Structural Integrity Associates, Inc. · 2012. 12. 2. · V Structural Integrity Associates, Inc. 1.0 PURPOSE The purpose of this calculation package is to calculate crack growth

Structural Integrity Associates, Inc. File No.: 0800368.326

CALCULATION PACKAGE Project No.: 0800368Quality Program: Z Nuclear I] Commercial

PROJECT NAME:

Davis Besse Phase 2 Alloy 600

CONTRACT NO.:49151, Rev. 1

CLIENT: PLANT:Welding Services Inc. (WSI) Davis-Besse Nuclear Power Station, Unit 1

CALCULATION TITLE:Crack Growth Evaluation of Reactor Coolant Pump Discharge Nozzle with Weld Overlay Repair

Document Affected Project Manager Preparer(s) &Revision Pages Revision Description Approval Checker(s)Signature & Date Signatures & Date

01 - 30 Initial Issue Preparers:A-1 - A-3

Stan S. Tang Peihua Jing07/20/09 07/20/09

Checker:

Jim Wu07/20/09

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Structural Integrity Associates, Inc.

Table of Contents

1.0 PURPOSE ...................................................................................................................... 4

2.0 M ETHODOLOGY .................................................................................................... 4

3.0 DESIGN INPUTS ..................................................................................................... 4

3.1 Geom etry ...................................................................................................... 4

3.2 Fracture M echanics M odels ........................................................................... 5

3.3 Loads .......................................................................................................... 6

3.4 Crack Growth Laws ...................................................................................... 9

3.4.1 Alloy 82/182 Fatigue Crack Growth Law ................................................... 9

3.4.2 Alloy 82/182 PWSCC Growth Law ................................................................ 9

3.4.3 Treatment of Negative Stress Intensity Factors ........................................... 10

4.0 ASSUM PTION S ...................................................................................................... 10

5.0 CALCULATION S .................................................................................................. 11

6.0 CONCLUSIONS AND DISCUSSION S ............................................................... 12

7.0 REFERENCES ........................................................................................................ 14

APPENDIX A COMPUTER FILE DESCRIPTIONS ................................................... A-1

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V Structural Integrity Associates, Inc.

List of Tables

Table 1: Stress Coefficients for Various Loadings at the DMW ........................................ 15

Table 2: Discharge Nozzle Bounding Piping Interface Loads .......................................... 16

Table 3: Bounding Thermal Transients for the Discharge Nozzle ................................... 16

Table 4: Sequence of Events and Cycles for Fatigue Crack Growth ................................. 17

Table 5: Crack Growth Results for PATHs 1, 2, and 3 ..................................................... 17

List of Figures

Figure 1: Sections Used For Crack Growth ...................................................................... 18

Figure 2: Stress Path Definitions for Maximum Weld Overlay for ThermalTransient Analyses at 0, 90 and 180 Degree Locations ...................................... 19

Figure 3: Stress Path Definitions for Minimum Weld Overlay forMechanical Load Analyses (pressure, axial force, and moment loads)0, 90 and 180 D egree Locations ........................................................................ 20

Figure 4: Critical Paths Used for Through-wall Mapped Stresses of MinimumWeld Overlay for Residual Stress Analyses ..................................................... 21

Figure 5: Time Histories of Linearized Membrane-plus-Bending Stress at theInside Surface for Reactor Trip 8A Transient .................................................... 22

Figure 6: Through-wall Residual Stress Distribution at 70'F and CurveFits at the D M W ................................................................................................. 23

Figure 7: K-vs-a Plots for Paths 1, 2, and 3 Residual Stresses at 70'F ............................ 24

Figure 8: Circumferential Flaw Model, Non-Moment Loading ........................................ 25

Figure 9: Circumferential Flaw Model, Moment Loading ............................................... 26

Figure 10: A xial Flaw M odel ............................................................................................ 27

Figure 11: K-vs-a at Normal Steady State Operating Conditions for PATH 1 ................. 28



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1.0 PURPOSE

The purpose of this calculation package is to calculate crack growth in the dissimilar metal weld (DMW)for the reactor coolant pump discharge nozzle with optimized weld overlay (OWOL) repair. Loadsconsidered are external piping loads, internal pressure, thermal transients, and residual stress. Bothfatigue crack growth (FCG) and Primary Water Stress Corrosion Cracking (PWSCC) are considered.FCG is due to cyclic loading and PWSCC is due to sustained loading at steady state normal operatingconditions.

2.0 METHODOLOGY

Representative fracture mechanics models (see Section 3.2) are used to determine stress intensity factors(K). The stress intensity factors for each type of load are computed as a function of crack depth in theoriginal weld (DMW) and superimposed for the various operating states. Stresses that contribute tofatigue crack growth are compiled from previous calculations (References 4 and 6). These stressesresult from primary loads such as internal pressure and external piping loads, and secondary loads suchthermal gradient stresses (due to thermal transient events), and residual stresses. The through-wallstresses are extracted and fitted to a third order polynomial. FCG (or combined FCG and PWSCCgrowth if PWSCC is active) is computed using linear elastic fracture mechanics (LEFM) techniques.PWSCC is determined by computing the stress intensity factor versus flaw depth curve (K-vs-a) atsteady state normal operating conditions. A crack growth law for Alloy 600 weld metals (Alloy82/Alloy 182), with a multiplier to account for crack growth in a pressurized water reactor (PWR)environment, is used at the DMW.

Cases for both optimized weld overlay (OWOL) and full structural weld overlay (FSWOL) will beconsidered.

For circumferential flaws, a postulated initial flaw of 50% (75%) of the original base metal thickness isassumed for computing crack growth in the nozzle with an OWOL (FSWOL). This assumption is basedon the fact that for circumferential flaws, the depth of the inspection volume of the nozzle with anoverlay is limited to the outer 50% of the original base metal thickness. Thus the time it takes for apostulated initial circumferential flaw of 50% (75%) of the original base metal thickness with an OWOL(FSWOL) to reach 75% (100%) of the original base metal thickness is computed and reported herein.For axial flaws, the depth of the inspection volume of the nozzle with an overlay is limited to the outer25% of the original base metal thickness. Therefore, an initial axial flaw of 75% of the original basemetal thickness is considered for nozzles with both an OWOL and FSWOL.

3.0 DESIGN INPUTS

3.1 Geometry

Details of the discharge nozzle geometry are provided in the finite element model calculation package[1]. Three sections are selected to evaluate for crack growth, as shown in Figure 1. Note that in thefigure, the minimum and maximum dimensions of each section (due to the use of minimum or OWOL


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design and maximum, or FSWOL design in the finite element models [1]) are shown. The thinnersections are used for pressure, piping interface loads and residual stresses. The thicker sections are usedfor all local thermal gradient stresses. This approach assures that the actual applied overlay and resultingstresses are bounded. See Section 3.3 for descriptions of the different loads applied to the nozzle.

The typical approach for computing crack growth is to select the sections that give highest stresses foreach loading condition and map the corresponding stress on one representative section, which is thenused for crack growth. However, an initial analysis for this particular nozzle showed that using all thebounding stresses on one section lead to overly conservative results. This conservatism occurs with (1)residual stress distributions (see Section 3.3 under "Residual Stress" for details) and (2) moment load(see Section 3.3 under "pipe interface loads" for details), both of which show significant variationdepending on the position within the DMW. To remove this conservatism, the three sections shown inFigure 1 are selected for computing crack growth using a residual stress and moment stress distributionthat is representative for that section. For all other load types (internal pressure, piping loads excludingmoment, and thermal transients) the bounding stresses are used on each path (see Section 3.3 for details).

3.2 Fracture Mechanics Models

Three crack models are utilized to compute the stress intensity factors, two from the EPRI DuctileFracture Handbook [2] and the third from Tada-Paris-Irwin [3], are shown in Figures 8 through 10. Thethree models are described below:

o Circumferential flaw, all the loading type except the moment loading (EPRI Ductile FractureHandbook model): This model is applied to the axial loading due to piping loads and transientsconditions. Full 3600 flaw in a cylinder with the actual Ri/t ratio is used, where 1 < Ri/t < 10. Riis the inside radius and t is the thickness of the selected section for analysis. The Ri/t ratios arecalculated as follows (geometric dimensions obtained from Figure 1):

for PATH 1:o DMW min-WOL: Ri/t= (14.0)/(3.99) = 3.48o DMW max-WOL: Ri/t= (14.0)/(4.40) = 3.20

for PATH 2:o DMW min-WOL: Ri/t= (14.0)/(3.82) = 3.66o DMW max-WOL: Ri/t-- (14.0)/(4.21) 3.33

for PATH 3:o DMW min-WOL: Ri/t= (14.0)/(4.09) 3.42o DMW max-WOL: Ri/t= (14.0)/(4.49) = 3.12

It is determined in Reference 12 that the influence coefficients for calculating K must be computed usingthe plots provided in the reference as opposed to using the provided equation.

o Circumferential flaw, moment loading only(Tada-Paris-Irwin model): This model applied tomoment loads from various piping loading and transient conditions. Full 3600 flaw in a cylinder


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with the actual inside radius-to-outside radius ratio Ri/Ro is used. Ri is the inside radius and Ro isthe outside radius with overlay thickness at the thinnest section. The Ri/Ro ratios are calculated asfollows (geometric dimensions obtained from Figure 1):

for PATH 1:o DMW min-WOL:o DMW max-WOL:



Ri/Ro = (14.0)/(17.99) = 0.778Ri/Ro = (14.0)/(18.40) = 0.761

Ri/Ro = (14.0)/(17.82) = 0.786R/R= (14.0)/(18.21) = 0.769

RiiFo = (14.0)/(18.09) = 0.774Ri/Ro = (14.0)/(18.49) = 0.757

o Axial flaw (EPRI Ductile Fracture Handbook model): a semi-elliptical inside surface flaw withan aspect (depth-to-length) ratio of 0.167 in a cylinder is used for FCG and PWSCC per ASMECode Section XI [9].

Stress intensity factors using the above flaw models for all loads (see Section 3.3) are all calculated via aMicrosoft Excel Visual Basic for. Applications (VBA) macro in spreadsheets"StressIntensityFactors*.xls." (where * =1,2,3) at the DMW. The macro is verified to ensure theequations from the EPRI Ductile Fracture Handbook [2] and the Paris-Tada-Irwin solution [3] arecorrectly used.

3.3 Loads

Loads considered (described in detail in the following subsections) are internal pressure, interface pipingloads, local thermal gradient stresses due to thermal transients, and residual stresses. Through-wallstresses are curve fitted with a third order polynomial in the form shown below:

2 C 3o)= CO + CIX±+C2x2 +C3x (1)

where:

= stress (axial or hoop)x = normalized distance from the inside surface, 0<x<1, x equals distance divided by the

path length

Through-wall stresses were obtained for through-wall paths in the DMW (Figure 2 and 3). These pathsare defined in the thermal and mechanical stress analysis calculation package [4]. It is important to notethat the mechanical stresses and thermal stresses are extracted from models with the minimum andmaximum overlays, respectively (see Section 3.1). The intent for this approach is to characterize thestresses for each of the different loading conditions for three regions within the DMW: a path near the

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nozzle interface within the weld butter, a path in the approximate center of the susceptible material(which includes the weld butter, the postulated ID weld repair, and the weld), and a path near the elbowside of the weld. As long as the correct stresses are extracted from the correct model (minimum ormaximum overlay model depending on the load type), the resulting stress intensity factors areconservative for the sections shown in Figure 1. As explained in Section 3.1, residual stresses and unitmoment load that are representative of each section are used for crack growth.

Curve fits for residual stresses are calculated in spreadsheet "normalized RESfactors.xls", based on thespreadsheet "DB-0800368_324_RES.xls" obtained from the residual stress analysis [6]. Linearizedstresses and curve fits for local thermal gradient stresses (and stresses due to mechanical loads) arecompiled in spreadsheet "ThermStressCoeff(DMW)Normalized.xlsm". The curve fit coefficients areused to calculate the

K-vs-a values using a K-solution from Paris-Tada-Irwin [3] for circumferential flaw moment loading(see Figure 9) or input into the EPRI Ductile Fracture Handbook models [2] for the circumferential (non-moment loading) and axial flaws (see Figures 8 and 10). These spreadsheets are included in thecomputer files. Table 1 shows the polynomial coefficients for all loads at the DMW. Details of how theTable 1 coefficients are obtained are explained in the following subsections. This set of coefficients arestored in spreadsheet "TableOfCoeffcients.xls", which is used in conjunction with spreadsheet"StresslntensityFactors.xls".

Internal Pressure

In the thermal and mechanical stress analysis calculation package [4], a unit internal pressure load (1000psi) was applied to the discharge nozzle finite element model. The resulting through-wall stressdistributions within the DMW and weld butter interface were extracted and given a third orderpolynomial curve fit. Files "DB-PRES P* MAP.OUT" (* =7-15), listed in Appendix A in the tablelabeled "Stress Output," contain the through-wall stress distributions. These output files are obtainedfrom Reference 4. The CSV file versions of these files contain the resulting stress coefficients for theunit pressure loading condition. The resulting stress coefficients are shown in Table 1. Stress intensityfactors resulting from the stresses in Table 1 are scaled by actual pressure values during the transient.Note that a constant through-wall stress of 1000 psi is added to the Co coefficient of the "Unit Pressure"stresses to account for the internal pressure acting on the crack face.

Piping Interface Loads

The bounding piping interface loads were determined in the design loads calculation package [5] andshown in Table 2. Finite element analyses for an applied unit axial force (1000 lbs) and unit moment(1000 in-lb) at the free end of the piping interface were performed in [4]. Through-wall stressdistributions within the DMW were extracted from the analyses in [4] and included in this calculationpackage. See files "DB-AXIAL P* -MAP.OUT" (* =7-15), and "DB-MOMENTP*"NMAP.OUT" (*=7-15)" in Appendix A in the table labeled "Stress Output." These files are included in the computerfiles. For the axial stresses due to the unit moment load, only the maximum stress in the section is usedbecause a constant stress is required in the fracture mechanics model that is used for moment loading(see Figure 9). Stress intensity factors using the fracture mechanics models described in Section 3.2


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were determined from these stresses. Because a unit force and unit moments were performed inReference 4, the resulting stress intensity factors are scaled to actual values by the axial force values (Fz)in Table 2 for the force Ks or by the square root sum of the squares (SRSS) of the transverse momentvalues (Mx and My) in Table 2 for the moment Ks. Then according to Reference 4, because the thermalpiping interface loads shown in Table 2 are assumed to be at the normal operating temperature of 556°F,thermal piping loads for other temperatures are scaled by (T - 70)/(556 - 70), where T is the fluidtemperature during the transient. These temperature factors are shown in the "T factor" column inTable 3.

The resulting stress coefficients for the unit axial and unit moment cases are shown in Table 1.

Local Thermal Gradient Stresses

Bounding thermal transients for crack growth analysis are shown in Table 3, which were developed inthe design loads calculation package [5]. Determining the thermal gradient stresses due to thesetransients is a two-step process. First, a bounding path in the DMW is selected by comparing thethermal gradient stresses at the nine representative paths in the DMW (Paths 7-15 in Figures 2 and 3) forthe transients. Second, the times at which the maximum and minimum inside surface membrane-plus-bending axial and hoop stresses during each transient listed in Table 3 are determined so that the worstthrough-wall thermal gradient stresses may be extracted.

To select the bounding path in the DMW, the time histories of the inside surface linearized membrane-plus-bending stresses for each transient are plotted for axial and hoop stresses. A typical plot is shownin Figure 5 for axial and hoop stresses for the Reactor Trip 8A transient. The linearized membrane-plus-bending stresses and corresponding mapped stresses, fit with a third order polynomial, are contained infiles "DB-SR**J P* MAP.csv" (where **=1-6, * = 7-15). Figure 5 shows, for example, that Path 12 isused for the maximum axial stress and Path 7 for the minimum axial stress for the Reactor Trip 8Atransient. Table 1 shows the bounding paths used at the DMW. Note that it is possible that a transienthas more than one maximum-minimum pair, in other words more than one peak-valley pair. Thenumber of cycles for this kind of transient is multiplied by the number of peak-valley pairs for thatparticular transient. Table 4 shows the number of peak valley pairs for each transient.

Once the bounding path for the DMW is determined, the times at which the maximum and minimummembrane-plus-bending axial and hoop stresses during each transient can be determined. Note thatalthough the inside surface linearized membrane-plus-bending axial and hoop stresses were used inselecting the critical times, the stress coefficients resulting from the through-wall mapped stresses at thecritical times are based on total stresses. The resulting bounding thermal gradient stress coefficients dueto the thermal transients at the times of maximum and minimum inside surface linearized membrane-plus-bending stresses are shown in Table 1.

Residual Stresses

Residual axial and hoop stresses were extracted from the residual stress analysis [6] for three pathswithin the DMW. These paths from Reference 6 are Paths 1, 2, and 3, and correspond (roughly) to Paths9-12-15, 8-11-14, and 7-10-13 in Figure 2 and Figure 3. Stresses were obtained from file


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"normalizedRESfactors.xls" of Reference 6. The resulting stresses were curve fit with a third orderpolynomial in this spreadsheet in worksheet "Path Data." The residual stress curve fits were determinedfor all three paths of the DMW and used for the crack growth analyses. Residual stresses at 70'F areshown in Figure 6 and the resulting K distributions are shown in Figure 7.

The resulting residual stress coefficients at 70'F and at steady state pressure (2255 psig) and temperature(556'F) are shown in Table 1 at the DMW.

3.4 Crack Growth Laws

3.4.1 Alloy 82/182 Fatigue Crack Growth Law

NUREG/CR-6907 [7] indicates that "The CGRs of Alloy 82/182 in the PWR environment are a factor5 higher than those of Alloy 600 in air under the same loading conditions." Thus the fatigue crackgrowth rate for the DMW (made of Alloy 82/182 filler metal) used in this analysis is that for Alloy 600in air (Equation (2) below) multiplied by 5. The fatigue crack growth rate for air obtained fromNUREG/CR-6721 [8] is given by:

(da/dN)air = CA600 (1-0.82R)-2 2 (AK)4"1 , units of m/cycle (2)where:

CA600 = 4.835x10-14 + 1.622x10-16T- 1.49 x10-18T2 +4.355 x10-21T3

T = temperature inside pipe, 'C (taken as the maximum during the transient)R = R-ratio = (Kmin/Kmax)

AK = Kmax - Kmin = range of stress intensity factor, Mpa-m° 5

Note that Equation (2) in accordance with NUREG/CR-6907 is independent of rise time.

3.4.2 Alloy 82/182 PWSCC Growth Law

When appropriate PWSCC growth in the DMW is computed using Equation (3) below. This is forAlloy 182 weld metal and is obtained from Eq. 4.5 of MRP-1 15 [11, pgs 4-4 to 4-5 for US customaryunits].

d = exp[- T -I , j]a(K)i< (3)

where:_ crack growth rate at temperature T in in/hr.

Qg= thermal activation energy for crack growth (31 kcal/mole)R= universal gas constant = 1.103 x 10 kcal/mole- R


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T= absolute operating temperature at location of crack, K = 556°F (1015.67 R)Tref= absolute reference temperature used to normalize data = 617'F (1076.67 R)a= power-law constant =2.47 x 10-7 at 617°FK= crack tip stress intensity factor, ksi (in.)0 5

3= 1.6

3.4.3 Treatment of Negative Stress Intensity Factors

Because of the beneficial compressive residual stresses produced by the weld overlay, the stress intensityfactors for many load cases are negative. This condition is handled as follows in the FCG analyses:

1. For Alloy 600 and its weld metals (Alloy 82/Alloy 182), the crack growth law in Equation(2) above includes an R-ratio correction (1-0.82R)-2. 2 that applies to both positive andnegative R-ratios [7, 8]. For negative R-ratios, the factor is less than 1, yielding acorresponding decrease in crack growth rate when Km. is negative. Therefore, Equation (2)is used directly for crack growth in the DMW when Kmax is greater than zero, for bothpositive and negative Kmin. As noted, a factor of 5 [7] is applied for PWR environmentaleffects.

2. If both Kmax and Kmin in a load cycle are negative, zero fatigue crack growth is assumed. Thisis a reasonable assumption based on the work on compression fatigue crack growth (FCG forwhich Kmax and Kmin, are negative) in Reference 10, in which it was shown that although FCGis present, the values of FCG are several orders of magnitude smaller than for FCG for whichKmx and Kmmi are not negative.

4.0 ASSUMPTIONS

Basic assumptions for the analysis are listed below:

o Through-wall stresses are curve fitted with a third order polynomial.

o See Section 3.2 for assumed flaw models

o See Section 3.4 for the crack growth laws and related assumptions.

o For FSWOL, a postulated initial circumferential flaw 75% of base material thickness is assumed;a postulated initial axial flaw 75% of base material thickness is assumed

o For OWOL design, a postulated initial circumferential flaw 50% of base material thickness isassumed; a postulated initial axial flaw 75% of base material thickness is assumed

For FCG, there is no requirement to bound the load pairing between transients per the ASME Code,Section XI [9]. Each thermal transient that was analyzed in the thermal and mechanical stress analysis


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calculation package [4] is analyzed sequentially per Table 4, and the cumulative effect of all transients issummed. In addition, incremental growth due to PWSCC (if active) is computed and added toincremental growth due to FCG. This approach is consistent with the ASME Code, Section XI, C-3200.

5.0 CALCULATIONS

A Microsoft Excel VBA routine is implemented to calculate combined FCG and PWSCC growth. Thiscombined FCG and PWSCC calculation is based on a yearly basis: one year of PWSCC (if present)followed by one year of FCG. Note that for more accuracy, crack growth may also be based on amonthly basis. Combined FCG and PWSCC growth is calculated until the flaw depth reaches the 75%of the base material. The number of cycles and sequence of events for FCG are shown in Table 4.Crack growth is calculated based on 60 years of operation. Thus, the number of cycles/year shown inTable 4 are multiplied by 1.5 for 60-year operation and divided by 60 years. The PWSCC portion of thecrack growth is only active if, during the growth of the flaw, the stress intensity factor at steady statenormal operating conditions (NOC) is a positive value, which is in accordance with MRP- 115 [11, page4-2], which states that "there is insufficient data to justify a stress intensity factor threshold other thanzero." The Ks from spreadsheets "StresslntensityFactors*.xls" (where *=1,2,3) are imported intospreadsheets "CGDischargeNozzleDMW*.xls"(where *=1,2,3) to compute crack growth at the DMW.The FCG and PWSCC calculations are described below.

FCG

For FCG, the individual terms that constitute nominal Kmax and Kmin for the calculation of AK inEquations (2) are summarized in the tabulations below. The individual Ks for nominal Kmax arecombined (summed) with all appropriate scale factors applied. Similarly, the individual Ks for nominalKmfi are combined (summed) with all appropriate scale factors applied. AK is computed by taking thedifference of the resulting summed Kmax and Kmin. Note that Kresidual and Kdead weight are constant loadsand do not contribute to the AK range.

Kresidual Uresidual

Kpressure,state 1 Kpressure,state2

Kdead weight Kdead weight

Kthermal piping load-state 1 Kthermal piping state 2

Kthermal state 1 Kthermal state 2

OBE is treated as a separate event that the OBE combines with the highest K value for the Kmax side andthe OBE combines the lowest K value for the Knin side. Table 4 indicates how OBE is combined withthe transients.


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PWSCC

The K-vs-a curves for both circumferential and axial flaws at steady state normal operating conditions(NOC) are calculated in the PWSCC worksheets of spreadsheets "CGDischargeNozzleDMW*.xls"(where *=1,2,3) and shown in Figure 11 through 13 for section Path 1 through 3, respectively, in Figure1. The stresses at steady state NOC include internal pressure stresses (P = 2255 psig), residual stresses(at 70'F), steady state thermal stresses at 556°F, and stresses due to the non-cyclic piping loads(including deadweight). Note that an additional 2255 psig was added to the Co coefficients for thestresses labeled "Resid @ 2255psig+556F" in Table 1 to account for crack face pressure. This crackface pressure is applicable for both the FCG and PWSCC evaluation. For both axial and circumferentialflaws, the models described in Section 3.2 were used to calculate the stress intensity factors.PWSCC is a time dependent phenomenon and occurs at a sustained loading condition. Given that thegreat majority of plant operation is at normal steady state operating conditions (NOC), PWSCC isdefined by stress conditions at NOC. The 50% (or 75%) initial crack is grown using the cyclicalloadings described previously. At steps in the evaluation, the value of the crack tip K is continuouslychecked. If the K is less than zero, then no PWSCC is assumed for the next step of fatigue crackgrowth. If the crack tip K becomes greater than zero, then the PWSCC crack growth rate in Section3.4.2 is used to calculate an incremental PWSCC crack growth, which is added to the total crack growth.

In this case the Ks at normal operating conditions are positive for PATH 1 through PATH 3 at a flawdepth of 50% of the original base metal thickness for the circumferential flaws.

6.0 CONCLUSIONS AND DISCUSSIONS

The crack growth results are shown in Table 5.

For PATH 1:For an initial circumferential flaw of 50% of the original base metal thickness at the analyzed section ittakes approximately 23 years to reach 75%. Whereas, for an initial circumferential flaw 75% of theoriginal base metal thickness, it takes approximately 31 years to reach the overlay. An initial axial flawof 75% of the original base metal thickness at the analyzed section remains 75% after 30 years.

For PWSCC, this analysis showed that PWSCC is active at NOC at a flaw depth of 50% and 75% of theoriginal base metal thickness at the DMW analyzed section for the circumferential flaw.




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7.0 REFERENCES

1. SI Calculation Package No. 0800368.322, "Finite Element Models of the Reactor CoolantPump Discharge Nozzle with Weld Overlay Repair," (for revision refer to SI ProjectRevision Log, Latest Revision).

2. Zahoor, A., EPRI Report No. NP-6301-D, Ductile Fracture Handbook, Volumes 1, 2, and 3,(N14-1), Research Project 1757-69, June 1989.

3. Hiroshi Tada, Paul C. Paris, and George R. Irwin, "The Stress Analysis of CracksHandbook," Third Edition, ASME Press, 2000.

4. SI Calculation Package 0800368.323, "Thermal and Unit Mechanical Stress Analyses forReactor Coolant Pump Discharge Nozzle with Weld Overlay Repair," (for revision refer to SIProject Revision Log, Latest Revision)

5. SI Calculation Package 0800368.311, "Design Loads for the 28" I.D. Reactor Coolant Pump(RCP) Suction and DischargeNozzles," (for revision refer to SI Project Revision Log, LatestRevision)

6. SI Calculation Package 0800368.324, "Residual Stress Analysis of Reactor Coolant PumpDischarge Nozzle with Weld Overlay Repair," (for revision refer to SI Project Revision Log,Latest Revision)

7. NUREG/CR-6907, "Crack Growth Rates of Nickel Alloy Welds in a PWR Environment,"

U.S. Nuclear Regulatory Commission (Argonne National Laboratory), May 2006.

8. NUREG/CR-6721, "Effects of Alloy Chemistry, Cold Work, and Water Chemistry onCorrosion Fatigue and Stress Corrosion Cracking of Nickel Alloys and Welds," U.S. NuclearRegulatory Commission (Argonne National Laboratory), April 2001.

9. ASME Boiler & Pressure Vessel Code, Section XI, , 2001 Edition with Addenda through2003.

10. Lenets, Y. N., "Compression Fatigue Crack Growth Behavior of Metallic Alloys: Effect ofEnvironment," Engineering Fracture Mechanics, Vol. 52, No. 5, 1997.

11. Materials Reliability Program Report MRP- 115, "Materials Reliability Program: CrackGrowth Rates for Evaluating Primary Water Stress Corrosion Cracking (PWSCC) of Alloy82, 182, and 132 Welds," September 2004.

12. SI Calculation 0800554.301, "Computation of Influence Coefficients for Two Stress IntensityFactor Solutions From EPRI Ductile Fracture Handbook," Rev. 0.


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Table 1: Stress Coefficients for Various Loadings at the DMW

Transient Name Nozzle-to-Safe End Weld

Time Path Used Axial Stress Coefficients, psi Time Path Used Hoop Stress Coefficients, psi

(sec) Co C1 C2 C3 (sec) Co C1 C2 C3

Unit Pressure (1) 9 3855.6 -2568.9 1003.9 -582.7 - 13 6526.8 -2604 875.9 -314.4

Unit Axial 7 3.4 -1.4 -0.4 0.3 - 13 0.8 -1.2 0.3 -0.1

Unit Moment 15 Max Stress at Each Path (4) 10 0 0.2 -0.1 0.1

Plant Heatup, HIGH 0 7 0 0 0 0 28080 13 5659.4 72131.2 -160326 90461.2

Plant Heatup, LOW 17532 7 -20440 116250.6 -178198 95618.1 4383 9 -4400 34065 -61992.1 32294.1

Plant Cooldown, HIGH 10800 9 -8794.3 87792.5 -171203 87412.6 2700 13 9685.1 52486.8 -140980 83249.8

Plant Cooldown,LOW 0 7 -16129.4 98232.2 -164943 97411 46800 12 329.4 10446.4 -22692 10483.1

ReactorTrip 8A, HIGH 150 12 -22750.6 183600.9 -332320 165379.3 150 13 7247.4 61974.6 -145278 83600.2

ReactorTrip 8A, LOW 16.5 7 -18190.8 112135.9 -189477 110485.9 16.5 9 -1612.4 78295.8 -170149 91055

ReactorTrip 8C, HIGH 280 12 -22937.6 184745.2 -334298 166444.1 280 13 6997.1 63191 -146908 84403.8

Reactor Trip 8C, LOW 35 7 -23146.2 143406.7 -241819 137197 40 12 -5801.3 95335.9 -177402 86201.2

Change of Flow, HIGH 50 12 -22242.2 179403.3 -324242 160991.6 70 13 7325 61011.9 -143139 82369

Change of Flow, LOW 360 7 -16581.9 100847.4 -168942 99356.4 360 9 174.8 66094.8 -148097 79063.8

Hydrotest, HIGH 1 9 -1476.3 13147.2 -24874.1 12647.9 2 13 3899.5 51188.6 -114829 63967.5

Hydrotest, LOW 2 13 -14485.9 94739.9 -169225 94931.5 1 12 157.4 4616 -10126.1 4648.8

Resid70, Path 1(3) 63643.61 -544931.84 802965.9 -250409 54940.44 -792286.6 1618604 -768639.7

Resid70, Path 2 (3) 73150.29 -539081.67 686144.5 -135506 27962.384 -730746.59 1612025 -813639.7

Resid70, Path 3 13) 66760.06 -448070.23 499272.2 -45438.2 -1532.997 -486664.43 1147729 -570109.8

Resid @ 2255psig+556F, Path 1(2)(3) 46564.44 -342188.42 455442.9 -99947.1 68916.725 -701647.38 1428069 -687401

Resid @ 2255psig+556F, Path 2 (2)(3) 51811.33 -331455.44 351421.6 3946.245 42707.041 -619933.73 1392511 -718379.8

Resid @ 2255psig+556F, Path 3(2)(3) 41816.55 -221064.86 93768.03 169346 16508.952 -380771.23 941740.3 -477377.4

Notes:

1. 1000 psi was added to the Co coefficient term of the Unit Pressure case to account for crack face pressure.2. 2255 psi was conservatively added to the Co coefficient term of the residual stresses at normal operating pressure and temperature cases to account for crack

face pressure. This is needed for calculating stress intensity factors at normal steady state operating conditions.3. Residual paths, for actual path correlations see Figure 4. Pathl corresponds to Paths 9-12-15, Path 2 to Paths 8-11-14, Path3 to Paths 7-10-13 in Figures 2 and

3.

4. The Maximum Axial Stress used for Unit Moment Load is 0.533psi for Path 1, 0.4533psi for Path 2 and 0.376psi for Path 3.


Page 15 of 30

F0306-01R0


Table 2: Discharge Nozzle Bounding Piping Interface Loads

Load CaseDeadweight

ThermalOBE

Notes:

Fx6512

10933444160

Forces, lbsO1 )Fy

146005010059600

Fz8768

19237877946

Mx150071774158718501

Moments, in-lbsO1 )

My4 500583 813 13082884 586 4905840 45

Mz396951332187384

1. Bounding loads between joints 83 and 138, listed as absolute values.2. z is axial to the nozzle.

Table 3: Bounding Thermal Transients for the Discharge Nozzle

Description Time, sec T, 'F P, psia Cycles T factorPlant Heatup 0 70 15 240 0.0001A 17532 557 1050 1.002

23400 557 2250 1.00224480 579 2250 1.047

Plant Cooldown 0 550 2250 240 1.008lB 10800 300 350 0.473

21600 280 250 0.43243200 140 15 0.144

Reactor Trip 0 556.5 2250 590 1.0018A 12 570 2500 1.028

30 550 2200 0.98725200 550 2250 0.987

Reactor Trip 0 556.5 2200 188 1.0018C 2 560 2240 1.008

10 565 2400 1.01815 562 2500 1.01220 585 2620 1.05930 590 2500 1.07040 580 2200 1.04960 565 2100 1.018100 552 2025 0.991

Change of Flow 0 556.5 2190 21060 1.00110 30 546.5 2130 0.980

150 557.5 2250 1.003180 559.5 2200 1.007

Hydrotestt 1 ) 100 15 20 0.06212 400 3125 0.679

100 15 0.062Notes:

1. Data from a similar plant.


Page 16 of 30

F0306-01


Table 4: Sequence of Events and Cycles for Fatigue Crack Growth

Events Event ID 40-yr Cycles (60-yr Cycles) Peak-Valley Pair

Transient 1 (Plant Heatup)Transient 2 (Plant Cooldown)Transient 3 ( Reactor Trip 8A)Transient 3 (Reactor Trip 8A)+ OBETransient 4 (Reactor Trip 8C)+OBETransient 5 (Change of Flow)Transient 6 (Hydrotest)

1234567

240(360)240 (360)128(192)462 (693)188(282)

21060(31590)20(30)

2211111

Table 5: Crack Growth Results for PATHs 1, 2, and 3

Circumferential Flaw in Circumferential Flaw in Axial Flaw in PATH 1PATH 1 PATH 1 _

Time for an initial flaw 50% Time for an initial flaw Flaw Depth as % of Base Metalof the Base Material 75% of the Base Material Thickness for an Initial FlawThickness to Reach 75% of Thickness to Reach the with 75% of the Base Materialthe Base Material Thickness Interface Thickness After 30 years

-[23 years J--31 years ]75

Circumferential Flaw in Circumferential Flaw in Axial Flaw in PATH 2PATH 2 PATH 2


-13 years -- I 26 years 75

Circumferential Flaw in Circumferential Flaw in Axial Flaw in PATH 3PATH 3 PATH 3


-12 years -- 33 years 75


Page 17 of 30

F0306-0t1


PATH1 PATH3PATH2

DMWR=14

Figure 1: Sections Used For Crack Growth


F0306-01


Figure 2: Stress Path Definitions for Maximum Weld Overlay for Thermal Transient Analyses at0, 90 and 180 Degree Locations

(Note: Paths 7 through 15 are for Crack Growth. The inside node is located on the inside face of the nozzle/weld/elbow for allpaths.)


Page 19 of 30

F0306-O1


Figure 3: Stress Path Definitions for Minimum Weld Overlay for Mechanical Load Analyses(pressure, axial force, and moment loads) 0, 90 and 180 Degree Locations

(Note: Paths 7 through 15 are for Crack Growth. The inside node is located on the inside face of the nozzle/weld/elbowfor all paths.)


Page 20 of 30

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Residual stress analysis

Figure 4: Critical Paths Used for Through-wall Mapped Stresses of Minimum Weld Overlay forResidual Stress Analyses


Page 21 of 30

F0306-O V


Axial Stress

.J

E

500

-500

-1500

-2500

-3500

-4500

-5500

-6500

-7500

-8500

UUU(

MWM--"

--- Path7

--N-- Path8

Path9

Path 10

--- Path 11

-0- Path 12

Path 13

- Path 14

Path 1V

rimels]

Hoop Stress1bUUU

15000

14000 -

13000

S12000 ~

D11OUUU

9000

8000

0 5000 10000 15000

Time [s]

________________ -- Path7-s- PathR

-*- Path9

Path 10

Path 11

- Path 12

P---Path 13

Path 14

Path 15

20000 25000 30000

Figure 5: Time Histories of Linearized Membrane-plus-Bending Stress at the Inside Surface forReactor Trip 8A Transient


Page 22 of 30

F0306-01


Path 1 Through-Wall Residual Stress

y = -250409x3 + 802966x2 - 544932x -t- 63644

y = -768640x 2 + 2E+06x2 - 792287x + 54940140120100

_ 60g; 40

N 200~

-20 0 2-40 - -Axioal 70'F

-60 -,--F-Hoop70*P

-80 Poly. (Axial 70*P)

___Poly. (Hoop 701F)Normalized Distance from ID Strae

U-

y=

y =

120

100

80

60

40

20

0

-20

-40

-60

-80

Path 2 Through-Wall Residual Stress-1 35506x3 + 686145x 2 - 539082x + 73150

-813640x3 + 2E+06x2 - 730747x + 27962

-N- Axial 70°F

-- R- Hoop 70°F

-- P oly. (Axial 70 °F)

-- Puly. (Houp 70-F)IL J

Normalized Distance from ID Surface

Path 3 Through-Wall Residual Stressy = -45438x3

+ 499272x 2 - 448070x + 66760y = -570110x 3

+ 1 E+06x2 - 486664x - 1533

C

100

80

60

40

20

0

-20

-40

-60

-80

KJ

0. 0.4 1 1.2

i~~I -J ~--Hoop 70OF-- Poly. 0

- Poly.(Hoop 70"F)

Normalized Distance from ID Surface

Figure 6: Through-wall Residual Stress Distribution at 70'F and Curve Fits at the DMWNote: Pathl corresponds to Paths 9-12-15, Path 2 to Paths 8-11-14, Path3 to Paths 7-10-13 in Figures 2 and 3.


Page 23 of 30

F0306-01*


Axial Flaw

0

'U

LA.

20

0

-20

-40

-60

-80

-100

-120

-140

-160

-1•o

3.5

Flaw Depth [in]

Circumferential Flaw

0U

Li.

4-.C

1A

4-j

80

60

40

20

0

-20

-40

-60

-80

-100Flaw Depth [in]

Figure 7: K-vs-a Plots for Paths 1, 2, and 3 Residual Stresses at 701FNote: Pathl corresponds to Paths 9-12-15, Path 2 to Paths 8-11-14, Path3 to Paths 7-10-13 in Figures 2and 3.


Page 24 of 30

F0306-01


I ,

R,

Source: Reference 2 (Zahoor model, 1 <_ R/t < 10)

Figure 8: Circumferential Flaw Model, Non-Moment Loading


Page 25 of 30

F0306-011


Mt

4Mro

KiD = KA ios 0

Source: Reference 3

"F" is defined below (also from Reference 3)

/ 1'I-

S 1.0

7

Figure 9: Circumferential Flaw Model, Moment Loading


Page 26 of 30

F0306-Ot


T aI 2c

Source: Reference 2 (Zahoor model, 1 <-I/t <- 10)

Figure 10: Axial Flaw Model


F0306-01'


Axial Flaw50 .T...

0'

0

0

-50 : r

4

-100 -


60 -

LQ

C>

~40-0

LL

20

3

------ ---

0

Figure 11: K-vs-a at Normal Steady State Operating Conditions for PATH I Note: Initial flaw depth =50% of original base metal thickness at the analyzed DMW section = 1.45", 75% of original base metalthickness =2.175"


Page 28 of 30

F0306-01


Axial Flaw

IL,0

C

0

0()0

LL

0C4)C

000

4-Ci)

30

20

10

0

-10

-20

-30

-40

-50

-60

-70

-80

- - - -- - - - - - - -

- - - -- - - - - - - -

- - - -- - - - - - -

----- ---- -- -

------ -- _ _4-

Flaw Depth, Inches


60

40

(0X 40

0

I.)

(/)U-

020t-

o2

(0

0)

LLn C:rl-

00 1

1

2Flaw Depth, Inches

3 4

Figure 12: K-vs-a at Normal Steady State Operating Conditions for PATH 2Note: Initial flaw depth = 50% of original base metal thickness at the analyzed DMW section = 1.45", 75% oforiginal base metal thickness =2.175"


Page 29 of 30

F0306-01


Axial Flaw

0Q

40

4-a

40

P-

co

50

4030

2010

0-10-20

-30-40

-50

-60

-70-80

------------------

- - - - - - - - - - - - - - - - -. .

----------

- -- ------ ) -5---------------- A-----------------

L -----------------

----------------------------------

-----------------

----------------------------------

Flaw Depth,


60

ID

400

20

CI

00 1 2 3 4

Flaw Depth, Inches

Figure 13: K-vs-a at Normal Steady State Operating Conditions for PATH 3Note: Initial flaw depth = 50% of original base metal thickness at the analyzed DMW section = 1.45", 75% oforiginal base metal thickness =2.175"


Page 30 of 30

F0306-01


APPENDIX A

COMPUTER FILE DESCRIPTIONS


F0306-O1RO

Page A- I of A-3

VStructural Integrity Associates, Inc.

Stress Output

Filename Description

DB-$$ P** MAP.OUT Mapped stress output file for thermal transient analyses(CSV file version also included)($$ = SR1, SR2, SR3, SR4,SR5,SR6) for path **

where ** = 7-15 for Paths 7 through 15, shown in Figure 3

DB-AXIALP**_MAP.OUT Through-wall stresses for unit axial load run for path **(CSV file version also included) where ** 7-15 for Paths 7 through 15, shown in Figure 2

DB-PRES_P**_MAP.OUT Through-wall stresses for unit pressure run for path **

(CSV file version also included) where ** = 7-15 for Paths 7 through 15, shown in Figure 2

DB-MOMENT* P** MAP.OUT Through-wall stresses for unit moment run for path **

where *=X,Z(CSV file version also included) ** =7-15 for Paths 7 through 15, shown in Figure 2


Page A-2 of A-3

F0306-OIRO


Spreadsheets

Filename Description

Spreadsheets that contains Microsoft Visual Basic macroStresslntensityFactors*.xls for calculating stress intensity factors at the DMW.

(*=1,2,3, corresponds to PATHS 1,2,3)

ThermStressCoeff(DMW) Spreadsheets that contains extraction of linearizedNormalized.xlsm stresses; source of Table 1 ,

Spreadsheet that contains stress coefficients for thermalTableOfCoefficients.xls transient stresses at the DMW; used as input to

StressIntensityFactors spreadsheets.

Spreadsheet that contains a copy of through-wall residualstresses from SpreadsheetN dt"DB-0800368 324 RES.xls" of Reference 6 and the

coefficients for a third order polynomial fit.

Spreadsheets calculation of crack growth at the DMW forthe circumferential and axial flaws.

CGDischargeNozzleDMW*_%.xls (*=1,2,3, corresponds to PATHS 1,2,3%=FWOL, OWOL corresponds to FWOL crack growth andOWOL crack growth


Page A-3 of A-3

F0306-O1RO

Documents

Structural Integrity Associates, Inc. · 2012. 12. 2. · V Structural Integrity Associates, Inc. 1.0 PURPOSE The purpose of this calculation package is to calculate crack growth