ML24347A227
| ML24347A227 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 12/12/2024 |
| From: | Ameren Missouri, Framatome, Union Electric Co |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML24347A225 | List: |
| References | |
| ULNRC-06910 | |
| Download: ML24347A227 (1) | |
Text
Enclosure 1 to U LN RC-06910 Cracking Assessment for Framatome Replacement Steam Generator (RSG)
Channel Head Assembly, Revision 2
0402-Ol-FOl (Rev. 023, 06/20/2024) framatome CALCULATION
SUMMARY
SHEET (CSS)
Document No.
86 9366726 002 Safety Related: EYes D No Title Cracking Assessment for Framatome RSG Channel Head Assembly PURPOSE AND
SUMMARY
OF RESULTS:
PURPOSE:
The EPRI SGMP (Steam Generator Management Program) investigated the crack initiation and propagation in the SG (Steam Generator) channel head assembly for Westinghouse SGs, therefore similar evaluation as presented in Reference [1] is needed for Framatome supplied RSGs (Replacement Steam Generators) in the United States. The purpose of this analysis is to demonstrate by flaw tolerance assessment that a postulated initial flaw in the RSG channel heads meets the ASME Section Xl, IWB-3612 acceptance criteria (Reference [6])
over the design life of the RSGs. The analysis is applicable to the RSGs at Callaway Uniti
, Prairie Island Units 1&2, Salem Unit 2.
Rev. 001 : This summary document is updated to address NRC audit questions in support of Callaways license renewal commitments 34 and 35.
Rev. 002: Rev. 002 is released to remove a bookmark error and revert status back to non-proprietary, consistent with Rev. 000.
RESULTS:
The flaw tolerance evaluation of the RSG channel head assembly is performed with the stress profiles provided by a detailed finite element analysis. The bounding transients (along with the design cycles) and support loads out of these units are used in the analysis. It is concluded that the RSG channel heads are not compromised by the postulated circumferential or axial flaw initiating from the divider plate over the design life of the RSGs. In addition, it cannot be determined that the RSGs meet the requirement of at least 22 wt% Cr in the tube-to tubesheet welds.
Rev. 001: Results in Rev. 000 remain unchanged.
Rev. 002: Results in Rev. 000 remain unchanged.
Export Classification US EC:
N Part 810 EAR ECCN: N/A If the computer software used herein is not the latest version per the EASI list, THE DOCUMENT CONTAINS AP 0402-01 requires that justification be provided.
ASSUMPTIONS THAT SHALL BE THE FOLLOWING COMPUTER CODES HAVE BEEN USED IN THIS DOCUMENT:
VERIFIED PRIOR TO USE CODE/VERSION/REV CODE/VERSION/REV El Yes N/A No Page 1 of 31
frarriatorrie 040201F01 (Rev. 023, 06/20/2024)
Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly Review Method:
Design Review (Detailed Check)
Alternate Calculation Does this document establish design or technical requirements?
YES NO Does this document contain Customer Required Format?
YES NO Signature Block Name and Title Signature and Date Role Scope I Comments Kaihong Wang K WANG Advisory Engineer 12/9/2024 P
All.
Jennifer Nelson JA NELSON Principal Engineer 12/9/2024 R
All.
Craig Wicker CA WICKER Supervisory Engineer 12/9/2024 A
All.
Beverly Watson BJ WATSON Proj ect Manager 12/9/2024 PM Approval of customers references.
Role Definitions:
P/R/A designates Preparer (P), Reviewer (R), Approver (A);
LP/LR designates Lead Preparer (LP), Lead Reviewer (LR);
M designates Mentor (M);
PM designates Project Manager (PM)
Page 2
frarnatorne 040201F01 (Rev. 023, 06/20/2024)
Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly Record of Revision Revision Pages I Sections I No.
Paragraphs Changed Brief Description I Change Authorization 000 All Initial release.
001 Pages 1
- 3 Updated with new form (0402-Ol-FOl Rev. 023).
Page 12/Section 3.2.5 Added explanation for Callaway-1 on the RTNDT value.
Pages 12-1 3/Section 4.2 Updated the statement about the 2 ksi uncertainty.
Page 23/Section 6.1.2 Corrected the typos in the HTC units.
Page 25/Section 6.1.3 Added a paragraph to explain the path line selections.
Page 31/Section 9.0 Added references 22 and 23.
002 Page 1-3 Updated to Rev. 002 and reverted to non-proprietary to be consistent with Rev. 000.
Page 25/Section 6.2.1.1 Removed a bookmark error.
Page 3
frarnatorne Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly Table of Contents Page SIGNATURE BLOCK 2
RECORD OF REVISION 3
LISTOFTABLES 5
LIST OF FIGURES 6
1.0 INTRODUCTION
7 2.0 PURPOSEANDSCOPE 7
3.0 ANALYTICAL METHODOLOGY 8
3.1 Finite Element Model and Stress Analysis 8
3.2 Flaw Tolerance Evaluation 8
3.2.1 Postulated Flaws 8
3.2.2 Stress Intensity Factor Solutions 9
3.2.3 Fatigue Crack Growth in Low Alloy Steel 9
3.2.4 Methodology for Flaw Growth Analysis 10 3.2.5 Acceptance Criteria II 4.0 ASSUMPTIONS 12 4.1 Unverified Assumptions 12 4.2 Justified Assumptions and Modeling Simplifications 12 5.0 INPUTS 13 5.1 Geometry 13 5.2 Material 14 5.3 Loads 17 5.4 Finite Element Model 18 6.0 CALCULATIONS 21 6.1 Finite Element Stress Analysis 21 6.1.1 Design Conditions 21 6.1.2 Thermal Analysis 23 6.1.3 Stress Analysis 23 6.1.4 Steady State Stress on Tubesheet Primary Side Perforated Area 25 6.2 Flaw Evaluation 25 6.2.1 Applied Stresses 25 6.2.2 Fatigue Crack Growth Analysis 27 6.3 Tube-to-Tubesheet Weld Material 28 7.0 RESULTSANDCONCLUSION 29
8.0 REFERENCES
31 Page 4
frarnatorne Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly List of Tables Page Table 3-1 : Relevant Sources of Stress for Fatigue Flaw Growth Analysis II Table 5-1: RSG LowerAssembly Major Dimensions 13 Table 5-2: RSG LowerAssembly Materials 15 Table 5-3: SA-508 Grade 3 Class 2 [3I4Ni-lI2Mo-Cr-V]
15 Table 5-4: SB-166, Alloy 600 UNS N06600 [72Ni-l5Cr-8Fe]
16 Table 5-5: SB-163, Alloy 690 UNS N06690 [58Ni-29Cr-9Fe]
16 Table 5-6: SA-403 Type 304L [l8Cr-8Ni]
16 Table 5-7: Material Strength 17 Table 5-8: Enveloped Transients and Bounding Cycles 17 Table 6-1 : Equivalent Axial Force and Bending Moment at P1/P3/P5 26 Table 6-2: Equivalent Axial Force and Bending Moment at P2/P4/P6 26 Table 6-3: Axial Stresses Due to Seismic Loads 26 Table 6-4: Initial and Final Circumferential Flaw Sizes 27 Table 6-5: Initial and Final Axial Flaw Sizes 28 Table 6-6: Framatome RSG Tube-to-Tubesheet Welds Materials and Chromium Content 29 Table 7-1: Final Circumferential Flaw Evaluation 30 Table 7-2: Final Axial Flaw Evaluation 30 Page 5
frarnatorrie Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly List of Figures Page Figure 3-1: Postulated Inside Surface Partial Through-wall Semi-elliptical Flaws 9
Figure 5-1: RSG LowerAssembly FEM Dimensions 14 Figure 5-2: 3-D Solid Model 19 Figure 5-3: Meshed Finite Element Model 20 Figure 6-1: Displacement in Design Conditions Case I 21 Figure 6-2: Stress Intensity in Design Conditions Case I 22 Figure 6-3: Displacement in Design Conditions Case 2 22 Figure 6-4: Stress Intensity in Design Conditions Case 2 23 Figure 6-5: Crack Growth Path Line Locations 24 Page 6
frarnatorne Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly
1.0 INTRODUCTION
There are several cases ofcrack indications in Alloy 82/182 and Alloy 600 material in the divider plate assembly in Westinghouse SGs (Steam Generators) in operation outside the US (United States). US utilities want to avoid having to define and execute an Aging Management Program at units where the RSG (Replacement Steam Generator) channel heads contain Alloy 82/1 82 or Alloy 600 material. The EPRI SGMP (Steam Generator Management Program) funded work beginning in 2006 and ending in 2014 to investigate crack initiation and propagation in the SG channel head assembly, which concluded that visual examinations of SG divider plate and tubesheet welds are adequate for inspecting the structural integrity ofthe SG channel head. The US NRC agreed with this conclusion, but required plants to ensure SGs are bounded by the analysis performed by the SGMP and documented in EPRI Technical Report 3002002850 (Reference [1]).
However, the SGMP work is performed using a bounding case Westinghouse 5G. Because ofgeometrical and material differences (notably in the use of PWSCC (Primary Water Stress Corrosion Cracking) susceptible materials) and potential differences in loading, results and conclusions presented in Reference [1] are not necessarily applicable to Framatome supplied replacement steam generators. It was determined by Framatome that additional analysis is needed to cover the RSGs supplied to the US fleet by Framatome SAS. In particular, the RSGs in the following plant/unit are identified for this investigation:
Callaway Unit I (Model 73/19T, 4 SGs), or Callaway-1 thereafter Prairie Island Units I & 2 (Model FRA-56/1 9, 2 SGs each unit), or P1-1/2 thereafter Salem Unit 2 (Model 61/19T, 4 SGs), or Salem-2 thereafter 2.0 PURPOSE AND SCOPE The engineering analysis conducted herein is consistent with EPRIs SGMP (Reference [1]), which is performed to address similar concerns in SGs supplied by other vendors. The objective is to assess crack growth in the tubesheet to divider plate weld ofthe Framatome RSGs to determine necessary inspections following license renewal. The Alloy 600 and Alloy 690 materials for both base and weld metals that are used in the fabrication of the channel heads ofthese Framatome RSGs are documented in Reference [2].
Consistent with Reference [1], two regions are considered in the stress and flaw evaluation analyses:
1)
Thejunction ofthe channel head and the tubesheet is assessed assuming that the divider plate and tubesheet have separated through-thickness over a length of25% ofthe radius ofthe channel head from the triple point (approximately 1 5 inches).
2)
The Alloy 82/1 82 tubesheet cladding.
Stresses at the channel head/tubesheet juncture under various loading conditions are evaluated in the original stress analyses. Transient loads are selected based on potential contribution to fatigue crack growth from the postulated separation ofthe tubesheet from the divider plate. The tubesheet cladding is addressed by looking at the stresses in the cladding during 100% steady state operation. The analysis in Reference [1] concluded that the cladding is in compression during steady state operation, making PWSCC impossible. As long as the analysis of the Framatome supplied SGs demonstrates that the primary surface ofthe Alloy 82/1 82 cladding is in compression throughout the drilled region ofthe tubesheet at 100% steady state conditions, no further analysis is necessary, and it can be concluded that PWSCC is not a concern. The detailed 3-D stress FEA (Finite Element Analysis) is documented in Reference [3].
For the triple point region, an ASME Section XI fatigue crack growth analysis is performed using the stresses (and metal temperatures) documented in Reference [3]. The objective of the Section XI analysis is to demonstrate that fatigue crack growth of the initial flaw over the design life of the RSGs meets the ASME Code,Section XI, Page 7
frarnatorne Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly IWB-3612 acceptance criteria. Note that the potential for a crack through the Alloy 82/182 cladding existing anywhere along the circumference ofthe channel head-to-tubesheetjuncture is covered by this analysis, i.e., it is not limited to considering a crack only at the triple point location. The flaw evaluation is documented in Reference [4].
3.0 ANALYTICAL METHODOLOGY 3.1 Finite Element Model and Stress Analysis A representative FEM (Finite Element Model) is developed based on the detailed review ofthe four units, and a set of bounding transient data are determined. The following is the general methodology of FEM development and stress analysis:
1)
Building a 3-D model ofhalfofthe RSG channel head assembly with ANSYS (Workbench) (Reference
[5]). The model incorporates the SG bottom channel head, the divider plate, tubesheet, and associated welds. The model also includes the stainless steel channel head cladding and Alloy 82/1 82 tubesheet cladding. The 3-D model is converted into a 3-D FEM, with appropriate materials properties and boundary conditions. There are two FEMs consisting ofthermal and structural elements, respectively so as to enable the thermal and structural analysis using ANSYS (Reference [5]).
2)
Applying the design conditions of pressure and temperature (as temperature affects the material properties only) to the structural finite element model and obtaining the deformation and stresses in the model. The deformation field is used to verify the expected behavior ofthe model and correct modeling of boundary and load conditions.
3)
Applying the thermal loads resulting from the plant operating transients (in the form of transient temperatures and corresponding heat transfer coefficients versus time). Evaluating the results of the thermal analysis by examining the magnitude oftemperature differences between key locations of the model. The time points ofthe maximum temperature gradient are those at which the maximum thermal stresses develop.
4)
Applying the corresponding pressure and thermal loads (nodal temperature) at each time point identified in step 3 and other time points of analytical interest in the structural finite element model and obtaining the stress results.
5)
Defining path lines near the triple point and extracting axial and hoop stresses, metal temperatures along these path lines for the subsequent fatigue crack growth evaluation 3.2 Flaw Tolerance Evaluation 3.2.1 Postulated Flaws As shown in Figure 3-1, an inside surface-connected, partial through-wall, semi-elliptical circumferential flaw and an inside surface-connected, partial through-wall, semi-elliptical axial flaw are postulated to exist before it penetrates to the channel head base metal. For the circumferential flaw, the initial flaw depths (a) are taken to be the thickness of the cladding (0.2 minimal or the actual cladding thickness of the flaw path line) from its inside surface and a flaw length equal to the divider plate thickness (1= 2c = 2.08). This assumption yields a longer initial flaw than if using the aspect ratio of all = 1/6 recommended by ASME Code Section XI, Table L-3210-1 (Reference [6]). For the axial flaw, the aspect ratio of all = 1/6 is assumed.
Page 8
framatome Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly t
a b
Figure 3-1 : Postulated Inside Surface Partial Through-wall Semi-elliptical Flaws 3.2.2 Stress Intensity Factor Solutions With the stresses near the triple point provided by Reference [3], the SIF (Stress Intensity Factor) (K) is calculated with the Framatome Excel-based macro code (AREVACGC 6.0) using the weight function method. The technical basis for this implementation is documented in Reference [7]. The weight function methodology is used to compute K for the postulated flaw geometries mentioned above in this analysis.
3.2.3 Fatigue Crack Growth in Low Alloy Steel Per Article A-4300 of Reference [6], the crack growth due to fatigue in LAS (Low Alloy Steel) is characterized by:
da
= C0(1K where C0 and n are constants that depend on the material and environmental conditions, AKi is the range of applied SIF in terms of ksiqin, and da/dN is the incremental flaw growth in terms of inches/cycle.
From Article A-4300(b)(2) of Reference [6], the fatigue crack growth constants for flaws exposed to the primary water environment are:
/IK1 = Kmax K,77117. If K,711 0, use R = 0.
0RO.25, AK1<17.74 (a) semi-elliptical inside surface axial flaw Both (a) and (b):
a0 initial flaw depth
/0 = 2c initial flaw length I = wall thickness R, = radius ofthe channel head inside surface x = flaw propagation direction (b) simi-elliptical inside surface circumferential flaw x
Page 9
OL e6e
- I-E I4L U! ZU1WWflS an qMOJ )JD13 fl1J JOJ SSSJS JO S3JflOS U1?AjJ qJ J{A!dSaI ssss I!x pu dooq cq UAU am sM1t.J 1!V11JWflDJ!3 pui IP pnsod qjo pijddi s!s1jui qoi piJ ioj S!SAIEUV LIIMOJO MId JO:I A6oopoqej I*C
[81 3UJJ>J SM9JJO S!SIC{1U :uowpuoD Ix UO!DS Q!!Axx) wp ccoc H3 ot im U! E1IN q pqs!{qs S! JOWJ UO!3flpJ (o)
.ulw)J XI3UI)J J)Jy ?3UV [
l22t1v1bU [ x ( 0) <
ulu/y xvUIy pU1 0 > 1 JO:I
- E/xnuI)J (y _ [) =I)JJ7 /3Ut? [ =
Ac v211\\/oa [x (so) ulu1)*,J xDtu)J pU1
> f JOJ XrnU)JJ)J1-17pUl3[ç o°i
- qiuaiis I!SU W!flfl S! 1/D pU qUIJS P1!X
(-°
+ o) = Io i(q pugp S! ssais ojj qj 1o ssais ojj pui v qdp joio uo spudp iyjz j > i oj
- tuIut)J XZ3W)J =
PU1 [
1 0 aIqM (i
z *c = c cq UA! S! pU1 O!1J [
.iOj UflO33fl O wiuid U!Inos i S! c S01-O[ x 661 =
03 LO*E = U
- an UWUOJ!AU U! 49J JOJ SUSUO3 flMOJ )31JD nThj
[9] 3UJJ}J Jo ({)(q)ooE-v psn q pjnoqs ui U!
SUWUO.HAU 4L WOJJ Utq.TMO S! SUUJUOJ!AU
.iooiai qll WOJJ iu i°° !WJ qJ! [91 3UJJJ jo ()(q)oo-v id IIUo!!ppv LcZ 01 x I0*[
03
= S c6[ = U tO[ E XV S, 01 x ED! = 03 9LII = S c6c = U frOEI > XV 001 1 c90 S 01 x [o[ = 03 900 + icz
= S c6[ = U c,o[(cEL c
[6 9t)/(90 0 + jc Jiz z I xv S 01 x ED! = 03 169E= S c6c U
çj.0[(cL c
[6 9E)/(90 0 + icz E)] frL LI > )117 c9 0 >
> c 0 S 01 x 101 = 03 0*1= S c6[ = U L LI XV S, 01 x ED! = 03 0*1= S c6c = U Aqwessy peed euueq ewoewej J04 uewssessv 6UIpJ3 OO9L99E6-99 ON uewnooa OLUO3LLIJJ
frarnatonie Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly Table 3-1: Relevant Sources of Stress for Fatigue Flaw Growth Analysis Inside Surface-Connected, Partial Through-Wall, Semi-Elliptical Circumferential Flaw Residual Axial Stress at Shutdown Condition Axial Stress from Transients Axial Stress due to Pipe Loads (Deadweight, Thermal Expansion)
Axial Stress due to Normal/Upset Pressure (Acting on Crack Face)
Inside Surface-Connected, Partial Through-Wall, Semi-Elliptical Axial Flaw Residual Hoop Stress at Shutdown Condition Hoop Stress from Transients Hoop Stress due to Normal/Upset Pressure (Acting on Crack Face)
For each transient, the cycles are assumed to be uniformly distributed through the design lifetime. The cycles from all the transients are sorted based on the time that they are assumed to occur. Fatigue flaw growth is calculated by considering the assumed sequence oftotal transient stresses which may consist ofa collection of sub-cycles (peaks and valleys) within any transient. Through-wall metal temperatures are provided in Reference
[3].
The fatigue crack growth ofthe inside surface-connected, partial through-wall, semi-elliptical axial flaw is controlled by the values ofK and AK at the flaw depth location. The axial flaw growth is conservatively taken to be self-similar so that the initial flaw aspect ratio ofthe axial flaw is retained during flaw growth.
The fatigue crack growth calculations in the tubesheet base metal are performed by the Framatome Excel-based macro Code AREVACGC 6.0 (Reference [7]), which is verified for use by running verification test cases. The results generated by the test runs are identical to those documented in Reference [7].
3.2.5 Acceptance Criteria The allowable flaw depth is determined using ASME Code Section XI, Appendix A methodology and IWB-3600 acceptance criteria (Reference [6]).
Per ASME Code Section Xl, IWB-3612 (Reference [6]), any flaw exceeding the limits ofIWB-3500 is acceptable ifthe applied SIF and the flaw size satisfy the following criteria:
I )
For normal conditions K1 < K1/q1O 2)
For emergency/faulted conditions and conditions where pressurization does not exceed 20% ofthe Design Pressure K1 < Ki / q2
- where, K1 = the maximum applied total SIF (including stress due to weld residual stress, pressure, and thermal loadings) for normal and upset (N/U) conditions, including test conditions, or emergency and faulted (E/F) conditions for the end-of-evaluation period flaw size.
K1 = fracture toughness based on crack initiation for the corresponding crack-tip temperature.
Per ASME Code Section XI, Article A-4200 (Reference [6]), Figure A-4200-1, a lower bound curve for K1 is prescribed for low alloy/ferritic steels as:
K1 = 33.2 + 20.734 exp[0.02(T RTNDT)]
Page 11
frarnatorne Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly where T is the evaluated metal temperature, and RTNDT is the reference nil-ductility temperature of the material.
The maximum K1 is limited to an upper-shelfvalue of200 ksiqin. The RTNDT of 10°F is taken as the bounding value based on the non-ductile failure risk reports of all units (References [9], [101, [1 1] and [12] for Callaway-1, p1-i, P1-2 and Salem-2, respectively). For Callaway-1, the Certified Design Report (Reference [22]) states the RTNDT value for Callaway replacement steam generators shall be no higher than 1 0°F. The Framatome ANP Procurement Specification (Reference [23]) for the Callaway-1 RSGs also states the RTNDT value shall be no higher than 10°F. Reference [22] certifies that the Callaway-1 RSGs comply with the requirements ofthe Certified Technical Specification, which includes Reference [23]. Based on this information, it is concluded that testing was performed to verify the RTNDT value for Callaway-1 RSGs is 10°F or lower.
4.0 ASSUMPTIONS 4.1 Unverified Assumptions There is no unverified assumption used in this analysis.
4.2 Justified Assumptions and Modeling Simplifications 1)
The impact ofthe primary nozzles and manways is assumed to be negligible, consistent with the modeling in Reference [1]. The channel head is modeled as a continuous semi-spherical shell without any openings.
2)
Cycle counts used in the original Design Reports will be used in the crack growth analysis and are assumed to cover any proposed period of extended operation.
3)
The analysis considers a separation between the tubesheet and the divider plate from the triple point (i.e.,
thejuncture ofthe tubesheet, divider plate, and channel head) extending toward the center of the tubesheet over 25% ofthe length ofthe divider plate. The separation is assumed to occur through the Alloy 82/1 82 cladding and modeled explicitly. Note that based on the symmetrical nature ofthe model, this actually simulates a separation at both triple points.
4)
Weld material ofEQ3O8L/EQ3O9L or E308L/E309L is assumed to have the same properties as the stainless steel type 304 material such as SA-403 Type 304.
5)
As discussed in Reference [1], prior analyses have shown that the tubesheet remains essentially isothermal during the thermal transients ofthe steam generator channel head due to the thermal interaction ofthe tubes and the tubesheet. Consequently, vertical through-thickness thermal gradients are seen only in the top 2-inch layer ofthe tubesheet. A coupling ofthermal DOF is applied to simulate the condition in the thermal analyses.
6)
The initial flaw is assumed to be 100% through the cladding, growing into the LAS ofthe channel head, i.e., the initial flaw depth (a0 in Figure 3-1) is the cladding thickness at the location where the postulated flaw is assumed. Both axial and circumferential flaw orientations are considered.
7)
Residual stresses are not explicitly calculated as part ofthis project. Since the cladding welds (both Alloy 82/182 as well as the stainless-steel welds) are post weld heat treated, the residual stresses are expected to be insignificant and the discussion of cladding residual stresses in Reference [13] indicates that the residual stresses at the clad-base metal interface has a typical uncertainty of +/-2 ksi. Residual stress of +2 ksi (tensile) is then conservatively assumed to exist through the entire thickness ofthe cladding, and no residual stress is assigned to the LAS material.
Page 12
frarnatorne Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly 8)
This analysis does not include PWSCC (Primary Water Stress Corrosion Cracking) crack growth analysis in any material. Initial cracks through the susceptible material are postulated as described above.
9)
Stresses for LOCA and seismic loading used in the crack growth analysis are determined by applying an equivalent axial force load to the model that leads to the same axial membrane force from both axial and bending.
- 10) The initial flaw (axial or circumferential) is assumed to be semi-elliptical and the crack shape (i/a ratio) remains constant during crack growth. The magnitude of crack growth increment is driven by the K1 values at the deepest point (AREVACGC 6.0, Reference [7]).
5.0 INPUTS 5.1 Geometry The major dimensions used to build the FEM are shown in Figure 5-1, with values listed in Table 5-1. For the tubesheet perforated region, the effective Youngs modulus and the effective Poissons ratio are calculated from Appendix A of the ASME Code (Reference [14]), consistent with the values determined in the original stress reports.
Table 5-1: RSG Lower Assembly Major Dimensions Component Dimension Symbol Value Tubesheet OD (in.)
A 135.65 ID, primary side, base metal (in.)
B 126.33 ID, secondary side (in.)
C 130.2 Height, overall (in.)
D 39.01 Height, primary side, base metal (in.)
E 13.82 Thickness (in.)
F 21.34 Diameter, perforated (in.)
G 12.350 Divider plate lane, solid (in.)
H 4.3588 Cladding thickness, tubesheet surface (in.)
I 0.315 Cladding thickness, ID surface (in.)
J 0.20 Cladding height, Alloy 600/690 (in.)
K 2.165 Fillet radius, primary side (in.)
L 1.58 Channel Spherical head inside radius, base metal (in.)
M 65.12 Head Spherical head outside radius (in.)
N 70.32 OD, cylinder portion (in.)
0 135.65 ID, cylinder portion (in.)
P 126.33 Height, base metal (in.)
Q 50.1 Cladding thickness (in.)
R 0.2 Divider Thickness (in.)
S 2.08 Plate Weld toe height, on tubesheet cladding (in.)
T 1.29 Angle(°)
U 5.5 Weld toe height, on channel head cladding (in.)
V 1.29 Angle(°)
W 15 SS weld layerthickness (in.)
X 0.2 Page 13
framatome Document No. 86-9366726-002 5.2 Material Materials of the modeled components are listed in Table 5-2. The cladding and weldment materials are taken from Reference [2]. Note that SA-508 Cl. 3a is the prior designation of SA-508 Gr. 3 Cl. 2, i.e., they are the same material.
Cracking Assessment for Framatome RSG Channel Head Assembly Figure 5-1: RSG Lower Assembly FEM Dimensions Page 14
framatome Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly Table 5-2: RSG Lower Assembly Materials Note:
Region Component Typical Material Base Metal Tubesheet SA-508 Cl. 3a or SA-508 Gr.3 Cl.2 Channel head SA-508 Cl. 3a or SA-508 Gr.3 Cl.2 Lower shell SA-508 Cl. 3a or SA-508 Gr.3 Cl.2 Divider plate (& closure) (1)
SB-168, UNS06690 Cladding Tubesheet primary side flat surface (2)
FM 82/182 Tubesheet primary side cylindrical surface E308L/E309L, EQ3O8L/EQ3O9L Channel head inside surface EQ3O8L/EQ3O9L Weld Divider plate to tubesheet cladding (2)
FM 152 Divider plate to channel head (2)
FM 152 Tubesheet to channel head (3)
(1) Equivalent SB-163 Alloy 690 UNS N06690 properties are used.
(2) Equivalent SB-166 Alloy 600 UNS N06600 properties are used (3) Base metal material properties are used in the analysis.
The FEA uses the thermal properties mean coefficient ofthermal expansion (ci), specific heat (C), thermal conductivity (k) and the mechanical properties modulus of elasticity (E), Poissons ratio (ii), density (p). The detailed values (thermal & structural) for these materials are listed in Table 5-3 to Table 5-6.
Youngs Modulus (E)
- [106 psi]
Poissons Ratio (ii)
- [unitless]
Density (p)
- [lb/in3]
Coefficient of Thermal Expansion (a)
- [106 inlin-°F]
Thermal Conductivity (k)
- [10 Btu/sec-in-°F]
Thermal diffusivity (Td)
- [in2/sec]
Specific Heat (C = k / (p*Td)
- [Btu/lb-°F]
The Youngs modulus (E) at 100°F or 650°F is an interpolated value.
Table 5-3: SA-508 Grade 3 Class 2 [3I4Ni-lI2Mo-Cr-V]
Component: tubesheet, lower shell, channel head Temp,°F E
i p
ci k
C 70 27.80 0.3 0.2841 6.4 5.046 0.1057 100 27.64 0.3 0.2839 6.5 5.093 0.1081 200 27.10 0.3 0.2831 6.7 5.185 0.1148 300 26.70 0.3 0.2823 6.9 5.185 0.1202 400 26.10 0.3 0.2817 7.1 5.162 0.1259 500 25.70 0.3 0.2809 7.3 5.093 0.1314 600 25.20 0.3 0.2802 7.4 4.977 0.1366 650 24.90 0.3 0.2797 7.5 4.931 0.1399 700 24.60 0.3 0.2794 7.6 4.861 0.1426 Reference
[15]
assumed
[16]
[15]
[15]
Calculated Page 15
framatome Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly Table 5-4: SB-I 66, Alloy 600 UNS N06600 [72Ni-I5Cr-8Fe]
Component: tubesheet cladding Table 5-5: SB-163, Alloy 690 UNS N06690 [58Ni-29Cr-9Fe]
Component: divider plate & its weld Temp,°F E
i p
ci k
C 70 30.30 0.3 0.3063 7.7 1.574 0.1028 100 30.12 0.3 0.3060 7.8 1.620 0.1034 200 29.50 0.3 0.3053 7.9 1.759 0.1075 300 29.10 0.3 0.3045 7.9 1.898 0.1113 400 28.80 0.3 0.3038 8.0 2.037 0.1140 500 28.30 0.3 0.3030 8.1 2.176 0.1173 600 28.10 0.3 0.3023 8.2 2.315 0.1189 650 27.85 0.3 0.3019 8.2 2.384 0.1204 700 27.60 0.3 0.3016 8.3 2.454 0.1218 Reference
[15]
assumed
[16]
[15]
[15]
Calculated Table 5-6: SA-403 Type 304L [I 8Cr-8Ni]
Component: stainless steel cladding Temp,°F E
t p
ci k
C 70 28.30 0.3 0.2864 8.5 1.991 0.1151 100 28.14 0.3 0.2862 8.6 2.014 0.1157 200 27.60 0.3 0.2853 8.8 2.153 0.1209 300 27.00 0.3 0.2844 9.0 2.269 0.1246 400 26.50 0.3 0.2836 9.2 2.407 0.1286 500 25.80 0.3 0.2827 9.4 2.523 0.1313 600 25.30 0.3 0.2818 9.5 2.616 0.1334 650 25.05 0.3 0.2814 9.6 2.685 0.1348 700 24.80 0.3 0.2810 9.7 2.731 0.1358 Reference
[15]
assumed
[16]
[15]
[15]
Calculated Temp,°F E
.t p
c k
C 70 31.00 0.3 0.3063 6.8 1.991 0.1055 100 30.82 0.3 0.3060 6.9 2.014 0.1068 200 30.20 0.3 0.3053 7.2 2.106 0.1106 300 29.90 0.3 0.3045 7.4 2.222 0.1140 400 29.50 0.3 0.3038 7.6 2.338 0.1166 500 29.00 0.3 0.3030 7.7 2.454 0.1184 600 28.70 0.3 0.3023 7.8 2.569 0.1221 650 28.45 0.3 0.3019 7.9 2.616 0.1224 700 28.20 0.3 0.3016 7.9 2.685 0.1243 Reference
[15]
assumed
[16]
[15]
[15]
Calculated Page 16
frarnatorne Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly Table 5-7 lists the value of yield strength (up) and ultimate strength (ui,) at various temperatures per Reference
[15] for the tubesheet base metal.
Table 5-7: Material Strength Temp.
Yield Strength, u Ultimate Strength, au/i Material Component
[°F]
[ksi]
[ksi]
70 65.0 90.0 SA-508 Gr. 3 C1.2 Tubesheet 600 54.7 90.0 (SA-508 Cl. 3a) base metal 650 53.9 90.0 700 52.9 90.0 As aforementioned for the reference nil-ductility temperature ofthe tubesheet base metal, the bounding value RTNDT 10°F is used in this analysis.
5.3 Loads The transient data (Normal, Upset and Test conditions) from the four units are reviewed. Enveloped transients along with the bounding numbers of cycles are listed in Table 5-8.
The RSG design life is designated in References [17], [18], [19] and [20] for Callaway-1, Salem-2, P1-I and P1-2, respectively.
Table 5-8: Enveloped Transients and Bounding Cycles Condition Abbr.
Transient name Typical Occurrences Normal HU Heatup @IOOF/hr 200 CD Cooldown @200F/hr 200 UL Unit loading 15-100% offull power (5%/mm) 18,300 UU Unit unloading 100-15% offull power (5%/mm) 18,300 SLI Step load increase of 10% offull power (from 90%)
2,000 SLD Step load decrease of 10% offull power (from 100%)
2,000 LLD Large step load decrease with steam dump 200 FC Feedwater cycling at hot shutdown 2,000 RTR Reduced temperature return to power 2,000 Upset TRT Turbine roll test 20 LOL Lossofload 80 LOP Loss of power 40 LOF Loss offlow 80 RT Reactor trip 400 CRD Control rod drop 80 ISI Inadvertent safety injection 60 EFF Excessive feedwater flow 30 OBE Operating Basis Earthquake 400 Page 17
frarnatorrie Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly Condition Abbr.
Transient name Typical Occurrences Test PSHT Primary side hydrostatic test, primary side 15 SSHT Secondary side hydrostatic test, secondary side 10 PSLT Primary side leak test, primary side 200 SSLT Secondary side leak test, primary side 120 There are two types of supports in the RSGs: the support ring at the tubesheet location; four support lugs attached to the lower outside surface ofthe channel head. The reaction loads at the support ring or lugs are conservatively used in the stress analysis ofthe lower assembly (including the channel head but not inlet/outlet nozzles) performed by Framatome SAS. Out ofthe four units, the support lug loads are identified to generate the highest axial force and bending moment at the triple point cross-section and is therefore used as the bounding loads for the subsequent fracture mechanics analysis. The comparison is documented in Reference [3], with the data taken from References [17], [18], [19] and [20] for Callaway-1, Salem-2, PT-I and P1-2, respectively.
5.4 Finite Element Model The finite element model is developed with ANSYS (Reference [5]). The solid model is shown in Figure 5-2. The model is meshed with 3-D 20-Node SOLID9O elements in the thermal analysis, and with 3-D 20-Node 50L1D186 elements in the stress analysis. The meshed model is shown in Figure 5-3.
In addition, contact elements (CONTAI 74 with TARGE1 70) are inserted at the separation between the tubesheet Alloy 600 cladding and the divider plate Alloy 690 weld from the triple point extending toward the center of the tubesheet over 25% of the length ofthe divider plate. In the thermal analysis, nodes on either side of the crack are coupled and no thermal resistance is considered for the small crack.
Page 18
frarliatorrie Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly Figure 5-2: 3-D Solid Model Page 19
framatome Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly Figure 5-3: Meshed Finite Element Model
/
Page 20
framatome Document No. 86-9366726-002 6.0 CALCULATIONS Cracking Assessment for Framatome RSG Channel Head Assembly 6.1 Finite Element Stress Analysis 6.1.1 Design Conditions The following Design conditions are simulated in the model by applying a uniform and reference temperature of 650°F throughout the model:
1 )
Maximum primary to secondary pressure 2)
Maximum secondary to primary pressure The purpose is to provide a basis for verification ofthe correct behavior ofthe model, the structural boundary conditions, and to verify stress attenuation at regions away from the weld connections. For pressure loads only, the pressure on the hot leg and cold leg remains the same. The global coordinate system is shown in Figure 5-2.
For the first case, the displacement and stress intensity are shown in Figure 6-1 and Figure 6-2, respectively. For the second case, the displacement and stress intensity are shown in Figure 6-3 and Figure 6-4, respectively.
The detailed view of the local region in Figure 6-1 indicates there is 25% separation ofthe divider plate starting from the triple point. Accordingly the very high peak stresses occur near the crack front and the numerical value cannot be treated as the actual stress values due to the stress singularity at this region.
Figure 6-1: Displacement in Design Conditions Case I Unit: inch Scale: 80
.00705
.936E04
.014005
.027917
.020961
.034873
.041829
.055741
.048785
.062697 Page2l
frarnatonie Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly Figure 6-2: Stress Intensity in Design Conditions Case I Unit: psi Scale: 80 S1.!911 41409.9 82738 20745.8 62073.9 103402 124066 165394 144730 186058
.007373
.021759
.036145
.050531
.064917
.014566
.028952
.043338
.057724
.072109 Figure 6-3: Displacement in Design Conditions Case 2 Page 22
framatome Document No. 86-9366726-002 6.1.2 Thermal Analysis Cracking Assessment for Framatome RSG Channel Head Assembly Figure 6-4: Stress Intensity in Design Conditions Case 2 The results ofthe thermal analyses are evaluated to identify the maximum and minimum temperature gradients between critical locations in the model and the corresponding time points. These temperature gradients generate maximum and minimum thermal stresses, which in turn contribute to the maximum range of stress intensities in the model.
In the thermal analysis on the primary side (both the cold leg and hot leg channel), a forced convection HTC (Heat Transfer Coefficient) is calculated to have a range between 0.0119 to 0.0136 Btu/sec-in2-°F (details in Reference [3]). The HTC ofO.0136 Btu/sec-in2-°F is then used for the primary side surfaces. On the secondary side near the RSG tubesheet, an HTC ranging from 0.000802 to 0.001027 Btu/sec-in2-°F is calculated at 15%
normal power without recirculation. The HTC of 0.001 027 Btulsec-in2-°F is applied for the secondary side surfaces. In addition, for the perforated regions the HTC on either side is reduced by a factor of 0.52 (Reference
[30] in [3]) to account for the reduced surface area due to the perforation.
6.1.3 Stress Analysis The nodal solution from the thermal analysis is loaded into the structural analysis with ANSYS. Time points selected from the thermal analysis include those with max/mm temperature gradients as well as those where the internal pressure changes its rate. Internal pressure at each time point is added as the mechanical load. In the stress analysis, the symmetric boundary conditions are applied to both the vertical and horizontal cut-off sections.
Unit: psi Scale: 80 90.5324 25260.8 50431.1 75601.4 100772 12675.7 37846 63016.3 88186.6 113357 Page 23
framatome Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly As shown in Figure 6-5, a total of six path lines are defined for the crack growth analysis. Path lines (P1 to P4) are located on each side of the divider plate near the triple point. Path P5 is between P1 and P3, and P6 is between P2 and P4; both are through the center ofthe divider plate but are not shown in the figure. The axial and hoop stresses, and the metal temperatures along these path lines are extracted for each transient.
Figure 6-5: Crack Growth Path Line Locations Front view I
Tubesheet Cladding (FM 82/1182)
Divider Plate Weld (FM 152)
Divider Plate (SB-168)
Center piece iso view from the right V
Channel Head Cladding (stainless steel, extended to tubesheet cylindrical side)
Center piece right view corner detail Center piece left view corner detail Center piece iso view from the left Page 24
frarnatorne Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly During the stress analysis, local stresses near the triple point and through the base metal are reviewed for every transient and steady state conditions. The path lines are defined passing through the locations that experienced the most extreme stress conditions (the maximum in magnitude and/or in variations).
6.1.4 Steady State Stress on Tubesheet Primary Side Perforated Area In the tube-to-tubesheet region, the possibility that PWSCC may lead to a primary to secondary leak is investigated by determining the stress condition ofthe cladding surface at the steady state operation.
The first load step ofthe unit unloading transient (UU) is steady state operation at 100% power. Post-processing of stress results on the cladding surface over the tube-to-tubesheet region is conducted. The three principal stresses (Gi, G2, 03) on each node ofthe surface are obtained and arranged such that i > G2 c13. For all nodes on the surface, it is demonstrated that G3 > O, indicating that the compressive stress conditions are justified.
6.2 Flaw Evaluation 6.2.1 Applied Stresses 6.2.1.1 Transient and Residual Stresses The cyclic operating stresses needed to calculate fatigue crack growth are obtained from a linear, thermo-elastic finite element analysis described in Section 6. 1. These cyclic stresses are developed for all applicable transients at a number oftime points to capture the maximum and minimum stresses due to fluctuations in pressure and temperature. Enveloped transients along with the bounding numbers of cycles are listed in Table 5-8 for the RSGs design life listed in Section 5.3.
The transient stresses, metal temperatures and pressures on path lines (P1 to P6) are collected from the output files generated in Reference [3] into spreadsheets. These spreadsheets are used by AREVACGC, which reads the appropriate transient stresses, metal temperatures and pressures for the applicable path line.
In addition, a residual stress of+2 ksi (Reference [13]) is added to the thickness ofthe cladding, and no residual stress is assigned to the tubesheet base metal material (see Assumption #6 in Section 4.2).
6.2.1.2 Sustained Stresses due to Support Loads Axial forces and bending moments from the RSG support may introduce sustained axial stresses at the flaw location. There are two types ofsupports in the RSGs: the support ring at the tubesheet location; four support lugs attached to the lower outside surface ofthe channel head. The reaction loads at the support ring or lugs are conservatively used in the stress analysis of the lower assembly (including the channel head but not inlet/outlet nozzles) performed by Framatome SAS. As aforementioned, the support lug loads are found to generate the bounding axial force and bending moment at the triple point cross-section and are therefore used as the bounding loads for the subsequent fracture mechanics analysis. The total axial forces and bending moments are listed in Table 6-1 and Table 6-2.
Page 25
frarnatorne Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly Table 6-1: Equivalent Axial Force and Bending Moment at P1/P31P5 Faxiai Mbending Mb force Loading lbs in-lbs in-lbs Deadweight (DW) 1,100,000 1,767,767 8,192,709 Pressure 200,000 2,828,427 2,730,903 Thermal Exp. (TH) 1,200,000 9,333,810 5,461,806 OBE 2,800,000 16,122,035 218,472,237 DBE 4,000,000 18,384,776 327,708,355 Pipe Rupture 6,000,000 36,062,446 491,562,532 Table 6-2: Equivalent Axial Force and Bending Moment at P21P41P6 Faxiai Mbending Mb force Loading lbs in-lbs in-lbs Deadweight (DW) 1,100,000 1,767,767 7,957,285 Pressure 200,000 2,828,427 2,652,428 ThermalExp.(TH) 1,200,000 9,333,810 5,304,856 OBE 2,800,000 16,122,035 212,194,260 DBE 4,000,000 18,384,776 318,291,390 Pipe Rupture 6,000,000 36,062,446 477,437,084 6.2.1.3 Seismic Event The effect ofthe seismic loads on fatigue crack growth is addressed by modeling the OBE (Operating Basis Earthquake) seismic event as a transient event. The axial stresses due to the axial force and bending moment from the seismic loads (OBE in Table 6-1 and Table 6-2) are calculated. The results are given in Table 6-3, where R and R0 are the inside and outside radius, respectively.
Table 6-3: Axial Stresses Due to Seismic Loads Path Line OBE (+/-)
P1/P31P5 I
P2/P4/P6 By axial force, [psi]
1,256 1,402 By bending moment, at R,, [psi]
3,093 3,362 By bending moment, at R0, [psi]
3,363 3,622 The baseline through-wall axial stress distribution for each path line is obtained from the stress state at steady state conditions. The OBE seismic transient is only applicable to the evaluation ofcircumferential flaws, which are driven by axial stresses. Semi-elliptical axial flaws are driven by hoop stresses, and there are no significant hoop stresses due to seismic loads.
6.2.1.4 Crack Face Pressure Loads For the fatigue crack growth analyses, it is conservatively assumed that primary water gets into the flaw and the crack faces are subjected to pressure loads. Time-dependent pressure loads for each transient are included in the crack growth calculation.
Page 26
frarnatorne Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly 6.2.1.5 Combination of Stresses Axial and hoop residual stresses at the shutdown condition (+2 ksi over the cladding thickness) are combined with the transient stress results, and sustained stresses such as loads due to deadweight and thermal expansion, and pressure acting on the crack faces ofthe postulated flaws to obtain the combined stresses over each path line.
These results are used to perform the fatigue crack growth calculation.
6.2.2 Fatigue Crack Growth Analysis For every postulated flaw type, a crack growth analysis is performed with the life time cycles listed in Table 5-8 and the final crack depth (and length) is calculated. The results are documented in Reference [4]. The maximum applied total SIF (Ki) is calculated for both the initial and final flaw configurations and compared with the flaw acceptance criteria outlined in Section 3.2.5.
The following subsections provide the fatigue crack growth analyses and the flaw size evaluations for the postulated circumferential and axial flaws. Based on the Design Specifications ofthese units, the following load combinations are used in the calculation ofthe maximum K1.
Normal Conditions (including Normal, Upset and Test Conditions):
DW + Pressure + OBE + Thermal Emergency/Faulted Conditions:
DW + Pressure + SRSS(DBE, Pipe Rupture) + Thermal 6.2.2.1 Circumferential Flaw For the circumferential flaw, the initial and final flaw sizes at each location are summarized in Table 6-4. The maximum SIF is calculated with the initial and final flaw sizes and the results are documented in Reference [41.
For the Emergency/Faulted Conditions, transient stresses at the beginning of HU and at the end of HU during steady state are taken as the instantaneous stress conditions. The stresses are then combined with the external stresses due to support pad loads to calculate the maximum SIF to be compared with the acceptance criteria.
Table 6-4: Initial and Final Circumferential Flaw Sizes Path Condition Depth (a), inch Length (1), inch Ratio (i/a)
Ratio (a/t)
I Initial 0.330 2.080 6.303 0.061 Final 1.338 8.435 6.303 0.246 2
Initial 0.200 2.080 10.400 0.041 Final 0.659 6.851 10.400 0.136 3
Initial 0.330 2.080 6.303 0.061 Final 1.148 7.238 6.303 0.212 4
Initial 0.200 2.080 10.400 0.04 1 Final 0.235 2.444 10.400 0.048 5
Initial 0.330 2.080 6.303 0.061 Final 0.375 2.365 6.303 0.069 6
Initial 0.200 2.080 10.400 0.041 Final 0.203 2.114 10.400 0.042 Page 27
frarnatorrie Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly 6.2.2.2 Axial Flaw Similarly for the axial flaw, the initial and final flaw sizes at each location are summarized in Table 6-5.
Table 6-5: Initial and Final Axial Flaw Sizes Path Condition Depth (a), inch Length (1), inch Ratio (i/a)
Ratio (a/t) 1 Initial 0.330 1.980 6.000 0.061 Final 0.443 2.660 6.000 0.08 1 2
Initial 0.200 1.200 6.000 0.041 Final 0.214 1.282 6.000 0.044 3
Initial 0.330 1.980 6.000 0.061 Final 0.357 2.140 6.000 0.065 4
Initial 0.200 1.200 6.000 0.041 Final 0.211 1.266 6.000 0.043 5
Initial 0.330 1.980 6.000 0.061 Final 0.331 1.983 6.000 0.061 6
Initial 0.200 1.200 6.000 0.041 Final 0.200 1.200 6.000 0.041 6.2.2.3 Resolution of Fatigue Crack Growth in LAS with the 2019 Edition of the ASME Code, Section Xl Note that the fatigue crack growth for the tubesheet base material is only implemented for ASME Code years of 1 992 and 1 995 with 1 996 Addenda in AREVACGC (Reference [7]). For this analysis, the Code year of 1 995 is utilized in AREVACGC. The difference between the applicable Code year ofASME B&PV Section XI, Article A-4300, year 2019, Reference [6] and the utilized Code year of 1995 is in the determination ofzlKi when R < 0.
The following method is applied for computing zlKi when R < 0 per the ASME B&PV Code Section XI, Article A-4300, Code year 1995:
For2R0 zIK1K,nax.
For R < 2 zlKj= (1 R) KmaI3.
The parameters R, Kmax, Kmin, and (0.8) x1.12oça, are evaluated conservatively for the initial flaw size of the postulated circumferential and axial flaws for all transients evaluated. The computed Kmax Krnin for these transients are all less than (0.8) xJ l2uy&a. Therefore, the computed ztKi performed by AREVACGC (Reference
[7]) with 1995 version ofASME B&PV Code Section XI yields the same results as the applicable ASME Code Section XI, year of 201 9 (Reference [6]). Therefore, there is no impact on the results ofthis analysis.
6.3 Tube-to-Tubesheet Weld Material A materials assessment is performed in order to determine whether or not the tube-to-tubesheet welds have a chromium content of 22%, consistent with the requirements of EPRI Technical Report 3002002850 (Reference
[1]) and with NRC License Renewal Interim StaffGuidance 2016-01 (LR-ISG-2016-01) (Reference [21]) which identifies for units with thermally treated Alloy 690 steam generator tubes with tubesheet cladding using Alloy 600 weld material, a plant-specific aging management program (AMP) is necessary unless the applicant confirms that the industrys analyses for tube-to-tubesheet weld cracking (e.g., chromium content for the tube-to-tubesheet is approximately 22 wt % and the tubesheet cladding is in compression) are applicable and bounding for its unit, Page 28
frarriatonie Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly and the applicant will perform general visual inspections ofthe tubesheet region looking for evidence of cracking (e.g., rust stains on the tubesheet cladding) as part ofthe steam generator program.
Framatome replacement steam generators (RSGs) listed in Section 1.0 are evaluated for the chromium content of the tube-to-tubesheet welds. The methodology used to determine the chromium content in Reference [2] for the tube-to-tubesheet welds and the results ofthis evaluation are shown in text and Table 6-6, respectively.
Chromium content for each material is based on the ASME B&PV Code Section II minimum design requirements A weld dilution of 50% is considered for the Tube material and Tubesheet cladding material Table 6-6: Framatome RSG Tube-to-Tubesheet Welds Materials and Chromium Content Operating Unit Tubesheet Cladding Material Tube Material Cr wt%
Callaway-1 UNS W86182/ENiCrFe-3 (FM 182) 58-163-690
<22 P1-2 & P1-2 UNS W86182/ENiCrFe-3 (FM 182)
SB-163-690
<22 Salem-2 UNS W86182/ENiCrFe-3 (FM 82)
SB-163-690
<22 It is noted in Reference [1] Section 2.6.2, a more appropriate equation for weld dilution is:
%Crweld
= %Crtube(O.52) + %Crclad(O.48)
Eq. 1 Calculating the weld dilution for Alloy 690 and FM 1 82 using Eq. 1 yields a chromium content ofthe weld of below the 22 wt% threshold. It is noted Reference [1j Section 2.7 calculates a mean chromium content value using Eq. 1 for Alloy 690 and FM 182 of22.15 wt%. Therefore, it is possible a record search ofthe certified material test reports (CMTRs) for the RSGs (which is outside the scope ofthis task) with Alloy 690/FM 1 82 tube-to-tubesheet welds may identify chromium content values, when input into Eq. 1, will yield a chromium content which exceeds 22 wt%.
However, based on this evaluation, it cannot be determined that the Callaway-1, P1-I & P1-2, and Salem-2 RSGs meet the requirement ofat least 22 wt% Cr in the tube-to-tubesheet welds.
7.0 RESULTS AND CONCLUSION The flaw tolerance evaluation ofthe Framatome supplied RSG channel head and tubesheet (Callaway-1, P1-1/2, Salem-2) is performed with the stress profiles provided by a detailed finite element analysis. The bounding transients (along with the design cycles) and support loads out of these units are used. It is concluded that the RSG channel heads are not compromised by the postulated circumferential or axial flaw initiated from the divider plate for the design life of the plant, by the criteria per ASME Code Section XI IWB-3600 (Reference [6]).
The final flaw evaluation results are summarized in Table 7-1 for the circumferential flaws and in Table 7-2 for the axial flaws (bold fonts for limiting values).
Page 29
frarnatorne Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly Table 7-1: Final Circumferential Flaw Evaluation Path P1 P2 P3 P4 P5 P6 Final Depth (a), inch 1.338 0.659 1.148 0.235 0.375 0.203 Flaw Length (1), inch 8.435 6.851 7.238 2.444 2.365 2.114 Size Ratio (1/a) 6.303 10.400 6.303 10.400 6.303 10.400 Ratio(a/t) 0.246 0.136 0.211 0.048 0.069 0.042 Normal Kmax, ksWin 49.1 37.2 52.5 30.1 37.8 16.2 Kmax Event PSHT EFF RT EFF PSHT PSHT Allowable, ksigin 63.2 63.2 63.2 63.2 63.2 63.2 Emergency/
Kmax, ksWin 56.1 40.9 52.2 1 9.5 32.2 20.6 Faulted Kmax Event HU end HU end HU end RU end RU end RU end Allowable,ksigin 141.4 141.4 141.4 141.4 141.4 141.4 Table 7-2: Final Axial Flaw Evaluation Path P1 P2 P3 P4 P5 P6 Final Depth(a),inch 0.443 0.214 0.357 0.211 0.331 0.200 Flaw Length (1), inch 2.660 1.282 2.140 1.266 1.983 1.200 Size Ratio (1/a) 6.000 6.000 6.000 6.000 6.000 6.000 Ratio (alt) 0.081 0.044 0.065 0.043 0.061 0.04 1 Normal Kmax, ksigin 19.687 15.682 20.353 15.521 10.186 4.971 KmaxEvent SSRT SSHT SSHT SSHT RT SSHT Allowable, ksWin 63.2 63.2 63.2 63.2 63.2 63.2 Emergency/
Kmax, ksigin 3.1 1.5 2.7 1.5 5.9 2.8 Faulted Krnax Event RU begin RU begin RU begin RU begin RU end HU end Allowable, ksiJin 72.2 72.2 72.2 72.2 141.4 141.4 Based on the evaluation presented in Section 6.3, it cannot be determined that the RSGs at Callaway-1, P1-1/2, and Salem-2 meet the requirement of at least 22 wt% Cr in the tube-to-tubesheet welds.
Page 30
frarriatorrie Document No. 86-9366726-002 Cracking Assessment for Framatome RSG Channel Head Assembly
9.0 REFERENCES
References identified with an (*) are maintained within Framatome SAS Records System and are not retrievable from Framatome Records Management. These are acceptable references per Framatome Administrative Procedure 0402-01, Attachment 7. See page 2 for Project Manager Approval of customer references.
I.
EPRI Steam Generator Management Program Report 3002002850, Investigation ofCrack Initiation and Propagation in the Steam Generator Channel Head Assembly, EPRI, Palo Alto, CA. 2014.
2.
Framatome Document 51-9268036-000, EPRI SGMP for Channel Head Aging ofthe Framatome RSG Designs.
3.
Framatome Document 32-9360111-001, Framatome RSG Channel Head and Tubesheet Stress Analysis for Flaw Evaluation.
4.
Framatome Document 32-9364633-001, Framatome RSG Channel Head and Tubesheet Flaw Tolerance Evaluation.
5.
ANSYS Finite Element Computer Code, Version 19.2, ANSYS, Inc., Canonsburg, Pa.
6.
ASME Boiler and Pressure Vessel Code Section XI, Rules for Inservice Inspection ofNuclear Power Plant Components, 2019 Edition.
7.
Framatome Document 32-9055891-007, Fatigue and PWSCC Crack Growth Evaluation Tool AREVACGC.
8.
Code ofFederal Regulations, Title 10, Part 50.55a, Domestic Licensing ofProduction and Utilization Facilities, Codes and Standards, Federal Register Vol. 80.
9.
1885 Rev. B, Callaway Unit I Replacement Steam Generators Section 13: Non Ductile Failure Risk.
1 0.
- BUCRPI/NGV 1746 Rev. E, Prairie Island Unit I Replacement Steam Generators Section 16 : Non Ductile Failure Risk.
I 1.
2596 Rev. A, Prairie Island Unit 2 Replacement Steam Generators Section 16: Non Ductile Failure Risk.
12.
- BUCR5ANGV 1998 Rev. E, Salem Unit 2 Replacement Steam Generators Section 14: Non Ductile Failure Risk.
1 3.
EPRI-Framatome Project Agreement 10012545, Divider Plate Cracking Assessment for Framatome Replacement Steam Generators, EPRI Task ID 1-072913-04-01, May 29, 2020.
14.
ASME Boiler and Pressure Vessel Code,Section III, Division 1, 1 995 Edition with Addenda through N97.
1 5.
ASME Boiler and Pressure Vessel Code,Section II, Part D, I 995 Edition with Addenda through 1997.
16.
Framatome Document NPGD-TM-500 Rev D, NPGMAT, NPGD Material Properties Program, Users Manual (03/1985).
17.
- M1 1 83 (Q) Rev. 3, Technical Specification for Replacement Steam Generators Callaway Plant Unit 1.
I 8.
- 52RCMD50397 Rev. 3, Design Specification for Replacement Stream Generators Salem Unit 2.
I 9.
- M530.0001..00510, Certified Design Specification for Replacement Steam Generators Northern States Power Company Prairie Island Nuclear Generating Plant Unit I.
20.
- M5300001.007..05, Certified Design Specification for Replacement Steam Generators Northern States Power Company Prairie Island Nuclear Generating Plant Unit 2.
21.
NRC License Renewal Interim Staff Guidance LR-ISG-2016-01, Changes to Aging Management Guidance for Various Steam Generator Components, 2016, ML16237A383.
22.
- BUCRCA/NGV 1872 Rev. F, Callaway Unit I Replacement Steam Generators Design Report.
23.
- BUHSCA/NGV0001 Rev. C, Procurement Specification SA-508 Class 3a Heavy Forgings for Steam Generators Callaway Plant Unit 1.
Page 31