ML20072M005

Evaluation of Indications in Plant Hatch Unit-2 Core Shroud Welds H1,H2,H3 & H4

ML20072M005
Person / Time
Site:	Hatch
Issue date:	07/31/1994
From:	Marisa Herrera, Mehta H, Ranganath S GENERAL ELECTRIC CO.
To:
Shared Package
ML19353C431	List: HL-4672, Responds to GL 94-03 Re IGSCC of Core Shrouds in Bwrs.Ge Evaluation of Indications in Plant Hatch Unit-2 Core Shroud Welds H1,H2,H3 & H4 & Proprietary Info Re Unit Shroud Restraint Sys Encl.Proprietary Info Withheld ML20072M005
References
GENE-523-A86-05, GENE-523-A86-0594, GENE-523-A86-5, GENE-523-A86-594, NUDOCS 9409010163
Download: ML20072M005 (67)

Text

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DRF 137-0010-7 EVALUATION OF THE INDICATIONS-IN THE PLANT HATCH UNIT-2 CORE SHROUD WELDS H1, H2, H3 and H4 July 1994 Performed By:

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E' hiar60s L. Her'rera, Principal Engir.ser Structural Mechanics Projects Verified By:

Hardayal S. Mehta, PhD Principal Engineer Structural Mechanics Projects Approved By: -

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~ rr-Sampath RanganatX PhD.

Manager Engineering and Licensing Consulting Services GE Nuclear Energy

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San Jose, CA 9409010163 940824

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GENuclear Energy GENE $2.M86-030 IMPORTANTNOTICE REGARDING CONTENTS OF THIS REPORT Please Read Carefully The only undertakings of the General Electric Company (GE) respecting information in this document are contained in the contract between Southern Nuclear Operating 4

Company and GE, and nothing contained in this document shall be construed as changing the contract. The use of this information by anyone other than Southern Nuclear

-5 Operating Company or for any purpose other than that for which it is intended under such.'

contract is not authorized; and with respect to any unauthorized use, GE makes no representation or warranty, and assumes no liability as to the completeness, accuracy, or _-

usefulness of the Information contained in this document, or that its use may not infringe privately owned rights.

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Table of Contents t

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1. INTRODUCTION 1-1 t

1 1.1 References 1-4

2. ULTRASONIC INSPECTION RESULTS 21

3. FLAW EVALUATION 3-1 3.1 Structural Anslysis 31 3.1.1 Applied leads and Calculated Stresses 31 3.1.2 Fracture Mechanics Analysis 3-3 3.1.3 Limit Load Analysis 3-5 3.2 Allowable Through-Wall Flaws 3-5 3.2.1 Allowable Through Wall Circumferential Flaw Size '

35 3.2.2 Fracture Mechanics Analysis 3-6 3-6 J.2.3 Limitlead Analysis 3.3 Summary of Allowable Through-Wall Flaws 3-7 3.4 References 3 4. EVALUATION OF INDICATIONS 4-1 4.1 Weld H1 Evaluation 41 4.2 Weld H2 Evaluntloa '

43 4.3 Weld H3 Evaluation 45 4.4 Weld H4 Evaluation 4-7

5.

SUMMARY

AND CONCLUSIONS 5-1 APPENDIX A 2 EXAMINATION

SUMMARY

SHEETS.

APPENDIX B -

DETERMINATION OF EFFECTIVE FLAW LENGTH ~

- APPENDIX C.

BASIS FOR CRACK GROWTH RATE t

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1. INTRODUCTION The structural integrity analysis of the indications found in the H1, H2, H3 and H4 core shroud welds at Plant Hatch Unit-2 is presented in this report. Ultrasonic (UT) inspection of these welds was recently performed (March-April 1994). A screening criteria was developed to evaluate the detected indications for acceptance for continued operation over the next two cycles of operation. The methodology used in this evaluation is consistent with that in the BWR Owners' Group Core Shroud Evaluation (Reference 1-1). The results of the evaluation demonstrate that the stmetural integrity of the core shroud with the indications is assured for at least 2 operating cycles.

Although UT was performed, which demonstrated significant remaining ligament, a flaw evaluation based on the assumption that all UT detected indications were through-wall was used. This is obviously conservative since no credit is taken for any of the remaining ligament as verified by the UT inspections.

G' The guiding parameter used in the flaw evaluation is the allowable through-wall flaw size, which already includes the ASME Code,Section XI safety factors. If all of the UT detected indications are assumed to be through-wall, then the longest flaws, or combination of flaws, would have the limiting margin against the allowable through-wall flaw size. In reality, the indications are not through-wall, and therefore, the criteria ed methods presented in this report are conservative.

l The result of this evaluation is the determination of the effective flaw lengths which are used to compare against the allowable flaw lengths. The determination of effective flaw length is based on ASME Code,Section XI, Subarticle IWA-3300 (1989 Edition) proximity criteria. These criteria provide the basis for the combination of neighboring indications depending on various geometric dimensions. Crack growth over the next two operating cycles is factored into the criteria.

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Flaws are considered in the same plane if the perpendicular distance between the planes is

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3" (2 times the shroud cylinder thickness) or less.

6 The selection ofindications for further evaluation can be performed by evaluating the resulting effective flaw lengths. Indications with cliective flaw lengths greater than the allowable flaw sizes would require more detailed analysis. The procedure described here is conservative since all of the indications are assumed through-wall and are being compared against the allowable through-wall flaw size.

A list of conservatisms used in this evaluation is summarized in Table 1-1.

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'; W Table 1-1 Conservatisms Included In Screening Evaluation i

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1. All indications were assumed to be through-wall for analysis.

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2. All indications were assumed to be grouped together for the limit load calculation' 1

and no credit was taken for the spacing between indications.

3. ASME Code primary pressure boundary safety margins were applied even though 4

the shroud is not a primary pressure boundary.

4. ASME Code,Section XI proximity rules were applied.

5. An additional proximity rule which accounts for fracture mechanics interaction between adjacent flaws was used.

6. Both LEFM and limit load analysis were applied (for weld H4). LEFM underestimates allowable flaw size for austenitic materials and is not required per ASME Code,Section XI procedures.

7. Fracture toughness measured for similar materials having a higher fluence was used.

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8. The se ai#8 c< cu <e -ta estim tea re<tae extt-e r i cvcie - >i ci a a i-s flaw lengths used for evaluation.

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1.1 References 1-1 BWR Owners' Group Core Shroud Evaluation, GENE 523-148-1193, April 1994.

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2. ULTRASONIC INSPECTION RESULTS I

Ultrasonic inspection of the H1, H2, H3 and H4 welds and neighboring shroud cylinder material was recently performed. The results of UT inspections are provided in the

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examination summary sheets which are located in Appendix A. Tables 2-1_through 2-4 summarize the inspection results. These were used in the structural integrity evaluation of the shroud.

In addition there were locations which could not be inspected due to access limitations.

The uninspected zones were considered in the evaluation as described in Section 4.0. The uninspected zones are summarized in the examination summary sheets and taken into account in the flaw evaluation presented in Section 4.0.

The four upper most shroud circumferential welds (H1, H2, H3, and H4) were inspected -

by ultrasonic volumetric examination from the outer diameter (O.D.). The inspection was performed using the General Electric O.D. Tracker UT scanner, the GE SMART 2000 Data Acquisition / Analysis system, and a PC based motion controller (GE Motion Controller).

The search unit used by the O.D. Tracker scanner typically consists of four transducers:

two 45' Shear,2.25 MHz, one looking up and the other looking down, and two 60* RL, 4 MHz, again one looking up and the second looking down. The system was calibrated on a calibration block representative of the Plant Hatch Unit-2 shroud just prior to and immediately following the examination of each weld.

The O.D. Tracker was installed into the vessel and placed on top of the shroud discharge plenum. Two cam rollers were used to straddle the shroud head ring with one roller riding on the I.D. of the steam dam and the other riding on the O.D. of the ring itself. Two drive rollers riding on top of the steam dam enable the tool to be moved remotely about the circumference of the shroud to position the tool at an appropriate inspection location. A 2-1

GENulee Energy GENE 53,48MSN positioning cylinder is used to incate the O.D. Tracker relative to a particular shroud head

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lug. This, combined with the read out of the encoders associated with the tooling motors, 7

enables the location of the search package to be known within

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applies for when the search unit is extended several feet away from the tooling body as in j

the case of H4; much tighter tolerances apply for those packages that inspect welds proximate to the tooling body as in the case of H1 through H3). The O.D. Tracker scanner supports four different configurations: the first is an arm that extends onto the shroud upper barrel and is used to inspect welds H1 and H2, a second actuating arm is used to inspect H3, and extended arms are used to inspect H4. For H1 through H3, spring force only is used to ensure proper transducer contact. The configuration for H4 uses the additional force of a reaction waterjet to apply the transducers to the shroud with adequate force. Once the tool is located off a particular lug, air cylinders are actuated to securely fix the tool in that location for the duration of the scan. Approximately 15' can be inspected in one scan before the air cylinders are retracted and the tool moves to the next desired shroud head lug using the drive rollers. The air cylinders are actuated to secure the tool and the process is repeated until the exam is complete.

- Because of the multiple interferences present in the annulus between the shroud O.D. and the Reactor Pressure Vessel I.D., the O.D. Tracker was periodically taken off the shroud, manually moved around the obstacle (s) and reinstalled to resume scanning. These interferences included the shroud lifting lugs and core spray spargers.

The entire RF waveform of the data was collected and stored on optical disk for future review. The data was then reduced by GE Level III UT operators using the GE SMART 2000 system, and a complete report given to the plant owners.

In addition to the UT inspection discussed above, five shroud welds (H5, H6A, H6B, H7, and H8) were partially examined by visual techniques from the outside diameter surface.

The welds were visually inspected according to the recommendations provided in GE SIL 572, Rev.1. The IVVI was performed using the IST-1250 black and white underwater 2-2

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The areas of visual inspection were the accessible weld locations above the access hole covers at 0 and 180 degree azimuths No indications were found. The inspection was Performed by a Level II VT and reviewed by a Level III VT.

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Table 2 Weld H1 Indications - 1*=1.65" Indication '

Distance from 0 Total Length Maximum

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' Onch)

Onch)

' Depth Onch)

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'378.2-1.1 0.5 -

Lower.

2 482.9 0.4 0.32-

- Lower-3 524.5 8.6 0.47 Lower -

4 545.5 4.1 0.28 Lower 5

559.2 0.2 0.16 Lower.

Table 2 Weld H2 Indications - 1*=1.65" Indication Distance from 0 Total Length Maximum Side ofWeld (inch)

(inch)

Depth Onch) 1 43.6 9.5 0.53 Upper 2-64.4 17.1 0.52-Upper 3

86.5 161.7 0.6 Upper 4

381.8 1.0 0.27-Upper 5

395.2 15.8 0.28 Upper 6

428.3 2.4 0.22

Upper 7

477.2 11.0 0.33 Upper

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528.8 15.9

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Table 2 Weld H3 Indications - 1 =1.55" 7.sQ Indication Distance from 0 Total Length Maximum Side of Weld

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(inch)

Depth (inch) 1.

33.8 3.4 0.23 In Weld 2

.48.1 1.8 0.19 In Weld 1

3 98.7 16.8 0.68 In Weld 4

118.7 0.3 0.59 In Weld 5

125.4 0.2 0.54.

In Weld 6

130.1 0.7 0.66 In Weld 7

136.1 9.0 0.60 In Weld 8

500.2 1.2 0.37 In Weld Table 2 Weld H4 Indications -1 =1.55" Indication Distance from 0 Total Length Maximum Side of Weld (inch)

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Depth (inch) 1 194.2 1.5 0.35

- In Weld 2

321.5 2.8 0.22 In Weld

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3 331.2 3.9 0.17 In Weld 4

332.0 3.7 0.32 Upper.

5 339.5 5.0 0.16 In Weld 6

374.6 1.0 0.16-Upper 7

377.7 3.5 0.35 In Weld 8

384.1 4.2 0.41 In Weld 9

396.8 3.6 0.24 In Weld 10 406.7 1.7 0.28

- In Weld 11 415.1 1.4 0.51 In Weld 12 468.9 1.8 0.43 In Weld 13 516.0 1.6

.0.34 In Weld 14 518.9 1.3 0.39 In Weld 15 522.2 10.9 0.49 In Weld n.

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3. FLAW EVALUATION In this section the flaw evaluation and methodology for the H1 through H4 weld indications are presented. This involves determining the appropriate effective flaw lengths and allowable flaw sizes.

3.1 Structural Analysis This section describes the details of the structural analysis performed to determine the allowable flaw lengths. The stmetural analysis consists of two steps: the determination of stress magnitudes in the shroud, and the calculation of the allowable flaw lengths. Both the fracture mechanics (LEFM) and limit load methods were used in the calculation of allowable flaw length for weld H4 since it is near the core. Only limit load was used for -

welds H1, H2, and H3 since they are located at a sufficient distance from the core such i

that fluence effects on material fracture toughness are not significant.

3.1.1 Applied Loads and Calculated Stresses The applied loads on the shroud consist ofinternal differential pressure, weight and seismic. The seismic loads consist of a horizontal shear force at the top of the shroud and an overturning bending moment. The shear force produces a shear stress ofinsignificant magnitude, and is not considered. The bending moment stress at a shroud cross-section varies as a function ofits vertical distance from the top of the shroud. Because of the inherent ductility of the material, residual stresses and other secondary stresses do not affect structural margin. Thus, they need not be considered in the analysis.

The magnitudes of the applied loads were obtained from the seismic stress analysis, FSAR and system information reports. The nominal shroud radius and thickness (1.5 in) were used to calculate the stresses from the applied loads. The stresses are essentially based on 3-1 y

i GENuclear Energ GENE-SD A86-0394 l-rm the strength of materials formulas. The specific loads at each weld location were used in

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this evaluation. Figure 3-1 shows the weld designation and relative locations in the shroud.

j Table 3-1 shows the calculated seismic stress for the four welds ofinterest. The pressure difference used for the evaluation of the indications was 29 psi and 12.02 psi corresponding to the shroud head AP for increased core flow conditions for the faulted and upset conditions, respectively (Reference 3-1).

Table 3-1 Seismic Axial Stresses at Shroud Welds (SSE=2xOBE)

Weld SSE Moment OBE Moment Stress (ksi)

Designation (in-lbs)

(in-lbs) '

SSE-OBE HI 84.6x10' 42.4x10*

2.04 1.02 H2 114.6x10' 57.4x10' 2.76 1.38 H3 117.6x10' 58.8x10' 3.23 1.62 H4 183.2x10' 91.6x10' 5.02 2.51 fsb The structural analysis for the indications at weld H4 uses two methods; linear elastic fracture mechanics (LEFM) and limit load analysis. For welds H1, H2, and H3, only limit load was used due to the distance from the core region. Since the limit load is concerned with the gross failure of the section, the allowable flaw length based on this approach may be used for comparison with the sum of the lengths of all the flaws at a cross-section. On the other hand, the LEFM approach considers the flaw tip fracture toughness and thus, the allowable flaw length based on this approach may be used for comparison with the largest effective flaw length at a cross-section. The technical approach for the two methods is described below.

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.l-that the structural integrity analysis can be performed entirely on the basis oflimit load. In fact, J-R curve measurements (Figure 3-2) made on a core shroud sample taken from an s-2 20 n/cm ) showed stable crack extension and overseas plant having higher fluence (8x10 ductile failure. The ASME Code recognizes this fact in using only limit load techniques in Section XI, Subsubanicle IWB-3640 analysis. Nevertheless, a conservative fracture I

mechanics evaluation was performed using an equivalent Kje corresponding to the material J c. The Kje for the overseas plant shroud was approximately 150 ksiVin. Use of I

this equivalence is conservative since; i

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i) The calculated fluence for Plant Hatch Unit-2 (peak of = 6x10 n/cm )is lower

, than that for the overseas plant from which J-R curves were obtained.

values well above the J e, confirming that there is load ii) The J-R curves show Jmax I

capability well beyond crack initiation (See Figure 3-2).

The J-R curves shown in Figure 3-2 can be used to make the following conclusions

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regarding behavior of the shroud material:

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Shroud material with fluence up to at least 8x10 n/cm contains significant ductility.

2 LEFM is conservative for fluence up to at least 8x10 n/cm.

There is significant margin between J. and Ju, demonstrating that there is substantial load carrying capability beyond Ju.

The J-R curves were determined from samples considering through-wall crack' growth in the weld heat affected zone and thus contain some effects of the weld.-

Further consideration for weld metal effects would likely have a'small impact on allowable flaw size.

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/V) 53.6 ksiVin. For faulted conditions the allowable K,is 107 ksiVin using a safety factor of 1.4. For the analysis presented here, the LEFM analysis is confined to the H4 weld. The fluence corresponding to welds H1, H2, and H3 is an order of magnitude lower and the associated fracture toughness is comparable to that of the unirradiated material. For those locations, limit load analysis is used.

An additional consideration that applies only to the fracture mechanics analysis is the question, "When is a flaw independent of an adjacent flaw?" The ASNE Code proximity rules consider how flaws can link up and become a single flaw as a result of proximity.

However, even when two flaws are separated by a ligament that exceeds the criterion, they may not be considered totally independent of each other. That is, the flaw tip stress intensity factor may be affected by the presence of the adjacent flaw. This can be accounted for by using the finite width correction factor for a flaw in a finite plate. For a through-wall flaw in an " infinite" plate, the stress intensity factor is:

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K = cV(na)

For a finite plate, the K value is higher as determined by the finite width correction factor, F. In this evaluation it is assumed that the plate is " infinite" if the correction factor F is less than 1.1. As seen in Figure 3-3, if the width of the plate exceeds 2.5L (or a/b less than 0.4), then there would be no interaction due to plate end edge effects. If this same condition is applied to two neighboring flaws, then there will be no interaction between the two indications if the tips are at least 0.75(Ll'+L2') apart. If the distance between indications is greater than 0.75(Ll'+L2'), then they are considered as two separate flaws.

However, if they are closer, for the purpose of fracture analysis, the equivalent flaw length is the sum of the two individual flaws.

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A through-wall circumferential flaw was assumed in this calculation. A limit load approach was used in these calculations. The flow stress was taken as 3Sm. The Sm value for the shroud material (Type 304L stainless steel) is 14.4 ksi at the normal operating temperature of 550 F.

Safety factors similar to those used in the ASME Code (2.8 for normal and upset and 1.4 for emergency and faulted) were used in the analysis. The seismic stress at each weld location is shown in Table 3-1.

It should be noted that this method assumes that all indications arejoined and positioned in the limiting location to obtain a conservative allowable flaw size. Alternatively, the safety factor for limit load can be determined for the actual indication pattern. Typically, this mee J shows that significantly higher safety margins exist.

V 3.2 Allowable Through-Wall Flaws Allowable through-wall flaw sizes were determined using both fracture mechanics and limit load techniques for circumferential flaws. It should be emphasized that the allowable through-wall flaws are based on many conservative assumptions and are intended for use only in this conservative flaw evaluation. More detailed analysis can be performed to justify larger flaws (both through-wall or part through-wall).

3.2.1 Allowable Through-Wall Circumferential Flaw Size Both the LEFM and limit load methods were used to evaluate the allowable through-wt.ll flaws.

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GENuclear Energy GEN!:-311.As6-0394 3.2.2 Fracture Mechanics Analysis LJ LEFM was used to evaluate the H4 weld. The total axial pressure and seismic stress correspoiading to the faulted condition (limiting condition)i~ 5.88 for weld H4.

s To determine the allowable flaw size based on LEFM methods, the conservatively estimated irradiated material fracture toughness K cI value of 150 ksiVin was used.

Applying a safety factor of 1.4 for the faulted condition, the allowable K of 107 ksiVin I

was obtained. The allowable flaw size was calculated using the following equation:

K = Gm *c'V(na).

I where Gm is a curvature correction faeror as defined in Figure 3-4 (Reference 3-2), o is the axial stress, and 'a' is the half flaw length. The allowable through-wall circumferential flaw length (2a) was determined to be 73 inches for weld H4.

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3.2.3 Limit Load Analysis A through-wall circumferential flaw was assumed in this calculation. The limit load approach was used in these calculations. The flow stress was taken as 3Sm. The Sm value for the shroud material is 14.4 ksi at the normal operating temperature of 550 F.

For the faulted condition, the axial force stress was 0.92 ksi for H1 and H2 and 0.86 ksi for H3 and H4. The bending moment stress was 2.04 ksi for H1,2.76 ksi for H2,3.23 ksi for H3 and 5.02 ksi for H4. Based on these stresses, the allowable flaw length was determined to be approximately 377 in. for H1,362 in, for H2,333 in. for H3, and 305 in.

for H4 including the ASME Code,Section XI safety factors.

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The determination of the allowable through-wall flaws has been described in Section 3.2.

The objective was to use the allowable flaw size as the basis for acceptance of the indications. If the allowable flaw size criteria are exceeded, the option of doing further detailed evaluation remains. The effective flaw lengths (Lleg L2 g etc.) determined by e

combining indications using the proximity and interaction rules, are used in the comparison with the allowable flaw sizes. The determination of effective flaw sizes are discussed in detail in Appendix B. The allowable through-wall flaws are shown in Table 3-2.

Table 3 Allowab!c Through-Wall Circumferential Flaw Sizes

_ eld.

Cumulative Allowable Flaw Length LEFM Allowable (in.)

W (in.)(Limit Load)

H1 377 O

H2 362 V

H3 333 H4 305 73 It should lie noted that when considering LEFM based evaluations, the crack interaction criteria described in Appendix B, must be applied in comparing against the allowable lengths. For example, the adjacent flaws where the spacing S is less than 0.75 (Ll' +

L2'), the length L=Ll' + L2' is used for comparison with the LEFM based allowable flaw length.

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3.4 References 3-1 GE Letter, J. Charnley to J.F. Henning,

Subject:

Hatch 2 Increased Core Flow Analysis, October 2,1980.

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Rooke, D.P. and Cartwright, D.J., " Compendium of Stress Intensity Factors," The

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Hillingdon Press (1976).

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Support Ring H3 c

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GENuclear Enerv GENE-523 A86-0594 ~

j

4. EVALUATION OF INDICATIONS The application of the screening criteria to the indications at H1 through H4 is presented in this section. The first step in this evaluation is the determination of the effective flaw lengths. The determination of the effective flaw lengths is based on the observed indications and their relative locations, and also includes consideration for locations which could not be inspected. The examination summary sheets are presented in Appendix A.

4.1 Weld H1 Evaluation The indications observed at weld H1 are summarized in Table 2-1. Table 4-1 summarizes the inspected weld areas at Hl.

Table 4-1 Weld H1 Inspected Zones Angle length Angle length

. location (*) '.

. Length

Angle O

lxcation (*)

(inch) lxcation(*)

(inch)

(inch) 1 26.9-32.24 -

8 81 11 127.0 132.2 8.7 21 266.9-272.3 8.86 2

36.89-42.23 8.81 12 136.9 142.2 8.78-22 276.9-282.3 8.81 3

46.89-52.24 8.83 13 146.9 152.3 8.86 23 286.9 292.2 8.66 -

4-56.9142.23 8.78 14 156.9-162.2 8.79 24 2 %.9 302.2 8.84 5

66 9 72.26 8.84 15 206.9-212.2 8.83 25 306.9-312.2 8.78 6

76.92-82.26 8.81 16 216.9-222.2 8.84 26 316.9 322.3 8.83 _

7 86.92-92.27 8.83 17 226.9-232.3 8.83 27 326.9 332.2 8.73 8

96 9 102.26 8 81 18 236.9-242.2 8.81 28 336.9-342.3

' 8.91 9

106.0.I12.2 8.76 19 246.9-252.2

' 8.78 10 116.9-122.3 8.94 20 256.9 262.2 8.78 Indication 1 falls within inspected zone 17, indication 2 within zone 23, indication 3 within zone 26, indication 4 within zone 27 and indication 5 within zone 28. For purposes of this evaluation, indications 1,2,4, and 5 were assumed to equal the length of the zone in which they were found. It is also reasonable to assume that since the lengths of indications 1,2,4, and 5 were well within their respective zones (so that the ends of the indications are well defined within the zone), and that the neighboring uninspected zone lengths are relatively short (= 8.8 inches), that the neighboring uninspected zones are free ofindications. In addition, since indication 3 was nearly the let.gth of zone 26, it will be 4-1

L GENuclear Energy

' GENE-32M86-e3N f

assumed that the length ofindication 3 equals that of the zone it was found in, plus the' '

length of the neighboring uninspected zones. Since all other zones were relatively close, it f

is reasonable to assume that the neighboring uninspected zones are also free ofindications.

except as noted above.

l The resulting modified lengths are summarized in Table 4-2.

Table 4-2 Modified Indication Lengths Indication Modified Length (inch)

Measured Indication (inch)-

4' 1

8.83 1.1; i :2 8.66 <

< 0.4 j

3 --

24.23-

8.6 -

' 4' 8.73 ~

4.1i i

5 8.91 0.2 In addition to the uninspected zones between the inspected zones shown in Table 4-l,'

there were two larger areas which could not be inspected due to the proximity _of the shroud head locking lugs and core spray downcomers.' These occurred between 342.27 j

to 26.9' and the second between 162.24 to 206.86*. The equivalent lengths are 73.6 inches for each of these uninspected zones. To address potentialindications in the uninspected zones, it is reasonable to assume that the percentage of these zones with indications is the same as that for the inspected zones.

Based on the inspection results,6% of the inspected areas contain indications. Assuming -

this same percentage in the uninspected zones results in an additional 8.8 inches of indication. Adding this length to the previously calculated effective length for the inspected zones results in a cumulative effective length of 68.2 inches.

i 2"

Thus, the total length of the mumed indications used for evaluation purposes is -

approximately 68.2 mches. This is significantly higher than the actualindication length detected by UT of 14.4 inches. Adding crack growth at each end of the indications (total

i i

of five indications for two cycles) results in a cumulative effective length of 80.2 inches j

i 4-2c j

L H

H

M

. i ki GENuclear Energy GENE-53 A8G03N-

't Tj This compares against the allowable flaw length of 377 inches using limit load. Thus, the

, 1,)

structural integrity of the H1 weld is assured. It should be added that significant margin i

would exist even if the entire uninspected zones (342.27' to 26.9* and 162.24' to 206.86 ) were assumed to contain throughwall indications (=147).

4.2 Weld H2 Evaluation J

n.

The indications observed at weld H2 are summarized in Table 2-2. Inspection was not 1

performed in two zones due to their proximity to the core spray downcomers. These -

. zones were located between 167* to 209' and 347 to 17*.

- Based on the examination summary sheet for weld H2 (in Appendix A), the depth of the deepest indication is 0.6 inch. Ifit is assumed that all of the indications are 0.6 inch in depth, the indication would be determined to be through-wall based on a crack growth -

rate of 5x10'S in/hr after two operating cycles. Thus, these indications were assumed to be.

through-wall in this evaluation. The remainder of the weld region is assumed to be free of -

%/

indications. It should be noted that based on UT inspection results'of a shroud at a European plant, a crack growth rate of 2x10 5 in/hr has been observed.- If this value were used for weld H2, crack growth through the shroud wall in two cycles would not be expected.

The total length of the indications detected by UT is approximately 236.8 inches. The -

4 approximate length of the zones which were not inspected is 118.8 inches. ' As stated in Appendix B, neighboring indications are combined if the indication crack tips are within -

5.4" of each other. Based on the information in Table 2-2, Indications 2 and 3 must be combined. The modified indications are summarized in Table 4 3 (crack growth not -

included).

E 4-3 h

A

~

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t

?'

GENuclear Dwrzy

_ GENE-323-AM-0394

.j[

-xn' Table 4 Weld H2 Combined Indications '

,5

. Modified Indication #.-

1 Modified Length (in)

Comprised ofIndications.

f(from Table 2-2) M

, l 1

- 9.5

. < li,

2-183.75

. 2 and 3

.3

- 1.0 4

c. - -

y

'4 15.8:

c5, l

5 2.4

.6' 6

11.0

.71

1. 7 2.4-

'8' 8

15.9

'9:

r i

The total length of the modified indications is 241.75 inches. Crack growth over the next two cycles must also be factored into this calculation. Since there are 8 (modified) indications, crack growth from each of these must be considered. Using a crack growth rate of 5x10 ir uhe crack growth from 16 crack tips is ;

.- b-Total crack growth = 2(5x10)(12000)(16) = 19.2 inches.

s Adding this crack growth to the total modified crack length, results in an effective length of 260.95 inches.

Finally, the uninspected zones must be considered. Due to the proximity to the core spray downcomers, inspection between the azimuths of 167 to 209* and 347 to 17 could not be performed. This is equivalent to an uninspected region of118.8 inches. To address potential indications in the uninspected zones, it is reasonable to assume that the

. percentage of these zones with indications is the same as that for the inspected zones.

Based on the inspection results,50% of the inspected areas contain indications. Assuming

Q

.this same percentage in the uninspected zones results in an additional 59.4 inches of y

1 4-4 j

-o

M

. GENudeerEnerxy

' GENE.$1Msgesu 1

indication.' Adding this length to the previously calculated effective length for the inspected zones results in a cumulative erTective length of 320.4 inches.

7 The allowable flaw length is 362 inches using limit load. Therefore, the structural integrity-E ofweld H2 is assured.

Alternatively, it can be demonstrated that the structural integrity of weld H2 is assured if -

the entire uninspected zones'are assumed to contain through-wall indications.- This can be demonstrated by using the limit load method and accounting for the actual locations of-indication-free ligaments. This calculation involves determination of the neutral axis such that the limiting safety factor is obtained Results of this calculation for weld H2 show a safety factor well in excess of the ASME Code Section XI safety factors (safety factor = 6). This alternate method also demonstrates that the structural integrity of weld H2 is assured even when assuming ~that.

the uninspected regions are assumed to contain through-wall indications.

1 4.3 Weld'H3 Evaluation The indications at weld H3 are summarized in Table 2-3. Inspection was not performed ini two zones due to their proximity to the core spray downcomers. These zones were i

I located between 173' to 197* and 354 to 19 l

' The total length of the indications detected by UT is approximately 33.4 inches. The ~

approximate length of the zones which were not inspected is 76 inches. To address.

-l u

potential indications in the uninspected zones, it is reasonable to assume that the percentage of these zones with indications is the same as that for the inspected zones.

u m

L 4-5 t

uae a.

,e--

w

.,5 ~

GENulev Eurg GENE-DMH-tm

.E j"y.

~ Based on the inspection results,7% of the inspected areas contain indications. Assuming

,V this same percentage in the uninspected zones results in an additional 5.3 inches of I

indication.

Based on the locations of the indications, it was determined that indications 3 and 4 L

require combination and indications 5 and 6 require combination per the previously discussed proximity criteria (S<5.4"). The modified indications are summarized in Table -

4-4 (crack growth not included).

Table 4 Weld H3 Combined Indications Modified Indication # -

Modified Length (in)

Comprised ofIndications -

(fro'm Table 2-3)-

1-

. 3.4 1-2-

1.8 :

,722 3 '-

20.3 3 and 4 -

.4;

. 5.4 ~

5 and 6 S'

9.0 17

.6 1.2 8:

The total length of the modified indications is 41.1 in. Crack growth from the 6 modified indications is:

4 Total crack growth = 2(5x10 )(12000)(12) = 14.4 in.

Adding this to the modified lengths results in an effective length of 55.6 in. Adding the length of the uninspected zones gives a cumulative in' ication length of 60.9 in.

d Since this length is well below the allowable flaw length of 333 inches, structural integrity -

of weld H3 is assured from a limit load viewpoint. It should be added that significant 4-6

GENacient Ewgy GENE-323.A8M55 n

a fg) safety margin exists even if the entire length of the uninspected zones were assumed to -

contain through-wallindications.

4.4 Weld H4 Evaluation I

The indications found in weld H4 are summarized in Table 2-4; Inspection was not -

performed in two zones between 174 to 202 and 354 to 19. Application of the proximity criteria requires the combination of some of the indications (S<5.4").

The total equivalent length for the uninspected zones is 81.8 inches. To address potential indications in the uninspected zones, it is reasonable to assume that the percentage of these zones with indications is the same as that for the inspected zones.

Based on the inspection results,10% of the inspected areas contain indications. Assuming this same percentage in the uninspected zones results in an additional 8.2 inches of

,f indication.

I' Table 4-5 shows the results of the proximity criteria application including crack growth consideration over two additional cycles.

Table 4-5 Weld H4 Combined Indications Combined Indication

' Length Comprised ofIndications:

1 3.9 I c-2 5.2 -

2 3

15.7 3,4 and 5 4

16.2 6;7, and 8 5

6.0

~9 o

6 4.1

'10' 7'

3.8 11 8

4.2 124 9-19.6 113,14, and 15

.10 3.8-

. Uninspected Zone 1 -

Q l1 4.3 -

- Uninspected Zone 2 L

F l

4-7

~ GENucleeEneray

. GENE.323.As6 0394 1

'O

.b The total length of the combined indications is approximately 87 inches. Since this length is well below the allowable flaw length of 305 inches, structuralintegrity of weld H4 is assured from a limit load viewpoint. It should be added that significant margin exists even if the entire uninspected zones were assumed to contain through-wall indications.

~.

The proximity check for LEFM combination (S<0.75(Ll'+L2')) results in a maximum length of 17 in. (12.2 in. plus crack growth from indications 14 and 15 in Table 2-4). This is well below the LEFM allowable flaw size of 73 inches.

O i

~

.I 6

LO 4-8

i GENasclear Eneray GENE.323.As6-03%

i-

5.

SUMMARY

AND CONCLUSIONS A conservative evaluation of the Plant Hatch Unit-2 core shroud has been performed to

. demonstrate that the structural integrity with the indications at welds H1 through H4 is assured for the next two operating cycles. Application of the screening criteria to the UT

-detected indications demonstrates that the stmetural integrity of welds H1 through H4 is

+-

assured for the next two operating cycles.

The flaw evaluation was presented in this report. The flaw evaluation assumed through-wallindications. By meeting the allowable flaw size criteria, the ASME Code Section XI safety margins are satisfied.

The flaw evaluation considered both linear elastic fracture mechanics (LEFM) and limit load concepts to determine acceptable through-wallindication lengths.

The screening criteria also uses the ASME Code Section XI criteria for combining flaws -

based on the proximity ofindications. In addition, a second method for including the interaction between neighboring indication tips was considered for the LEFM allowable flaw size calculation. The resulting effective flaw lengths were compared against the allowable flaw size to determine if the structural integrity of the shroud was maintained.

5-1

t GE NuclearEneT GENE-323-A86-0594 j

APPENDIX A p]

\\

Examination Summary Sheets U

i i

)

O A-1

REPORT NO.:

EXAMINATION

SUMMARY

SHEET R.soa GE Nuclear Energy Q

PROJECT:M.CH UNIT 2 PROCEDUREt UT-MAT.so3Vo litEV; fL FRR: _N/A

,N/A

_1EBT3 1

t SYST.EM: SHRQ1)D VESSEL N!A REV: h/A FRR: _ N!A N/A N/A WELD NO,: H-1 (GIRTH WELD)

N/A REY: N/A FRR: _Nas CONFIGURATIONLCIRCUMFERENTIAL WFLO sg N/A N/A EXAMINER:

P. ANDERSON LEVEL: tl C MT C PT S UT C VT EXAMINER:

T. ROCKWOOD LEVEL: 11 S CIRCUMFERENTIAL WELD TYPE:

EXAMINER: A CONTI LEVEL: ti O LONGITUDINAL 9 OTHER SHROUD DATA SHEET NO.(S): DS-009.DS oio 0S 011 CAL SHEET NO,(S): cs no7 cs.nna es noe a es ein

_DS412 DS-ot3 DS-014 A

.DS.019 Dunng the examination of the above referenced weld, frve (5) indications associated with IGSCC/LASCC were recorded by the Sma system utilaing 45* shear wave and 60* refracted longitudinal wave search unrts.

The 45' sheer wave search unit also recorded non-relevant indcations, welding discontinuities, along with four (4) of the previously referenced indicatens from both sides of the weld. as well as inside surface geometry from the fillet weld crown on the upper side of the weld and inside surface geometry and outside surface weld crown geometry from the lower side of the weld.

The 60* RL also recorded non-relevant indications, welding discontinuities. along with the five (5) previously referenced indcations from both A

sides of the weld, as well as fillet weld crown geometry from the upper side of the weld.

The indications referenced in the first paragraph have the following parameters:

Indication Distance Tota' Remaining Thruwan Side Type Search Number From Lo Length Legament Denension of Weld Reflector Unit 1

378 2" 1.1" 1.00"

.50" Lower IGSCC/LASCC 45*/60*

2 482 9" 1.18"

.32" Lower IGSCC/LASCC 60*

3 524 5" 86" 1.03" 47" Lower IGSCC/lASCC 45*/60*

4 545.5" 4 1" 1.22"

.28' Lower IGSCC/MSCC 45*/60*

5 559 2"

.2" 1.34"

.16" Lower IGSCC/LASCC 45'/60*

This examination was also limited to 'L' dimensions of 26 90* to 32.24*, 36 89* to 42.23*,46 89* to 52.24*,56 91* to 62.23*,66 90* to 7 76 92* to 62.26*,86 92* to 92.27*,96 92* to 102.26*,106 92* to 112.23*,116.89* to 122.31*,126.96* to 132.23*,136.89* to 142.21*,14 152.25*,156 91* to 162.24*,206 86* to 212.21*,216 88* to 222.24*,226.90* to 232.25*,236.90* to 242.24*,246.90* to 252.22*,256 262.22*,266 88* to 272.25*,276 92* to 282.26*,286 94* to 292.19*,296 87* to 302.23*,306 91* to 312.23*,316 90* to 322.25*,326 332.20*, and 336 87* to 342.27* from vessel'0' due to the prorrnity of the shroud head locking lugs and corespray downceme

'L' denensions for all examination scans were recorded in angular units in leeu of knear units. The conversion factor for circumferential measurements is 1.65" per degree C EXAM cCMPLETS S PARMALLY ExAMINEo (Expt.AM IN COMMENTS)

O g y,g gcom m noN m RWP No.OH-1910 A

No. OF RECoRDAaLE NsMThoess S CouPantoTo CPsi 2ist REPORT Noast N/4 t J No oMANos

,a I

ExAWenAnooi Riau TS :.

OAoCEPTAatt C UNACCsPTAsLE No.OP REPoRTAaLE pecocAnotra 5 nos uAN Rsu M.

E 4'W-#

[

V/r//, y SU MAftY BY LEVEL DATE UTILffY M DATE I

%A

• N N,

M A.

PAGE 1 OF:_38 OE REVIEWED BY LEVEL DATE ANil REVIEW DATE

,e.,v a A-2.

REPORT NO.:

EXAMINATION

SUMMARY

SHEET p

nsc2 GE Nucient Energy O

PROJECT:_ HATCH UNIT 2 PROCEDUREL UI-BAI 503VD REV: 0-FRR: N/A

,_1EST3 y

SYSTEM:_SBROUDNESSEL N/A REVL.MA FRR: __MA

_fd/A N/A WELD NO.: H-2 (GIRTH WFI D) t CONFIGURATION:_CIRCUMFERENTIALJELD SEAM _

-- N/A REVL WA FRR:

_ N/A EXAMINER: T. ROCMOOD LEVEL: 11 C MT C PT S UT Z VT EXAMINER:.. P. ANDERSON LEVEL: ti B CIRCUMFERENTIAL -

EXAMINER:._A_ CONE LEVEL: 11 C LONGITUDINAL S OTHER SBBQUD DATA SHEET NO.(S):_DSa15 DS-015 DSa17 CAL SHEET NO.(S): es ots es at2 cs ci3 a esat4 DS-01B_ DS.n?0 a DS.021 Dunn0 the examination of the above referenced weld, six (6) indications associated with IGSCC/lASCC along with three (3)10 connected pla fisws were recorded by the Smart 2000 system utilizing 45' shear wave and 60* refracted longitudinal wave search units.

The 45* shear wave search unit also recorded non-relevant indications from both sides of the weld, along with inside surface geometry from the fillet weld crown from the lower side of the weld. as well as outsde surface geometry from the weld crown, inside surface geometry, welding discontinuttees, and the nine (9) previously referenced ID connected indications from the upper sde of the weld.

The 60* RL also recorded non-relevant indications and the nine (9) previously referenced 10 connected indications from both sides of the weld,

%/

along with insde surface geometry from the filet weld crown from the lower side of the weld as well as welding discontinuites from the upper side of the weld The indications referenced in the first paragraph have the following parameters:

Indicat on Distance Total Remaining Thruwall Sbe Type Search Number From Lo Length Ligament Dimension c4 Weld Reflector Unit 1

43 6" 95"

.97"

.53" Upper PLANAR 45*/60*

2 64 4" 17.1"

.98*

.52" Upper PLANAR 45*/60*

3 86 5" 161.7"

.90"

.60" Upper PLANAR 45*/60*

4 381.8" 1.0" 1.23"

.27" Upper IGSCC/1ASCC 45*/60*

5 395 2" 15 B" 1.22"

.28" Upper IGSCC/lASCC 45*/60*

6 428 3" 24" 1.28"

.22" Upper IGSCC/tASCC 45*/60*

7 477.2*

11.0" 1.17"

.33" Upoor IGSCC/1ASCC 45*/60*

8 505.1*

24" 1.16"

.34" Upper IGSCC/tASCC 45*/60*

9 528.8" 15 9" 1.14"

.36" Upper IGSCC/lASCC 45*/60*

This examination was also limited to *L' dimensions of 17' to 167* and 209' to 347* from vessel'0' due to the proximity of the corespray Circumferential'L' dimensions for all examination scans were recorded in angular un#ts in lieu of linear units The conversion downcomers fador for circumferential measurements is 1.65* per degree-C EXA8 Co#PLETE S PART1ALLT EXAmmED (EXPLAM M CoelWENTS)

C COM W CotamATloN wtN frwP eso 294 1110..

ADorTIOstAL DATA SMEETs 8&A gyg y

,g CoesPAtt0 To C Pat C tal REPoAT 88o.tst N/A C 880 cMANGs EAAumATioe# assutT3 :

CACCEPTAaLE C UNACCEPTAaLEf eso, of REPostTAaLEINosCAftoess' O 1 MAN R$M d

L h

I 4-Il-M M

d/ y y i

~~

DATE Ut414ARY BY LEVEL DATE

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REPO8tT NO.:

.EXAMINA lON

SUMMARY

SHEET a.so, GE Nuclear Energy t

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PROJECT!_ HATCH UNIT 2 PROCEDURE: UT. HAT.sosvo REVL fL. FRR: N/A N/A

__1ESI3

- g, SYSTEM:_ SHROUD VESSEL N/A REVL L/A FR R: N 'A

- N/A MA WELD NO.: H.3 (GIRIH WFLD)

CONFIGURATION? ctRCUMFERENTIALWELD SEAM

- N/A REV: N/A FRR: _NA

_. N 'A EXAMINER:..I LOYD LEVEL: ll O MT O PT 3 tit O v7 EXAMINER: P ANDERSON LEVEL: il 5 CIRCUMFERENTIAL WELD TYPE:

EXAMINER: N/A LEVEL:A g

DATA SHEET NO.(S): osa Os-oa2 Ds oo3 CAL SHEET NO.(S): cs.co1 a cm2 JLDs-ood Dunng the examination of the above referenced weld. eght (8) ID connected planar flaws within the weld material were recorded by t 2000 system utilizing 45' shear wave and 60* refracted longitudinal wave search units.

The 45' shear wave search unit also recorded non4 levant indications welding discontinuities, inside surface and weld crown geometry, along with the eght (8) previouby referenced indications above from the lower side of the weld.

The 60* RL also recorded non-relevant indications. sheer component, welding discontinuities, inside surface and weld crown geometry, along

[

with the eight (8) previousty referenced indications from the lower side of the weld.

v The indications referenced in the first paragraph have the following parameters indication Distance Total Remaining Thruwall Side Type Search Number From Lo Length Ligament Dmension of Weld Reflector Unit 1

33 8" 34*

1.27'

.23*

In Weld Planar Flaw 45*/60*

2 48.1*

1.8*

1.31'

.19" in Weld Planar Flaw 45*/60*

3 98 7*

16 8*

.82*

.68*

In Weld Planar Flaw 45*/60*

4 118 7*

.3*

.91 *

.59" in Wekt Planar Flaw 45*/60*

5 1254"

.2*

.96*

.54' in Wold Planar Flaw 45*/60*

6 130 1*

.7*

.84*

.66*

In Weld Planar Flaw 45*/60*

7 136 1*

90*

.90*

.60*

In Weld Planar Flaw 45*/60*

8 500.2*

1.2" 1.13"

.37' in Wold Planar Flaw 45*/60*

No examination was performed from the upper sde of the weld due to the component configurstxm. and the examination from the lo the weld was lanited due to the proxirnity of the outsde diameter fillet weld. Thrs examination was also inned to 'L' dimensions of 19' and 197* to 354' from vessel'0' due to the prox'rnrty of the corespray downcomers. Circumferential'L' dmonsions for all exammation scans were recorded in angular units in lieu of knear units The conversion factor for circumferential rnessurements is 1.55' per degree.

O ex^m cometrie p,4=1sattT exi.,~co <cx,ta,u in co.. wisi O g,y,9 4co= = ma =

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VEL DATE UTILITY REVIEW DATE N

A PAoE 1 oF:_2z

. pfviEwto aY LEVEL DATE ANil REfiEW DATE

_,..n.

A-4

j Os REPOM NOa EXAMINATION

SUMMARY

SHEET e.no3 GE Nuclear Energy

,(J l

PROJECT: _ HATCH UNIT 2 PROCEDUREt LfT-HAT.so3Vo REV: 0.

FRR: _N/A

._N/A 1EST3 R!A SYSTEM:._SERQUD_ VESSEL

._.N/A REW.k!A FRR: N!A

_,fL'A R/A WELD NO.: H-4 (GlRTH WFLD)

CONFIGURATION:_C18CUMFERENTLALWELQ SENL

-N/A REW_N/A FRR: _._N/A

_N/A M'A EXAMINER:_fLRfDERSON LEVEL: _JJ Q MT O PT 5 UT C VT EXAMINER:_A_CONTI LEVEL: 11 5 CIRCUMFERENTIAL EXAMINER:_N/A LEVEL: _ N/A O LONGITUDINAL 5 OTHER SHROUD DATA SHEET NO.(S): cs-co.LDs.cos os.co7-CAL SHEET NO.(S): es oos es-ooa es oos a es.cos

.LDS-008 Dunng the examination of the above referenced weld, two (2) indications associated with IGSCC/tASCC along with thirteen (13) ID connec planar P.aws within the weld matenal were recorded by the Smart 2000 system utilmng 45' shear wave and 60* refracted longtudinal wave search units The 45' shear wave search unit also recorded non-relevant indications, insde surface geometry, weld dscentinuities, and inside and outside surface geometry from the weld crown on both sides of the weld, along with the fifteen (15) previously referenced ID connected indications-The 60* RL also recorded non-relevant indications, welding discontinuites, shear component and inside surface geometry from the weld crown, O

along with the fifteen (15) preveusly referenced ID connected indications from both sides of the weld.

The indications referenced en the first paragraph have the following parameters:

Indication Distance Total Remaining Thruwall Sde Type Search Number From Lo Length Ligament Dimension of Weld Reflector Unit 1

194 2" 1.5" 1.15"

.35" In Weld PLANAR 45*/60*

2 321.5" 2 8" 1.28'

.22" In Weld PLANAR 45*/60*

3 331.2" 39" 1.33"

.1T in Weld PLANAR 45*/60*

4 3320" 37" 1.18"

.32" Upper IGSCC/LASCC 45'/60*

5 339 5" 50" 1.34"

.16*

In Weld PLANAR 45*/60*

6 374 6" 1.0" 1.34"

.16" Upper IGSCC/lASCC 45*/60*

7 377.7" 3 5" 1.15"

.35" in Weld PLANAR 45*/60*

8 384.1" 4 2" 1.09"

.41" In Weld PLANAR 45*/60*

9 396 8" 3 6" 1.26"

.24" In Weld PLANAR 45*/60*

10 406 7" 1.T 1.22"

.28" In Weld PLANAR 45*/60*

11 415.1" 1.4"

.99"

.51" in Weld PLANAR 45*/60*

12 468 9" 1 8" 1.07"

.43" in Weld PLANAR 45*/60*

13 516.0" 16" 1.16"

.34" in Weld PLANAR 45*/60*

14 518 9" 13*

1.11"

.39" tr: Weld PLANAR 45*/60*

15 522.2*

10.9" 1.01"

.49" In Wold PLANAR 45*/60*

M Comm 5 e AmtsAt.tv sxAuiuto texetAm iu coeurwTil G exam co=*LaT w cousi=ATion wrTw DATA RHfft1 mai riw Awp Wo.:_._ 2944 110 ADomONAL oATA sMtETs N/A gyg gggg cow *AREo To' C est U isi REPo47 No.(el: N/A La No cMANot yng a EXAmmAfiON RisukTS :

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DATE

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PAGE 1 OF; M_.

EWED5Y LEVEL DATE ANil RIVIEW DAtt

. wen i A-5

O;

REPORT NO.:

EXAMINATION

SUMMARY

R-S03 GE Nuclear Energy CONTINUATION SHEET

' (k, PROJECT:__ HATCH UNIT 2 WELD NO.: H4 (GlRTH WFl D)

_1EST3 CONFIGURATION: CIRCUMFERENTIAL WFLD SEAM This examsnaten was tensted to 1* dimensions of 19' to 174* and 202* to 354' from vessel'0' due to the proximMy of the corespray downcomers.

~

Circumferential t' denensons for all examination scans were recorded in angular unas in issu of knear units. The converson factor for occumferential measurements is 1.55' per degree.

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' GENuclear Eneray GENE-5D-A86-0394*

APPENDIX B

. O norta >xiriox or rut tertcrivt rtAw otuoru i

The effective flaw lengths are based on ASME Code,Section XI proximity criteria as presented in Subarticle IWA-3300. The procedure addresses circumferential flaws.

Indications are considered to be in the same plane if the perpendicular distance between the planes is less than 3" (2 times the maximum shroud cylinder thickness). All flaws are considered to be through-wall. Therefore, indications on the inside and outside surface should be treated as if they are on the same surface. When two indications are close to each other, rules are established to combine them based on proximity. These rules are.

described here.

B.1 Proximity Rules-The flaw combination methodology used here is similar to the ASME Code,Section XI proximity rules concerning neighboring indications. Under the rules, if two surface indications are in the same plane (perpendicular distance between flaw planes <3") and are within two times the depth of the deepest indication, then the two indications must be r

considered as one indication.

In Figure B-1, two adjacent flaws L1 and L2 are separated by a ligament S. Crack growth would cause the tips to be closer. Assuming a conservative crack growth rate of 5x10-5 in/hr, crack extension at each tip is 1.2 in. for 2 fuel cycles (each of 12,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> duration, see Appendix C for crack growth rate discussion). Therefore, combining the crack :

growth and proximity criteria, the flaws are assumed to be close enough to be considered as one continuous flaw if the ligament is less than (2 x 1.2 + 2 x shroud thickness)J For a.

1 shroud thickness of 1.5 in., this bounding ligament is 5.4 in. Thus, if the ligament is less than 5.4 inches, the effective length is (Ll+L2+S+2.4"). Note that the addition of 2.4 in.

is to include crack growth at the other (non-adjacent) end of each flaw (See Figure B-2).

i B-1

GENucleu Emu GENE SD-Aussu

~

If the ligament is greater than 5.4 in., then the effective flaw length is determined by V

adding the projected tip growth to each end of the flaw. For this example, Ll r= L1 +

ef 2.4", and L2 y= L2 + 2.4".

ef After the flaws have been combined per the ebove criteria, a map of the effective flaws in the shroud can be made, and the effective flaw length can be used for subsequent analysis.

In order to demonstrate the proximity criteria, an example is described below.

Consider two circumferential indications as shown in Figure B-2a. If the distance between the two flaw tips is less than 5.4", the indications must be combined such that the effective length is (See Figure B-2b):

L r= L1 + S + L2 + 2.4" ef where: L1 = length of first circumferential indication L2 = length of second circumferential indication p

S = distance between two indications V

If the distance between the two tips is greater than 5.4", the effective flaw lengths are (See Figure B-2c):

Llefr= L1 + 2.4"

' L2efr= L2 + 2.4" B.2 ~ Application of Effective Flaw Length Criteria The application of the effective length criteria is applied to two adjacent indications at a time. Figure B-3 is a schematic which illustrates the process. For example, using the 0*

azimuth as the starting location for a circumferential weld or plane, the general procedure would be as follows:

B-2

-=

~

w

GENuclear Energy GENE.523486 0394 Moving in the positive azimuthal direction, the first indication encountered is indication 1.

The next indication is indication 2.

f Apply proximity rules to the pair ofindications (indications 1 and 2). Combine the flaws if necessary (Ll+L2+S+2Aa). Ifindications are combined, combined indication becomes new indication 2.

Continue along positive azimuthal direction until the next indication is encountered. This becomes indication 3.

Apply proximity rules to indications 2 and 3. Ifindication 2 is a combined flaw, do not add and additional Aa, since it is included in the effective flaw length previously determined.

Continue proximity rule evaluation until all indications along the subject weld or plane have been considered.

O B-3

GENuclear Enero GENE.52M86-03H O

A

~

s-x ComNnd L1 i

Flaw l

l l

f I f D1

)k 4

=

L S

D2 4

y A

u I

l l

l 1 f 1f I

Figure B 1: ASME Code Proximity Criteria p'd B-4

GENuclear Energy GENE.323.A86 0594

\\

l r

i.

~

4 www As-Found

\\

(a)

-Lt-d-3 7

--- u _%

n-w S < 5.4*

L, =L1 + S + L2 + 2(17)

(b) w.=

4 5

i e

%J a-S >5.4*

L1.n =L1 + 2 (17)

(c)

L2, =L2 + 2(1.2")

i 4u,->lg l

4 -. 1 r - > < -- u,r->-

Figure B-2: Application of Proximity Procedure to Neighboring Circumferential Flaws

(~'N V

B-5

s GENuclear Fm GENE-523-A8G05N Start at Theta = 0 Move in + Theta Direction t

I i=1 Y

First Flaw is Flaw I 6

Y Next Flaw is Flaw i+1 Y

Apply Proximity Rules to Flaws i and i+1

/

Combine Flaws if Necessary and Determine Effective Length I I If Flawis Combined f

Combined Flaw = Flaw i+1 I

No Last Flaw?

Yes

+

Done Figure B-3: Process for Determining Effective Circumferential Flaw Length OU B-6

-.-------~- -

---~ -

GENular Eurg GE,VE 3D-A%.03N APPENDLX C

,em

)

U BASIS FOR THE CRACK GROWTH RATE b

The basis for the crack growth rate used in the screening criteria is provided in this section. The Plant Hatch Unit-2 shroud cylinder was fabricated from Type 304L stainless steel plate. For purposes of the crack growth rate calculations, the materialis assumed to be Type 304. Crack growth rates for Type 304L material are bounded by those for Type 304 material. The shroud is subjected to neutron fluence during the reactor operation which further increases the effective degree of sensitization. The other side-effect of neutron fluence induced irradiation is the relaxation of weld residual stresses. The slip-dissolution model developed by GE quantitatively considers the degree of sensitization, the stress state and the water environment parameters, in predicting a stress corrosion cracking (SCC) growth rate. The crack growth rate predictions of this model have shown good correlation with laboratory and field measured values. This model was used to predict a Plant Hatch Unit-2 specific crack growth rate and a conservative value was then p) selected.

C.1 Slip-Dissolution Model Figure C-1 schematically shows the GE slip-dissolution film rupture model(Reference C-

1) for crack propagation. The crack propagation rate V is defined as a function of two t

i constants (A and n) and the crack tip strain rate, c'a.

V = A(c'a)*

(C-1) i where s'a = CK' (for constant load)

A = 7.8x10n" (from Reference C-2) n is defined in Reference C-2 The constants are dependent on material and environmental conditions. The crack tip strain rate is formulated in terms of stress, loading frequency, etc. When a radiation field, O

such as the case for the shroud, is present, there is additional interaction between the V

C-1

s k-GENuke Euru GENE.3234N-03N gamma field and the fundamental parameters which affect intergranular stress corrosion cracking (IGSCC) of Type 304 stainless steel (see Figures C-2 and C-3).

The increase in sensitization (i.e., Electrochemical Potentiokinematic Reactivation, EPR) as a function of neutron fluence (>1MeV) is given as the following:

EPR = EPRo + 3.36x10-24 (fluence)l.17 (C-2) 2 where, EPR is in units of C/cm2, fluence is in units of n/cm and the calculated value of EPR has an upper limit of 30.

The constant C is defined as the following:

for fluence $ l'.4x1019 n/cm2: C = 4.1x10-14 (C-3a) 2 2

19 n/cm but $ 3x1021 n/cm :,

(C-3b) for fluence > 1.4x10 C = 1.14x10-13 n(fluence) - 4.98x10-12 I

for fluence > 3.0x10 ' n/cm : C = 6.59x10 0 (C-3c) 2 2

C.2 Calculation of Parameters The parameters needed for the crack growth calculation by the GE model are: stress state and stress intensity factor, effective EPR, water conductivity, and electro-chemical -

corrosion potential (ECP).

The stress state relevant to IGSCC growth rate is the ste'ady state stress which consists of weld residual stress and the steady applied stress. Figure C-4 shows observed through-wall weld residual stress distribution for large diameter pipes. This distribution is expected to be representative for the shroud welds also. The maximum stress at the surface was nominally assumed as 35 ksi. The steady applied stress on the shroud is due C-2

GENE-313.A86-05N GE Nuclear Energy to core differential pressure and its magnitude is small compared to the weld residual 7_s b

stress magnitude. Figure C-5 shows the assumed total stress profile used in the evaluation. Figure C-6 shows the calculated values of stress intensity factor (K) assuming a 360 circumferential crack. It is seen that the calculated value of K reaches a maximum of approximately 25 ksiVin. The average value of K was estimated as 20 ksiVin and was used in the crack growth rate calculations.

The weld residual stress magnitude is expected to decrease as a result of relaxation produced by irradiation-induced creep. Figure C-7 shows the stress relaxation behavior of Type 304 stainless steel due to irradiation at 550 F. Since most of the steady stress in the shroud comes from the weld residual stress, it was assumed that the K values shown in Figure C-6 decrease in the same proportion as indicated by the stress relaxation behavior of Figure C-7.

The second parameter needed in the evaluation is the EPR. In the model, the initial EPR value is assumed as 15 for the weld sensitized condition. Using Equation (C-2), the predicted increase in EPR value as a function of fluence is shown in Figure C-8.

The third parameter used in the GE predictive modelis the water conductivity. The reactor water conductivity at Plant Hatch Unit-2 has recently been good (approximately S/cm ). This has a significant impact on the predicted crack growth rate (See Figure 2

0.1 C-9). To demonstrate that the GE model conservatively reflects the effect ofconductivity, f

Figure C-10 shows a comparison of the GE model predictions with the measured crack growth rates in the crack advance verification system (CAVS) units installed at several BWRs. The comparison with CAVS data in Figure C-10 also demonstrates the conservative nature of crack growth predictions by the GE model.

The last parameter needed in the GE prediction model is the ECP. For the determination of a conservative crack i;rowth rate, the ECP used in this calculation will correspond to

(

that for no hydrogen injection. Figure C-11 shows the measured values of ECP at two C-3

' GEVE-523.AtMSN GENuclear Energy locations in the core. The ECP values at zero H injection are relevant in Figure C-11 for 2

no hydrogen injection. It is seen that the ECP values at zero H injection rate range from 2

150 mV to 225 mV. Therefore, a value of 200 mV was used in the calculation.

C.3 Crack Growth Prediction 4

Based on the discussion in the preceding section, the crack growth rate calculations were conducted as a function of fluence assuming the following values of parameters:

Initial K

= 20 ksiVin EPRo

= 15 C/cm2 Cond.

= 0.1 pS/cm2 ECP

= 200 mV Figure C-12 shows the predicted crack growth rate as a function of fluence. It is seen that the predicted crack growth rate initially increases with the fluence value but decreases later as a result of significant reduction in the K value due to irradiation induced stress 2

i 20 n/cm,

relaxation. The crack growth rate peaks at 4.5x10-5 n/hr at a fluence oflx10 Thus, a bounding value of 5x10-5 n/hr can be conservatively used in the structural i

integrity evaluation for the shroud.

This bounding crack growth rate is quite conservative as can be shown in Figure C-13 from NUREG-0313, Rev. 2. It is seen that the crack growth rate of 5x10-5 n/hr at i

20 ksiVin is considerably higher than what would be predicted by using the NRC curve.

This further demonstrates the conservatism inherent in the assumed bounding value of crack growth rate.

O C-4

GENuclear Laergy GENE-523.A8MSN C.4 Conclusion

,O I

A crack growth rate calculation using the GE predictive model was conducted considering the steady state stress, EPR, conductivity and ECP values for the Plant Hatch Unit-2 shroud. The evaluation accounted for the effects ofirradiation induced stress relaxation and the increase in effective EPR. The evaluation showed that a bounding crack growth rate of 5x10-5 n/hr may be used in the structural integrity evaluation of shroud.

i

~

O i

C-5

4 GENuclear Energy GENE.3.13.A8MSN C.5 Reference C-1 F.P. Ford et al, " Prediction and Control.of Stress Corrosion Cracking in the i

Sensitized Stainless Steet/ Water System," paper 352 presented at Corrosion 85, _

Boston, MA, NACE, blarch 1985

'C-2 F.P. Ford, D.F. Taylor, P.L. Andresen & R.G. Ballinger," Environmentally Controlled Cracking of Stainless Steel and Low Alloy Steels in LWR Environments," 1987, (EPRI Report NP50064M, Contract RP2006-6).

O I

s t

O C-6

1 GENuclear Eaery GEVE 3D.A8M394 O

i O

l l

S cT d i Z

yT Crack-tip advance by enhanced oxidation at strained crack tip 1 r O

V, = A 6",

Where:

VT

=

crack propagation rate -

constants, dependent on material and environmental -

A, n

=

conditions Sci crack-tip strain rate, formulated in

=

terms of stress, loading frequency, etc.

Figure C-1: The GE PLEDGE Slip-Dissolution - Film Rupture Model of Crack

/]

Propagation l

V 1

C-7 l

GENuclear Energy GENE.323.A86 0594 l

O 1

+

SOLUTION RENEWAL OXIDE RUPTURE RATE TO CRACK.TIP STRESS RATE AT

\\

CRACK.TIP A4 ANIONIC TRANSPORT b

ENVIRONMENT MICRO.

HARDENING 1 RELAXATION STRUCTURE 7 - FIELD O

1 CRACK TIP $ [A)*,pH N-FLUENCE PASSIVATION RATE AT CRACK TIP G.B. DENUDATION I SEGREGATION Figure C-2: Effects of Fast Fluence, Flux & Gamma Field on Parameters Affecting IGSCC of Type 304 Stainless Steel C-8

li GENuclear Energy GENE 323484-03N O

V = A6;

~

T w

O J,J T

h r

g HO-r-

2 n-u 4

{

1Y P.5,NI,St O

5 Vr = Ash n = { e f(K)/ (ef(K) + e f(9)c f(EPR) q i t 1 Figure C-3: Parameters of Fundamental Importance to Slip-Dissolution Mechanism ofIGSCC in Sensitized Austenitic Stainless Steel 4 C-9

GENxclear E=ersy GENE-5%486-0394 } OBSERVED RESIOU/iL STRESS PROFILg3 IN H AZ OF 24".2'/ 01 A. SCH. 60 PIPING l l I I I I I l l l +300 40 ~ Og +200 -l g 3 20 b a\\ $/ / a\\ + I00 Af$n/ m s g goc'Y m \\ E N = 0 0 ~ ~~ c o 0 0 g l N8 8 /3 \\d -100 O

1. \\@ U

/ W -20 s4 y]-*- -2" -40 -300 I I I I I I I I I l O O.1 0.2 0.3 0.4 0.5 0.8 0.7 0.8 03 1.0 INSIDE FMACTIGd CF TMOUGH MLL OUTSIDE WALL DIMENSION WALL Figure C 4: Through-wall Longitudinal Residual Stress Data Adjacent to Welds in 12 to 28 inch Diameter Stainless Steel Piping C40

= -. _. GENuclow Eurgy GENE $UJ8M394

LO

.4 4 i j -) STRESS (KSI) - 40 D OD 30 - 20 - Total Stress Profile 10 - Applied Load Stress 0 . I 40 0 0.2 0.4 0.6 0.8 1 1.2 1.4 j DEPTH (INCHES) ] Figure C-5: Conservative Representation of the Shroud Total Through-wall Stress Profile i C-11 -l

i e i GENuclear Ewsy GENE-323486-03% ^O I 9 J Y STRESS INTENSITY, K (KSPINCH^0.8) 26 24 22 20 18 16 14 12 y 10 g. 6-4- 2-0 0 0.2 0.4 0.4 0.4 1 CRACK DEPTH, A (INCHES)

l 6

() - Figure C-6: Shroud Through-wall Stress intensity Factor c42 e-

GENuclear Energy GENE-523.A8MSN e 'O 4 i 1 \\ stress Relaxation Behavior from Irradiation Creep e 0.8 5 c 'E E e c 0.6 E Average Data 2 g o 0.4 e O h ew 0.2 Type 304 Stainless Steel at 284'C 0 1 8 82 10 10 o 10 ' 10 8 Neutron Fluence, n/cm (E>1 MeV) Figure C.7: Stress Relaxation Behavior of Type 304 Stainless Steel Due to Irradiation at 288T C43

'd: GENulom Enerv GENE-323 A8MSN a ea* (~N ,d t 4 e 1 30 u 25 E 20 = o 15 e 10 19 1E+19 1E+20 1 E + 21 %/ FLUENCE ,i Figure C 4: EPR Versus Neutron Fluence fS . V. C44- --~ w

L +- GENuclear EnerO GENE-523 A8M594 4 ~O t. t-1975-1984 - 200 mV r O 0001 5.000E-05 100 mV g 1992-1993 ' 200 mV a: 0.00001 300 mV 5 is e 0.0000ui O / 0.0000001 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Conductuty,pS/cm PLEDGE: 20 ksiJid,15 CIcm2 ~ ) 1 1 1 '~ Figure C-9: GENE PLEDGE Model Prediction for a BWR4 (Sensitized - Type 304 Crack Growth Rate) i C45 ~ ~

GENuclearEm GENE s2Munu 10: Y 0.0001 200 mV h 5.000E 05 i .g 0.00001 s cc O c o o wo C O b IS B u, 5 0.000001 av v N o s C O ue m c M O O T MM M 1E-07 O.05 0.1 0.15 0.2 0.25-0.3 0.35 ConductMty.yS/cm PLEDGE: 20 ksl6,15 C/cm2 CAV: 20-25 ksl5,13 C/cm2,100160 mV 5 + Figure C-10: Effect of Conductivity on Sensidzed Type 304 Crack Growth Rate C46

e. L ' GENuclear EnerKY GENE-323-ASM3M

• Q

,.V f i-I 300 c: ^ 200 th-100 (II k O. E Just Below Top Guide Level a- -100 d -e -200 Just Above Core Plate Level ~ -300 -400 O 10 20 30 40 50 60 70 80 90 Feedwater H2, SCFM Figure C-11: In-Core Bypass ECP versus Feedwater Hydrogen for BWR-4 m C47

u 2 i-GENuclew EnerO GENE-523-A8MSN $' f . %) i' 'i .h t 1.00E-04 n a 11 11 ,g: g C $ 1.00E-05 E4 AL) 1.00E-06 1E+19 1E+20 1 E + 21 Fluence (n/cm"2) Stress Intensity = 20 ksid, Initial EPR = 15 C/cm2 1 \\ ((-)\\ Figure C-12: Growth Rate versus Fluence C48 i - ' " ~

GENE-323-A86-05N GENuclear Energy I -5 'O i i i I NRC CURVE G r l 1in /yr /, 10-4 e 8 S A f Arg ~ .f g ~ fjff -5 ? 10 [ b O,.b g V a.2 pm. o ; sensitian at tiso'r/2 m r <tn, is u 8i.a w A o.2 pom o ; sensitised at tiso'r/t n r 8 O o.:(tre = to ucm ). ca CE ,,e o i seasitise .t itso'rire a r z .a +B o a.: o,;se,.r.ir seasitie.4 @ 10-6 O s e,= o,s in iittied at tiso rt < n a e ni m mi co Ento @ AM. ( Cao g c) HONspaso3Ii#'d'I"'idI"'I 2 <:t us at in rir. (sen g - 0.04 inlyr 3 a pee c 5 **'8'd ** III'!*'/18 "i"I' 2 8 l 6 a een(sn'r/24 h) (tre 4 c/cs )c 5 ' " *i8'd ** (18'8 + ~ l 2 I + (sn'r/24 h) (tre a 4 c/cs ) "** '

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