ML20132C558

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Rev 0 to Design Rept for Evaluation & Disposition of IGSCC Flaws at Plant Ei Hatch Unit 1
ML20132C558
Person / Time
Site: Hatch Southern Nuclear icon.png
Issue date: 05/17/1985
From: Acojido B, Gustin H, Wenner T
NUTECH ENGINEERS, INC.
To:
Shared Package
ML20132C522 List:
References
TAC-55236, XGP-09-106-R00, XGP-9-106-R, NUDOCS 8509270088
Download: ML20132C558 (62)
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  • l t XGP-09-106 Revision 0 May 1985 XGP009.0106 DESIGN REPORT FOR EVALUATION AND DISPOSITION OF IGSCC FLAWS AT PLANT E. I. HATCH UNIT 1 Prepared for Georgia Power Company Prepared by:

NUTECH Engineers, Inc.

San Jose, California Reviewed by: Approved by:

A my H. L. Gustin, P.E. T.J. Wenner, P.E.

Project Engineer Engineering Manager Issued by:

M Date: 5 8 5

y. . D. coj ido, El.E.

Project Manager t

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8509270000 050917 1 PDR ADOCK 050 i

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REVISION CONTROL SHEET TITLE: Design Report for Evaluation DOCUMENT FILE NUMBER: XGP009.0106 and Disposition of IGSCC Flaws at Plant E.I. Hatch Unit 1 -

XGP-09-106 C. H. Froehlich/ Staff Engineer CM NAME / TITLE INITIALS H. L. Gustin / Principal Engineer NAME/ TITLE INITIALS

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M. E. Kleinsmith/ Consultant I CO NAME / TITLE INITIALS NAME / TITLE INITI A LS AFFECTED DOC PREPARED ACCURACY CRITERIA REMARKS PAGEIS) REV BY 10 ATE CHECK BY / DATE CHECK BY / DATE iv-vii 0 g{ 3 0 gf MEY/i-l7*86 ON7[S*M85 1.1-1.4 0 2.1-2.1n 0 3.1&3.2 0 4.1&4.2 0 5.1-5.lu 0 6.1-6.lo 0 y g 7.1-7.3 0 if a B.156.2 0 f 0 5')Iii YCk/5'I? Si CH3ls.n.ss PAGE I 0F 1 Ctp J 3.1.1 ACV 1

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CERTIFICATION BY REGISTERED PROFESSIONAL ENGINEER I hereby certify that this document and the calculations contained herein were prepared under c.y direct supervision, or reviewed by me, and to the best of my knowledge are correct and complete. I f urther certify that, to the best of my knowledge design margins required by the original Code of Construction have not been reduced as a result of the repairs addressed herein. I am a duly Registered Professional Engineer under the laws of the State of Illinois and am competent to review this document.

Certified by:

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  • ! p!NEs5cIE j*L Nl o I H. L. Gustin, P.E.

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$l }h C-lF % Registered Professional Engineer State of Illinois Registration No. 062-039110 Dates b 17, l9 T

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e v TABLE OF CONTENTS Pace LIST OF TABLES vi LIST OF FIGURES vii

1.0 INTRODUCTION

1.1 2.0 REPAIR DESCRIPTION 2.1 3.0 EVALUATION CRITERIA 3.1 3.1 Weld Overlay Repair Criteria 3.1 3.2 Flawed Pipe Analysis Criteria 3.2 4.0 LOADS 4.1 4.1 Mechanical and Internal Pressure Loads 4.1 4.2 Thermal Loads 4.1 4.3 Weld Overlay Shrinkage-Induced Loads 4.2 5.0 EVALUATION METHODS AND RESULTS 5.1 5.1 Description of Geometries Analyzed 5.1 5.2 Code Stress Analysis 5.2 5.3 Treatment of Axial Flaws 5.3 5.4 Effect on Recirculation and Residual 5.4 Heat Removal Systems 5.5 Evaluation of Flaws in Unrepaired Welds 5.6 XGP-09-106 iv Revision 0

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TABLE OF CONTENTS (Concluded)

Pace 6.0 LEAK-BEFORE-BREAK ASSESSMENT 6.1 6.1 Net Section Collapse 6.1 6.2 Tearing Modulus Analysis 6.2 6.3 Low Toughness Material Concerns 6.3 6.4 Leak Versus Break Flaw Configuration 6.5 6.5 Axial Cracks 6.6 6.6 Multiple Cracks 6.7 6.7 Nondestructive Examination 6.7 6.8 Leakage Detection 6.8 6.9 Historical Experience 6.9 7.0

SUMMARY

AND CONCLUSIONS 7.1

8.0 REFERENCES

8.1 l

l l

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LIST OF TABLES Number Title Pace 1.1 Plant E. I. Hatch Unit 1 Flaw Disposition - 1.3 Fall 1984 Outage 1.2 Plant E. I. Hatch Unit 1 Flaw Disposition - 1.4 Fall 1982 Outage 2.1 Weld Overlay As-Built Dimensions 2.3 5.1 12" Pipe-to-Elbow Code Stress Results 5.9 5.2 20" Pipe-to-Elbow Code Stress Results 5.10 5.3 22" Pipe-to-End Cap Code Stress Results 5.11 5.4 24" Pipe-to-Pipe Code Stress Results 5.12 5.5 28" Pipe-to-Elbow Code Stress Results 5.13 (Bounds 28" Elbow-to-Pump Case) 5.6 Weld Stress Information - 1984 Analyses 5.14 5.7 Plant E. I. Hatch Unit 1 Weld Overlay, Induced 5.15 Shrinkage Stresses 6.1 Effect of Pipe Size on the Ratio of the Crack 6.10 Length for 5 GPM Leak Rate and the Critical Crack Length (Assumed Stress s = Sm/2.)

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D O LIST OF FIGURES Number Title Page 2.1 Typical Configuration of 12" Elbow-to-Pipe 2.4 Weld overlay 2.2 Typical Configuration of 20" Elbow-to-Pipe 2.5 Weld overlay 2.3 Typical Configuration of 22" End Cap Weld 2.6 Overlay 2.4 Typical Configuration of 24" Pipe-to-Pipe 2.7 Weld Overlay 2.5 Typical Configuration of 24" Pipe-to-Pipe 2.8 Weld overlay Leak Barrier 2.6 Typical Configuration of 28" Pipe-to-Elbow 2.9 Weld Overlay 2.7 Typical Configuration of 28" Elbow-to-Pump 2.10 Weld Overlay 5.1 Plant E. I. Hatch Unit 1 Recirculation 5.16 System Piping Model 5.2 Crack Growth Versus Time - 22" Sweepolet 5.17 5.3 Crack Growth Versus Time - 28" Pipe-to-Elbow 5.18 6.1 Typical Result of Net Section Collapse 6.11 Analysis of Cracked Stainless Steel Pipe 6.2 Stability Analysis for BWR Recirculation 6.12 System (Stainless Steel) 6.3 Summary of Leak-Before-Break Assessment 6.13 of BWR Recirculation System 6.4 Typical Pipe Crack Failure Locus for Combined 6.14 Through-Wall Plus 360' Part-Through Crack i

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1.0 INTRODUCTION

This report summarizes the analyses performed by NUTECH to demonstrate the adequacy of weld overlay repairs and to evaluate unrepaired flaw indications in the Reactor Recirculation and Residual Heat Removal (RHR) systems at Georgia Power Company's Plant E. I. Hatch Unit 1.

Ultrasonic (UT) examination of welds in these systems during both the fall 1982 and fall 1984 outages identi-fled flaw indications in a total of 27 welds which were judged to be due to intergranular stress corrosion cracking (IGSCC). All of the flaws are in Type 304 stainless steel material. Tables 1.1 and 1.2 contain a description of each flaw indication as well as its disposition.

Weld overlays were applied to 6 of these welds during the fall 1982 outage and 17 of these welds during the fall 1984 outage. The purpose of each overlay is to arrest any further propagation of the cracking and to restore the required safety margins to the weld.

Flaw evaluations were performed for one weld (lB31-lRC-22AM-1BC-1) during the fall 1982 outage and four welds (including weld 1B31-lRC-22AM-1BC-1) during the fall l

1984 outage. The purpose of the evaluations was to XGP-09-106 1.1 Revision 0 nutagh

, e assure that the original design safety margins for these welds has not been reduced, and that the flaws would not I

grow to an unacceptable size during the next fuel cycle. The evaluations determined that these four welds did not require weld overlay repair. Tables 1.1 and 1.2 contain a description of these flaw indications. l All weld overlays were designed, and all flaws were evaluated in accordance with NRC Generic Letter 84-11 (Reference 1).

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e e Table 1.1 PLANT E. I. HATCH UNIT 1 FLAW DISPOSITICN FALL 1984 OUTAGE l

Overlay Design Weld Number Flaw Description t III L/2 1B31-1RC-12AR-F-2 Circ. 20-30% x 360* 0.23 2.0 1B31-1RC-12AR-F-3 Cire. 20-30% x 360' O.23 2.0 1B31-1RC-12AR-H-2 Cire. 20-30% x 360* 0.23 2.0 1B31-1RC-12AR-H-3 Circ. 20-30% x 360' O.23 2.0 1B31-1RC-12AR-K-2 Circ. 30% x 360' O.23 2.0 1B31-1RC-12AR-K-3 Cire. 30% x 360* 0.23 2.0 1B31-1RC-12AR-J-3 Cire. 20-30% x 360' O.23 2.0 1B31-1RC-12BR-C-2 Circ. 20-30% x 360* 0.23 2.0 1B31-1RC-12BR-C-3 Cire. 25% x 360' O.23 2.0 1B31-1RC-12BR-D-3 Circ. 20% x 360* 0.23 2.0 1B31-1RC-12BR-E-2 Cire. 25% x 360* 0.23 2.0 1B31-1RC-12BR-E-3 Cire. 30% x 360* 0.23 2.0 1E11-1RHR-24A-R-13 Axial 50% x 1.75" two layers (2) 1B31-1RC-28A-10 circ. 50% x 360* 0.42 4.25 I3) 1B31-1RC-28B-11 Circ. 49% x 360* 0.42 4.25(3) 1B31-1RC-28B-3 Circ. 32% x 360* 0.44 3.0 1B31-1RC-28B-4 Cire. 31% x 360' -

0.44 3.0 1B31-1RC-28B-16 Axial 17% x 1" No Overlay IB31-1RC-28A-6 Axial 16% x 0 5" No Overlay IB31-1RC-22AM-1BC-1 Intermittent Circ.; Nom. 11% No Overlay Spot 18%

IB31-1RC-22BM-1BC-1 Intermittent Circ.; Max. 29% No Overlay Notes: 1. The effective thickness, t, is exclusive of the thickness of the initial layer.

2. L/2 = C/2 + 0.75" on valve side; L/2 = C/2 + 2.25" on tee side.
3. L/2 = entire overlay length, which is on the elbow side of the groove weld centerline.

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e e Table 1.2 PLANT E. I. HATCH UNIT 1 FLAW DISPOSITION FALL 1982 OUTAGE Overlay Design Weld Number Flaw Description t L/2 1B31-1RC-22AM-1 Axial 63% x 1/2" 0.25

  • 1831-1RC-22AM-4 Axial 72% x 1/2" 0.25
  • IB33-1RC-22BM-4 Axial 67% x 1/2" 0.25
  • 1E 11-1RHR-20B-D-3 Axial 94% x 3/8" 0.4 3.5 Circ. 33% x 1-1/2" 0.4 3.5 1E 11- 1R.9R-24B-R- 13 Axial 47% x 1/2" 0.3 4.0 1B31-1RC-22AM-1BC-1 Tran= verse 12% x 1/2" Maximum No Overlay
  • I/2 = 3.0" on pipe sider L/2 = 3.5" on end cap side l

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. o 2.0 REPAIR DESCRIPTION The UT flaw indications requiring repair have been remedied by increasing the pipe wall thickness through the deposition of weld metal 360* around and to either side of the existing weld. Elbow-to-pump welds 1931-1RC-28A-10 and 1B31-lRC-285-ll were only overlaid on the elbow side of the groove weld centerline, however, to avoid welding on the cast pump casing, which is resistant to IGSCC.

The weld-deposited band provides additional wall thick-ness to restore the original design safety margin. In addition, the welding process produces a strongly com-pressive residual stress distribution on the inside portion of the pipe wall which inhibits initiation of new IGSCC flaws. The deposited weld metal is Type 308L with controlled delta ferrite content of 5-20 FN, which is resistant to IGSCC. Design and as-built information for all overlays is presented in Tables 1.1 and 2.1, respectively. Typical overlay designs are shown in Figures 2.1 to 2.7. Note that Figures 2.1 through 2.7 I define the overlay taper angle as typically 45*. It has been shown that much larger values are acceptable (Reference 2).

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. e The nondestructive examination of each weld overlay included:

1) Delta ferrite content measurement of the first and final overlay layers, using a Severn gauge.
2) Surface examination of the base material, first overlay layer, and completed weld overlay by the liquid penetrant examination technique in accord-ance with ASME Section XI (Reference 1).
3) Volumetric examination of the completed weld over-

, lay by the ultrasonic examination technique to demonstrate proper bonding and quality of the applied overlay material.

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Table 2.1 WELD OVERLAY AS-BUILT DIMENSIONS As-BuilyII As-Built Thic knes s Length Weld I.D. (Inches) (Inches) 1 B 31-l RC- 12AR-F-2 0.569 4.0 IB31-lRC-12AR-F-3 0.263 4.0 1B31-lRC-12AR-H-2 0.475 4.0 1B31-lRC-12AR-H-3 0.359 4.25 1B 31-l RC-12 AR-K-2 0.309 4.625 1B31-lRC-12AR-K-3 0.313 4.25 1B31-lRC-12AR-J-3 0.279 4.188 1B31-lRC-12BR-C-2 0.461 4.0 1 B 31-l RC-12BR-C-3 0.325 4.0 IB31-lRC-12BR-D-3 0.344 4.125 1 B 31-l RC-12 BR- E-2 0.353 4.0 1B31-1RC-12BR-E-3 0.347 4.0 lE l l-l RHR-2 4 A-R-13 0.191 4.0 IB31-lRC-28A-10 0.503 4.5 1B 31-l RC-28 B-l l 0.480 4.625 1B31-lRC-28B-3 0.534 6.0 1831-l RC-28 8-4 0.636 6.125 (1) Not including first overlay layer.

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l age TYPICAL #

TYPE sost WELD CVERLAY 2.0~ unn -,

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a a / 12".0.sas- TwiCK WALL.304 SS PIPE 0.23" MIN i

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Asweteso suRPACs Loua ACCEPTA8LEPQR gacius OVERLAY TAMR ggow inAmsmons PXGP85.0241 PATENT APPLIED PCR Figure 2.1 TYPICAL CONFIGURATION OF 12" ELBOW TO-PIPE WELD OVERLAY l

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46' TYPICAL TYPE 308L WELD CVERLAY 3.5" MIN -

d a 20" DIAMETER PIPE 0.4" MIN e--

LARGEST AXIAL INDICATION APPROX 94% THROUGH WALL

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N r x PIPE TO EL80W WELD 1E111RHR-208 0 3 I

o AS WELDED SURFACE ACCEPTABLE POR OVERLAY TAPER ,

TRANSITIONS aADIUS ELBOW PATENT APPLIED FOR FXGP85.0242 Figure 2.2 TYPICAL CONFIGURATION OF 20" ELBOW-TO-PIPE WELD OVERLAY XGP-09-106 2.5 Revision 0 nutggb

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TYPICAL CONFIGURATION OF 22" END CAP WELD OVERLAY Fxcres.02cs 1

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_q 24" DIAMETER ,1.14" TillCK STAINLESS SIEEL PIPE D PATENT APPLIED FOtt Figure 2.4 IS jQ TYPICAL CONFIGURATION OF 24" PIPE-TO-PIPE FXGre60244 WELD OVERLAY l7

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2.25" MIN -> e 0.75" MIN 4 5 O AS WELDED SURFACE 7o TYPE 308L WELD OVERLAY ACCEPTABLE FOR

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-g 24" DIAMETER ,1.14" THICK STAINLESS STEEL PIPE PATENT APPLIED FOtt

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h Figure 2.5 TYPICAL CONFIGURATION OF 24" PIPE-TO PIPE WELD OVERLAY LEAK BARRIER

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TYPE 300L l wtLD OVERLAY 3.0" MIN 28",1.28" THICK a a WALL',304 $3 mPE 0.44" MtN ====am me--

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ir A8 WELDEO SURFACE ACCEPTAOLE FOR QVERLAY TAPER TR AN5871ONS A ADIUS sLsow FXGP85.0243 Figure 2.6 TYPICAL CONFIGURATION OF 28" PIPE TO ELBOW PATENT APPLIED POR XGP-09-106 2.9 Revision 0 nutggb

l PUMP f'

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450 TYPICAL #

TYPE 308L WELD OVERLAY

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0 M +- 28" DIAMETER, 1.088" THICK WALL, 0.42" MIN + /

, p 304 SS PIPE 4.25" MIN y

AS WELDED SURFACE ACCEPTABLE FOR ELBOW OVERLAY TAPER TRANSITIONS PATENT APPLIED FOR Figure 2.7 TYPICAL CONFIGURATION OF 28" ELBOW TO-PUMP WELD OVERLAY XGP-09-106 2.10 Revision 0 nutggb

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3.0 EVALUATION CRITERIA This section describes the criteria used to establish the acceptability of the weld overlay repairs and flawed pipe analyses. All evaluations and repairs were per- 1 l

formed in accordance with NRC Generic Letter 84-11, l dated April 1984 (Reference 1).

3.1 Weld Overlay Repair Criteria Highly conservative assumptions were used for all evalu-ations. All flaws requiring repair were assumed to be through-wall for the measured length and were evaluated in accordance with the criteria of References 1, 3 and

5. All designs were performed in accordance with the requirements of ASME Section XI, Paragraph IWB-3641-1 (Reference 3), and NRC Generic Letter 84-11 (Reference
1) when circumferential flaws were present. For the repair to weld 24A-R-13 which contained only an axial flaw, the leakage barrier approach (Reference 2) was used.

Due to the nature of these repairs, the geometric con-figuration is not specifically covered by Section III of the ASME Boiler and Pressure Vessel Code (Reference 4),

However, the which is intended for new construction.

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materials, fabrication procedures, and quality assurance requirements used for weld overlay repairs are in accordance with applicable sections of this Code. The intent of the design criteria is to assure equivalent margins of safety for strength and fatigue considera-tions as provided in the ASME Section III Design Rules. In addition, because of the IGSCC conditions that led to the need for repairs, IGSCC resistant materials were used for the weld overlay.

3.2 Flawed Pipe Analysis Criteria Those flawed welds which were determined not to require weld overlay repair were shown to meet the criteria given in Paragraph IWB-3600 of Reference 3 and Reference

1. Reference 1 defines the acceptable end-of-cycle flaw depth to be 2/3 of the Reference 3 allowable depth. A highly conisrvative crack growth correlation was used to demonstrate that evaluated flaws will not grow to an unacceptable flaw size by the IGSCC mechanism during the next fuel cycle.

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4.0 LOADS The loads considered in the evaluation of the UT flaw indications included mechanical loads, internal pres-sure, differential thermal expansion loads, and weld overlay shrinkage-induced loads. The mechanical and internal pressure loads used in the analyses are described in Section 4.1. A discussion of the thermal transient conditions which cause differential thermal expansion loads is presented in Section 4.2. The loads induced by weld overlay shrinkage are discussed in Section 4.3.

4.1 Mechanical and Internal Pressure Loads The design pressures of 1325 psi (discharge side) and 1050 psi (suction side) were obtained from Reference

6. The deadweight and seismic loads were obtained from Reference 7.

4.2 Thermal Loads The thermal expansion loads for each weld were obtained from Reference 8. These loads were calculated based on information found in Reference 6, which defines several types of transients for which the Recirculation and RHR XGP-09-106 4.1 Revision 0

systems are designed. These transients were conserva-tively grouped into three composite transients. The first composite transient is a startup/ shutdown trans-ient with a heatup or cool down rate of 100*F per hour. The second composite transient consists of a 50*F step temperature change with no change in pressure. The third composite transient is an emergency event with a 416*F step temperature change and a pressure change of 1325 psi. In the five year overlay design life,- there are 38 startup/ shutdown cycles, 25 small temperature change cycles, and one emergency cycle.

4.3 Weld Overlay Shrinkage-Induced Stresses Application of a weld overlay causes a small amount of axial shrinkage underneath the overlay. This shrinkage may induce bending stresses in the remainder of the piping system, depending on the location of the over-lay. Shrinkage-induced stresses were calculated using NUTECH computer program PISTAR (Reference 9), together with field overlay shrinkage measurements. The result-ing stresses are included in the crack growth analyses for all unrepaired flaw locations.

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5.0 EVALUATION METHODS AND RESULTS The flawed welds shown in Table 1.1 were identified by UT inspections during the fall 1984 outage at Plant E. I. Hatch Unit 1. Stress information for these welds is presented in Table 5.6. Note that for 28A-6 and 28B-16 only a composite stress value is given. These welds contained only axial flaws, and were evaluated for crack growth using the hoop stress. The flawed welds shown in Table 1.2 were identified during the fall 1982 outage at Unit 1. Each flawed weld was evaluated to determine if an overlay was required to meet the requirements of References 1 and 3. Where a repair was shown to be necessary, a weld overlay was designed to met the requirements of Paragraph IWB-3641 of Reference 3 assuming the flaw was through-wall for its measured length. Since flaws were assumed through-wall, the beneficial effects of weld overlays on crack growth were not addressed. The effect and significance of weld overlay shrinkage-induced stresses are discussed in Section 5.5.

5.1 Description of Geometries Analyzed Six distinct flaw geometries required weld overlay repair at Hatch Unit 1. These were: 12-inch diameter XGP-09-106 5.1 Revision 0 ,

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pipe-to-elbow (12 cases), 28-inch diameter pipe-to-elbow (two cases), 28-inch diameter elbow-to-pump (two cases),

24-inch diameter pipe-to-pipe (two cases), 22-inch diameter pipe-to-end cap (four cases), and 20-inch diameter elbow-to pipe (one case). Code stress and fatigue evaluations which bound the cases listed in Tables 1.1 and 1.2 are summarized in Tables 5.1 to 5.5. For additional information see Reference 10.

Analysis results for the locations with only axial flaws are discussed in Section 5.3.

5.2 Code Stress Analysis Finite element models of the bounding weld overlay repairs were developed using the ANSYS (Reference ll) computer program. The models were based on a composite worst case flaw and on minimum design overlay thick-4 4

ness. The as-built thickness exclusive of the first overlay layer is greater than or equal to the minimum design thickness at Hatch 1 . The stresses in the overlaid weld due to the design pressure and applied moments as described in Sections 4.1 and 4.2 were calculated using the ANSYS models.

The results of stress analyses per Reference 4 are pre-sented in Tables 5.1 through 5.5. (The 28" elbow-to-XGP-09-106 5.2 I Revision 0

pump repair is bounded by the 28" pipe-to-elbow case).

The allowable stresses from Reference 4 are also given. The weld overlay repairs at Hatch 1 satisfy the Reference 4 requirements.

For the purpose of fatigue evaluation, the temperature distribution at the weld overlay repaired locations, subject to the thermal transients defined in Section 4.2 were calculated using charts 16 and 23 of Reference 12, as discussed in Referenc6 10.

5.3 Treatment of Axial Flaws Axial IGSCC crack length is limited on either end by the original weld and the extent of sensitized material in the weld heat affected zone (HAZ). The tabulated allowable axial crack sizes in Reference 3 Paragraph IWB-3640 are truncated at a maximum depth of 75% of the pipe thickness and are therefore very conservative for axial IGSCC.

The ASME Code minimum wall thickness is based on main-taining a factor of safety of 3.0 on load against pipe failure. Pipe thickness in excess of the Code minimum thickness provides a reserve margin which can be used to tolerate short, through-wall (or less than through-wall)

XGP-09-106 5.3 Revision 0

axial cracks. The length of through-wall axial cracks which maintains a factor of safety of 3.0 on load during normal operation is calculated in Reference 5 as a func-tion of the applied stress.

1 i

4 Whenever the combination of an axial crack and applied load results in a factor of safety of 3.0 or more on load, the axial crack, even if it is through-wall, main-l tains the originally required Code safety factor. For i

such cases, only a " leakage barrier" overlay is re-J quired. Such an overlay not only adequately repairs the j known axial flaw, but also produces a compressive residual stress distribution on the inside surface of i

the pipe. This distribution will inhibit further IGSCC initiation.

5.4 Effect on Recirculation and Residual Heat Removal Systems The effects of the radial shrinkage of the weld overlay are limited to the region adjacent to and underneath the overlay. The stresses due to the radial shrinkage are 4

less than yield stress at distances greater than four inches from the ends of the overlay (Reference 13).

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The effects of the axial weld shrinkage on the repaired systems were evaluated with the NUTECH computer program PISTAR (Reference 9) using the piping model shown in Figure 5.1. The measured shrinkages of all wold overlay repairs were imposed as boundary conditions on this model. Since the ASME Code does not limit weld residual stresses, all stress indices were set equal to 1.0.

Weld residual stresses are steady state secondary stresses. They are not limited by the ASME Code (Refer-ence 4), and therefore, the Code acceptability of these welds is not in question.

The highest shrinkage-induced stresses calculated by the PISTAR analysis occurred at riser nozzles N2D, N2C, N2H, N2J, and N2G. These stresses were in the range of 12-16 ksi. Steady state secondary stresses of this magnitude are judged to have negligible effect on the integrity of these locations, but may affect IGSCC crack growth at locations with unrepaired flaws.

Table 5.7 presents weld overlay shrinkage-induced stresses for all welds with flaw indications. The maximum shrinkage stress value at any location con-taining an unrepaired flaw is less than 1 ksi.

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Stresses of this magnitude have a negligible effect on the acceptability of the weld without repair.

5.5 Evaluation of Flaws in Unrepaired Welds The prediction of crack growth for the flaws in un-repaired welds required the following inputs:

1) Steady state applied stress.
2) Weld residual stress.
3) Flaw characterization.
4) Crack growth model.
5) Crack growth law.

Conservative assumptions were used for applied stress, residual stress, crack growth model and crack growth law. Thus, the result of the analysis is a very con-servative prediction of crack depth versus time.

The moments and forces due to operating pressure, dead weight and thermal expansion were obtained from Refer-ences 6, 7, and 8. In addition, the stress due to the axial weld shrinkage of the overlays was added to the other steady state stresses (Section 5.4) for the final crack growth calculations.

XGP-09-106 5.6 Revision 0

A conservative IGSCC crack growth correlation for weld sensitized material was used based upon Reference 14:

ff=3.59x10 -8K *1 where:

da = Differential crack size (inch) dT = Differential time (hour)

K = Applied stress intensity factor (ksi/in)

The crack growth model is a linear interpolation between an inside diameter (I.D.) cracked cylinder and an edge-cracked plate. The crack growth model assumes a 360' crack. The magnification factors for an I.D. cracked cylinder and an edge-cracked plate were obtained from Reference 15. -

r; The predicted crack growth for the unrepaired flaws was calculated with the NUTECH computer program NUTCRAK (Reference 15). Allowable crack depth was obtained by taking 2/3 of the IWB-3641-1 (Reference 3) source equation values, as required by Reference 1. This analysis demonstrates that the unrepaired flaws at Hatch Unit I will not exceed their allowable depths during the {

XGP-09-106 5.7 Revision 0 nutggb

next fuel cycle (see Figures 5.2 and 5.3 for bounding crack growth curves).

XGP-09-106 5.8 Revision 0 nutggb

Table 5.1 12" PIPE-TO-ELBOW CODE STRESS RESULTS l

1 l

ACTUAL STRESS SECTION III EQUATION CATEGORY NUMBER OR NB ALLOWABLE USAGE FACTOR S N/A N/A S, = 14,300 PSI PRIMARY (9) 18,700 PSI 21,450 PSI (10) 34,200 PSI 42,900 PSI ARY PEAX (29,500)S*

CYCLE 1 (11) (13,000)S* N/A CYCLE 2 (135,500)S*

CYCLE 3 USAGE

FACTOR N/A 0.03 1.0 (5 YR)
  • THE FACTOR OF 5 IS THE CONSERVATIVELY ASSUMED FATIGUE STRENGTH REDUCTION FACTOR.

XGP-09-106 5.9 Revision 0 nutggh l

Ta ble 5.2 20" PIPE-TO-ELBOW CODE STRESS RESULTS l

l 4

ACTUAL EQUATION STRESS SECTION III CATEGORY NUMBER NB ALLOWABLE OR THICKNESS S N/A* N/A S, = 16,800 PSI 10,200 25,200 PSI PRIMARY (9) pg fgy (10) 50,400 PSI Ik600 PEAK (16,200)5*

(11) (8,800)5 N/A f 8 ,900)5 CYCLE 3 USAGE FACTOR N/A 0.01 1.0 (5YR)

  • THE FACTOR OF 5 IS THE CONSERVATIVELY ASSUMED FATIGUE STRENGTH REDUCTION FACTOR.

XGP-09-106 5.10 Revision 0 nutggb

Table 5.3 22" PIPE-TO-END CAP CODE STRESS RESULTS ACTUAL EQUATION STRESS SECTION III CATEGORY NUMBER NB ALLOWASLE OR THICKNESS S N/A N/A S, = 16,800 PSI 10,590 PRIMARY (9) p5g 25,200 PSI PRIMARY + 18,950 (10) pgg 50,400 PSI SECONDARY PEAK CYCLE 1 (23,370)5*

CYCLE 2 (11) (16,950)5 N/A CYCLE 3 (129,300)5 USAGE FACTOR N/A 0.02 1.0 (5 YR)

  • THE FACTOR OF 5 IS THE CONSERVATIVELY ASSUMED FATIGUE STRENGTH REDUCTION FACTOR.

XGP-09-106 5.11 Revision 0 nutggb

Table 5.4 24" PIPE-TO-PIPE CODE STRESS RESULTS 1

ACTUAL EQUATION STRESS SECTION III CATEGORY NUMBER NB ALLOWABLE OR THICKNESS S N/A N/A S, = 16,800 PSI PRIMARY (9) 12,300 PSI 25,200 PSI (10) 16,000 PSI 50,400 PSI 40ARY PEAK CYCLE 1 (19,500)5*

(11) (12,950)5 N/A CYCLE 2 CYCLE 3 (125,400)5 USAGE FACTOR N/A 0.019 1.0 (5 YR)

  • THE FACTOR OF 5 IS THE CONSERVATIVELY ASSUMED FATIGUE STRENGTH REDUCTION FACTOR.

XGP-09-106 5.12 Revision 0 nutgsb

-me---- ---m-.-um g--.m

o .

Table 5.5 28" PIPE-TO-ELBOW CODE STRESS RESULTS.

(Bounds 28" Elbow-to-Pump Case)

EQUATION A AL FREM SECTION lli OR USAGE NUH9ER N8 ALLOWABLE FACTOR S N/A N/A S = 16,800 pel m

PRIMARY (9) 20,000 poi 25,200 psi "a -

S, gag; noi .. p - .4 PEAK 5 (64,200)'

CYCLE 1 (11) 5 (5,400) N/A CYCLE 2 5(74, 2 )

CYCLE 3 USAGE FACTOR N/A 0.71*** 1.00 (5 YR)

NPRE83.62 36

' A FACTOR OF 5 IS THE CONSERVATIVELY ASSUMED FATIGUE STRENGTH REDUCTION FACTOR.

    • ACCEPTABLE BASED ON THE SIMPLIFIED ELASTIC / PLASTIC DISCONTINUITY ANALYSIS.
      • USAGE IS BASED ON A BOUNDING ANALYSIS WHICH USED A 360" CRACK TO REPRESENT A UT MEASURED CRACK LENGTH OF 50*. ACTUAL USAGE FACTOR IS MUCH LOWER.

XGP-09-106 5.13 Revision 0 nutggh t

35 Table 5.6

$y WELD STRESS INFORMATION - 1984 ANALYSES ES oa 3 E' Crack W.O.L.

om Calc. Design Pipe Pipe Hall Deadweight Thermal F .smic Pressure DW+TH DW+SE1 Weld No. O.D. Thickness Stress Stress Stress Stress +P +P 28B-3 28.00" 1.116" 828 1093 1559 5819 7722 8206 288-4 28.00" 1.116" 568 917 1652 5819 7304 8039 12AR-K-2 12.75" 0.568" 415 3260 1936 7436 11111 9787 12 A R-H-2 12.75" 0.568" 646 1481 1720 7436 9563 9802 12AR-J-3 12.75" 0.568" 1050 1497 1132 7436 9983 9618 12BR-C-2 12.75" 0.568" 534 1481 2032 7436 9451 10002 12AR-K-3 12.75" 0.568" 756 4215 2977 7436 12407 11169 12AR-H-3 12.75" 0.568" 731 2915 2358 7436 11082 10525 m 24A-R-13 24.00" 1.020" 1036 5111 4350 7749 13896 13135

,, 12BR-C-3 12.75" 12.75" 419 2915 2146 7436 10770 10001

  • 12BR-D-3 12.75" 0.568" 453 1497 2527 7436 9386 10416 12BR-E-2 12.75" 0.568" 442 1200 2225 7436 9078 10103 12BR-E-3 12.75" 0.568" 784 1855 3190 7436 10075 11410 12AR-F-2 12.75" 0.568" 419 1200 2064 7436 9055 9919 12AR-F-3 12.75" 0.568" 489 1855 2892 7436 9780 10817 28A-10 28.00" 1.088" 408 492 1647 6755 7655 8810 288-11 28.00" 1.088" 494 492 1618 6755 7741 8867 22AM-1BC-1 22.00" 1.00"* 61 1588 903 7288 8937 8252 22BM-1BC-1 22.00" 1.00"* 145 1588 906 7288 9021 8339 28A-6 28.00" 1.116 - - - -

13172 -

28B-16 28.00" 1.263 - - - -

14687 -

  • Since sweepolet wall thickness va ries, thickness conservatively assumed to be 1. 0 0" .

I

Table 5.7 PLANT E. I. _ HATCH UNIT 1 WELD OVERLAY INDUCED SHRINKAGE STRESSES Weld ID Stress (psi) 28A-10 77 24A-R-13 676 12AR-J-3 3025 12AR-K-2 1661 12AR-K-3 714 12AR-H-2 2991 12AR-H-3 2071 12AR-F-2 1165 12AR-F-3 1112 28B-11 58 28B-3 241 28B-4 112 12BR-C-2 2443 12BR-C-3 1398 12BR-D-3 2813 12BR-E-2 1438 12BR-E-3 566 2 4 B-R-13 932 20B-D-3 590 22AM-1BC-1 810 22BM-1BC-1 581 28A-6 246 28B-16 189 XGP-09-106 5.15 Revision 0 l

)

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"*%." 'rs HATCH 1 LOOP A HATCH 1 LOOPS l

Figure 5.1 PLANT E.I. HATCH UNIT 1 REACTOR RECIRCULATION 3 SYSTEM PIPING MODEL b

80 - = = - - - - - - - - - - - - - - - - - - - - - - - -- -

ALLOWABLE 40 -

E

  1. ~ A z INITIAL DEPTH 31 a

5 20 -

10 -

i i i i 5 10 15 20 25 TIME (MONTHS)

Figure 5.2 CRACK GROWTH VERSUS TIME - 22" SWEEPOLET XGP-09-106 5.17 Revision 0 gd

l i

l go . - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ .

ALLOWABLE 40 -

E 30 -

5 5

6 20 -

% INITIAL DEPTH 10 -

5 10 15 20 25 TIME (MONTHS)

Figure 5.3 CRACK GROWTH VERSUS TIME - 28" PIPE-TO-ELBOW XGP-09-106 5.18 Revision 0 Qd

6.0 LEAK-BEFORE-BREAK ASSESSMENT For welds with undetected flaws, or containing IGSCC indications which are judged to be small enough to not require a repair, the following considerations provide additional support for continued plant oper-ation for another fuel cycle.

6.1 Net Section Collapse The effect of IGSCC on the structural integrity of piping is evaluated through the use of a simple

" strength of materials" approach to assess the load carrying capacity of a piping section after the cracked portion has been removed. Studies have shown (References 16 and 17) that this approach gives a conservative, lower-bound estimate of the loads which would cause unstable fracture of the cracked section in wrought 304 stainless steel piping material.

Typical results of such an analysis are shown in Figure 6.1 (Reference 17). This figure defines the locus of limiting crack depths and lengths for cir-cumferential cracks which are predicted by the net section collapse method to cause failure. Curves are presented for both typical piping system stresses and stress levels equal to ASME Code limits. Note that a f

i i

[

l XGP-09-106 6.1

! Revision 0

very large percentage of pipe wall can be cracked be-fore reaching these limits (40% to 60% of circum-ference for through-wall cracks, and 65% to 85% of wall thickness for 360* part-through cracks).

Also shown in Figure 6.1 is a sampling of cracks which have been detected in servica, either through UT examination or leakage. In each case there has been a significant margin between the size of crack observed and that predicted to cause failure under service loading conditions. Also, as discussed be-low, there is still considerable margin between these net section collapse limits and the actual cracks I which would cause instability.

6.2 Tearino Modulus Analysis l

Elastic-plastic fracture mechanics analyses are pre-I sented in Reference 17 which give a different repre-sentation of the crack tolerance capacity of wrought I

l stainless steel piping material than the net section collapse approach described above. Figures 6.2 and 6.3 graphically depict the results of such an analy-sis (Reference 17). Through-wall circumferential defects of arc length equal to 60' through 300* were assumed at various cross sections of a typical BWR XGP-09-106 6.2 Revision 0

- . _. _ - _ _ . . . _ _ _ _ _ = - _ _ _ - _ _ _ . _ - - - . - . ___ . _._- _ _ . . __. .-- _ . - - _ -

t Recirculation System. Loads were applied to these sections of sufficient magnitude to produce not section limit load, and the resulting values of tear-ing modulus were compared to that required to cause unstable fracture (Figure 6.2). Note that in all cases there is substantial margin, indicating that the not section collapse limits of the previous section are not really failure limits. Figure 6.3 summarizes the results of all such analyses performed for 60* through-wall cracks in terms of margin on tearing modulus for stability. The margin in all cases is substantial. l l

6.3 Low Touchness Material Concerns As mentioned in Sections 6.1 and 6.2, the generic statements made here regarding not section collapse and tearing modulus results as a basis for justifying leak-before-break arguments assume inherently high j toughness and ductility of wrought stainless steel piping material. Recently, concerns about the valid-i

! ity of these arguments have been raised because of >

t l

experimental work which suggests that the toughness of weld metal in stainless steel butt welds deposited ,

I i by flux shielded processes may be substantially lower

' than that of the surrounding base metal. '

l XGP-09-106 6.3 Revision'0

.m--.- ,w,-,w-_-#,m-y-e-,- ,...,,-,,,,-,,._,,,w, __ _ , _-y__ m%w p.- my ,-y- i.-,~,,-,., , . . . ,

Potentially, this could lead to brittle failure of I

the weld material at an applied load appreciably below the not section collapse load of the adjacent piping material. As of the date of this report, there is no formal regulatory or Code guidance on l this issue.

l To address this situation for Hatch 1, NUTECH review-ed the weld overlays and unrepaired flaws discussed earlier in this report. All weld overlays were applied with the GTAW process, which is of less con-cern with regard to material toughness than are flux l

l shielded processes. All circumferential flaws were 1

l assumed through-wall, and were sized as 360' long.

The overlay designs were thus based upon 360' l

through-wall flaws, so the toughness of the original butt weld material is not im'portant.

Unrepaired flaws fall into two categories. Two welds (28A-6 and 288-16) contained only very short, shallow axial flaws, and were thus not of concern.

l Two sweapolet to header welds (22AM-1BC-1 and 22 Bit-1BC-1) contained short circumferential flaws and required further evaluation. A Tearing Modulus analysis for these welds was conducted using the XGP-09-106 6.4 Revision 0

worst case material properties for the butt weld metal. Although the actual flaws were very shallow, for the purpose of the analysis they were assumed to be through-wall. For the bounding applied loads, the flaws were shown to be stable. For three times the bounding applied loads, the flaws were shown to be marginally stable. Because of the conservative nature of the analysis the flaws are judged to be acceptable.

6.4 Leak Versus Break Flaw Configuration of perhaps more significance to the leak-before-break argument is the flaw configuration depicted in Figure 6.4. This configuration addresses the concerns raised by the occurrence of part-through flaws grow-ing circumferentially before break ~ing through the outside surface to cause leakage. Figure 6.4 pre-sents typical size limitations on such flaws based on the conservative net section collapse method of Section 6.1. Note that very large crack sizes are predicted. Also shown on this figure are typical detectability limits for short through-wall flaws (which are amenable to leak detection) and long part-through flaws (which are amenable to detection by UT). The margins between the detectability limits, XGP-09-106 6.5 Revision 0 nutgrJ)

and the conservative, not section collapse failure limits are substantial. It is noteworthy that the likelihood of flaws developing which are character-ized by the vertical axis shown in Figure 6.4 (con-stant depth 360' circumferential cracks) is so remote as to be considered impossible. Material and stress asymmetries always tend to propagate one portion of the crack faster than the bulk of the crack front, which will eventually result in " leak-before-break." This observation is borne out by extensive field experience with BWR IGSCC.

6.5 Axial Cracks Several of the IGSCC occurrences at Plant E. I. Hatch Unit 1 were short, axial cracks. These can grow through the wall but remain short in the axial direc-tion. This behavior is consistent with expectations for axial IGSCC since the presence of a sensitized weld heat-affected zone is necessary, and this heat-affected zone is generally limited to approximately 0.25 inch on either side of the weld. Since the major loadings in the net section collapse analysis l

are bending moments on the cross section due to seismic loadings, and since these loads do not exist in the circumferential direction, the above leak-XGP-09-106 6.6 Revision 0

j . .

before-break arguments are even more persuasive for axially oriented cracks. There is no known mechanism for axial cracks to lengthen before growing through-wall and leaking, and the potential rupture loading on axial cracks is less than that on circumferential cracks.

6.6 Multiple Cracks I

Analyses performed for EPRI (Reference 18) indicate that the occurrence of multiple cracks in a weld, or cracking in multiple welds in a single piping line does not invalidate the leak-before-break arguments discussed above.

I 6.7 Nondestructive Examination The primary means of nondestructive examination for l IGSCC in BWR piping is ultrasonics. This method has been the subject of considerable research and devel-opment in recent years, and significant improvements l in its ability to detect IGSCC have been achieved.

Figure 6.4 illustrates a significant aspect of UT detection capability with respect to leak-before-break. The types of cracking most likely to go un-detected by UT are relatively short circumferential XGP-09-106 6.7 Revision 0 I

or axial cracks which are most amenable to detection by leakage monitoring. Conversely, as part-through cracks lengthen, and thus become more of a concern with respect to leak-before-break, they become more readily detectable by UT.

6.8 Leakace Detection Typically, leakage detection for BWR reactor coolant system piping is through sump level and drywell activity monitoring. These systems have sensi-tivities on the order of 1.0 gallon per minute (GPM). Plant technical specification and administra-l tive limits typically require investigation /

corrective action at 5.0 GPM unidentified leakage, or l

l when there is a 2.0 GPM increase in unidentified

! leakage in a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period.

Table 6.1 provides a tabulation of typical flaw sizes t

which cause 5.0 GPM leakage in various size piping assuming a membrane stress of S,/2. l l

Also shown in this table are the critical crack lengths for through-wall cracks based on the net section collapse method of analysis discussed above. For conservatism, the leakage values are XGP-09-106 6.8 Revision 0

based on pressure stress only, while the critical crack lengths are based on the sum of all combined loads, including seismic. Considering other normal operating loads in the leakage analysis would result in higher rates of leakage for a given crack size.

l Note that there is considerable margin between the crack length which produces 5.0 GPM leakage and the critical crack length, and that this margin increases l

with increasing pipe size.

l 6.9 Historical Experience l

The above theories regarding crack detectability have I been supported by experience (Reference 18). Indeed, of the large number of IGSCC incidents to date in BWR piping, none have come close to violating the struc-tural integrity of the piping.

l l

XGP-09-106 6.9 Revision 0

Table 6.1 EFFECT OF PIPE SIZE ON THE RATIO OF THE CRACK LENGTH FOR 5 GPM LEAK RATE AND THE CRITICAL CRACK LENGTH (ASSUMED STRESS s = S m /2)

NOMINAL CRACK LENGTH FOR CRITICAL CRACK gjg LENGTHe l Un.) c PIPE SIZE 5 GPM LEAK (in.)

4" SCH 80 4.50 6.54 0.688 10" SCH 80 4.86 15.95 0.305 24" SCH 80 4.97 35.79 0.139 Pcetss.asco XGP-09-106 6.10 Revision 0

L

\

d eM

-* %t i

1.0 -CCCC-CCCS-C g O

\

\

\

\

0.8 4 g  %

g Pm = 6 ksi, Pb=0 G9  %*%* * == .

1 P = 6 ksi, Pm+Pb = 1.5 S m

.m 0.6 -

m 3 ...

0 Field Data - Part-

'l 0.4 ## Through Flaws i 4 O Field Data - Leaks E S, = 16.0 ksi

@ og = 48.0 ks!

0.2 -

Values at 5500F 4

0 0 0.2 0.4 0.6 0.8 1.0 Fraction of Circumference. 0/w Figure 6.1 TYPICAL RESULT OF NET SECTION COLLAPSE ANALYSIS OF CRACKED STAINLESS STELL PIPE l

XGP-09-106 6.11  !

Revision 0 l nutgqh

l l

ss* -

- 2108 W

, gP o 4' f **'

t pH ar sno /  !

/\ oneener,

/

300 T=0 250 - Meisnel 200 - (Unsinkiel M

N I (Stable) 150 -

a 2e - 12e

'.' -u.ue, # - ee 100 -

2e = 1908 50 - , , , , , , , , , , , i l Jlc 2e - 30e 0, , , , , , , ,

12.5 25.0 82.5 100.0 137.5 175.0 212.5 250.0 50.0 T

PGPC33.03 37 Figure 6.2 STABILITY ANALYSIS FOR BWR RECIRCULATION 9YSTEM

( STAIN!.ESS STEEL)

XGP-09-106 6.12 Revision 0 nutagh

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A NS 5 20 m e L

  • 4

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SNOI1YAH3S80 JO H3EWGN XGP-09-106 6.13 Revision 0 nutgsb

I 2=

1 1 '

1 .

t a PIPE CROSS SECTION 0, 7 0.6 ----- ..

1 0.5 - l l

0. 4 -

l

" i 0.3 - l 0.2 - ISI 0.1 LEAK MONITOR 0.0 VA , , , ,

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 e/w Figure 6.4 1

TYPICAL PIPE CRACK FAILURE LOCUS FOR COMHINED .

I THRCUGH-WALL PLUS 360' PART-THROUGH CRACK l

I XGP-09-106 6.14 l Revision 0 1 1

m 1

7.0

SUMMARY

AND CONCLUSIONS Evaluation of the weld overlay repairs to the Recir-culation and RHR systems at Hatch Unit 1 shows that the resulting stress levels are acceptable for all design conditions. The stress levels have been assessed from the standpoint of load capacity.of the components and the resistance to crack growth.

Acceptance criteria for the analyses have been established in Section 3.0 of this report which demonstrate that:

1. There is no loss of design safety margin over that provided by the current Code for Class 1 piping and pressure vessels (ASME Section III,

. Subsection NB).

~

2. During the design evaluation period of one cycle for each repair, the observed cracks will not grow to the point where the above safety margins would be reduced.

Analyses have been performed and results are pre-sented which demonstrate that the repaired welds satisfy theno criteria by a large margin.

XGP-09-106 7.1 Revision 0

r -

. n

! Additicnal margin is incorporated in the weld overlay design criteria. All overlay designs are based on the assumption that flaws are through-wall for the measured length, even though ultrasonic measurement l of flaws demonstrates that flaws are much less severe i

(see Tables 1.1 and 1.2) in general. Furthe rmore, the design and analysis of the weld overlays takes no credit for the first weld overlay layer, in accord-

{' ance with NRC Generic Letter 84-11 (reference 1) .

I i The above arguments support the conclusion that the weld overlay repairs at Hatch Unit 1 are conserva-tively adequate for their intended purpose.

l j

Analyses have also been performed which demonstrate l

l that those welds with unrepaired flaws satisfy the acceptance criteria of References 1 and 3.

Furthe rmore, it is concluded that IGSCC experienced I

in the Recirculation and Residual Heat Removal sys-l l tems at Plant E. I. Hatch Unit i does not increase the probability of a design basis pipe rupture at the plant. This conclusion expressly considers the nature of the cracking which has been identified at Plant E. I. Hatch Unit 1, and the likelihood that other similar cracking may have gone undetected. The XGP-09-106 7.2 Revision 0

conclusion is based primarily on the extremely high inherent toughness and ductility of the stainless steel piping material, and on evaluation in accord-ance with IWB-3642 (Reference 3) for the potentially lower toughness and ductility associated with the l butt weld material. Cracks in such piping grow through-wall and leak before affecting its suructural load carrying capacity.

XGP-09-106 7.3 Revision 0

r 4 b--

8.0 REFERENCES

1. NRC Generic Letter 84-11, dated April 19, 1984, NUTECH File No. COM096.0010.0001,
2. Structural Integrity Letter PCR-84-098,

" Reconciliation of W'ld e Overlays With Large End Angles" from P. C. Riccardella (SIA) to R. Godby (GPC) dated December 17, 1984.

3. ASME Boiler and Pressure vessel Code Section XI, 1983 Edition, Winter 1983 Addendum.
4. ASME Boiler and Pressure Vessel Code,Section III, (Subsection NB and Appendix I) 1980 Edition with Addenda through Summer 1980.
5. NUTECH Report COM-76-001, " Weld Overlay Design Criteria for Axial Cracks," Revision 0, March 1984, NUTECH File COM076.0208.
6. General Electric Design Specification 22A1344, Rev. 3.
7. GE Letter No. G-GPC-4-500, " Hatch 1 Seismic Evaluation for Replacement Recirculation Valve Operators," NUTECH File XGP009.0025.
8. NUTECH Calculation Package No. GPC-04-303, " Weld Overlay Thermal Analysis, PISTAR Piping Analysis,"

NUTECH File XGP009.0025.

9. NUTECH Computer Program PISTAR, Version 2.0, Users Manual, Volume 1, TR-76-002, Revision 4, File No. 08.003.0300.
10. NUTECH Report GPC-04-104, Revision 1, " Design Report for Recirculation System and Residual Heat Removal System Weld Overlay Repairs and Flaw Evaluation at E.

I. Hatch Nuclear Power Plant Unit 1" March, 1983, File No. GPC004.0104.

11. ANSYS Computer Program, Swanson Analysis Systems, Revision 4, NUTECH File No. 08.061.
12. Schneider, P.J., " Temperature Response Charts," John Wiley and Sons, 1963.
13. NUTECH Report NSP-81-105, Revision 2, " Design Report for Recirculation Safe End and Elbow Repairs, Monticello Nuclear Generating Plant," December 1982, File No. 30.1281.0105.

XGP-09-106 8.1 Revision 0 L

?

o *^ 7,

14. NUREG 1061, Volume 1, " Investigation and Evaluation of Stress-Corrosion Cracking in Piping of Boiling Water Reactor Plants," Second Draft, April 1984.
15. NUTECH Computer Program NUTCRAK, Version 2.0, Revision 2, December 1983, File No. 08.039.0005.
16. EPRI-NP-2472, "The Growth and Stability of Stress Corrosion Cracks in Large-Diameter BWR Piping," July 1982.
17. EPRI-NP-2261, " Application of Tearing Modulus Stability Concepts to Nuclear Piping," February 1982.
18. Presentation by EPRI and BWR Owners Group to U. S.

Nuclear Regulatory Commission, " Status of BWR IGSCC Development Program," October 15, 1982.

En~' '

o 8.2 nutg.Gb L

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