based on the *MOPERMAP command to transfer stresses by nodal interpolation from a dissimilar finite element model (e.g., residual stresses) to the crack model. Stresses from an identical finite element model (e.g., operational stresses), are simply copied from the stress model to the crack model.
Page 13
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and 81nauns company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Figure 2-2: Finite Element Crack Model Page 14
Controlled Document A
AR EVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair 2.1.3 Crack Growth Considerations The fundamental expression for the crack tip stress intensity factor is Ki = a Since the crack model is developed for a single flaw size, stress intensity factors are updated at each increment of crack growth by the square root of the flaw size; i.e.,
K,(a,÷l) = K,(a).!ai,
where a = flaw size i= increment of crack growth.
Since the stress intensity factor is directly proportional to the magnitude of the stress and both residual and operating stresses decrease in the direction of crack growth, this procedure produces conservative estimates of stress intensity factor as the crack extends into the head and stresses diminish over the expanding crack face.
2.1.4 Plastic Zone Correction The Irwin plasticity correction is used to account for a moderate amount of yielding at the crack tip. For plane strain conditions, this correction is
- 1 IK 1(a)2 6rn
[Ref. [7], Eqn. (2.63)]
where K1(a) = stress intensity factor based on the actual crack size, a Cy = material yield strength.
A stress intensity factor, K,(ae), is then calculated for an effective crack size, ae =a+rY, based on the same scaling technique utilized for crack growth; i.e.,
Kl(a.)= K (a) -
Page 15
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair 2.2 Linear-Elastic Facture Mechanics Article IWB-3612 of Section Xl [11] requires that the applied stress intensity factor, KI, 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 and upset conditions:
K I < K 1a / vri where KIa is the fracture toughness based on crack arrest.
Emergency and faulted conditions:
KI < K /-..2 where K1c is the fracture toughness based on crack initiation.
2.3 Elastic-Plastic Facture 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, whereas limit load analysis would be used to check for plastic collapse.
2.3.1 Screening Criteria Screening criteria for determining failure modes in ferritic materials may be found in Appendix H of Section X1. Although Appendix H, Article H-4200 [11] 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 head, as follows:
- Let, Kr' = Kiapp/ Kic SrI = amax / Of Then the appropriate method of analysis is determined by the following limits:
LEFM Regime:
EPFM Regime:
Limit Load Regime:
Kr'/ S," _1.8 1.8> Kr'/Sr' >0.2 0.2 > Kr'/Sr' 2.3.2 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 (Jmrt) J-integral, and T is the tearing modulus, defined as (E/a 2)(dJ/da). The crack driving force, as measured by Japp, 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 welded nozzles, Page 16
Controlled Document A
Document No. 32-9136508-002 ARE VA-AREVA NP Inc.,
an AREVA and Siemens company DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair 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 1 for primary and secondary stresses, respectively. For EPFM analysis of faulted conditions, safety factors of 1.5 and 1 will be used for flaw stability assessments and 1.5 and 1 for evaluations of crack driving force.
The general methodology for performing an EPFM analysis is outlined below.
Let E' = E/(1-v 2)
Final flaw depth = a Total applied KI = Kiapp Ki due to pressure (primary) = Kip (from Appendix B)
K, due to residual plus thermal (secondary) = Kj, = Kiapp - 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 ae = a + [1/(6n)] [ (Kip + KI.)
Cry ]a, which is used to update the stress intensity factors based on K1lp
= Kip e
Va and K'
= KI8 - a,
- aa The applied J-integral is then calculated using the relationship Japp = (SFp*K'Ip + SFs*K'is)2/E'.
The final parameter needed to construct the J-T diagram is the tearing modulus. The applied tearing modulus, Tapp, is calculated by numerical differentiation for small increments of crack size (da) about the final crack size (a), according to E Japp(a+da)-Jpp(a-da)1 Tapp =I 2 Lf 2(da)
Page 17
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Using the power law expression for the J-R curve, Jmat = C(Aa)m,
the material tearing modulus, Treat, can be expressed as Tmat = (E/af2)Cm(AajmT'.
Constructing the J-T diagram, Unstable Region Tapp _> 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.
Page 18
Controlled Document A
AREVA Document No. 32-9136508-002 AREVA NP Inc.,
an AREVA and Siemens company DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair 3.0 ASSUMPTIONS This section discusses assumptions and modeling simplifications applicable to the present evaluation of the DB-1 CRDM nozzle remnant flaw.
3.1 Unverified Assumptions There are no assumptions that must be verified before the present analysis can be used to support the CRDM nozzle IDTB repair at Davis Besse Unit 1.
3.2 Justified Assumptions The size of the J-groove weld prep and the thickness of the buttering are based on nominal dimensions. This is considered to be standard practice in stress analysis and fracture mechanics analysis. It is conservatively assumed that the postulated flaw extends through the entire J-groove weld and butter.
3.3 Modeling Simplifications The finite element computer models used to generate residual stresses and transient operational stresses do not include the ID temper bead repair weld. This is deemed to be an appropriate modeling simplification considering the very local effect of the repair weld on stresses in the J-groove weld.
Page 19
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair 4.0 DESIGN INPUTS This section provides basic input data needed to perform a fatigue crack growth analysis and a flaw evaluation of the final flaw size.
4.1 Materials 4.1.1 Mechanical and Thermal Properties Table 4-1, Table 4-2, and Table 4-3 list the temperature dependent values of modulus of elasticity (E),
Poisson's ratio (v), and coefficient of thermal expansion (a) properties used in the finite element crack models. These properties are obtained from a previous stress analysis model of the Davis Besse CRDM nozzle and reactor vessel head [8]. Mechanical properties for the low alloy steel head are also provided in Table 4-1, where the flow stress is the average of the yield and ultimate strengths. The yield and ultimate strength values are obtained from Supplemental Requirements for SA-533 Manganese-Molybdenum-Nickel Alloy Steel Plates in the 1968 original construction code [9].
Component Material RV head Cladding J-grqove weld filler J-groove weld butter SA-533 Grade B Class 1 [2]
Stainless steel (useType 316 properties)
Alloy 182 [2] (use Alloy 600 properties for SB-167)
Alloy 182 [2] (use Alloy 600 properties for SB-167)
Table 4-1: Material Properties for Head Component Head Material SA-533 Grade B Class 1 Temperature E (106 psi) v a (10-6 in./in./°F) c (ksi) au (ksi) caf (ksi) 70 29.00 0.29 7.06 50.00 80.00 65.00 100 29.00 0.29 7.06 50.00 80.00 65.00 200 28.50 0.29 7.34 47.15 76.45 61.80 300 28.00 0.29 7.43 45.25 76.40 60.83 400 27.40 0.29 7.58 44.50 76.40 60.45 500 27.00 0.29 7.70 43.20 76.40 59.80 600 26.40 0.29 7.83 42.00 76.40 59.20 700 25.30 0.29 7.94 40.60 76.40 58.50 Page 20
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Table 4-2: Material Properties for Weld Metal Component Weld Butter and Weld Filler Material Use Alloy 600 (SB-167)
Temperature E (106 psi) v a (10-6 in./in./°F) 70 30.82 0.3 6.90 100 30.82 0.3 6.90 200 30.20 0.3 7.20 300 29.90 0.3 7.40 400 29.50 0.3 7.57 500 29.00 0.3 7.70 600 28.70 0.3 7.82 700 28.20 0.3 7.94 Table 4-3: Material Properties for Cladding Component Cladding Material Use Type 316 (16Cr-12Ni-2Mo) Stainless Steel Temperature E (106 psi) v a (10.6 in./in.f°F) 70 28.14
-0.3 8.54 100 28.14 0.3 8.54 200 27.60 0.3 8.76 300 27.00 0.3 8.97 400 26.50 0.3 9.21 500 25.80 0.3 9.42 600 25.30 0.3 9.60 700 24.80 0.3 9.76 Page 21
Controlled Document A
AR VA Document No. 32-9136508-002 AREVA NP Inc.,
an AREVA and Siemena company DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair 4.1.2 Reference Temperature Based on a highest measured RTNOT of {
}, a value of { } OF will be used as a conservative estimate of the RTNDT for the SA-533, Grade B, Class 1 low alloy steel head material.
4.1.3 Fracture Toughness From Article A-4200 of Section Xl [11], the lower bound Kia fracture toughness for crack arrest can be expressed as Kia = 26.8 + 12.445 exp [0.0145 (T - RTNDT)],
where T is the crack tip temperature, RTNDT is the reference nil-ductility temperature of the material, Kia is in units of ksiIin, and T and RTNDT are in units of OF. In the present flaw evaluations, KIa is limited to a maximum value of 200 ksiq/in (upper-shelf fracture toughness). Using the above equation with an RTNDT of { ) OF, KIa equals 200 ksi*/in at a crack tip temperature of {
} OF.
A higher measure of fracture toughness is provided by the Kic fracture toughness for crack initiation, approximated in Article A-4200 of Section XI [11] by KI, = 33.2 + 20.734 exp [ 0.02 (T - RTNDT)].
4.1.4 J-integral Resistance Curve The J-integral resistance (J-R) curve, needed for the EPFM method of analysis, is obtained from the following power law expression for nuclear reactor pressure vessel steels [12],
JR = C(Aa)m,
where thecoefficient, C, and exponent, m, depend on the Charpy V-notch upper-shelf energy, CVN, and the flow stress, a, or af, as shown in Figure 4-1 and Figure 4-2.
An estimated value of the Charpy V-notch upper-shelf energy is available from a generic study of plate materials used in B&W fabricated reactor vessels [13]. This statistical analysis of {
} determined with a 95% confidence that at least 95% of the population exhibited upper-shelf energies exceeding a lower tolerance value of { } ft-lbs in the transverse (weak) direction.
Using the above referenced Charpy V-notch upper-shelf energy correlation for the J-integral resistance curve with a Charpy V-notch upper-shelf energy of { } ft-lbs, the coefficients of the power law are found to be:
C={
}
m={
}
Page 22
Controlled Document A
AREVA AREVA NP Inc.,
an ARE VA and Siemens -company.
Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair 15 10 C
I I
I I
I I
I TESTED AT 1.6T-CT IT-CT (0C)
A 120 a
- 150, o
150 170 0
o 200 0
0 go/4 0 0 0
,0 0
A 00 G&
.0 or 09-
- 1.
L I
ý5
.0-0.0 0.4 0.8 1.2 1.6 2.0 CVN/100 Figure 4-1: Correlation of Coefficient, C, of Power Law with Charpy V-Notch Upper Shelf Energy m
0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
0 2
4 6r 8
10
'2 14 16,
ýC+ 11.5(Th 20
' (0"0)
Figure 4-2: Correlation of Exponent, m, of Power Law with Coefficient, C, and Flow Stress, qo Page 23
Controlled Document A
AR EVA Document No. 32-9136508-002 AREVA NP Inc.,
an AREVA and Siemens company DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair 4.1.5 Fatigue Crack Growth Rate Flaw growth due to cyclic loading is calculated using the fatigue crack growth rate model from Article A-4300 of Section XI [11],
da dN where AKI is the stress intensity factor range in ksi*/in and da/dN is in inches/cycle. The crack growth rates for a surface flaw will be used for the evaluation of the comer crack since it is assumed that the degraded condition of the J-groove weld and butter exposes the low alloy steel head material to the primary water environment.
The following equations from Section Xl [11] are used to model fatigue crack growth.
AKI = Klmax -
Klmin R = Klmin / Klmax 0 *_ R *5 0.25:
AKI < 17.74, n = 5.95 C, = 1.02 x 10-12 X S S = 1.0 AKI _ 17.74, n = 1.95 Co = 1.01 x 10-7 X S S= 1.0 0.25*_< R _ 0.65:
AK, < 17.74 [ (3.75R + 0.06) (26.9R - 5.725) ]0.25 n =5.95 C = 1.02 x 10-12 x S S = 26.9R - 5.725 AKI _ 17.74 [ (3.75R + 0.06) (26.9R - 5.725) ]0.25, n = 1.95 Co = 1.01 x10 7 xS S = 3.75R + 0.06 0.65*< R < 1.0:
AKI < 12.04, n = 5.95 C. = 1.02 x 10-12 X S S = 11.76 AKI >,12.04, n = 1.95 Co = 1.01 x 10 7 x.S S = 2.5 Page 24
Controlled Document A
AR VA Document No. 32-9136508-002 AREVA NP Inc.,
an AREVA and Siemens company DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair 4.2 Basic Geometry The reactor vessel head and original CRDM nozzle penetration are described by the following key dimensions:
Radius to base metal
= {
} in. [14]
Head thickness (minimum)
= {
} in. [14]
Cladding thickness (nominal)
= {
} in. [15]
Butter thickness (nominal)
= {
} in. [16] or{
= {
} in. [16]
Penetration angle at outermost nozzle - {
} deg. [16]
Details of the CRDM nozzle penetration and J-groove weld are provided in the description of the finite element crack model in Appendix C.
4.3 Operating Transients The most significant normal and upset condition transients for fatigue crack growth may be combined into a 'full-range' transient comprised of heatup to 100% power (HU), a Type B reactor trip (RT), and subsequent normal cooldown (CD). Full-range transients are associated with operating events that include a zero state of stress. The reactor coolant functional specification [17] provides pressure and temperature time-histories for these transients, and lists 240 design cycles for the heatup/cooldown transient and {
} cycles for the Type B reactor trip. The temperatures for these design transients have been modified to reflect a reactor coolant fluid temperature under the closure head of {
} OF, based on a recent calculation to determine the DB-1 specific full load core exit temperature [18].
The rod withdrawal accident (RWA) upset transient was also selected since it experiences a high reactor coolant pressure of {
} psig. This is especially significant for EPFM flaw evaluations where primary pressure loads are subjected to higher safety factors than secondary thermal loads. Since it is not expected that a rod withdrawal accident will occur during a four year period of operation, the RWA transient is not included in the calculation of fatigue crack growth, but it is addressed when evaluating the acceptability of the final flaw size. Transient 11 of the functional specification represents this design transient as an in-surge to the pressurizer which is based on the event that results in the greatest RCS pressure and temperature change. This event is initiated from 15% power and results in a 550 psi increase in RCS pressure and a 15 OF increase in temperature. The transient is of short duration, lasting approximately 20 to 30 seconds, producing only a minimal increase in head temperature. The functional specification transient bounds the expected change in the RCS pressure and temperature from the same event if initiated from full power conditions. As provided in Figure 15.2.2-1 of the DB-1 UFSAR [19], a rod withdrawal event from full power results in an increase of only 30 psi and 1.5 OF.
The functional specification also specifies one emergency condition transient, a stuck open turbine bypass valve, and two faulted condition transients, a steam line break and a loss of coolant accident.
Appendix F of the Section III stress analysis for the CRDM nozzle IDTB weld repair [20] concludes that the stresses resulting from the emergency and faulted condition transients are bounded by those for the reactor trip transient. And since the safety factors on fracture toughness are higher for normal/upset conditions than for emergency/faulted conditions (Table 1-1), and the KI, fracture toughness for crack initiation is higher than the Ka fracture toughness for crack arrest (Section 4.1.3), it follows that the Page 25
Controlled Document A
AR vA Document No. 32-9136508-002 AREVA NP Inc.,
an AREVA and Siemens company DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair present flaw evaluations for normal/upset conditions also serve as a bounding analysis for emergency and faulted conditions. No further consideration of the emergency and faulted transients is therefore warranted.
4.4 Applied Stresses Two sources of applied stress are considered for the present flaw evaluations, residual stresses from welding and stresses that occur during normal operation.
4.4.1 Residual Stresses Residual stresses are obtained from a three-dimensional elastic-plastic finite element stress analysis performed by Dominion Engineering, Inc. [21]. Hoop stresses on the radial plane through the weld and butter are then mapped to the three-dimensional finite element crack model described in Section 2.1.1.
Hoop stresses are used since these stresses are perpendicular to the crack face and therefore open the crack.
The DEI analysis simulated welding of the J-groove buttering, a post-weld heat treatment, welding of the J-groove partial penetration weld at the outmost CRDM nozzle, hydrostatic testing, operation at steady state temperature and pressure conditions, return to zero load conditions, removal of the original nozzle (Time 11006), and a second application of steady state loads. It is known from previous analysis that stresses at the outermost CRDM nozzle location conservatively bound stresses at all other nozzle locations [3]. The residual stresses in the remnant J-groove weld and butter are obtained from the load step corresponding to Time 11006, prior to the return to operating conditions The DEI finite element model is shown in Figure 4-3, prior to removal of the CRDM nozzle. Figure 4-4 provides a closer view of the J-groove weld after the nozzle is removed.
4.4.2 Operational Stresses Operational stresses are obtained by linear-elastic stress analysis using the three-dimensional finite element crack model described in Section 2.1.1, but with displacements normal to the crack face constrained to zero. Hoop stresses on a radial plane through the weld and butter are then copied directly to the crack model to facilitate the calculation of stress intensity factors along the entire crack front. Stresses are developed for the combined heatup/reactor trip/cooldown and rod withdrawal transients discussed in Section 4.3 using the thermal and structural finite element models described in Appendix D.
Figure 4-5 illustrates the "uncracked" finite element model used to calculate nodal temperatures (transient thermal analysis) and stresses (static stress analysis). The thermal phase of the solution is driven by wetted surface loads developed from time-dependent bulk fluid temperatures and convective heat transfer (film) coefficients. The structural model is then loaded by internal pressure (surface load) and nodal temperatures (body force loads from the thermal solution) to determine stresses at various times, as listed in Table 4-4. The critical time points are selected only after calculating stress intensity factors for each set of stresses output from the stress analysis solution. This process serves to maximize the stress intensity factors used in the fatigue crack growth analysis and the final flaw evaluations. The time points selected for use in the subsequent fracture mechanics analyses are identified in Table 4-4 by alphanumeric symbols.
Page 26
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Figure 4-3: DEI Finite Element Stress Model Page 27
Controlled Document A
AREVA AREVA NP inc.,
an ARMVA ond Siemehnws c*-*a Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Figure 4-4: DEI Finite Element Stress Model - Weld Region Page 28
Controlled Document A
AREVA AMEVA NP Ine.
an AREVA awd Skwnws cmpany Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Figure 4-5: Finite Element Stress Model for Operational Stresses Page 29
Controlled Document A
ARE VA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for I.DTB Repair Table 4-4: Transient Analysis Time Points for Operational Stresses Load Time Temp.
Pressure Step (hours)
(F)
(psig)
Combined Heatup/Reactor Trip/Cooldown SD 1
Zero stress state 2
End of heatup ramp 3
After heatup ramp 4
Steady state at 8% power 5
End of power loading ramp (8%-100%)
6 After power loading ramp (8%-100%)
SS 7
Steady state at 100% power RT1 8
Reactor trip 10 Reactor trip 11 Reactor trip 12 Reactor trip RT2 13 Reactor trip 14 Reactor trip 15 Cooldown 16 Cooldown 17 Cooldown 18 End of cooldown ramp Rod Withdrawal Accident 1
RWA 2
Maximum pressure 3
4
- Symbols:
= Shutdown
= Steady State
= Reactor Trip time 1
= Reactor Trip time 2
= Rod Withdrawal Accident Page 30
Controlled Document A
ARE VA Document No. 32-9136508-002 AREVA NP Inc.,
on AREVA and Siemens company DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair 5.0 CALCULATIONS Propagation of a postulated initial flaw in the J-groove weld and butter is calculated to determine the final flaw size after a four year service interval. Flaw evaluations are then performed to assess the acceptability of the final flaw size.
5.1 Fatigue Crack Growth Although it is believed that a PWSCC flaw would be confined to the J-groove weld and butter, it is postulated that a fatigue flaw would initiate in the low alloy steel head, combine with the PWSCC flaw, and propagate farther into the head under cyclic loads. Fatigue crack growth is calculated from stress intensity factors derived from a finite element crack model using residual stresses from a DEI stress analysis [21] and operational stresses calculated herein. The actual flaw growth calculations are presented in Table 5-1, along with a comparison of the final stress intensity factor with the LEFM acceptance criteria for each of the five significant load steps identified in Table 4-4. This table therefore serves several purposes; it determines the final flaw size at the end the designated service interval, it compares stress intensity factors at the final flaw size with LEFM acceptance criteria, and it serves as a means of identifying the controlling load steps for EPFM evaluation.
Crack growth is calculated for each heatup/cooldown cycle. Since the original design basis [17]
specifies 240 heatup/cooldown cycles over a 40 year period, the corresponding time increment is one-sixth of a year.
Stress intensity factors are provided in Table 5-1 for all locations along the postulated crack front, including the cladding. It is apparent from the stress intensity factors listed in these tables for the initial flaw sizes that the highest value in the low alloy steel head occurs at the bored surface.
Page 31
Controlled Document A
AR EVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDMV Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Table 5-1: Flaw Growth and LEFM Evaluation INPUT DATA Initial Flaw Size:
Fracture Toughness:
Depth along bore, Reference temperature of head, Upper shelf toughness, ao =
2.035 RTndt =
I UST =
200 in.
F ksi1in KIc = 33.2 + 20.734 exp [ 0.02 (T - RTndt) ]
Kla = 26.8 + 12.445 exp [0.0145 (T - RTndt) ]
< UST
< UST Stress Intensity Factors:
Cladding Surface Bored Surface Condition*
SD SS RT1 RT2 RWA Temperature 70
] Z 630 532 600 Pressure 0
2155 2450 1720 2745 Sy 50.0 41.7 41.6 42.8 42.0 KIc 58.5 200.0 200.0 200.0 200.0 Kla 41.2 200.0 200.0 200.0 200.0 Crack Front Stress ntensity Factor, KI Position (psi-4in)
(psiin)
(psiqin)
(psi in)
(psNin) 1 72012 93645 98490 126998 113102 2
57085 80022 85054 107657 98142 3
51528 76247 81503 101098 94057 4
50744 76792 82152 99156 94199 5
51092 77639 82959 97602 94399 6
50355 76403 81504 93813 92098 7
50354 76220 81039 89789 90395 8
55409 83992 89074 96389 98404 9
58477 93556 99531 107438 110130 10 61779 101703 108389 117216 120167 F
psig ksi ksifin ksi4in
- Condition Description SD SS RT1 RT2 RWA Time step 1 at 0 hr. of heatup/reactor trip/cooldown (shutdown w/ only residual stress)
Time step 7 at 10.0000 hr. of heatup/reactor trip/cooldown (steady state at 100% power)
Time step 8 at 10.0028 hr. of heatup/reactor trip/cooldown (during reactor trip)
Time step 13 at 10.1184 hr. of heatup/reactor trip/cooldown (during reactor trip)
Time step 2 at 0.0044 hr. into rod withdrawal accident (high pressure condition)
Page 32
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Table 5-1: Flaw Growth and LEFM Evaluation (Cont'd)
FATIGUE CRACK GROWTH Transient
Description:
240 cycles over 40 years AN =
6 cycles/year Crack Front Position 10 Operating RT2 SD SS RT1 RWA Cycle Time a
KI(a)max KI(a)min AKI Aa KI(a)
Kl(a)
Kl(a)
(end of yr.)
(in.)
(ksibin)
(ksiIin)
(ksi'in)
(in.)
(ksi'in)
(ksi1in)
(ksiqin) 0 0.000 2.03500 117.216 61.779 55.437 101.703 108.389 120.167 1
0.167 117.305 61.826 55.479 101.781 108.472 120.259 2
0.333 117.395 61.873 55.522 101.858 108.554 120.350 3
0.500 117.484 61.920 55.564 101.936 108.637 120.442 4
0.667 117.574 61.968 55.606 102.013 108.720 120.534 5
0.833 117.663 62.015 55.649 102.091 108.803 120.626 6
1.000 117.753 62.062 55.691 102.169 108.885 120.717 7
1.167 117.843 62.109 55.733 102.247 108.968 120.809 8
1.333 117.932 62.157 55.776 102.325 109.051 120.901 9
1.500 118.022 62.204 55.818 102.403 109.135 120.994 10 1.667 118.112 62.251 55.861 102.481 109.218 121.086 11 1.833 118.202 62.299 55.903 102.559 109.301 121.178 12 2.000 118.292 62.346 55.946 102.637 109.384 121.270 13 2.167 118.382 62.394 55.989 102.715 109.467 121.363 14 2.333 118.472 62.441 56.031 102.793 109.551 121.455 15 2.500 118.563 62.489 56.074 102.871 109.634 121.548 16 2.667 118.653 62.536 56.117 102.950 109.718 121.640 17 2.833 118.743 62.584 56.159 103.028 109.801 121.733 18 3.000 118.834 62.632 56.202 103.107 109.885 121.826 19 3.167 118.924 62.679 56.245 103.185 109.969 121.918 20 3.333 119.015 62.727 56.288 103.264 110.052 122.011 21 3.500 119.106 62.775 56.331 103.342 110.136 122.104 22 3.667 119.196 62.823 56.374 103.421 110.220 122.197 23 3.833 119.287 62.871 56.416 103.500 110.304 122.290 24 4.000 119.378 62.918 56.459 103.579 110.388 122.383 Page 33
Controlled Document A
AR.EVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Table 5-1: Flaw Growth and LEFM Evaluation (Cont'd)
LEFM FRACTURE TOUGHNESS MARGINS Period of Operation:
Flaw Size:
Time =
4 years a= {
Iin.
Loading Conditions SD SS RT1 RT2 RWA Fracture Toughness, KIc 58.5 200.0 200.0 200.0 200.0 ksi'in Fracture Toughness, Kla 41.2 200.0 200.0 200.0 200.0 ksi-4in Position 10 KI(a) 62.918 103.579 110.388 119.378 122.383 ksihin ae 2.1948 2.4378 2.4847 2.5232 2.5612 in.
Kl(ae) 64.158 111.313 119.767 130.520 134.811 ksi'/in Margin = Klc / Kl(ae) n/a n/a n/a n/a n/a Margin = Kla / Kl(ae) 0.64 1.80 1.67 1.53 1.48 where:
ae = a + 1/(6n) [KI(a)/Syl2 Kl(ae) = KI(a)*4(ae/a)
Page 34
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair 5.2 LEFM Flaw Evaluations The results of the linear-elastic fracture mechanics flaw evaluations are summarized below for the final size of the postulated flaw after fatigue crack growth.
Flaw Size Initial flaw size, ai = 2.035 in.
Final flaw size after 4 years, a, = {
} in.
Flaw growth, a = {
}in.
Controlling Transients Shutdown Heatup/Cooldown Rod Withdrawal w/
Condition Low Temperature Temperature, T = 70 OF Fracture toughness, K1a = 41.2 ksi/in Final stress intensity factor, KI(af) = 62.9 ksikin Effective flaw size, a, = 2.195 in.
Effective stress intensity factor, Kj(ae) = 64.2 ksiqin Fracture toughness margin (> 3.16),
KIa / KI(ae) = 0.64 Reactor Trip (RT2)
Normal I
})F 200.0 ksi4in 119.4 ksi4in 2.523 in.
130.5 ksi'in 1.53 Accident Upset
{
}OF 200.0 ksi'lin 122.4 ksiqin 2.561 in.
134.8 ksiqIin 1.48 Since the controlling fracture toughness margins are less than the Code required minimums, EPFM flaw evaluations will be performed to account for the ductile behavior of the low alloy steel during stable crack growth.
Page 35
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair 5.3 EPFM Flaw Evaluations I
The elastic-plastic fracture mechanics procedure described in Section 2.3 is used to evaluate the final size of the postulated flaw after fatigue crack growth.
Flaw Size Initial flaw size, Final flaw size after 4 years, Controlling Transients a, = 2.035 in.
aft= {
I}in.
Shutdown Heatup/Cooldown w/ Reactor Trip (RT2)
Rod Withdrawal Accident SCREENING PROCEDURE T = 70'F
{
}OF E = 29000 ksi 26808 ksi v = 0.3 0.3 E'= E/(1-v 2) = 31860 ksi 29450 ksi cy = 50.0 ksi 42.8 ksi au = 80.0 ksi 76.4 ksi af = 65.0 ksi 59.6 ksi
{
O 0 F 26400 ksi 0.3 29010 ksi 42.0 ksi 76.4 ksi 59.2 ksi 200.0 ksiqin 134.8 ksi/in Crack initiation toughness, Total applied K1, K, = 58.5 ksi'in KI(ae) = 64.2 ksi4in 200.0 ksiin 130.5 ksiqin
- Then, Ký' = KO(ae) / Kic = 1.096 0.653 0.674 From finite element stress analysis, the maximum crack face stresses due to residual stress, pressure, and thermal gradients are
- Then, Screening ratio, Umax = 66.4 ksi Sr' = Umax / lf = 1.022 Kr' / Sr' = 1.073 114.6 ksi 1.923 0.339 114.5 ksi 1.934 0.349 The analysis is therefore in the EPFM regime (1.8 > Kr' / Sr' - 0.2) for both loading conditions.
EPFM ANALYSIS Total applied K1, KI(a) = 62.9 ksi4in K, primary (pressure from Appendix E), K1p(a) =
0.0 ksi'/in K, secondary (residual plus thermal),
K1,(a)*= 62.9 ksi,1in-119.4 ksiqin 39.9 ksi'/in 79.5 ksi'Iin 43.6 ksi'din 86.9 ksiiin 122.4 ksi'lin 63.7 ksi'lin 58.7 ksiqin.
70.2 ksiq'in 64.7 ksi~iin Multiplying by 'I(ae/a),
K',p(a) =
0.0 ksix/in K',,(a) = 64.2 ksi/in Page. 36
Controlled Document A
AREVA Document No. 32-9136508-002 AREVA NP Inc.,
an AREVA and Siemens company DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Table 5-2, Table 5-3, and Table 5-4 develop all the data necessary to construct J-T diagrams for the controlling operating conditions. The J-T diagrams are presented in Figure 5-1, Figure 5-2, and Figure 5-3.
For shutdown conditions, Table 5-2 shows for an applied J-integral of 0.291 kips/in, corresponding to safety factors of 3 and 1.5, the applied tearing modulus, 0.945, is less than the material tearing modulus, 317.0, indicating flaw stability. Alternately, the applied J-integral is less than the J-integral, 3.415 kips/in, at the point of instability. For safety factors of 1.5 and 1, the applied J-integral of 0.129 kips/in is less than the J0.1 value of 1.350 kips/in, demonstrating that the crack driving force falls below the J-R curve at a crack extension of 0.1 inch.
For the heatup/cooldown transient with reactor trip, Table 5-3 shows for an applied J-integral of 2.317 kips/in, corresponding to safety factors of 3 and 1.5, the applied tearing modulus, 8.283, is less than the material tearing modulus, 20.69, indicating flaw stability. Alternately, the applied J-integral is less than the J-integral, 3.402 kips/in, at the point of instability. For safety factors of 1.5 and 1, the applied J-integral of 0.788 kips/in is less than the J0.1 value of 1.363 kips/in, demonstrating that the crack driving force falls below the J-R curve at a crack extension of 0.1 inch.
For rod withdrawal accident conditions, Table 5-4 shows for an applied J-integral of 3.258 kips/in, corresponding to safety factors of 3 and 1.5, the applied tearing modulus, 11.63, is less than the material tearing modulus, 12.88, indicating flaw stability. Alternately, the applied J-integral is less than the J-integral, 3.401 kips/in, at the point of instability. For safety factors of 1.5 and 1, the applied J-integral of 0.995 kips/in is less than the J0.1 value of 1.364 kips/in, demonstrating that the crack driving force falls below the J-R curve at a crack extension of 0.1 inch.
Page 37
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Table 5-2: EPFM Evaluation for Shutdown Conditions EPFM Equations:
Jmat = C(Aa)m Trnat = (E/(f2 )*Cm(Aa)mnl Japp = ( SFp*K'ip+SFs*K'is)2/E' Tapp = (E/a2)*(dJapp/da)
}
Ductile Crack Growth Stability Criterion:
Tapp <, Tmat Tapp = Tmat At instability:
Safety Factors SF*K',p SF*K'Is Japp Tapp Stable?
Primary Secondary (ksiqin)
(ksiqin)
(kips/in) 1.00 1.00 0.000 64.158 0.129 0.420 Yes 2.00 2.00 0.000 128.316 0.517 1.681 Yes 3.00 1.50 0.000 96.237 0.291 0.945 Yes 5.00 5.00 0.000 320.791 3.230 10.503 Yes 7.00 7.00 0.000 449.108 6.331 20.587 No Iterate on safety factor until Tapp = Tmatto determine Jinstability:
Ji 5.1412 51412 0.000 329.852 instability Tapp Tmat 3.415 11.105 11.105 at Jmat =
0.291 kips/in, Applied J-integral Criterion:
Treat 316.734 Japp < Jo:.
- where, Jo.1 = Jmat at Aa = 0.1 in.
SF*Khis Japp Jo.1 (ksi'/in)
(kips/in)
(kips/in)
Safety Factors Primary Secondary SF*Krrp (ksiq~in)
OK?
1.50 1.00 0.000 64.158 0.129 1.350 Yes Page 38
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Table 5-3: EPFM Evaluation for HeatuplCooldown with Reactor Trip EPFM Equations:
Jmat C(Aa)m Tmat (E/c12)*Cm(Aa)ml1 Japp = (SFp*K'ip+SFs*K'Is) 2/E' Tapp = (E/(l2)*(dJapp/da)
}
Ductile Crack Growth Stability Criterion:
Tapp < Tmat Tapp = Tmat At instability:
Safety Factors SF*K'1p SF*K'hs Japp Tapp Stable?
Primary Secondary (ksiqin)
(ksiqin)
(kips/in) 1.00 1.00 43.630 86.890 0.578 2.068 Yes 2.00 1.00 87.261 86.890 1.030 3.681 Yes 3.00 1.50 130.891 130.335 2.317 8.283 Yes 5.00 1.00 218.152 86.890 3.160 11.294 Yes 7.00 1.00 305.412 86.890 5.226 18.680 No Iterate on safety factor until Tapp = Tmat to determine Jinstability:
Jinstability Tapp Tmat 2.4252 2.4252 105.812 210.726 3.402 12.161 12.161 at Jmat =
2.317 kips/in, Applied J-Integral Criterion:
Tmat =
20.694 Japp < Jo.1
- where, Jo.1 = Jmat at Aa = 0.1 in.
SF*K'1s Japp 3o1 (ksiqin)
(kip~s/in)
(kipslin)
Safety Factors Primary Secondary SF*KW1p (ksilin)
OK?
1.50 1.00 65.445 86.890 0.788 1.363 Yes Page 39
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company.
Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Table 5-4: EPFM Evaluation for Rod Withdrawal Accident EPFM Equations:
Jmat = C(Aa)m Tmat = (E/df2)*Cm(Aa)m-1 Japp = (SFp*K'ip+SFs*K'is) 2/E' Tapp = (E/at2 )*(dJapp/da)
}
Ductile Crack Growth Stability Criterion:
Tapp < Tmat Tapp= Tmat At instability:
Safety Factors SF*K'Ip SF*K',s Japp Tapp Stable?
Primary Secondary (ksi'in)
(ksi1in)
(kips/in) 1.00 1.00 70.154 64.657 0.626 2.236 Yes 2.00 1.00 140.308 64.657 1.448 5.168 Yes 3.00 1.50 210.461 96.986 3.258 11.628 Yes 5.00 1.00 350.769 64.657 5.949 21.231 No 7.00 1.00 491.076 64.657 10.646 37.993 No Iterate on safety factor until Tapp = Tmat to determine Jinstability:
J 2.3301 2.3301 163.463 150.656 at Jmat =
3.258 kips/in, Tmat =
1 Applied J-integral Criterion:
Japp < Jo.i nstability Tapp Tmat 3.401 12.138 12.138 2.883
- where, Jo.1 = Jmat at Aa = 0.1 in.
Safety Factors SF*K'=p Primary Secondary (ksi'/in)
SF*K1 1
(ksi'~in)
Japp Jo.1 OK?
(kips/in)
(kips/in) 1.50 1.00 105.231 64.657 0.995 1.364 Yes Page, 40
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair 8
7 6
5 Cý (4
t-4 3
2 1
0 0
5 10 15 20 25 30 35 40 45 50 Tearing Modulus Figure 5-1: J-T Diagram for Shutdown Conditions Page 41
Controlled Document A
AR EVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair 8
7 6
5 4
3 2
1 0
0 5
10 15 20 25 30 35 40 45 50 Tearing Modulus Figure 5-2: J-T Diagram for HeatuplCooldown with Reactor Trip Page 42
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair 8
7 6
5 Cý 0.9 0/)*4 CM 3
2 1
0 0
5 10 15 20 25 30 35 40 45 50 Tearing Modulus Figure 5-3: J-T Diagram for Rod Withdrawal Accident Page 43
Controlled Document A
AREVA AR'EVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair 6.0
SUMMARY
OF RESULTS AND CONCLUSIONS Elastic-plastic fracture mechanics has been used to evaluate a postulated radial flaw in the J-groove weld and butter of an outermost CRDM nozzle reactor vessel head penetration. The final flaw size was determined-by linear elastic fracture mechanics for 4 years of fatigue crack growth.
6.1 Summary of Results Flaw Size Initial flaw size, Final flaw size after 4 years, Controlling Transients Temperature, Safety factors (primary/secondary),
Material tearing modulus, Applied tearing modulus (< Tmat)
Safety factors (primary/secondary),
Material J-integral, Applied J-integral (< J0.1) a, = 2.035 in.
af={
} in.
Shutdown T = 70 °F SF = 3/1.5 Tmat = 317.0 Tapp = 0.945 SF = 1.5/1 J0.1 = 1.350 kips/in Japp = 0.129 kips/in Heatup/Cooldown w/ Reactor Trip
{
}OF 3/1.5 20.69 8.283 1.5/1 1.363 kips/in 0.788 kips/in Rod Withdrawal Accident
{
}OF 3/1.5 12.88 11.63 1.5/1 1.364 kips/in 0.995 kips/in 6.2 Conclusion 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, a Davis Besse Unit 1 CRDM nozzle is considered to be acceptable for at least 4 years of operation following an IDTB weld repair.
Page 44
Controlled Document A
AR EVA Document No. 32-9136508-002 AREA NP Inc.,
an AREVA and Siemens company DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair
7.0 REFERENCES
- 1.
AREVA NP Drawing 02-9134305-004,"Davis Besse CRDM Nozzle ID Temper Bead Weld Repair."
- 2.
AREVA NP Document 08-9134304-000, "Davis Besse RVCH CRDM Penetration Modification,"
March 2010.
- 3.
AREVA NP Document 38-1288564-00, "Calculation Number C-3206-00-1, Rev. 0, Davis Besse CRDM Stress Analysis," December 2001.
- 4.
AREVA NP Document 51-5012047-00, "Stress Corrosion Cracking of Low Alloy Steel," March 2001.
- 5.
AREVA NP Document 32-9066059-000, "Watts Bar CRDM Nozzle IDTB J-Groove Weld Analysis," December 2007.
- 6.
ANSYS Finite Element Computer Code, Version 10.0, ANSYS Inc., Canonsburg, PA.
- 7.
T.L. Anderson, Fracture Mechanics: Fundamentals and Applications, CRC Press, 1991.
- 8.
AREVA NP Document 32-5011864-07, "CRDMH Connection 3D FE Model," March 2001.
- 9.
ASME Boiler and Pressure Vessel Code,Section II, Material Specifications: Part A - Ferrous, 1965 Edition with Summer 1968 Addendum.
- 10.
BAW-10046A, Rev. 2, "Methods of Compliance With Fracture Toughness and Operational Requirements of 10 CFR 50, Appendix G," B&W Owners Group Materials Committee Topical Report, June 1986.
- 11.
ASME Boiler and Pressure Vessel Code, Section Xl, Rules for Inservice Inspection of Nuclear Power Plant Components, 1995 Edition with Addenda through 1996.
- 12.
NUREG-0744, Vol. 2, Rev. 1, "Resolution of the Task A-I I 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.
- 13.
AREVA NP Document 77-2313-006 (BAW-2313, Revision 6), "B&W Fabricated Reactor Vessel Materials and Surveillance Data Information," AREVA NP Inc., November 2008.
- 14.
AREVA NP Drawing 02-142178E-05, "Closure Head Center Disc." (DB-1 Midland Head)
- 15.
AREVA NP Drawing 02-154613E-08, "Arrangement Reactor Vessel Longitudinal Section." (DB-1 Midland Head)
Page 45
Controlled Document A
ARE VA Document No. 32-9136508-002 AREVANP Inc.,
an AREVA and Siemens company DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair
- 16.
AREVA NP Drawing 02-142179E-10, "Closure Head Sub-Assembly." (DB-1 Midland Head)
- 17.
AREVA NP Document 18-1149327-003, "Functional Specification for Reactor Coolant System for Davis-Besse," July 2008.
.18.
AREVA NP Document 51-9.137401-000, "Evaluation of Fluid Temperature in DB RV Closure Head," May 2010.
- 19.
Davis-Besse Nuclear Power Station No. 1 Updated Safety Analysis Report, Revision 26, June 2008.
- 20.
AREVA NP Document 32-5012424-12, "CRDM Temper Bead Bore Weld Analysis," April 2004.
- 21.
AREVA NP Document 32-9134665-001, "DEI Residual Stress Analysis for DB-1 CRDM Nozzle IDTB Repair," DEi Calc. No. C-8616-00-01, Rev. 1, Davis Besse CRDM Nozzle Welding Residual Stress Analysis, May 2010.
- Reference 19 is not retrievable from the AREVA NP Records Management system but are referenced here in accordance with AREVA NP Procedure 0402-01, Attachment 8. This customer reference is a valid source of design input as authorized by the Project Manager signature on page 2.
Page 46
Controlled Document A
AREVA Document No. 32-9136508-002 AREVA NP Inc.,
an AREVA and Siemens comp*any DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair APPENDIX A:
VERIFICATION OF COMPUTER CODE ANSYS The ANSYS finite element computer program [6] is verified for use in the present flaw evaluation by executing three test cases from the ANSYS set of verification problems that utilize the SOLID90 thermal and SOLID95 structural 20-node 3-D solid elements. Test case VM161 determines heat flow in an insulated pipe. Test case VM148 analyzes a cantilevered, parabolic beam subjected to a static bending load. Test case VM143 calculates a stress intensity factor for a crack in a plate. All three test cases executed properly, as demonstrated below.
Verification Problem VM161 Thermal Analysis of an Insulated Pipe File: vm161.vrt VM161 RESULTS COMPARISON Surface Heat Flow Rate I TARGET I ANSYS I RATIO q (BTU/hr) 362.0 362.0 1.000 Verification Problem VM148 Bending of a Parabolic Beam File: vm148.vrt VM148 RESULTS COMPARISON End Displacement I
TARGET I ANSYS I RATIO Y Deflection (in.)
-0.01067
-0.01062 0.995 Verification Problem VM 143 Fracture Mechanics Analysis of a Crack in a Plate File: vm143.vrt VM143 RESULTS COMPARISON Stress Intensity Factor by Displacement Extrapolation I TARGET I ANSYS I RATIO 3-D ANALYSIS 1.0249 1.0620 1.036 Page A-1
Uontrolled VLocument A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair APPENDIX B:
COMPUTER FILES IN COLDSTOR The computer files listed below, which are unchanged from those listed in document 32-9134664-003, are stored in the AREVA NP COLDStor repository in directory "\\cold\\41304\\32-9134664-003\\official".
ANSYS Models Modified Installed File-Name Description Date Date UphillCrackModel.db Crack model for uphill J-groove weld 03-19-10 05-07-10 UphillUnCrackModel.db Model for calculating operating stresses 03-20-10 05-07-10 MatlAndMesh.dat Material data for thermal and stress analysis 04-04-10 05-07-10 ANSYS Thermal Analysis File Name Description Modified Installed Date Date HURX8BThermal.dat Input file for HU/RT/CD thermal analysis 05-03-10 05-07-10 HURX8BThermal.out Output file for HU/RT/CD thermal analysis 05-03-10 05-07-10 RWAThermal.dat Input file for RWA thermal analysis 04-05-10 05-07-10 RWA_Thermal.out Output file for RWA thermal analysis 04-05-10 05-07-10 ANSYS Stress Analysis File Name Description Modified Installed Date Date HURX8B_Stress.dat Input file for HU/RT/CD stress analysis 05-04-10 05-07-10 HURX8B_Stress.out Output file for HU/RT/CD stress analysis 05-04-10 05-07-10 RWAStress.dat Input file for RWA stress analysis 04-04-10 05-07-10 RWAStress.out Output file for RWA stress analysis 04-05-10 05-07-10 ANSYS Macros for Transferring Stresses to Crack Model Modified Installed File Name Description Date Date FormatStressesDriver.mac Driver to get residual stresses 03-28-10 05-07-10 FormatStresses.mac Macro to get residual stresses 03-28-10 05-07-10 GetStressesDriver.mac Driver to get operating stresses 05-04-10 05-07-10 Page B-1
Controlled Document A
ARE VA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair File Name Description Modified Installed Date Date GetStresses.mac Macro to get operating stresses 04-05-10 05-07-10 ANSYS Analysis to Calculate Stress Intensity Factors (SIF)
File Name Description Modified Installed Date Date UphillCrackPressure.inp Input file for pressure loading 03-23-10 05-07-10 PressUp.output Output file for pressure loading 04-07-10 05-07-10 GetRESI_SIFs.mac Macro to get SIFs for residual stresses 04-08-10 05-07-10 GetHUCDSIFs.mac Macro to get SIFs for HU/RT/CD stresses 05-04-10 05-07-10 GetRWASIFs.mac Macro to get SIFs for RWA stresses 04-05-10 05-07-10 MapStressesUp.mac Macro to map stresses from uncracked model 03-24-10 05-07-10 to crack model PrtKlup.mac Macro to write SIFs to output file 03-24-10 05-07-10 RESIu.output Output file for residual SIFs 04-08-10 05-07-10 HUCDul.output Output file for HU/RT/CD SIFs (load step 1) 05-04-10 05-07-10 HUCDu2.output Output file for HU/RT/CD SIFs (load step 2) 05-04-10 05-07-10 HUCDu3.output Output file for HU/RT/CD SIFs (load step 3) 05-04-10 05-07-10 HUCDu4.output Output file for HU/RT/CD SIFs (load step 4) 05-04-10 05-07-10 HUCDu5.output Output file for HU/RT/CD SIFs (load step 5) 05-04-10 05-07-10 HUCDu6.output Output file for HU/RT/CD SIFs (load step 6) 05-04-10 05-07-10 HUCDu7.output Output file for HU/RT/CD SIFs (load step 7) 05-04-10 05-07-10 HUCDu8.output Output file for HU/RT/CD SIFs (load step 8) 05-04-10 05-07-10 HUCDu9.output Output file for HU/RT/CD SIFs (load step 9) 05-04-10 05-07-10 HUCDuI0.output Output file for HU/RT/CD SIFs (load step 10) 05-04-10 05-07-10 HUCDul 1.output Output file for HU/RT/CD SIFs (load step 11) 05-04-10 05-07-10 HUCDu12.output Output file for HU/RT/CD SIFs (load step 12) 05-04-10 05-07-10 HUCDu13.output Output file for HU/RT/CD SIFs (load step 13) 05-04-10 05-07-10 HUCDu14.output Output file for HU/RT/CD SIFs (load step 14) 05-04-10 05-07-10 HUCDuI5.output Output file for HU/RT/CD SIFs (load step 15) 05-04-10 05-07-10 HUCDuI6.output Output file for HU/RT/CD SIFs (load step 16) 05-04-10 05-07-10 HUCDu17.output Output file for HU/RT/CD SIFs (load step 17) 05-04-10 05-07-10 Page B-2
Controlled Document A
AREVA AREVA NP Inc.,
an ARE'VA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair File Name Description Modified Installed Date Date HUCDu18.output Output file for HU/RT/CD SIFs (load step 18) 05-04-10 05-07-10 RWAul.output Output file for RWA SIFs (load step 1) 04-05-10 05-07-10 RWAu2.output Output file for RWA SIFs (load step 2) 04-05-10 05-07-10 RWAu3.output Output file for RWA SIFs (load step 3) 04-05-10 05-07-10 RWAu4.output Output file for RWA SIFs (load step 4) 04-05-10 05-07-10 "ANSYS Verification File Name Description Modified Installed Date Date vml6l.vrt Verification problem for thermal analysis 04-07-10 05-07-10 vm148.vrt Verification problem for stress analysis 04-07-10 05-07-10 vm143.vrt Verification problem for stress intensity factor 04-07-10 05-07-10 Page B-3
Controlled Document A
ARE VA Document No. 32-9136508-002 ARE VA NP Inc.,
an AREVA and Siemens company DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair APPENDIX C:
FINITE ELEMENT CRACK MODEL C.1 Introduction A non-radial partial penetration nozzle in a spherically shaped pressure vessel presents a challenging, set of geometric constraints for both stress analysis and fracture mechanics analysis of flaws, especially in the J-groove weld. Since there are no closed-form solutions available to calculate stress intensity factors for such flaws, a three-dimensional finite element crack model is developed in this appendix for use in evaluating "J-shaped" flaws in the area of the partial penetration attachment weld.
The three-dimensional finite element model is constructed using crack tip elements along the entire J-shaped crack front, extending from the inside surface of the cladding to the bored surface of the penetration. An uncracked model of the nozzle, J-groove weld and butter, and a portion of the reactor vessel head and cladding is first created using the ANSYS finite element computer program [6]. After removing a block of elements around the crack front and inserting a sub-model of crack tip elements, stress intensity factors can be obtained via the program's KCALC routine. The crack tip sub-model consists of 20-node isoparametric elements that are collapsed to form wedges, with the appropriate mid-side nodes shifted to quarter-point locations to create a l/l/r singularity in strain at the crack tip.
Page C-1
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Smiveas conpany Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair C.2 Base Finite Element Model A three-dimensional finite element model is constructed to represent an uncracked non-radial nozzle penetration in a hemi-spherical shaped head. This model utilizes the ANSYS SOLID95 3-D 20-node structural solid element, exclusively, so that a portion of the model can be readily removed and replaced with a crack tip sub-model.
C.2.1 Geometry As shown in Figure C-1, the model is a 180-degree segment of the head, cladding, weld butter, and J-groove weld.
Figure C-1: Overall Model of Reactor Vessel Head Penetration Page C-2
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Key dimensions are:
Radius to base metal Head thickness (minimum)
Cladding thickness (nominal)
Butter thickness (nominal)
Hole diameter (original)
J-groove weld center diameter J-groove weld angle Basic J-groove radius Basic J-groove height Additional height to base metal (nom.)
Horizontal distance to outermost nozzle Penetration angle at outermost nozzle
{
} in.
(
} in.
(
} in.
{
} in.
{
} in.
(
} in.
{
} deg.
(
} in.
{
}jin.
(
} in.
{
} in.
{
} deg.
[14]
[14]
[15]
[16] or {
[16] (near {
[16]
[16]
[16]
[16]{
[16] or {
[16]
}
} after machining [1])
}
C.2.2 Materials The material designations of the various components of the model are:
Component Material RV head Cladding J-groove weld filler J-groove weld butter SA-533 Grade B Class 1 (2]
Stainless steel (use Type 316 properties)
Alloy 182 [2] (use Alloy 600 properties for SB-167)
Alloy 182 [2] (use Alloy 600 properties for SB-167)
The mechanical and thermal properties for these materials are provided in Section 4.1.1.
C.2.3 Boundary Conditions The model includes a 180-degree segment of the weld and adjacent portions of the head. The vertical plane containing the vertical axes of the reactor vessel and the outermost penetration forms a plane of symmetry for the model. The displacements normal to this plane of symmetry are fixed (in the global Z-direction). Displacement constraints are also applied to the outer peripheral boundary of the spherical segment to simulate a state of membrane stress. By specifying meridional displacements to be zero in a spherical coordinate system, the head can only displace along a spherical radius parallel to this boundary.
C.3 Finite Element Crack Models The three-dimensional finite element crack model is developed by removing a portion of the head and butter and inserting a sub-model of crack tip elements, as illustrated in Figure C-2. Displacement constraints are also removed along the plane of symmetry for nodes on the crack face. Figure C-3 shows the final crack model used to analyze a postulated flaw in the J-groove weld and butter.
Page C-3
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and 8*knmns company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Figure C-2: Development of Crack Model Figure C-3: Final Finite Element Crack Model Page C-4
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Snn company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair APPENDIX D:
FINITE ELEMENT STRESS MODEL A three-dimensional linear-elastic finite element model is developed for use in obtaining operational stresses from transient loading conditions. The origin of this model is the uncracked stress model described in Section C.2, prior to transformation to a crack model. The ANSYS SOLID95 3-D 20-node structural solid elements of the stress model are converted to SOLID90 3-D 20-node thermal solid elements to create a thermal model for use in transient analysis to calculate nodal temperatures.
Three heat transfer regions are defined for applying thermal loads to the model in the form of time-dependent bulk fluid temperatures and convective heat transfer coefficients (HTC). Figure D-1 identifies these regions at the inside surface of the cladding, the bored surface of the head at the location of the nozzle, and the outside surface of the head. Table D-1 lists the bulk fluid temperatures and heat transfer coefficients for the heatup/reactor trip/cooldown full-range transient used in the present flaw evaluations. Table D-2 provides similar data for the rod withdrawal accident transient. Temperature-time history plots are presented in Figure D-2 and Figure D-3 for both transients.
Outside Surface of Head Figure D-1: Heat Transfer Regions of Thermal Model Page D-1
Controlled Document A
A#REVA AREVA NP Inc.,
an AREVA and Siemen's company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Table D-1: Heatup/Reactor Trip/Cooldown Transient Definition
References:
Section III Stress Analysis [20] and RCS Functional Specification [17]
Load Inside Outside Inside Cladding Inside Bore Outside Head Step Time Temp.
Temp.
HTC HTC HTC Comment (hr.)
(OF)
(O°F)
__Btu/hr/in 2_-OF)
Btulhr/in2_-OF).
Btu/hr/in2 -OF) 2 3
heatup 4
5 6
SS at 8% power 7
power increase 8
SS at 100% power 9
10, 12 reactor trip 13 14 15 16 17 cooldown 18 19 Table D-2: Rod Withdrawal Accident Transient Definition
References:
Section III Stress Analysis [20] and RCS Functional Specification [17]
Load Inside Outside Inside Cladding Inside Bore Outside Head Step Time Temp.
Temp.
HTC HTC HTC Comment (hr.)
(OF)
(OF)
(Btu/hr/in2-OF)
(Btu/hr/in2 -OF)
Btu/hr/in2-OF) 1 3
4 5
6 7
8 9
Page D-2
Controlled Document A
ARE VA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair I
Figure D-2: Heatup/Reactor Trip/Cooldown Temperature-Time History I
I Figure D-3: Rod Withdrawal Accident Temperature-Time History Page D-3
Controlled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair APPENDIX E:
STRESS INTENSITY FACTOR DUE TO PRESSURE The elastic-plastic fracture flaw evaluations of Section 5.3 utilize different safety factors for primary (pressure) and secondary stress (residual and thermal) intensity factors. In order to isolate the pressure term, Kip, stress intensity factors are developed for an arbitrary pressure load of 2500 psig at 600 OF.
Table E-1 presents stress intensity factors at the ten crack front positions defined in Figure 2-2. Since these values were determined for the initial crack size, they are adjusted by the square root of the crack size, considering the final crack size after four years of crack growth, in the same fashion as described in Section 2.1.3.
The Kip pressure terms used in the EPFM flaw evaluations of Section 5.3 are derived below.
- Let, S
a° P
KIP(a,P) = K1p(ao,Po) a x 0
Temperature, T = 600'F
- Pressure, P, = 2500 psig ao = 2.035 in.
Initial flaw size, From Table E-1, Kp(ao,Po) = 56.952 ksiqin Controlling Transients Temperature,
- Pressure, Shutdown T= 70'F P = 0 psig a = 2.1108 in.
Kip(a,P) = 0 ksi'/in
{
-}OF
{
}OF Heatup/Cooldown w/ Reactor Trip (RT2)
Rod Withdrawal Accident Final flaw size,
{
}psig 2.1108 in.
39.906 ksi'in
{
) psig 2.1108 in.
63.687 ksibin Final stress intensity factor, Page E-1
(ontrolled Document A
AREVA AREVA NP Inc.,
an AREVA and Siemens company Document No. 32-9136508-002 DB-1 CRDM Nozzle J-Groove Weld Flaw Evaluation for IDTB Repair Table E-1: Stress Intensity Factors for Internal Pressure Loading Temperature =
600 Pressure =
2500 Flaw size =
2.035 Inside Surface Bored Surface Position 1
2 3
4 5
6 7
8 9
10 F
psig in.
SIF (ksiqin) 56.697 51.258 49.563 48.028 46.116 43.286 39.883 41.978 50.267 56.952 70 60 50 4O 30 20
-Pressure Only 10 0
1 2
3 4
5 6
7 8
9 10 Position Page E-2