ML19072A096

Information Regarding Dissimilar Metal Weld 2-CV-2005-30 Flaw Characteristic and Repair Weld Overlay

ML19072A096
Person / Time
Site:	Calvert Cliffs
Issue date:	03/11/2019
From:	Flaherty M Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML19072A096 (23)

Text

,M,* 7

, b"' Exelon Generation Mark D. Flaherty Site Vice President Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, MD 20657 410 495 5200 Office 443-534-5475 Mobile www.exeloncorp.c om mark.flaherty@exeloncorp.com 10 CFR 50.55a March 11, 2019 U.S. Nuclear Regulatory Commission Attn: Document Control Desk 11555 Rockville Pike One White Flint North (P1-37)

Rockville, MD 20852 Calvert Cliffs Nuclear Power Plant, Unit 2 Renewed Facility Operating License No. DPR-69 NRC Docket No. 50-318

Subject:

Information Regarding Dissimilar Metal Weld 2-CV-2005-30 Flaw Characteristic and Repair Weld Overlay

References:

1) Letter from N. L. Salgado (NRC) to G. H. Gellrich (CCNPP), dated February 24, 2011, Relief from Requirements of the ASME Code (ML 11041062)

Examinations performed during the current refueling outage at Calvert Cliffs Nuclear Power Plant, Unit 2 have identified a change from previous examinations in a circumferential flaw in the 21A cold leg charging inlet nozzle-to-safe-end dissimilar metal weld. This examination was performed to meet the requirements of ASME Code Case N-770-2, Table 1, Note 5 and 10CFR50.55a(g)(6)(ii)(F). Exelon has elected to perform a full structural weld overlay repair of 2-inch nominal pipe size weld 2-CV-2005-30 in the current refueling outage. A report describing the flaw in the 21A cold leg charging inlet nozzle-to-safe-end dissimilar metal weld 2-CV-2005-30, including flaw characteristics detected during the weld examination, is contained in Attachment (1).

In Reference 1, Calvert Cliffs Nuclear Power Plant, LLC was granted a relief from certain requirements of the American Society of Mechanical Engineers (ASME) Code for dissimilar metal weld repairs. Reference 1 required that certain information related to a repair performed using this Code relief would be provided to the Nuclear Regulatory Commission prior to entry into Mode 4 following the weld repair. The information in Attachments (1) and (2) meets this requirement.

NRC March 11, 2019 Page2 If you have any questions concerning this letter, please contact Larry Smith at 410-495-5219.

Respectfully, Site Vice President MDF/KLG/lmd Attachments: 1) Description of Flaw in the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Dissimiiar Metal Weld

2) Full Structural Weld Overlay Sizing for the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Weld cc: Regional Administrator - NRC Region I NRC Senior Resident Inspector - Calvert Cliffs Nuclear Power Plant NRC Project Manager - Calvert Cliffs Nuclear Power Plant D. Tancabel, State of Maryland

Attachmen t 1 Descriptio n of Flaw in the 21 A Cold Leg Charging Inlet Nozzle-to-Safe-End Dissimilar Metal Weld

Attachment 1 Description of Flaw in the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Dissimilar Metal Weld Introduction 2-inch nominal pipe size Weld 2-CV-2005-30, summary number CCNP-2-152440-RI, was examined in CC2R23 (2019) in accordance with the Calvert Cliffs lnservice Inspection (ISi)

Program. The examination was performed as a successive examination based on ASME Code Case N-770-2, Table 1, Note 5 due to a flaw identified in CC2R22 (2017). The flaw size remains less than the critical flaw size identified in the 2017 analytical evaluation, however flaw growth may be beyond that predicted. Although the flaw growth was not significantly larger than expected UT examination variability, Calvert Cliffs chose to install a weld overlay repair in CC2R23 to eliminate future risk.

Discussion of 2019 Examination The 2019 examination was a fully encoded phased array ultrasonic examination (PAUT) and was qualified to ASME Code Section XI, Mandatory Appendix VIII, Performance Demonstration for Ultrasonic Examination Systems. The PAUT procedure is qualified to detect, length size, and depth size circumferential and axial flaws within the specified examination volume from the outside diameter. Full examination coverage was achieved to meet the requirements of ASME Code Case N-770-2 as conditioned by 10CFR50.55a and as indicated in Table 1 below.

Table 1 Required Volumetric Examination Coverage Achieved - 2019 Exam Applicable Material Circumferential Flaw Combined Coverage Axial Flaw Coverage Coverage Assessment 2-CV-2005-30 100% 100% 100%

The evaluation of the recorded Ultrasonic Testing (UT) data identified one (1) circumferentially oriented flaw. The flaw is ID surface connected with a 55% thru-wall extent, 0.33 inch flaw-height as measured from the ID surface. The length of the flaw, as measured from the inside diameter, was recorded as 1.40 inch. The flaw size remains less than the critical flaw size identified in the 2017 flaw evaluation. Figure 1 and 2 provide a graphic representation of the flaw identified in 2019.

/

Attachment 1 Description of Flaw in the 21 A Cold Leg Charging Inlet Nozzle-to-Safe-End Dissimilar Metal Weld Figure 1 Weld 2-CV-2005-30 Flaw Axial Location - 2019 Examination

~

0.60 in C/S ozzle 5/S Safe-lnd Stainless Steel 0.64 in Figure 2 Weld 2-CV-2005-30 Flaw Circumferential Location - 2019 Examination

~ t mo TDC]

/ Clad I

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Attachment 1 Description of Flaw in the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Dissimilar Metal Weld A comparison of the measured flaw sizes from the 2017 examination to the 2019 examination results in a 0.13" through-wall increase in size and a 0.17" length increase in size. ASME Code Section XI, Appendix VIII, Supplement 1O requires RMS errors to be less than 0.75" for length sizing and 0.125" for through-wall sizing. The differences in flaw size between the 2017 examination and the 2019 examination are slightly greater than the qualification through-wall sizing error and within the length sizing error band.

Conclusion The 2019 flaw size exceed the predicted flaw growth in the 2017 analytical evaluation. The flaw remained below the critical flaw size identified in the analytical evaluation. Based on the UT examination, flaw size change between 2017 and 2019, Calvert Cliffs chose to repair the flaw by full structural weld overlay in accordance with approved criteria.

Attachment 2 Full Structural Weld Overlay Sizing for the 21 A Cold Leg Charging Inlet Nozzle-to-Safe-End Weld

Attachment 2 Full Structural Weld Overlay Sizing for the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Weld FULL STRUCTU RAL WELD OVERLAY SIZING FOR THE TWO-INCH REACTOR COOLANT CHARGING SYSTEM INLET NOZZLE Table of Contents

2.0 DESCRIPTION

OF CONFIGURATION AND REPAIR PROCESS ........................ .

3.0 ASME CODE CRITERIA ........................................................................ .- ............. .

4.0 LOADS AND DESIGN INPUTS ........ ,................................................................... .

5.0 WELD OVERLAY THICKNESS SIZING ............................................................... .

6.0 WELD OVERLAY LENGTH REQUIREMENTS ..................................................... .

6.1 Structural Reinforcement. ...........................................................................

6.2 Preservice Examination .............................................................................

6.3 Area Limitation on Nozzle ......................_................................................... .

6.4 Maximum Overlay Sizing ...................*.................................................*......

7.0 DISCUSSIONS AND CONCLUSIONS ................................................................. .

8.0 REFERENCES

List of Tables Table 1: Safety Factors for Sizing - Circumferential Flaw ......................................... .

Table 2: Specified Forces and Moments at the Safe End-to-Elbow Weld Locations ..

Table 3: Forces and Moments at Weld Locations (Including Moment Adjustment Due to Safe End Length) .... ,..................................................................... .

Table 4: Dimensions for Overlay Sizing .................................................................... .

Table 5: Calculated Stresses .....................................................................................

Table 6: Allowable Stresses and Calculated Stress to Allowable Stress Ratios ........ .

Table 7: Minimum Required Overlay Length ............................................................. .

Table 8: Minimum Required Overlay Dimensions ..................................................... .

List of Figures Figure 1: Locations Examined for FSWOL Sizing .................................................*...

Figure 2: Full Structural Weld Overlay Geometry, Minimum Dimensions (Schematic Representation) .....*...................................................................................

Attachment 2 Full Structural Weld Overlay Sizing for the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Weld

1.0 INTRODUCTION

A weld overlay repair is being designed for the charging nozzle-to-safe end dissimilar metal weld (DMW) and safe end-to-elbow stainless steel weld (SSW) at the Calvert Cliffs Nuclear Power Plant (CCNPP), Units 1 and 2. This calculation documents the required structural sizing calculations for a full structural weld overlay (FSWOL) repair of these welds, based on plant-specific geometry, and loadings, and the design requirements of ASME Code,Section XI Code Case N-740-2 [4].

2.0 DESCRIPTION

OF CONFIGURATION AND REPAIR PROCESS The charging nozzle forging is A-105 Grade II carbon steel and the safe end is A-182 Type 316 stainless steel [9]. The attached charging piping is A-376 Type 316 stainless steel [10, Attachment D; and 12, page 5]. The DMW which joins the charging nozzles to the safe ends are fabricated using Alloy 82/182 [13] nickel-based weld metal.

The full structural overlay repair will be performed using primary water stress corrosion cracking (PWSCC) resistant Alloy 52M material deposited around the circumference of the configuration.

The overlay material will be deposited using gas tungsten arc welding (GTAW) process. For the Alloy 52M weld overlay filler metal, the selected material is88-166, Rod & Bar, Alloy 690 (58Ni-29Cr-9Fe) [5].

3.0 ASME CODE CRITERIA The applicable ASME Code,Section XI edition for Calvert Cliffs Nuclear Power Plant, Units 1 and 2 is the 2004 Edition of ASME Code,Section XI [2] per Section 1.4 of Reference 11. The basis for FSWOL sizing is the ASME Code,Section XI Code Case N-740-2 [4] and the ASME Code,Section XI, Division 1, Class 1 [2] rules for allowable flaw sizes in austenitic and ferritic piping (IWB-3640). The ASME Code,Section XI Code Case N-740-2 [4] incorporates the weld repair by overlay approach documented in Code Case N-504-3 [6], and the temper bead welding approach documented in Code Case N-638-1 [7], and applies these to similar and dissimilar metal welds.

To determine the overlay thickness, Code Case N-740-2 refers to the requirements of ASME Code,Section XI, IWB-3640. IWB-3640 of the applicable Code refers to Appendix C, which contains the specific methodology for meeting the allowable flaw sizes. The overlays are to be applied using the GTAW process, which is a nonflux process. Therefore, for circumferential flaws, the source equations in Appendix C, Section C-5320 (limit load criteria) are the controlling allowable flaw size equations for combined loading (membrane plus bending) and membrane-only loading. These equations are valid for flaw depth-to-thickness ratios for flaw lengths ranging from O to 100% of the circumference as defined in Section C-5320 of Appendix C. For purposes of designing the overlay, a circumferential flaw is assumed to be 100% through the original wall thickness for the entire circumference of the item being overlaid.

Attachment 2 Full Structural Weld Overlay Sizing for the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Weld The overlay is sized by using the source equations in Section C-5320 [2].

The allowable bending stress under combined membrane plus bending loads is given by the equation:

C-5321, where, a; =-;-2a1 ( 2-t aJ sin/J, for (B + /3) > n, The allowable membrane stress is given by the equation:

S 1

= a: C-5322, SFm where, and Sc = allowable bending stress for a circumferentially flawed pipe ifb = bending stress at incipient plastic collapse SFm = safety factor for membrane stress based on Service Level as shown in Table 1 [2, C-2621]

SFb = safety factor for bending stress based on Service Level as shown in Table 1 [2, C-2621]

a = flaw depth t = total wall thickness (includes overlay thickness, in this case)

Sr = allowable membrane stress for a circumferentially flawed pipe ifm = membrane stress at incipient plastic collapse e = half flaw angle [2, Figure C-4310-1 ], 180° or rr for a 100% full circumferential flaw

{3 = angle to neutral axis of flawed pipe in radians

<Ym = unintensified primary membrane stress at the flaw location

<Yt = flow stress= (Sy+ Su)/2 [2, C-8200(a)]

Sy = specified value for material yield strength [5] at the evaluation (operating) temperature

Attachment 2 Full Structural Weld Overlay Sizing for the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Weld Su = specified value for material ultimate strength [5] at the evaluation (operating) temperature Safety factors are provided in Appendix C of Section XI for evaluation of flaws in austenitic stainless steel piping. The safety factors used for the weld overlay sizing are shown in Table 1 and are taken from C-2621 [2].

Table 1: Safety Factors for Sizing - Circumferential Flaw Service Membrane Stress Bending Stress Safety Factor, SFm Safety Factor, SFb Level A 2.7 2.3 B 2.4 2.0 C 1.8 1.6 D 1.3 1.4 The overlay thickness must be established so that the flaw assumption herein meets the allowable flaw depth-to-thickness ratio requirement of the source equations [2, C-5320], for the thickness of the weld-overlaid item, considering primary membrane-plus-bending stresses, as well as membrane-only stresses, per the source equations defined previously. Since the weld overlay is austenitic material and applied with a nonflux welding process, which has high fracture toughness, the limit load failure mode is applicable [2, Figure C-4210-1 for nonflux welds] and hence limit load evaluation techniques are used here.

The non-overlaid piping stresses for use in the equations are usually obtained from the applicable stress reports for the items to be overlaid. However, in this calculation, since the stresses are not provided, they are calculated based on forces and moments at the welds using equations from C-2500 of Section XI, Appendix C as described below.

Primary membrane stress ( am) is given by:

O"m =pD/(4~, where:

p = maximum operating pressure for the Service Level being considered D = outside diameter of the component including the overlay t = thickness, consistent with the location at which the outside diameter is taken including the overlay (note that any inside diameter (ID) cladding is not counted toward wall thickness)

Primary bending stress ( O"b) is given by:

O"b = DMt/(21), where:

D = outside diameter of the component including the overlay d = inside diameter, consistent with the point at which the outside diameter is taken (note that ID cladding is not counted toward the inside diameter)

Attachment 2 Full Structural Weld Overlay Sizing for the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Weld Mb = resultant moment for the appropriate primary load combination for each Service Level (square root of the sum of the squares (SASS) of three moment components in X, Y, and Z directions)

I = moment of inertia, (rr/64) (D4- cf)

The contribution of axial and shear forces to piping stress (other than force couples contributing to moments) is not included based on C-2500 of Section XI, Appendix C [2].

The following load combinations are used for the full structural weld overlay. These are equivalent to the load combinations defined in Reference 8 (Section 4.3.7.1). Reference 8 refers to design seismic and maximum seismic, which are referred to in References 1O and 12 as operational basis earthquake (QBE) and design basis earthquake (DBE), respectively.

These two cases are equivalent and are referred to in this calculation as operational basis earthquake and design basis earthquake:

Service Level A (Normal): Pressure (P) + Deadweight (OW)

• Service Level 8 (Upset): P + OW + Operational Basis Earthquake (QBE)

Service Level C (Emergency): P +OW+ Design Basis Earthquake (DBE)

Service Level D (Faulted): P + OW + DBE + Pipe Rupture Pipe rupture loads are not present in the RCS Specification document [8] or previous CCNPP calculations [10, 12] and are assumed to be zero for this calculation. Therefore, it is assumed that the Service Level C stress ratios will govern over the Service Level D stress ratios since the safety factors for Service Level C condition (1.8 for SFm and 1.6 for SFb) are higher than the safety factors for Service Level D condition (1.3 for SFm and 1.4 for SFb) and the loads for the two service levels are the same.

Service Levels A, 8, C, and D in the ASME Code [2] are alternatively referred as Normal, Upset, Emergency, and Faulted conditions, respectively, in this evaluation. Per ASME Code Section XI C-5311 for the Combined Loading case, test conditions shall be included with the Service Level 8 Load combination. However, the hydrostatic pressure test is not applicable to the weld overlay repair and is not included in the FSWOL design. In addition, the leak test requirement per ASME Code Section XI, IWB-5220 is included in the design of the FSWOL since the leak test pressure (2250 psia given in Figure 7 of Reference 2) is the same as the operating pressure of 2250 psia

[8, Section 4.1 ]. Therefore, no additional test condition needs to be included with the Service Level 8 Load Combination.

The weld overlay sizing is an iterative process, in which the allowable stresses are calculated and then compared to the stresses in the overlaid component. If the stresses in the component are larger than the allowable stresses in the component then the overlay thickness is increased, and the process is repeated until it converges to an overlay thickness which meets the allowable stresses.

The thickness of the weld overlay is determined through an iterative process. The thickness of the overlay (toi) is assumed resulting in total thickness of (tp + to1) where tp is the original pipe thickness. The applied flaw size-to-thickness ratio based on a FSWOL (flawed through the original pipe wall thickness, tp) is t,J(tp + to1). The allowable stresses are then determined from the source equations (see Section 3.0). If this allowable stress value is greater than the

Attachment 2 Full Structural Weld Overlay Sizing for the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Weld calculated stress for the overlaid component, the overlay thickness (ta,) is reduced. On the other hand, if the allowable stress value is less than the calculated stress for the overlaid component, the overlay thickness (ta,) is increased. The process is repeated until the assumed overlay thickness results in a stress ratio of the calculated stress to the allowable stress that is equal or less than 1.0. As the maximum allowed value for alt is 0.75 [2, C-5320], ta, is initially set as t,)3.

If the overlay thickness of tp/3 meets the allowable stresses for pure membrane and combined membrane plus bending stresses, then no more iterations are performed. If the allowable stresses are not met, then the overlay thickness is increased until the ratio of the computed stress to the allowable stress is less than or equal to 1.0.

In this process, the allowable stresses and adjusted stresses due to overlay thickness iterations are calculated for all applicable Service Levels (A, B, and C) and compared. The service level with the maximum ratio of the calculated stress to the allowable stress will control the overlay thickness.

The axial length and end slope of the FSWOL are sized to be sufficient to provide for load redistribution (considering both axial force and bending loads) from the overlaid component to the weld overlay and back, such that applicable stress limits of the ASME Code, Section Ill, NB-3200

[3] are satisfied. Shear stress calculations are performed to assure that the weld overlay length meets these requirements.

4.0 LOADS AND DESIGN INPUTS Table 2 lists the forces and moments for each reactor charging nozzle as specified in the previous CCNPP calculations [10, pages 42 and 43; and 12, page 51]. In the CCNPP calculations, the loads are oriented locally with the nozzles so that the A-direction is axial to the nozzle in Unit 2 and the X-direction is axial to the nozzle in Unit 1. Therefore, the forces and moments do not need to be rotated into any local coordinate system for the sizing calculation. Table 3 contains the forces and moments that are used for the sizing calculation. In order to bound all four nozzles, the maximum resultant bending moment and corresponding forces are reported among the four nozzles and are used in the analysis. The bounding nozzle is 128 from Unit 1.

Tables 2 and 3 do not include forces and moments due to thermal expansion of the piping attached to the nozzle. For designing FSWOLs, only primary loads are considered and the secondary loads, such as thermal expansion, need not be included in the design calculations.

The moments for the various Service Levels, combined on an absolute basis, are shown in Table

3. That is, in Table 3, all forces and moments are taken as positive and hence assumed to produce tensile stresses.

In addition, the as-welded butt weld (AWBW) is specified as the butt weld between the nozzle and the elbow [1 O, page 11 ], which corresponds to nodes 125 (Nozzle 128) and 219 (Nozzle 11 A)

[1 O,* page 41 ]; and according to the loads tables [10, pages 42 and 43], the loads are taken at these nodes. In Reference 12 (page 5), it is stated that the piping model, in which the loads at the nozzle are tabulated, spans from the safe end of the charging nozzles. Thus, the loads shown in Table 2 are provided at the safe end-to-elbow weld (SSW). These moments are adjusted for the nozzle-to-safe end weld (DMW) to account for the eccentricity between the shear forces (Fx and Fz) at the SSW and the DMW centerlines. The unmachined safe end length of 2.25" is conservatively taken as the eccentricity [9]. The design drawings for the charging nozzle weld details are provided only for CCNPP, Unit 2 [9] and are also used for Unit 1 as well [1, 9].

Attachment 2 Full Structural Weld Overlay Sizing for the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Weld Table 2: Specified Forces and Moments at the Safe End-to-Elb ow Weld LocationsC1>

Unit 1 30" Cold Leg llA Fx (lhsi 3) Fy (lbs) Fz (lbs) Mx (in-lbs) My (in-lbs) Mz (in-lbs)

Dead Weight 1 1 30 -348 264 48 OBEC2)C 4 ) 27 37 10 168 216 984 DBEC2) 41 56 15 252 324 1476 Unit 1 30" Cold Leg 12B Fx Fy Fz Mx My Mz Dead Weight 23 32 135 -3804 120 924 OBEC2)C4 ) 15 41 27 816 616 456 DBEC2) 23 61 41 1224 924 684 Unit 2 30" Cold Leg 21A Fx Fy Fz Mx My Mz Dead Weight -1 -39 -3 360 -132 300 OBEC2)C 4 ) 23 9 11 104 800 288 DBEC2 ) *35 13 17 156 1200 432 Unit 2 30" Cold Leg 22B Fx Fy Fz Mx My Mz Dead Weight 14 30 -5 1236 -168 1776 OBEC2 )C4 ) 25 10 21 184 208 160 DBEC2) 37 15 31 276 312 240 Notes:

1) Forces and moments taken from Reference 1O [Section 8.3] and 12 [Section 4.6].

2) All earthquake loads are reversible.

3) 'x' denotes the nozzle axial direction. 'y' and 'z' are orthogonal to 'x'.

4) QBE values are conservatively taken as DBE/1.5 [10, Section 2.4; and 12, Section 1.2]. QBE scale factors for horizontal (1.875) and vertical (1.5} directions are different. The factor of 1.5 results in the highest QBE loads.

Attachment 2 Full Structural Weld Overlay Sizing for the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Weld Table 3: Forces and Moments at Weld Locations (Including Moment Adjustment Due to Safe End Length)

At safe end-to-pipe weld (SSW) At nozzle-to-safe end weld (DMW)

Msrss, Msrss, Forces, lbs Moments, in-lbs in-lbs Forces, lbs(4) Moments, in-lbs in-lbs Fx(3)

Fy Fz MxC3> My Mz - Fx(3)

Fy Fz Mx(3) My Mz -

DW 23 32 135 -3804 120 924 - 23 32 135 3804 424 996 -

OBE 15 41 27 816 616 456 - 15 41 27 816 678 548 -

DBE 23 61 41 1224 924 684 - 23 61 41 1224 1016 821 -

Service Level A (Nonnal) 23 32 135 3804 120 924 3916 23 32 135 3804 424 996 3955 Service Level B (Upset) 38 73 162 4620 736 1380 4878 38 73 162 4620 1101 1544 4994 Service Level C (Emergency) 46 93 176 5028 1044 1608 5381 46 93 176 5028 1440 1817 5537 Notes:

1) Service Level D is not calculated since it is bounded by Service Level G:

2) Msrss is the SRSS value of Mx, My and Mz.

3) 'x' denotes the nozzle axial direction. 'y' and 'z' are orthogonal to 'x'.

4) Forces at the DMW are assumed equivalent to the forces at the SSW.

Attachment 2 Full Structural Weld Overlay Sizing for the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Weld 5.0 WELD OVERLAY THICKNESS SIZING The normal operating pressure [8, page 9 of 104], nozzle/pipe dimensions [9], and overlay thickness are shown in Table 4. At the nozzle side of the DMW, Location 1A considers only the thickness of the pipe (excluding the thickness of the ID clad/buttering), while Location 1B includes the thickness of the nozzle plus the thickness of the ID clad/buttering (see Figure 1).

An initial alt value of 0.75 (the limiting value as stated in C~5322 of Appendix C of Section XI

[1]) was the initial input to the iteration. The assumed 360° flaw results in a flaw length-to-circumference ratio of 1.0. Figure 1 shows the locations for full structural weld overlay (FSWOL) sizing.

1A/1B 3 4 CHARGING SAFE END ELBOW Figure 1: Locations Examined for FSWOL Sizing Table 4: Dimensions for Overlay Sizing Location 1A Location 18 Location 2 Location 3 Location 4 Nozzle Side of Elbow DMW Nozzle Side of SE Side of DMW SE Side of SSW DMW w/ Butte1 Side of w/o Butter SSW p, psig 2235 2235 2235 2235 2235 0Dp, in 2.8750(2) 2.8750(2) 2.7500(2) 2.7500(2) 2.3750(4) 1Dp, in 2.1250(1) 1.6880(2)(3) 1.6880(2H3) 1.7340(2)( 3) 1. 7340(2) tp, in 0.3748 0.5935 0.5310 0.5080 0.3205 a/j 0.7484 0.7499 0.7499 0.7500 0.7431 to,, in 0.1260 0.1979 0.1771 0.1693 0.1108 tp+ot, in 0.5008 0.7914 0.7081 0.6773 0.4313 Dot, in 3.1270 3.2708 3.1042 3.0887 2.5966 lp+ol, .1n,4 3.691 5.220 4.159 . 4.024 1.788 Notes:

(1) Reference 9 provides nominal ID inside without the butter.

(2) From Reference 9.

(3) From Reference 1, Figure 2.

(4) OD based on 2" schedule 160 piping from References 10 (page 11) and 12 (page 5).

Attachment 2 Full Structural Weld Overlay Sizing for the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Weld The final calculated membrane stresses (a-m) and bending stresses (a-b) at each service level for the pipe + overlay configuration are shown in Table 5. This table also shows the ratio of the membrane stress ( a-m) to the flow stress ( O"t) at the selected locations. The material properties are evaluated at the normal operating temperature of 548° F [8, page 9 of 104] using Section II, Part D of the ASME Code [5].

Table 5: Calculated Stresses Location 1A Location1B Location 2 Location 3 Location 4 Nozzle Side of Elbow Nozzle Side of SE Side of SE Side of DMW Side of DMW w/ Butter DMW SSW SSW w/o Butter Service Level O'm, psi 3,487 2,309 2,449 2,548 3,364

. Sv, psi (52M) 27,708 27,708 27,708 27,708 27,708 Su, psi (52M) 80,512 80,512 80,512 80,512 80,512 O't, psi 54,110 54,110 54,110 54,110 54,110 O'm/O't 0.0644 0.0427 0.0453 0.0471 0.0622 A Normal O'b, psi 1,674 1,239 1,476 1,503 2,844 B Upset O'b, psi 2,114 1,565 1,864 1,872 3,542 Emergency O'b, C

psi 2,344 1,735 2,066 2,065 3,908 Note: Service Level D is bounded by Service Level C and therefore not evaluated.

Table 6 shows the allowable stresses as determined from the source equations discussed in Section 3.0. The membrane and bending stresses, from Table 5, are compared to the allowable stresses as shown by the ratios in Table 6. The limiting cases for the membrane and bending stresses are shown in bold. In the limit load analyses, the flow stress of the Alloy 52M weld overlay material is used, consistent with the assumption of a full 360° flaw through the original pipe wall for the design of the full structural weld overlay.

Attachm ent 2 Full Structural Weld Overlay Sizing for the 21A Cold Leg Charging Inlet Nozzle-to

-Safe-End Weld Table 6: Allowable Stresses and Calculated Stress to Allowable Stress Ratios Location Location 1B Location 2 Location 3 Location 4 1A Nozzle SidE Servi of ce Nozzle Side of DMW w/ SE Side of SE Side of Elbow Side of DMW Butter DMW SSW SSW Level w/o Butter 13 in radians 0.4699 0.5212 0.5148 0.5100 0.4868 acb, psi 19522 21441 21201 21020 20255 A Sc, psi 6292 7868 7676 7535 6689 B Sc, psi 7727 9373 9172 9024 8165 C Sc, psi 10651 12374 12162 12005 '11164 A at1Sc 0.2661 0.1575 0.1923 0.1995 0.4252 B atJSc 0.2736 0.1669 0.2032 0.2075 0.4338 C at1Sc 0.2201 0.1402 0.1699 0.1720 0.3500 C ,

am, psi 13,617 13,531 13,533 13,528 13,903 A Si, psi 5,043 5,011 5,012 5,010 5,149 B St, psi 5,674 5,638 5,639 5,637 5,793 C Si, psi 7,565 7,517 7,518 7,515 7,724 A am!St 0.6914 0.4608 0.4887 0.5085 0.6533 B Om/St 0.6146 0.4096 0.4344 0.4520 0.5807 C am!St 0.4609 0.3072 0.3258 0.3390 0.4355 Notes: acb_ Bending stress at incipient plastic collapse [2, C-5320]

Sc-Allo wable bending stress [2, C-5320]

Si-Allow able membrane stress [2, C-5320]

acm - Membrane stress at incipient plastic collapse [2, C-5320]

(All terms defined in Section 3.0)

Service Level D is bounded by Service Level C and therefore not evaluated.

6.0 WELD OVERL AY LENGT H REQUIREMENTS The weld overlay length must consider three requirements: (1) length required for structural reinforcement, (2) length required for preservice examination access of the overlaid weld, and (3) limitation on the area of the nozzle surface that can be overlaid.

Attachment 2 Full Structural Weld Overlay Sizing for the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Weld 6.1 Structural Reinforcement Structural reinforcement requirements are expected to be satisfied if the weld overlay length is 0.7sfiit on either side of the susceptible weld being overlaid [4], where R is outside radius of the item and tis the nominal thickness of the item at the applicable side of the overlay. However, to assure ASME Code, Section Ill, NB-3200 [3] compliance, detailed shear stress calculations are instead performed to determine the minimum required structural length.

The section along the length of the overlay is evaluated for axial shear due to transfer of axial load and moment from the overlaid item to the overlay. Subparagraph NB-3227.2 [3] limits pure shear due to Design Loadings, Test Loading or any Service Level loadings except Service Level D to 0.6 Sm (Service Level D is bounded by Service Level C and is not evaluated). Therefore, 0.6Sm is used for Service Levels A, B and C. These values are shown in Table 7 for the charging nozzle, pipe, and weld overlay materials.

Shear stress around the circumference at the overlay-base material interface due to axial force and moment loading equals:

r = p X TT X Ra2!As + Ml Ss ,

where, Ro = outside radius of overlaid item at crack L = length of overlay at outside surface of overlaid item on one side of crack As = shear area, 2KRoL Ss = rrR/L p = pressure M = resultant moment from piping interface loads at crack Thus r= p1rR/!(2rrRoL) + M/(1rR/L)

Solving for L and equating rwith the allowable shear stress ( Sa11ow) yields:

L = [pRJ2 + M/(1rR/)]ISa11ow, where, Sa11ow = 0.6Sm (Service Levels A, B, and C)

(Note: Service Level D is bounded by Service Level C and therefore not evaluated)

The evaluation for required length is documented in Table 7 for the charging nozzle and elbow.

The overlay weld metal is also evaluated (at the smallest diameter) as it may control if the base metal has a higher value of Sm. The greater value of the required overlay length will be taken. The material properties are evaluated at the normal operating temperature of 548° F [8, page 9 and 76 of 104] using Section II, Part D of the ASME Code [5].

Since the overlay ends on the nozzle at the one end and the elbow at the other end, and extends over the safe end, the surface shear transfer into the base metal occurs onto the nozzle and elbow only. In this configuration, the requirements for shear lengths at intermediate locations (safe end) are not relevant and would have no influence on the required overlay.

Attachment 2 Full Structural Weld Overlay Sizing for the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Weld The required overlay length is calculated at Locations 1A, 1B and 4 along the nozzle/safe end/elbow configuration (both sides of the DMW and SSW). Note that Location 4 is evaluated twice; with weld overlay metal and with elbow base metal (see Table 7). The design drawing implements a configuration that meets all the designed FSWOL thickness and length requirements.

The lengths shown in Table 7 ensure adequate shear stress transfer along the length of the weld overlay. Service Level C is the most limiting of all cases. This length is sufficient to transfer the imposed loads and maintain stresses (shear) within the appropriate ASME Code allowable limits

[3].

In addition to the necessary shear transfer length, the overlay must be inspectable by POI qualified UT methods. Any additional length determined to be necessary by the UT personnel for proper POI qualified inspection will be noted on a design drawing.

Table 7: Minimum Required Overlay Length Location 1A, 1B Location 4 Location 4 Weld Metal Nozzle Side of Elbow side of at Elbow DMW SSW Side of SSW Ro, in 1.438 1.188 1.188 A-376 Type Material A-105 Grade II 316 Alloy52M Sm,ksi 19.020 17.52 23.3 Service Level A 0.6Sm, ksi 11.412 10.512 13.980 Service Level B 0.6Sm, ksi 11.412 10.512 13.980 Service Level C 0.6Sm, ksi 11.412 10.512 13.980 Su, ksi 70.0 71.8 80.3 Service Level A L, in 0.1936 0.2112 0.1588 Service Level B L, in 0.2066 0.2335 0.1756 Service Level C L, in 0.2134 0.2451 0.1843 Note: Service Level D is bounded by Service Level C and therefore not evaluated.

Attachment 2 Full Structural Weld Overlay Sizing for the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Weld 6.2 Preservice Examination Weld overlay access for preservice examination requires that the overlay length and profile be such that the overlaid weld and any adjacent welds can be inspected using the required NOE techniques. This requirement could cause the overlay length to be longer than required for structural reinforcement. The specific overlay length required for preservice examination is determined based on the examination techniques and proximity of adjacent welds to be inspected.

6.3 Area Limitation on Nozzle The total weld overlay surface area is limited to 500 in 2 [4, Section 1-1] (this value will be specified in the relief request) on the nozzle (ferritic steel base material) when using ambient temperature temper bead welding to apply the overlay. Using an outside diameter of 2.875", the maximum length is limited to 500/(nDo) = 55.36" on the ferritic steel nozzle material. The required overlay length on the nozzle is less than this limit (see Table 7).

6.4 Maximum Overlay Sizing This calculation documents the minimum overlay thickness and length necessary for structural requirements. Additional thickness and length may be added to address inspectability and crack growth concerns. In addition, a maximum overlay thickness (typically an additional 0.25") and a maximum overlay length will be determined. The determination of the maximum length is based on implementation factors and is intended to be large enough so as to not unnecessarily constrain the overlay process. These dimensions will be indicated on a subsequent design drawing to create a "box" within which the overlay is analyzed. In the subsequent analyses, the finite element models use the geometry (minimum or maximum) that will produce conservative results.

7.0 DISCUSSIONS AND CONCLUSIONS Table 8 and Figure 2 summarize the minimum required overlay dimensions. This calculation documents the development of a weld overlay design for the charging nozzle-to-safe end DMW, and the safe end-to-elbow SSW at the Calvert Cliffs Nuclear Power Plant, Units 1 and 2. The design meets the requirements of the ASME Code Section XI, Code Case N-740-2 [4] and ASME Code Section XI, Appendix C [2] for a full structural weld overlay.

The weld overlay sizing presented in Table 8 is based upon the primary loadings documented in Section 4.0 and using the criteria from the ASME Code,Section XI, Appendix C. The overlay thicknesses and lengths listed in Table 8 meet ASME Code stress criteria.

Attachment 2 Full Structural Weld Overlay Sizing for the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Weld Table 8: Minimum Required Overlay Dimensions Location Thickness, in Length, in Nozzle side of 1A/1B 0.1979 0.2134 DMW SE Side of DMW 2 0.1771 ----

SE Side of SSW 3 0.1693 ----

Elbow Side of 4 0.1108 0.2451 SSW 0.177 11 0.169" 0.111" CHARGING NOZZLE ELBOW Fignl'e 2: Full Stl'nctural Weld Overlay Geometry, Minimum Dimensions (Schematic Repl'esentation)

Attachment 2 Full Structural Weld Overlay Sizing for the 21A Cold Leg Charging Inlet Nozzle-to-Safe-End Weld

8.0 REFERENCES

1. SI Calculation No. CCNP-05Q-303, 'Weld Overlay Sizing for RCS Charging System Inlet Nozzle Assembly Number 507-01," Revision 0.

2. ASME Boiler and Pressure Vessel Code,Section XI, Rules for lnservice Inspection of Nuclear Power Plant Components, 2004 Edition.

3. ASME Boiler and Pressure Vessel Code, Section Ill, Rules for Construction of Nuclear Facility Components, 2004 Edition.

4. ASME Boiler and Pressure Vessel Code, Code Case N-740-2, "Full Structural Dissimilar Metal Weld Overlay for Repair or Mitigation of Class 1, 2, and 3 Items,Section XI, Division 1."

5. ASME Boiler and Pressure Vessel Code,Section II, Part D, Material Properties, 2004 Edition.

6. ASME Boiler and Pressure Vessel Code, Code Case N-504-3, Alternative Rules for Repair of Class 1, 2, and 3 Austenitic Stainless Steel Piping,Section XI, Division 1.

7. ASME Boiler and Pressure Vessel Code, Code Case N-638-1, Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead Technique,Section XI, Division 1.

8. CCNPP Design Specification No. 8067-31-5, "Project Specification for a Reactor Coolant Pipe and Fittings for Calvert Cliffs Units 1&2," Rev. 18, May 2004, PROPRIETARY SI File No. 0801014.201P.

9. Combustion Engineering Inc., Drawing No. E233-586/12024-0006, Revision 8, "Nozzle Details Piping," SI File No. 0801014.203.

10. CCNPP Calculation No. CA04756, Revision 0, "Unit 1 Charging and Aux.

Spray Piping Analysis," SI File No. 0801014.220.

11. Attachment (1) to Constellation Energy Letter to USN RC, December 29, 2008, "Fourth Interval lnservice Inspection Program Plan for Calvert Cliffs Nuclear Power Plant Units 1 and 2," Rev. 0, SI File No. 0801014.211.

12. CCNPP Calculation Number CA04877, Revision 0, "Unit 2 Charging and Auxiliary Spray Piping Class 1 and 2 Analysis," SI File Number 0801014.221.

13. CCNPP Table 21-4, "Unit 1 Alloy 82/182 Full Penetration Welds," SI File No.

0801014.205.