ML20091K953

IGSCC Flaw Evaluations & Weld Overlay Activities During Ei Hatch Unit 1 Fall 1991 Outage

ML20091K953
Person / Time
Site:	Hatch
Issue date:	01/10/1992
From:	Giannuzzi A, Gustin H STRUCTURAL INTEGRITY ASSOCIATES, INC.
To:
Shared Package
ML20091K949	List: HL-2000, Forwards Rev 2 to SIR-91-077, IGSCC Flaw Evaluations & Weld Overlay Activities During Ei Hatch Unit 1 Fall 1991 Outage. Rept Addresses Six Areas Noted in NRC Re Weld Overlay Designs,Per Generic Ltr 88-01 & NUREG-0313,Rev 2 ML20091K953
References
SIR-91-077, SIR-91-077-R02, SIR-91-77, SIR-91-77-R2, NUDOCS 9201270175
Download: ML20091K953 (41)

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I g Report No.: SIR-91-077 Revision No.: 2 Project No.: GPCO 200-2 January 1992

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IGSCC Flaw Evaluations and Weld Overlay Activities During the E. I. Hatch Unit 1 I Fall 1991 Outage I '

I Prepared for:

Georgia Power Company g- Prepared by:

StructuralIntegrity Associates,Inc.

l San Jose, CA I

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Prepared by:

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i g Table of Contents Section hgg 1.0 I NTR O D U CTI O N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I jE- 2,0 INSPECTION RESULTS DURING 1991 . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 E

3.0 WELD OVERLAY DESIGNS AND RECONCILIATION WITH AS. BUILT WELD OVERLAYS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1 ' De s ign Bas is . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.2 Weld Ove rlay Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

( 3.3 3.4 Ferrite /Carbt,a Level Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Comparison of Design and As-Built Weld Overlays . . . . . . . . . . . . . . . 9 3.5 Conclusions Regarding As-Built Overlays . . . . . . . . . . . . . . . . . . . . . . . 9 4.0 WELD OVERLAY SHRINKAGE EVALUATION . . . . . . . . . . . . . . . . . . . 14 ,

4.1 Effects of Shrinkage on Piping Supports and Pipe Whip Rei,traints . . . 14 4.2 Effect of Increase in Deadweight and Stiffness Resulting from Weld Overlays in the Piping Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

, 5.0 EVALUATION OF EMBEDDED INDICATIONS IN WELD O VE R LAYS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 5.1 Disposition of INF 191H1015 . . . . . . . . . . . . . . . . . . . . . . . . . . . '. . . . 26

'I 5.2 Disposition of INFs 191H1020,191H1021 and 191H1024 . . . . . . . . . . . 27 6.0 EFFECTIVENESS OF IHSI AT HATCH UNIT 1. . . . . . . . . . . . . . . . . . . . 29 7.0 EFFECTIVENESS OF HYDROGEN WATER CHEMISTRY AT HATCH g UNIT 1.................................................... 34 8.0 EVALUATION OF OBSERVED CRACK GROWTH IN FLAWED g wEtDS................................................... 36 9.0 CONCLUSI ONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

10.0 REFERENCES

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 APPENDIX A Weld Overlay Design Drawings APPENDIX B General Electric Plant Hatch Unit 1 Crack Arrest Verification l (CAV) System SIR-91-077, Rev. 2 i I s eT-c=n 4

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l Ust of Tables Table Eagt

-l 2-1 Results of Inspections: Flaw Characterizations . . . . . . . . . . . . . . . . . . . . . . . . 4 I 31 Con parison of Design and As Built Weld Overlay Dimensions . . . . . . . . . . . 10 l 32 Measured Delta Ferrite in Pfist biyers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3-3 Calculated Carbon Content in Diluted Weld 12yers . . . . . . . . . . . . . . . . . . . 12 I 4-1 Measured Shrinkage Values 1991 kid Overlays . . . . . . . . . . . . . . . . . . . . 17 l 42 Shrinkage Stresses at Unrepaired Welds in Hatcli Unit 1 Recirculation System Following 1991 Overlays . . . . . . . . . . . . . . . . . . . . . . . 18 4-3 Piping System Unit Weights Used in Dynamic Analysis . . . . . . . . . . . . . . . . . 21 I 4-4 Results of Dynamic Analysis Comparison of Natural Frequencies for First Twenty Modes - With and Without Overlays . . . . . . . . . . . . . . - . . . . . . 22 5-1 Identified Embedded Flaws . . . . . . . . . . . . . . . . . . . . . . . . . ........... 28 6-1 Sustained Stresses in Unrepaired 12 Inch Locations . . . . . . . . . . . . . . . . . . 31 62 Sustained Stresses iri Unrepaired Locations in Large (>12 inch) Pipe . . . . . . 33 1 Comparison of Flaw Characterizations with Previous Inspection Results . . . . 38 8-2 Weld Overlays: Design Thickness and Remaining Ligament . . . . . . . . . . . . . 39 g

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I SIR-91-077, Ruv. 2 ii STRUCTURAL nmxmm ASSOCIATESINC t _ _ _ _ ______--_- _____ _ _ _ _

I List of Figures Eigum Pm a

3-1 IGSCC Resistance Figure from Reference 6, with Worst Case 1991 Hatch Da ta Points Ad de d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 4-1 Finit: Element Models: Loops A and B . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 4

l 4-2 Hatch Seismic Response Spectra: Elev.146 ft. . . . . . . . . . . . . . . . . . . . . . . . 24

E 4-3 Hatch Seismic Response Spectra: Elev.172 ft. . . . . . . . . . . . . . . . . . . . . . . . 25

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1.0 INTRODUCTION

As part of the pre outage planning process at E. I. Hatch Unit 1, Structural Integrity Associates (SI) prepared weld overlay designs meeting the requirements of the NUREG.

0313, Revision 2 [1] " Standard Weld Overlay Design" for all unrepaired locations (2) prior to the Fall,1991 outage.

I During the Fall,1991 refueling and maintenance outage at the E.I. Hatch Unit 1 Nuclear Power Station, Georgia Power (GPC) applied weld overlays to six locations in the recirculation and residual heat removal systems. The weld overlay designs were based upon l l the previously developed designs. Five of these weld overlays were applied in response to observed indications representative ofIGSCC. The sixth overlay was applied to enhance the l inspectability of the underlying weld, although no flaw was observed in this location.

When overlays were completed, SI performed analyses of the weld overlay shrinkage-induced stresses with the as-applied weld overlays. Previous bounding analyses [3] had shown that application of any combination of these overlays would not result in unacceptable shrinkage stress effects in the system.

Section 2 of this report summarizes the GPr aspection plan, initial scope and scope expansion, and the results of these inspections. Section 3 discusses the design basis wcld overlays, and provides reconciliation of the design and as-built dimensions for all repairs.

Section 3 also discusses the observations made regarding 5-ferrite content in each weld overlays, and the SI conclusions regarding these observations. Section 4 discusses the effects of weld overlay shrinkage on the recirculction system. Section 5 summarizes the evaluation of observed embedded flaws in weld overlays including the criteria of ASME Section XI [7].

Section 6 evaluates the effectiveness of Induction Heating Stress Improvement (IHSI) applied previously to welds in the recirculation system, considering the cumulative effects of the weld overlays applied to the system. Section 7 discusses the effectiveness of Hydrogen I SIR-91-077, Rev. 2 1 I ~ ,,, _

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Water Chemistry (HWC', at Hatch. Section 8 addresses the ooserved changes in flaw charaLet under pre-existing weld overlays. Sectior,9 pituides a summary of the report and j the conclusions drawn from the previon:, sections.

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I 2.0 INSPECTION RESULTS DURING 1991 )

g During the Fall,1991 outar at Plant Hatch Unit 1, GPC inspected intergranular stress corrosion cracking-susceptNe welds in accordance with the requirements of Generic Letter 88-01 and NUREG-0313, Revision 2. The initialinspection plan included examination of 14 Categay C welds,25 Category E welds, and all 4 remaining Category F welds. As a l result of the inspection results during the initid scope, the inspection scope was expanded as requ! ed by the Generic Ixtter. Fourteen additional Category C'weL.., were examined, as were all 21 remaining Category E welds. The combined inspection scope therefore included 28 of 73 Category C welds,46 of 46 Category E welds, and 4 of 4 Category F l welds.

,l The inspection identified flaw indications in one Category C weld (28B-2) and confirmed or showed minor changes in four Category F welds. These inspection results are shown in Table 2-1.

Weld overlays meeting the design requirements of the NUREG-0313 " Standard Weld Overlay" were applied to the Category C weld (IB31-1RC-28B-2) and all four Category F welds (IB31-1RC-12BR A4,1B31-1RC-12BR-E4,1B31-1RC-12AR-G4, and IE11-1RHR-20B-D-4). In addition, a standard weld overlay was applied to an additional Category C weld (1E11-1RHR-20B-D-5) to improve inspectability of this weld, although no flaws were observed in this weld.

I As a result of the weld overlay activities, the overlaid welds are now reclassified as Category E welds for the purposes of future inspection. The Hatch recirculation system with related piping in the RHR system now includes 71 Category C welds. 52 Category E welds, and no Category F welds.

SIR-91-077, Rev. 2 3 C STRUCTURAL INTEGRITY

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I g Table 2-1 Rcsults of Inspections: Flaw Characterizations Weld Category Flaw Characterization Before 1991

1. Orientation I2ngth Depth 28B-2 C 1 Circ 22" 32 %

2 Cire 4.0 " 32 %

Circ I 12BR A-4 F 3

1 Cire 0.35" 4.0 "

19 %

26 %

12BR E-4 F 1 Cire 4.4 " 31 5 12AR-G 4 F ----- Unable to Size -- ---

l 20B-D-4 F 1 Axial -

10-15 %

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I I 3.0 WELD OVERLAY DESIGNS AND D ECONCILIATION WITil AS BUILT W8LD OVERLAYS I 3.1 Design Basis I Piping load data for each wcld location was taken from the General Electric (GE) stress report for the recirculation and RHR systems [4). Stresses were cakulated from the load data based upon conservative va:ues of wall thickness for each location. The weld oveto

• g designs are rimmaried in taw 31, and the design sketches are included in Appendix A.

g All weld overlay designs were pwoared assuming a b3 ding 360' ciretimferentially oriented through wall flaw, in accordance with the requirements of the NUREG 0313, Revision 2 l

" Standard Weld Overlay" design. Design thicknesses were determhed using the Si < omputer program pc-CRACK [5].

I The overlay lengths shown are minimums required for c!fective reinforcement. Greater l lengths are acceptat:c, and may be required to allow for adequate inspection or for other reasons.

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3.2 Weld Overlay Designs Weld overlay were applied to sir, locations during the Hatch Unit 11991 outage. Three of these weld overlays were applied to 12 inch pipe to safe end joints. Two were hpplied to 20 inch RHR suction welds, and one was applied to a 23 inch safe-end to pipe weld. The 28 inch location contained a newly identified flaw indication in a region where gemetry indications had previously been observed. One of the 20 inch locations (weld 20B D 5) eid I not contain any identified flaws, but a weld overlay was applied tising inconel 82 weld metal to improve inspectability of the le tion. The remaining four locations were prevbusly classi0ed as Category F, and contained previously identified flaw indicctions. Following the I SIR 91077, Rev. 2 5 I -

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I weld overlay of these latter four welds. there are no remaining Category F welds in the I llatch recirculation system.

I~ 3.3 m .jCarbon Level Considerations I Two welds in arge diameter piping (>12 inch) in the Hatch 1 recirculation and RHR system:, contain flaw indications which were repaired by the weld overlay technique using Type 308L stainless steel weld metal. The weld overlay locations are welds 1B31 1RC 28B 2 g and 1E111RHR 20B-D-4. In addition, three welds in tne 32 inch recirculation discharge piping were repaired by weld overlay using Type 308L stainless steel weld metal. Ther,e g welds are 1B31 1RC 12BR A4, IB31 1RC-12BR E4, and 1831 1RC 12AR G4. Delta ferrite measurements were made following the completion of the first layer of each of these weld l overlays, and in one case following the second and third layers, and the results are summarized in Table 3 2.

I Austenitic stainless steel mater!als with delta ferrite content equal to or greater than 7.5 FN l and with carbon content of 0.035 wt% max have been shoxn to be resistant to IGSCC.

Also, where carbon content is less than or equal to 0.035 wt%, wrought austenitic stainless l steels like Types 304L and 316L have been shown to be IG5CC resistant even wit? w delta ferrite present. If ferrite ccatent is less than 7.5 FN but greater than 5.0 FN, it is possible l to justify the IGSCC resistance of the resulting weld metal on a case by case basis, by considering a trade-off between delta ferrite content and carboa content,if the carbon level is less than 0.035 wtE Note that the 6 ferriv issue does not apply to weld 20B-D 5.

This approach is allowed by NUREG 0313, Re 'clon 2, and has been successtelly used previous'y at Hatch and other plants. The purpost f such an evaluation for Hatch is to e demonstrate the IGSCC resistance of the first weld layc , m. ... weld overlays above, in order to Justify including there layers in the design thickness of the overlays, when the ferrite level is t wve 5 FN and below 7.5 FN.

L SIR 91-077, Rev. 2 6 I-O STRUCTURAL D(TEGRFFY

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I The carbon coatent in the underlying base metal at each of these five weld overlay hwath as is reported in Table 3 2, based upon data from the component CMTRs. Two heats of weld metal were available for use in these overlays. IIcat # Pil9(J, which was used for the first layers of all of the locations except the G4 weld, has a reported carbon content of 0.008 %

IIcat # S57735, which was used for the G4 weld, has a carbon content of 0.014% reported in the CMTR.

I For both of the above weld metal heats, the carbon content is sufficiently low that the as.

l deposited carbon content of the first welded layer a,ualifies as IGSCC resistant (< 0.035 wt

%), even considering dilution of the first layer weld n.etal by the higher carbon base metal during the welding process. Consequently, there is significant benefit to be derived from a case by case evaluation of the ferrite carbon trade-off at these two locations.

I in od.r to charnarize the first welded layer carbon content for these weld overlays, a l dilution rate for the dilution of the first welded layer by the base metal v as determine.d, based upon physical examination and chemical analysis of the diluted first layer of welded l coupons made using the same welding procedures as were used in weld overlay application.

This led to a predicted dilution rate of 32.5 % Using this dihtion rate, the first layer of each of the applied weld overlays was calculated to have carbon content as shown in Table 3-3. In all cases, the diluted carbon level in the first layer is less than 0.035 wt% These catbon contents rnect the NUREG 0313 criterion for conforming IGSCC-resistant austenitic stainless steel base metal, even if no ferrite is present. The first layer weld material is also predicted to be IGSCC resistant by the results illustrated in Figure 3-1 from Reference 6 even with 5 FN de m ferrite, which is the lowest delta fertite allowed by NUREG 0313, y Revision 2 for conforming austenitic stainless steel weld metal.

I Figure 31 includes data points representative of each of the five stainless steel weld overlay locations. These data have been superimposed on the Reference 6 curve and data. These weld overlay data points reDect the as diluted first layer carbon content, and the lowest I SIR 91077, Rev. 2 7 I

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1 measured delta ferrite point ieported for each weld. This illustrates that the lowest measured delta ferrite which could be justified for acceptance of the first welded layer (5 FN), is limited by the NUREG criteria (discussed below) rather than by the data in Figure 3-1.

Although the above results support the position that the first layers of all five welds are sufficiently IGSCC resistant by the criteria of Figure 31, NUREG-0313, Revision 2 contains a cut-off minimum level of 5 FN which is defined to be IGSCC resistant. Based upon this requirement together with the above considerations, the first layers of the weld overlays on weld 28B 2 and 20H D-4 are considered as IGSCC resistant and therefore could have been g included as a part of the structural reinforcement weld material used in meeting the design thickness. The first layer of the overlay on 28Be2 was conservatively not considered as part l of the design thickness however. The first layer of the overlay on weld G4 is acceptable since all measured delta ferrite data are greater than 5 FN. The first layer of the overlay on weld E4 is not acceptable by the 5 FN minimum criterion, nor are the first two layers of the overlay on weld A4. The third layer of the overIny on weld A4 meets this criterion.

l Additional weld layers were added to the E4 and G4 welds to achieve a weld layer meeting the NUREG criterion. The weld metal considered in meeting the design thickness was only l that including and outboard of the conforming layer.

The weld overlay design drawings fu. these five overlays all contain a note stating that the first layer of the overlay must have delta ferrite greater than 7.5 FN. The intent of this note is that a first welded layer with measured delta ferrite equal to or greater 7.5 FN is acceptable for inclusion in the design thickness without further evaluation O.. uccordance with NUREG-0313). As discussed above, lower levels are acceptable following ease by case evaluation.

SIR-91-077, R:v. 2 8 gg INTEGIUTY I ASSOClKIESING

3.4 Comparison of Design and As Built Weld Overlays Contingency weld overlay designs for the six overlaid locations were originally presented in ,

[2]. The design for weld 28B 2 was revised to account for the as measured component wall g thickness on the safe end side of the weld. The as measured thickness data for the other weld overlays applied during this outage (welds 12 AR G4,12 BR A4,12 BR E4,20B D-4 and 20-B D 5) were reviewed and found to have no impact on the designs previously issued in [2]. The designs for the three 12 inch welds and weld 20B D 5 were modified subsequent to [2] only to illustrate the detail of blending the overlay into the adjacent component transitions. The design thicknesses of these overlays remain the same as in the previously issued revision [2].

3.5 Conclusions Regarding As Built Overlays Table 31 presents the design and as-built dimensions for the weld overlays applied during

, the 1991 outage. Thickness measurements (t) only represent layers which met l 6 ferrite / carbon criteria as presented in Section 3 3 for stainless steel overlays. These layers were included in meeting the design thickness. Additionallayers inboard of these layers may not have met 6 ferrite requirements and were not included in the design thickness. As may be seen from this table, the dimensions of the as built overlays meet or exceed the design dimensions in all cases. All of these six weld overlays therefore may be considered to meet the requirements of the NUREG 0313, Revision 2 " Standard Weld Overlay" category.

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Table 31 l

Comparison of Design and As Built Weld Overlay Dimensions I

Average Average  !

Weld Design t Design L Aa Built t As Built L (in) (in) (in)t 2 (in) l 12BR A-4 0.27 2.0" 0.44A).43 2.1 12BR E-4 0.27 2.0" 0.4/0.0" 2.1 12AR-G 4 0.26 2.0" 0.31/* 2.2 28B-2 0.52 8.0 0.57/0.69 8.4 200 D-4 -0.36 6.0 0.44/0.44 6. 2 " "

20B-D 5 0.33 "* *"

0.5/0.39 Measurement not meaningful due to transition angle.

length on pipe side only; on component side (safe-end, valve), blend into compcnent transition.

Upstream, blend into adjacen*, overlay, downstream, blend into transition.

l *"*

Downstream, blend into adjacent overlay.

Note: 1. All thicknesses are shown on upstream nnd downstream sides of girth l weld centerline.

2. Reported thickusses are only for layers which met the 6 ferrite / carbon I levels of Section 3.3 for stainless steel overlays.

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Measured Delta Ferrite in First Layers r,n _ 1st Layer 2nd layer 3rd Layer Weld Nurnber Location 0 90 180 270 0 90 180 270 0 90 180 270 H 1 B31-I RC-2SB-2, 54 Safe-End 7.5 6 63 73 8 7.5 8 7.5 N/R N/R N/R N,R Fipe 6 6 53 63 8 75 7.5 8 N/R N/R N/R N/R

.". Weld Wire irT# PB940 PB940 PB940 WX %C 0.008 0.006 0.008 s<: BM %C = 0.055 1 Ell-1RIIR-20B-D-4, N D,& wi 63 6 53 6 73 73 7 7 85 9 &S 9 Upstrearn 6 6 6 6 63 6 5 5 65 6 63 6 Weld Wire IIT# PB940 PB940 PB940 WR %C 0.008 0 008 0.008 BK %C = 0.056 1B31-1RC-12BR-A-4, g Safe-End 4 3.5 4 5 73 3.5 6 6 6 7 63 7 s Pipe 53 6 5 63 53 6 6 73 6 73 7 7.5 Weld Wire llT# PB940 PB940 PB940 W.M. %C 0.008 0.008 0.008 BR %C = 0.075 I B31-1 RC-12DR-E-4, Safe-End 5 5.5 43 53 10.5 93 93 10 N/R N/R N/R N,R Pipe 53 63 6.5 5.5 83 85 25 85 F/R N/R NiR N/R Weld Wire IIT# PB940 557735 W.M. %C 0.008 0.014 B.M. %C = 0.047 +

1B31-1RC-12AR-G-4, Safe-End 73 8 8 63 93 10.5 83 85 N/R N/R N/R N;R ripe 8 9 8 73 93 10 85 93 N/R N/R N/R N!R Weld Wire IIT# S57735 557735 WX %C 0.01 4 0.014 BX%C=0.075 Wrk! Wire ER30SL, HT# PB940,0.008%C,12.2FN (Magna Gage) per CMTR ll Weld Wire ER3081, IIf# S57735,0.014%C,11FN (Fig. NB-2433.1-1) per CMTR 9

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Calculated Carbon Content in Diluted Weld Layers Weld # Base Carbon % Weld Cartmn % Diluted Carbon %

28B 2 0.055 0.008 0.0233 20B D 4 0.056 0.008 0.0236 12BR A-4 0.075 0.008 0.0298 12BR E-4 0.047 0.008 0.0207 12AR G-4 0.075 0.014 0.0338 I

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M M M M M M M M M M M M M M -

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--. o.t o CLOSED SYM80L - IG5CC 6 OPEN SYMSOL - NO IGSCC

[ liALF FILLED SYMeOL -IGSCC - AT LE AST DNE SAMPLk

.d F STHESS C M I FAI URE5 CMD63 HATCHED SYMSOL - MINOR ENVlMONMTNTAL INF LUENCE ,

a Notes:

0 06 -

CF3MFS WELDgD A4, B2,34, Et Points i!!ustrate min.

I#'#N* *****'* ** **

S SE : IZED 0 97 -

h 5 $ G content at these welds.

Ct Point inustrates mir.imum tokrable ferrlie at cakulated carbon content at o 0S -

h $ this wekt.

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1 o su'cin.o*rin 4 yy 4 g eos

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c: g l 0 04 - O As-wt(DeD. Aw LTs. Aw 3 sNr V STELLITE HARDSURFACED c4 l

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Q I I I I I I I I l l l l I 1 is 30 22 24 as 2s a o 2 4 5 s a to s2 14 la FERRITE is!

IGSLt 7esistance Figure from Reference 6, with Worst Case 1991 Hatch ll Figure 3-1.

Data Points Added t;:

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4.0 WELD OVERLAY SF fRINKAGE EVALUATION I l I

When weld overlays were conspleted, measurements of axial shrinkage due to the weld l overlay application were made as presented in Table 4-1. Si performed analysis of the weld overlay shrinkage induced stresses at all locations on the affected piping, considering all weld overlays (1991 and previous). Previous bounding analyses (3) had shown that application of any combination of these overlays would not result in unaccepts ble shrinkage stress effects in the system.

A finite element model of each loop of the Hatch I recirculation system was developed.

The as measured shrinkage resulting from the application of all overlays on the loops, including the overlays applied during the 1991 outage, were imposed on the models. The l stiesses due to the aggregate shrinkage on each loop were calculated at each unrepaired location.

The shrinkage stress results at each unrepaired location are preser.ted in Table 4-2. These stresses are judged to be generally insignificant with regard to integrity of the piping system, but should be cansidered in any future flaw evaluations or crack growth calculations on these l systems.

l 4.1 Effects of Shrinkage on Piping Supports and Pipe Whip Restraints Subsequent to the application of weld overlays, visual inspections of piping supports and whip restraints were performed by GPC. These inspections included verification of spring hanger load settings, snubber pin to pin and stroke dimensions, and pipe whip restraint clearances for all piping supports in the recirculation loops. As built dimensions were documented by ISI personnel, and were evaluated against design requirements. The results of these inspections showed that the as built condition of piping supports is acceptable, with I

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no impact on plant operation. No adjustments to piping support settings or whip restraint clearances were required.

I 4.2 Effect of Increase in Deadweight and Stiffness Resulting from Weld Overlays in the g Piping Systems l When the mass of the piping system increases due to the number of weld overlays, the dynamic characteristics of th: system also change. These changes may have an effect on the l r.cismic stress due to varying the modal response of the system. Therefore, a second analysis was performed u 1xamine the effect of additional weld overlays on the modal frequencies of the recirculation piping system.

l The model used for the modal analysis is based on the weld shrinkap: finite element model with some modifications to permit it to be used for a dynamic analysis. These modifications l include adding the weight of the piping, valves, pump, motor, and wehl overlays and the snubber stiffnesses.

I Table 4 3 presents the unit weights of the recirculation system using nominal pipe sizes. The unit weights in:lude the pipe, water and insulation. The weight of the pump is 671(X)lbs.

and the weight of the valves are 10188 lbs. cach. The weight of the overlays were calculated assuming the overlay thickness is 0.5 inch'and the overlay length is 6 inches. These are nominal overlay sizes, however the analysis results will not be significantly affe-ted due to as built variations in these values. The resulting overlay weights are 76.16 lbs. for a 28 inch pipe,60.13 lbs. for a 22 inch pipe and 35.41 lbs. for a 12 inch pipe.

I A total of 11 snubbers was included in the recirculation system dynamic model. Two were placed on the suction side (SB7 & SB8). Three were placed on the discharge size (SB12, SB13 and SB14). The rest of the snubbers were used to restrain the pump and motor.

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I g, For the SD14 snubber, the stiffness was estimated from load and displacement results of the piping seismic aral.,ses performed by GE. The stiffness was estimated to be about 1.4 x 10' g Ib/in. *lle stHfness of the remaining snubbers (SB7, SB8, SB12 & SB13) were estimated from other recirculation piping dynamic analysis. These were estimated to be about 0.5 x l 1061b/in and wem t, sed at the pump location in the piping model to simulate all the snubbers connected to the pump and the motor. All other hangers in the recirculation piping were neglected because of low stiffness. All nozzles in the recirculation piping system were assumed to be fixed. Also, all welds in the recirculation system were assumed to be overlaid.

l This assumptlen is consistent with the most added mass to the piping system, and therefore, the most potential impact on the piping system dynamic analysis.

I Table 4-4 presene, the modal response analysis results. The firn mode was found to be l about 5.52 hz. for the recirculation system without any overlays. With the overlays, the first mode freque..cy decreases to about 5.49 hz. for a difference of 0.68% The biggest difference is about 2.1% for mode 20.

Figures 4 2 and 4-3 present the Hatch Unit I response spectra at reactor vessel elevations 146 ft. and 172 ft. They both show a peak response at a frequency range of about 3.5 h:

to 5 hz. With the first mode of 5.52 hz. when there are no overlays, the response is very close to the peak of the sr,ectrum. Even though a decrease in the mode frequency would correspond to an increased response for the given spectrum, the magnitude of the decrease in the first mode frequency is so small that it would not cause a significant change in the I response. With only about 50% of the welds overlaid, the change in the first mode frequency would be, even smaller. Therefore, it is concluded that the overlays, either in the current or any imagined future configuration, would have a negligible effect on the dynamic analysis of the system.

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Table 41 Measured Shrinkage Values g 1991 Weld Overlays I Weld Shrinkage (avg)

(in)

(Max) 12BR A-4 0.10 I 12BR E-4 0.20 0.14 0.25 12AR s 4 0.12 0.37 28B 2 0.05 0.1 l 20B D-4 20B-D 5 0,00 0.01 0.00 0.06 I

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'l Table 4 2 Shrinkap; Stresses at Unrepaired Welds in Hatch Unit 1 j Recirculation System Following 1991 Overlays

,g Weld Shrinkage Stress

ui) 28A 1 0.15 g

28A 3 0.12 l 28A 5 28A 5A 0.12 0.25 l 28A-9 28A-11 0.25 0.11 28A-13 0.19 28A 15 0.42 28A 16 0.46 28A-17 1.35 6.77

_ _ ' _ .2AR F-1 12AR-F-5 2.89 12AR-G-1 3.09 12AR-G 2 2.26

(-

12AR G 5 7.32 l 12AR H 1 12AR H-5 10.43 6.83 12AR J-1 4.66 12AR-J 2 4.31 12AR-J-4 7.20 12AR 3 5 8.58

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g Table 4-2 (continued)  ;

Shrinkage Stresses at Unrepaired Welds.in liatch Unit 1 Recirculation System Following )991 Overlays Weld Shrinkage Stress (ksi) ,

12AR K 1 5.35 l 12AR K-4 2.89 12AR K-5 3.65  !

28B 1 0 32 R 28B5 0.80 26 B-6 0.93 i -.

288-7 0.41

,l 28B 12 0.38 28is-17 0.55 .

l 28B 22AM 2 1.59 1.94 i 22.Gi-3 1.41 22BM 2 152 E 22BM-3 0.89 20B D 1 0.31 lI. 20B D-2 0.11 12BR-A 1 5.92 l

12BR-A 2 1.37 l

l 12BR A 3 12BR-A 5 0.18 2.17

-l 12BR B 1 5.68 LI SIR-91-077, Rev. 2 19 1

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Talfe 4-2 (concluded)

Shrinkage Stresses at Unrepaired Welds In llatch Unit 1 l Recirculation System Following 1991 Overlays  !

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E 12AR.K.1 2.19 I 17A9.K-4 12AR.K.5 1.59 1.57 l

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28B-1 12.93 28B.5 6.02 ,

j 288 6 5.51 28B 7 6.33 l 28B.12 9.42

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l Table 4 3 Piping System Un'! Weights Used in Dynamic Analysis Unit Weight (Ib/ft)

Itc._ Pipe Water Insulation Total (Ib/in) l 28" Pipe Suction 333 208 38 48.00 28" Pipe Disch. 389 208 38 $2.92 12" Pipe 91 42 20 12.75 22" Pipe 242 127 31 33.33 I

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M Table 4 4 l

Results of Dynamic Analysis Comparison of Natural Frequencies for First Twenty Modes . With and Without Overlays i

Recirculation Loop w/o w/ w/o w/

I overlays overlays overlays overlays Moda (hr) (hz) _ Diff(%) period (sec) 1 5.5245 5.4867 -0.68% 0.181010 0.182260 2 6.9959 6.9255 -1.01 % 0.142940 0.144390 3 7.6848 7.6401 . 0.50% 0.130130 0.130700 I 4 9.6416 9.6114 -0.31 % 0.103720 0.104040 5 10.4640 10.3410 -1.18% 0.095567 0.096702 6 12.5700 12.5350 D.28% 0.070554 0.079777 1 7 14.4610 14.3010 -1.11% 0.039149 0.069924 8 15.0970 15.0110 -0.57% 0.066237 0.066619 9 16.8210 16.7190 -0.61 % 0.059450 0.059811 10 18.1080 17.9230 -1.02% 0.055224 0.055796 i

11 18.2680 18.0110 -1.41% 0.054740 0.055521 12 19.2290 19.1100 -0.62% 0.052005 0.052327 1 13 20.6930 20.3850 -1.49% 0.048324 0.04b056 14 22.7780 22.4370 -1.50% 0.043901 0.044569 15 28.7640 26.6590 -0.3t% 0.03730A 0.037511 l 16 29.3070 29.1600 -0.50% 0.034122 0.034294 17 34.6740 34.4310 -0.70% 0.0P.8840 0.029044 18 36.5010 35.9100 -1,62% 0.027396 0.027847 1 19 38.2240 37.4960 -1.90% 0.026162 0.026669 20 39.7990 30.9620 -2.10% 0.025126 0.025666 I

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muhn amed W

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Figure 4-1. Finite Element Models: Loops A and B

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23M082 ag, uo, 10 NU3 EAR ENEROY BullNass CPIRAYlONS GEN ER AL O stictnic nev. 2 l . .

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< 10' 10' 10' 10' rRCOUCNCY CPS HWP UWlf I RPY HORl!0NTAL OBC MRSS Pi 19 CL.146'-O' >

Figure 4 2. Hatch Seismic Response Spectra: Elev.146 ft.

SIR 91-077, Rev. 2 24 STRUCTURAL INTEGRITY ASSOClKI'mINC

. 4 23M082 g,us 51 l nuet Aa mura:V tullNESS OPEaAfl0H5 GEN ER AL O streraic M W. 2 I

f

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.A PING l

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10 10' 10' 10, rRtotituci CPS .

HWP UWlf 1 RPV HOR 120WTRL OBE MRSS Pt 20 CL.172' O'

_l I Figure 4 3. Hatch Seismic Response Spectra: Elev.172 ft.

mucrona

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I 5.0 EVALUATION OF EMBEDDED INDICATIONS IN WELD OVERLAYS During the inspection of previously applied weld overlays at Hatch Unit 1, sub surface flaws I that are characteristic in most cases of lack of fusion were identified in several locations.

These locations and flaws are summarized in Table 51. These indications were documented I' in Georgia Power Company INFs 191H1015,1020,1021, and 1024.

I 5.1 Disposition of INF 191H1015 I 'ihls INF documents the flaws observed in the weld overlay on weld 28A-7. These flaws are summarized in Table 51. Six of the seven observed flaw indications were previously observed, in addition, a previously unobserved flaw Indication (Indication #3) was observed.

The new flaw indication (Indication #3) is acceptable without further action or repair. This conclusion is based upon the following considerations:

I 1. There is a remaining ligament of 0.64 inch outboard of the reported Indication g #3. The design overlay thickness for this repair location is 0.49 inches.

Therefore, the full design thickness of the overlay is outside of the flaw l indication, and the adequacy of the weld overlay is in no way affected by this flaw.

I 2. The indication is remote from other lack of fusion indications. The nearest l of the other fabrication.related detects appears to be Indicatiott #1, which is located approximately 1 inch axially and 6 inches circan ferentially from this l indication.

3. All other reported lack of fusion indications are located on the other side of the original girth weld.

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4. The reported location of the hidication app;ars to be sufficiently far away from the underlying IGSCC flaw indication that there is little potential for  !

connecting with the inside surface of the pipe. There is therefore no l

recognized mechanism for flaw growth.

5. This flaw indication and the other five indications can all be treated as unconnected to each other for the purpose of evaluation. Each of the reported indications is acceptable by the criteria of IWB 3500 of ASME l Section XI [7).

l 5.2 Disposition of INFs 191H1020,191H1021 and 191H1024 The indications <iocumented on INF 191H1020 (weld 28B-15,11/1/91), and INF 191H1024 (weld 24B-R-12,11/07/91) are summarized in Table 51. The indications reported in these INFs are acceptable without further action or repair. 'diis conclusion is based upon the following considerations:

1. There is a remaining ligament outboard of the reported indication in excess of the weld overlay design thickness at each indication location. In other words, the full design thickr.ess of the ov::rlay is outside of the flaw indication depth in all cases, and therefore thi adequacy of the wcld overlay is in no way affected by these flaws.

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2. Each of the reported indications is acceptable by the criteria of IWB.3500 of ASME Section XI, using Table IWB-3514-2 [7).

3. For these embedded flaws, there is no apparent mechanism for continued growth, since there is no detected connection with the inside surface of the pipe.

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I l Table 51 Identified Embedded Flaws l 28A-7 Weld Type of Flaws Lack of Fusion g (6 Total) 28B-15 Lack of Fusion (1 Total) 24B R-12 Lack of Fusion (7 Total)

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g 6.0 EFFECrlVENESS OF 111S1 AT HATCil UNIT i NUREG 0313, Revision 2, Section 4.5 states in part that "Becau e the effectiveness of the SI [ stress improvement) treatment is also related to the applied stress on the weldmeat, mitigation by Si is not recommended for weldments with service stresses over 1.0 S....". Ir practice, this limitation has been interpreted to mean that no credit may be taken for IHS1 or other stress improvement methods at weld locations where the sustained stresses (pressure, deadweight, thermal expansion, and weld overlay induced shrinkage stresses) total more than 1.0 S..

I Tables 61 and 6-2 summarizes the sustained stresses at all locations in the Hatch recirculation system which have not received weld overlays. None of these locations have identified unrepaired flaws. As can be seen from there tables, several locations in 12 inch pipe 1. ave combined sustained stresses greater than 1.0 S., while no locations in larger pipe have sustained stresses greater than 1.0 S . If future inspection results indicate that any of these highly stressed locations in 12 inch pipe have flaws requiring evaluation in accordance with the NUREG, the as welded residual stress distribution will be used in any crack growth calculations, rather than the more favorable post IHSI residual stress distribution. At other locations in the recirculatloa system, credit for lHSI may be taken consistent with the requirements in Section 4.5 of the NUREG.

g As stated above, NUREG 0313 Revision 2 does not consider stress improvement treatments to be effective for weldments with service stresses over 1.0 S., due to the concern that the g stress improvement might be reduced by an overload or stress relaxation condition.

Laboratory data has illustrated that, for unflawed weldments,11ISI is an effective mitigation measure against IGSCC for loadings well above the engineering yield strength at temperature, i. e.1.2 o,, [8]. When flaws exist in the structure, the mitigation measure may not be effectise even at loads of S . The EPRI GE Degraded Pipe Test Program [9] on four inch and twelve inch schedule 80 pipes observed that: 'The IHSI treatment of welded SIR 91077, Rev. 2 29

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I l piping will provide crack arrest where IGSCC cracks are approximately 17% of wall thickness or less, provided loading higher than the primary membrane stress (S ) is l avoided....... At higher applied stresses, the compressive residual stress benefit afforded by the 11-1S1 treatment is lost and crack growth occurs".

I The Daws in the IGSCC Category F weldments were all sized at greater than 17% through l wall and thus would have been expected to exhibit some growth. That is the principal reason that these welds have been subject to inspection during each refueling outage and why Georgia Power Company decided to overlay repair all Category F welda.

The deepest IGSCC indication in weld 28-D2 was located in tne same vicinity where root geometry had been called in the past. It is possible that the refined automated P Scan and

GE Smart 2000 detection capability used for inspection during this o*itage was able to resolve this indication as an IGSCC indication where previously, only a geometry call had been made using the manual inspection techniques. Discussion with the UT level 3 inspector revealed that the capability of the new GE Smart 2000 automated UT system with I digital signal data storage produced a significantly increased capability to resolve indications following the inspection. The detailed flaw evaluation can be performed remotely thereby reducing human radiation exposure and allowing for a more precise examination of the I component.

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1 l Table 61 Sustained Stresses in Unrepaired 12 Inch Locations I Weld Sustained Stress (ksi)1 _

12AR F 1 18.7 12AR F 5 15.6 12AR-G 1 15.5 12AR G-2 9.9 12AR G 5 15.9 l 12AR H 1 12AR H 5 27.6 21.0 l 12AR.J 1 17.0 12AR-J 2 12.3 l 12AR J 4 20.8 12AR J 5 22.2 12AR K-1 16.6 12AR K-4 13.3 12AR K 5 14.1 12BR A 1 18.6 12BR A-2 9.0 l 12BR-A 3 12BR A 5 7.3 13.9 12BR B 1 18.9 Note: 1. Sustained stresses include pressure, deadweight, thermal, and shrinkage stresses.

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I g Table 61 (continued)

Sustained Stresses in Unrepaired 12 Inch locations

, I

)

Weld Sustained Stress (ksi) 12BR B 2 10.3 12BR B-4 12.3 12BR B 5 12.2 12BR-C-1 31.3 12BR D 1 18.3 12BR D-4 16.6 12BR D-5 17.4 g 12BR E-1 20.5 I

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n Table 6 2

h. - C

.i[g Sustained Stresses in Unrepaired locations in Large (>12 inch) Pipe

. m <

y

, y 1.,.

I Weld Sustained " tress

.g;, .

..g (ksi)2

~.yt;q..gy - - - -

6 iVp  ; 28A-1 6.7 ,

' ~'

, 28A-3 1 6.4 28A 5 6.3 "

y 28A-5A 6.4 2RA-9 6.8 28B-1 7.5 \

"B-5 7.4

. 28W6 7.8 ,

28B-7 7.1 20B-D 1 9.9 20B-D-2 8.1 6

28A-11 5.8 28A-13 5.8 l 25A-15 63 -

E28A-16 6.8 28B-12 5.9 l_

28B-17 7.7 Note: 1. Sustained strerres include pressure, deadweight, thennal, and shriakage stresses. "

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l 7.0 EFFECTIVENESS OF HYDROGEN WATER CHEMISTRY AT HATCH UNIT 1 The hydrogen water chemisny mitigation measure is an extremely effective IGSCC mitigation measure in sensitized austenitic stainless steels if the electrochemical potential (ECP) of stainless steel in the BWR environment is reduced to a level below the protection potential of 230 mv SHE at the BWR operating tempermore. It has been demonstrated in laboratory programs that a factor of improvement of more than 10 can be expected in reduction in crack growth rates in the protective HWC environment. When combined with I excellent water quality, this mitigation measure is extremely effective in reducing or eliminating IGSCC in the BWR environment.

During the past few years, the hydrogen water chemistry system has been installed at Hatch and has operated during power operation. Prior to this operating cycle, cycle 13, the hydrogen system was unable to consistently reduce the electrochemical potential to below the protection potential for stainless steel. Durit.g the prior refueling outage, the condenser was changed from a copper based condenser to a titanium condenser in part to assist in reducing the electrochemical potential to below the protection potential. During this

'g operating cycle, the hydrogen injection system was consistently able to reduce the electrochemical potential to below the protection poteatial.

I Ne wa r : he "stry records at Hatch Unit I were reviewed to determiae the water quJty

-l during op. .ng cycle 13 as wel as the effectiveness of the hydrogen injection system. The ECP was obtained in the crack arrest verification system (CAVS) autoclave. The CAVS results revealed thct the HWC system was on and produced full protection for approximately L 41% of the time at power. During the remaining 59% of the time the system was either l partielly protective or not protective. The total time in which no protection was observed

was approximately 47% of the timr at temperature and pressure. No investigation was performed to ascertain why the system was providing no protection during this period of time during the cycle. However,it is noteworthy that for approximately 4500 hours0.0521 days <br />1.25 hours <br />0.00744 weeks <br />0.00171 months <br /> during

I SIR-91-077, Rev. 2 34 myrm-INTEGRITY g - ASSOCIKIESINC

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( this latest cycle, the HWC system was not providing effective protection to the recirculation system piping. Clearly, that quantity of time is adequate for additional IGSCC or crevice l corrosion to occur in the oxidizing BWR environment. This additional crack 'nitiation or growth is consistent with that observed during the IGSCC inspections following cycle 13.

l Additional detailed discussion of the operation of the HWC system duririg cycle 13 is presented in Appendix B to this report, prepared by the General Electric Company.

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8.0 EVALUATION OF OBSERVED CRACK GROWTH IN FLAWED WELDS I During the 1991 inspection, several locations yielded inspection results indicative of flaw grow *h. Inspections prior to 1991 were performed manually, while the 1991 inspections were I performed using automated P-Scan. The difference in inspection technique could be responsible in part for the recorded changes in indications. A comparison of prior and 1991 inspection results is presen'ed in Table 81.

'I\vo of the four existing Category F welds had identified flaw characteristics slightly different from previous inspection results. Weld 12BR-A4 had oberved flaw depth of 2L% as compared to the previous result of 17 22%. Weld 12BR-E4 had observed flaw depth of

32%, as compared with the previous result of 21-25%. These differences are considered to be within the bounds of the accuracy of the inspection technique, and are not indicative of significant crack growth. Both of these locations, as well as the other two Category F welds (12AR-G4 and 20B-D-4), were repaired during the 1991 outage using weld overlay designs g qualifying as NUREG-0313 " Standard Weld Overlay" repairs. These welds therefore are

reclassified as Category E locations for future inspections.

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In nddition to the above Category F welds, tiiree locations with existing weld overlays had j recorded inspection results which are indicative of flaw growth under the overlays. These three locations are welds 12-AR-H3, 12-AR-J3, and 24B-R-13. The new flaw L characterizations for these locations show a maximum flaw depth within the outer 25% cf the original base materit. In no case was propagation into the weld overlay material l observed. The reported remaining ligament outside of the crack depth for each of these three locations is summarized in Table 8-2.

Flaw growth calculations for these flaws, to determine if such growth is in line with predictions made in accordance with the methods of NUREG-0313 are not meaningful in these cases, sir.ce the starting depth of the underlying flaws is not known.

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I The weld overlays for these locations were applied in 1984. At that time, the reported flaw lengths on the two 12 inch weld locations (360" hiterrnittent) were such thrt a repair was required regardless of flaw depth. It was determined that the weld overlay design would not be affected by flaw depth, and so the decision was inade to minimize radiation exposure to l the inspection personnel by not requiring detailed depth sizing. Consequently, an accurate starting depth for use in flaw growth calculations is not available.

The flaw on weld 24B-R-13 was reported in 1984 as axially oriented and 47% deep. The recent inspection reported axial flaws with depths nearly through original pipe walt This is not inconsistent with the fact that sizing of axial flaws was .mprecise at best in 1984, and is still difficult today, especially through a weld overlay. The 1991 reported depth of the axial flaws in this weld may be indicative of either inspection variations or flaw growth, or a combination of both. In any case, the observed flaws do not reduce design margins in the weld overlay.

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l Table 8-1 Comparison of Flaw Characterizations with Previous Inspection Results WELD OVERLAY LOCATIONS:

I 12AR H3: OVERLAY 1984: 360 X 20-30%

1991: CIRC 3.8" X TO OVERLAY INTERFACE CIRC. L3" X 0.06 BELOW OVERLAY 12AR-J3: OVERLAY 1984: 360 X 20-30%

1991: CIRC 1.3" X 0.12" BELOW OVERLAY 24B-R-13: OVERLAY 1984: AXIAL X 47%

1991: MULTIPLE AXIAIS DEEPEST TO 0.4" OF OD CATEGORY F:

I 12BR-A4: PREVTOUS: ' 17 22%, PRESENT: 26%

12BR E4: PREVIOUS: 21-25%, PRESENT: 32%

12AR-G4: PREVIOUS: 13-19%, PRESENT: UNABLE TO SIZE DUE TO

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CONFIGURATION 20B-D-4: PREVIOUS: 16% AXIAL, PRESENT: 10-15% AXIAL I .

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, Table 8-2 Weld Overlays: Design 1Lickness and Remaining Ligament (Observed Flaws under Weld Overlay in Outer 25% of Base Metal)

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I Weld Min. Remaining Ligament Design Overlay Thickness 24B-R-13 0.4" 0.20" 12AR-H 3 0.46" 0.25" 12AR-J-3 0.5" 0.26" F

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9.0 CONCLUSION

S The inspection ar.d repair activities at Hatch Unit 1 during the Fall 1991 outage were performed in accordance with the requirements of NUREG-0313, Revision 2. The inspections, design, and weld overlay activities are discussed in detail in this report. Based upon the above discussion, several conclusions can be drawn regarding IGSCC mitigation activities at Hatch. These are:

1. We.1d overlays are effective in repairing IGSCC susceptible locations, and in arresting existing IGSCC. Weld overlays have been in service at Hatch 1 since early 1983, and UT examinations of portions of the base metal under the overlays show only minor changes in flaw character. Such changes may be due, in part, to improvements in I inspection techniques.

I 2. All weld overlays applied during 1991 (six total) meet or exceeded the design requirements, and therefore all qualify as NUREG-0313 " Standard Weld Overlay" repairs.

I 3. Weld overlay shrinkage stresses may be sufficiently high in 12 inch welds tliat, combined with other sustained stresses, total sustained stresses may exceed the 1.0 4

S. criterion of NUREG-0313 for effectiveness of stress improvement processes. If g future flaw evaluations need to be performed for 12 inch locations, no residual stress benefit due to IHSI may be assumed for such highly stressed locations. No evaluated locations in piping larger than 12 inch diameter exhibited combined sustained stresses greater than 1.0 S., so IHSI may still be considered effective for these locations.

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4. The cumulative effect of all overlays applied to the recirculation and associated l systems at Hatch is insignificant with regard to the design piping analysis and the operability of supports and pipe whip restraints.

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5. Embedded flaws identified in some overlays are acceptable for cor.tinued operation without sepair, based upon evaluation in accordance with ASME Section XI, g 1WB 3500.

6. The hydrogen water chemistry system at Hatch is effective in eliminating IGSCC growth when the system is operating. Even normal water chemistry was favorable during the past cycle, since excellent chemistry was achieved.

l 7. Although inspection results yielded some flaw characterizations which were different from those pteviously reported, the differences are generally not consider:d to be l significant. Apparent growth may be due in fact to improved inspection techniques, including the use of automated techniques, rather than actual flaw growth.

I I

l l

I -

I SIR-91-077, Rev. 2 4; C- STRUCTURAI, yINTEGRFIT ASSOCIATESIIC

l

10.0 REFERENCES

l 1. NUREG 0313, Revision 2, ' Technical Report on Material Selection and Processing Guidelines for BWR Coolant Pressure Boundary Piping" Revision 2, January 1988.

2. StructuralIntegrity Associates Report," Contingency Weld Overlay Designs for Hatch Unit 1" SIR 91-039, Revision 0, June,1991.

3. StructmalIntegrity Associates Report," Contingency Study Regarding the Effects of Additional Weld Overlays at E. I. Hatch Unit 1", SIR-90-044, Revision 0, July 11, 1990.

4. GE Stress Report, " Plant Piping Analysis Design Memo 170-113", September 26, 1984.

5. Structural Integrity Associates, pc-CRACK, Version 2.0, August,1989.

6. ASTM Special Technical Publication 756 " Stainless Steel Castings", Nove 1ber 1980.

Page 43,

7. ASME Section XI, IWB-3500, 1986 Edition.

'{ '8. EPRI " Induction Heating Stress Improvement", EPRI NP-3375. November 1983.

9. EPRI,' Assessment of Remedies for Degraded Piping", EPRI NP-5881-LD, June 1988 I

I-I I

I SIR-91-077, Rev. 2 42 STRUCTURAL

'a- a INTEGRITY g; ASSOCIATFSINC

, _ . s- _

j' il f

k

+

I APPENDIX A l Weld Overlay Design Drawings i

lI i

!(

!I s

I 3

I 1

1 SIR-91-077, Rev. 2 I .

)

y -

l FLOW A d B l

-l 45 ' MIN TYP l pp sh:m%pl2:gs8736k t y.., -

Qwy l ;' ; '  ;  : ,

Safe-end l Pipe s

I Q WELD Not to Scale p7 p ;y DESIGN DIMENSIONS WELD NUMBER COMMENTS CHARAC1ERIZATION t A I B 1B31-1RC'-28B-2 ' Assumed S60

• Cire. -

0.52" 4.0" 4.0" overlay Thickness 100% throughwall revise'.

flaw I i l 3E % s!& sisu R n?nten % w n ? w M @ n w g m M Kr&;y9:0%6;an;4twng; nww y;mspp@ygex:qp;;hxysg9x,;

l A / Overl I hM IO l NCC /0[A.2[S/ M /dfRI9 f on asay dimensions built based thickness.

, VlllV/

O h h h fit l91 -'

& tif4)

Revision Prepared by/ Date Checked by/ Date Approved by/ Date COMME?US 5m m,wwas- 4 m , m% + ,, -

.ms mm

1. 1. • Plant / Unit cPCO-20Q ,, STRUCTURAL i';

i F1b No:

Oco Power Company Plan Hatch Unit 1 INTEGRITY GPCO20Q401 /

/ ASSOCIATES, INC.

Dmwing No:

Tit}e; Steined Weld Overlay Design Sheet 1 of 2 G P C. S 2 0 c c.,

, , . - . . . . - . ~ . - _ _ -_ - - - ..-. . . . . . . - .

~ ,  ;

7. . - .

.i -

NOTES

1. LWeld w'.re material .is to _ be . type- ER308L,- with as-deposited delta ferrite content-greater than. 7.5 FN.

- 2. _ Component. surface is to be avamined by dye-penetrant lJ <

Wihod and accepted = as clean prior to overlay _ application in _ order L 1to-include the entire deposited overlay thickne:,s in meeting the

= design thickness requirement,; per NUREG-0313 Revision -2. 1

3. =In the event that the ' original component surface does not pass j; the note :2 requirements, the first deposited weld layer is to be.

avaminaA;by' dye penetrant method and; accepted as clean before

{

l 7  : procaading with subsequent layers. lT H t t ._

. 4. : First ; weld layer is to have a memaured delta ferrite content '

greater than 7.5~ FN. ' Ibis requirernent doeslnot apply to the anni M.1d11ayer.

J5. Design (thicknessLincludes no. allowance for surface conditioning p

< operations; to - facilitats Ur; inspections. ; I!

-p

}.

.n 6; Design length is;that required for structural reinforcement;. 3^

g greater length may be required for effective Ur inspection. This is tslbe# determined;in the field.

esanumsmawmmmswunwawwwammummarmsunamnocomqwn Job Ns:,- Plant / Unit? STRUCTURAL P11e .N3: -

Georgia Power Company- M_ . INTEGRITY Plant' Hatch Unit 1-- m 4/ ASSOCIATES, INC.

? GPCO-20Q401 -

DrawtagoNo:

2-GPCO-20Qgy

Title:

Standard Weh Overlay Design Sheet . 2,,_,. or

&> ...[h_ ,

'd,,-

- m .. . . - ..., ~ - . - m _ _ . _ _ . . _ _ . _m

s I-l E' FLOW II -  ;

A  : 14 -B  :

l i

45* MIN TYP l j

l l

AgAy esWe + % ..

y T

+ 1;e s

%_A llps:"'k: 3.) ^

s .- s.,,

r 4

.jy 4 m g; <

mmu

.pc l Mpe Q W,LD Not to Scale FIAW DESIGN DIMENSIONS N NM COMMFETS CHARACIERIZNDON t A B IE11-1RRR-20B-D4 Assmned 360

• Cire.

0.3G* 3.0" 3.0" 100% throughwd

, flaw

%Bn3Wes#d@Itsi@b(90maWnmap;tpenge2?ra@ips:w anMappp, sggpeppgegg e,agggy ,ag4 c egg n l

I O

~

Yh {$ / &ff9/ .

(, jg 9 j M on Prepared by/ Date Checked by/ Date Approved by/ Date COMMFETS

_?%e disser cet;Nwa 4

• 22#depaJW %WuP4s0 WM ~9manc Yym;r age;gggg:,> se wm; w*

Il GPCO-20Q Plant / Unit Georga Pom Company O STRUCTURAL yse No.

Plant Hatch Unit 1 INTEGRITY ig ' GPCO-20Q401 ASSOCIATES, INC.

Drawing No:

Title:

Standard Weld Overlay Design Sheet 1 of 2 GPC320Q13 f

,1 f

NOTES l 1. Weld wire material is to be type ER308L, with as-deposited delta ferrite content greater than 7.5 FN.

I Component surface is to be ernmined by dye penetrant I 2.

method and accepted as clean prior to overlay application in order >

to include the entire deposited overlay thickness in meeting the  ;

I design thic3rness requirement, per NUREG-0313, Revision 2.

I

3. In the event that the original component surface does not pass

.l- the note 2 requinunents, the first deposited weld layer is to be evnmined by dye penetrant method and accepted as clean before

.l proceeAlng with subsequent layers.

I 4. - First weld laycr is to have a measured delta ferrite content

'g greater than 7.5 FN. This sequhement does not apply to the final weld- layer.

5. Dedgn thickness includes no allowance for surface conditioning i

l operations to. facilitate Ur inspections.

L I

6. Design length is that required for structural reinforcement; ,

greater length may be required for effective Ur inspection. '1his is to be determined in the fleid.

.I mumm wwms wgwasme ew www. .m . . ..

wwg ea I cPco-20q Plant / Unit O STRUCTURAL Y / ASSOCIATES, File No,. ceorgta Power company Plant Hatch Unit 1 -

INTEGRITY j ' GPCO-20Q-401 INC.

Drawing No:

GPCO 20Q13

Title:

Standard weld Overlay Design Sheet 2 of 2

. =-. .

.ll l

A '~ B l

l '

I I

I i , -

@e21ay o g

^qqgggg+;g2gaygwad[~gl4gg"ygjjj@j;j$4sh,

• 2..0

- Weld 20B- , '~m-~ b '

' ~ ~ , ~ . -

u g.W J yPip .: n m ?11 %^~"g '3 g ,;%:4 L y 'g os

-l w;c;:r,e  : -a'w;rg;p

., m;%',;, ,- >

- :.:f s;% r ' G n:s?J as m ~ q

• e.s;?mp~;g; rp v 4

,py_ .

,..~m., ~ s- . . :n > ;s ~

g?un r. g.:9.6 py & : m,qq;499,% L%

l l

lInconel i Butter Bu'tter-Valve l Interface Not to Scale FIAW DESIGN DIMENSIONS WELD NUMBER COMMENIS

. CHARACIERI2ADON t A B LE11-1RHR-20B-D-5 Assumed 360' Cim. 0.33" Note 1 3" 100% throughwall flaw w;siserMuz1/mprestandeemsedezursesumamawwcetteemscenwewrauwwasswsh' Jh'b a Mn 6 eRh A/ 6 u n u "u m "c>o* t A L - - t-Redsed to show l 1~

/[ b ff[ff9/ , f////9/

////[9/ weld tunMhn detail

. .O k /8 9l Yff/ 6 If 91 Reviston Prepared by/ Date Checked by/ Date Approved by/ Date COMMENTS 3&skncu+weakaw + mbtw Outit%mawaww-  % Mn nk wt naimnUW*

Job Nm Pla21t/ht GPCO-20Q K N STRUCTURAL Georgia Power Company INTEGRITY I File No GPCO-20Q401 plant "'atch Unit 1 9 -

%y> ASSOCIATES, INC.

Drawing N

.l gg

Title:

Standard Weld overlay Design Sheet I of 2

~

NOTES i

l ..

1. Blend repair into adjacent repair on weld 20B D-4. Follow contour of transition with all weld layers. Repair should blend into valve body transition at an angle of 45 degrees or less with the component surface.  ;

i

! 2. Weld overlay material is to be typ ERNiCr-3.

I 3. Component surface is to be enmined by dye pen .trant method and accepted as clean prior to overlay application in order to include the l entire deposited overlay thickness in meeting the design thiamess requirement, per NUREG-0313, Revision 2.

4. In the event that the original component curface does not pass the note 3 tequirernents, the first deposited weld layer is to be examined by l dye pr-+ rant method and accepted as clean before proceeding with subscut layers.

5. Design thickness includes no allowance for surface conditioning operations to facilitate Ur inspections.

I 6. Design length is that required for structural reinforcement; greater length rnay be required for effective Ur inspection. ' Ibis is to be I detcrmined in the field.

On the valve side of the weld, the inspection volume shall include l 7.

the outer 25% of the girth weld and the Inconel butter, and shall extend approx.1" beyond the carbon steel valve - Inconel butter I interface.

8. Final structural evaluation and disposition shall be performed using

- as-built weld overlay dimensions. Pre- and post- overlay contoum are to be provided for use in evaluation and disposition.

I wm . . . .. n , , gwaw Job No: Plant / Unit STRUCTURAL Georgia Power Company INTEGRITY Plant htch Unit 1 GPCO-20Q401 / ASSOCIATES, INC.

I Drawing No:

GPCO-20Q14

Title:

Standard Weld Overlay Design heet 2 of 2 1

l 1

A :l: B l (Note 1) 45* MIN TYP l I .L t

1

[? .

I g 8; a  ;[

~

/

l g Pipe Safe-end g e' wem Not to Smle my DESION DIMENSIONS

" CHAhACIERIZATION CO N t A B IB31-1RC-12AR-G4 Assumed 360

• Cm., 0.26" 2.0" NA 100% throughwall I flaw h un 96, + oneu ,>:. ~ : w ent >

w <, ~ mm n q%t ,

I ,

1 -

h /p/21)9/ h g[2.T/9[ k/d/> 3 /T/ d trans on O. fM 4h1/ M/kf/ 699/

Revis:on lYepared by/ Date Checked by/ Date Approved by/ Date , COMMENTS l

.. e v f un'4 ces a m -

W ^ da m ) * " ,"* - s* w

1. D#

l cPco-20q Plant / Unit Georgia Power Company STRUCTURAL INTEGRITY

""h Plant Hatch Unit 1 lg aco-20q4ol k/ ASSOCIATES, INC.

Draq No:

cpCo-2Q28

Title:

Standard Weld overlay Design Sheet I of 2

5 NOTES I

1. Blend repair into transition.

I 2. Weld overlay wire ic to be type ER308L, with as-deposited

{

l delta ferrite content greater than 7.5 FN.

l 3. Component surface is to be eramined by dye penetrant method and accepted as clean prior to overlay application in order l to include the entire deposited overlay thickness in meeting the design thickness requirement, per NUREG-0313,1kvision 2.

lg

4. In the event that the original component surface does not pass

.l ,

the note 3 requirements, the first deposited weld layer is to be examined by dye penetrant method and accepted as clean before proceeding with subsequent-layers, l.

l

5. First weld layer fs to have a measured delta furite content greater than 7.5 FN. This requirement ches not apply to the firal layer.

l - 6. ; Design thickness includes no allowance for surface conditioning operations to facilitate Ul' inspections.

I

7. Design length is that required for structural reinforcement;

. l. greater length may be required for effective UT taspection. 'Ihis is tri be determined in the field.

.I l mww . . . . m- m, .

., ~, .

,. e n wwwww abum P14/ Unit arco.20q , N STRUCTURAL cargia Power Cornpany INTEGRITY File N m Plant Hatch Unit 1 GPCO-20Q402 ,,,/ ASSOCIATES, INC.

Drawing N

Title:

Standard Weld overlay Design Sheet 2 of_3_

2 Q 28

"( .

~

.I I

I '

A  ;

a l: B l (Note 1) i 45 ' MIN tit l I _ t_ l t

{' .?  ; '% " ' , i; ' ./'

I; l

[

Pipe l Safe-end

{

g Q WELD Not to Scale I DESIGN DIMENSIONS CHARA TION

~

t A B .-

I. Asstuned 360

• Cire.

Ir~ = tw.12BR-E4 O.27" 2.0" NA 100% throughwall I flaw

--') I kf', '

h ,k ) _g N h,' ,

_E : 1 _  %-_ 'N

[i '{,

4 k 5l [ . 6l ,_

y - (,

t {' f I:

y ) Revised to show

.g .

I f6)/0/23/9I dl22 /g> 5/4/ d14 !@I/4 / safe-end transition 0 ]l0 4llrl9( bllNfl lllk9l l Revision Prepared by/ Date Checked by/ Date Approved by/ Date mam ~ www . . , ww; .

COhBENIS w, e ,

Plant / Unit L _I- cPCO-20Q STRUCTURAL

• l File No:

Go Power Cornpany INTEGiUTY Plan Hatch Unit 1 TCO-20Q401 / ASSOCIATES, INC.

Title:

Stanrinrd Weld Overlay Desig's Sheet 1 of 2 )

I 20Q33

_ es* _

NOTES j 1

l,

1. . Blend repair into transition.

I 2. Weld overlay wire is to be type ER308L, with as-deposited

.l delta ferrite content greater than 7.5 FN.

3. _ Component surface is to be ernmined by dye penetrant method and accepted as clean prior to overlay application in order l to include the entire deposited overlay thickness in meeting the des!gn thinimess requirement, per NUREG-0313, Revision 2.

I

4. In the event that the original component surface does not pass the note 3 requirements, the first deposited weld layer is to be e.rnmined by dye penetrant method and accepted as clean before l- proceeding with subsequent layers.

l 5.- First weld layer is to have a measured delta ferrite content greater than 7.5 FN. 'Ihis requirement does not apply to the final l- layer.

-l- 6. Design thickness includes no allowance for surface conditioning operations to facilitate UT inspections.

7. Design length is that required for structural reinforcement; greater length may be required for effective UT inspection. ' Ibis is to be determined lu the fleid. <

.I rl w w w ann w .

a m ,

m ,

1. D" Plant / Unit GPCO M Q STRUCTURAL File No:

Georgia Power Company Plant Hatch Unit 1 INTEGRITY GPCM&1 / ASSOCIATES, INC.

Drawing No'-

Title:

Standard WeId Overlay Design Sheet 2 of 2 GPCO20Q33

I g

l 1

A :l* B -

l (Note 1) 45 ' MIN TIP l l

_t_ l /d, l t

[ > '* . ! U,

_ [

l C Pipe Safe-end Q WELD I Not to Scale I WELD NUMBER CHARACIERIZATION FIAW DESIGN DIMENSIONS t A B ComN I 1D31-1RC-12BR-A4 Assumed 360

• Circ- 0.27" 2,0" NA 100% through5Ad flaw cy 4 es:w s m w; e m - war; miwfp?6 cmm u ym wat w# # erw ,

~

I

. 1 I 1 Y lef23f]( h fif)5f91 /df> f% he $on 0 hlh YIN % /, Shllff/ b Gfiff7l

g Ref.ston Pmpamd by/ Date Checked g/ Date Approved by/ Date COMMENIS mum m

.m . . x w ase un ,- o,n wa 8 .

1. ** Plant / Unit

-g orcO-20q STRUCTURAL Plan Hatch Unit 1 Power Company ~^

INTEGRITY

/ MGM INC.

l Drawing No-GPCO-20Q401

Title:

s, b20Q42 Standard Weld Overlay Design Sheet 1 of 2 I

NOTES

1. Blend repair into transition.

2. W Id overlay wire is to be type ER308L, with as-deposited l delta ferrite content greater than 7.5 FN.

3. Component surface is to be examined by dye penetrant me.thod and accepted as clean prior to overlay application in orxler

.l to include the entire deposited overlay thickness in meeting the design thickness requirement, per NUREG-0313, Revision 2.

Il

4. In the event that the original component surface does not pass

_l the note 3 requirements, the first deposited weld layer is to be cam 11ned by dye penetrant method and accepted as clean before

-l proceeding with subsequent layers.

l 5. First weld layer is to have : measured delta ferrite content greater than 7.5 FN. '1 bis requirement does not apply to the final

.l layer.

l_ 6. Design tinckness includes no allowance for surface conditioning operations, to facilitate UT inspections.

7. Design length is that required for structural reinforcement:

greater k.ngth may be required for effective Ur inspection. ' Ibis is to be determined in the field.

l: men w x -- w - .> .-

wa r m u l cPco-20q Plant / unit Gergia Power Company

, 5 STRUCTURAL INTEGRITY Plant Hatch Unit 1 g GPco200401 ,/ ASSOCIATES, DiC.

Drawi'ag No- 2 GPC420Q42

Title:

Standard Weld Overlay Design Sheet 2 of

_ , . .._ . _ _ . - _ . . . _ _ _ ._. _ _ ~ . _ _ _ . _ . _ _ _ __ _ _ _ __

t il ,

I I

l APPENDIX B E- General Electric Plant Hatch Unit 1 E Crack Arrest Verification (CAV) System 4IL LI LI LI:

as

.g ll:

g .

SIR-91-077, Rev. 2 -

Th *- RF' ' Dx 13.91 11:41 P.02

. "O DEC 171991

^

b i.. : h;legrity

~

SASR-523-147-1291

' DRF 137-0100 December 1991 I PLANT HATCH UNIT 1 CRACK ARREST VERIFICATION (CAV)

SYSTEM I

SUMMARY

REPORT TUEL CYCLE 13 Report period:

June 1990 to September 1991 I

Prepared by: _ lC I I Don Hale, Lead Engineer -

Materials Monitoring & Structural Analysis Services Verified by:  ! ^& id/v/9 /

Kevin D'las "

' (

I l

Haterials Monitoring & Structural Analysis Services Approved by _

S.Rarganath, Maidagar Materials Monitoring & Structural Analysis services HATREP03.WP1.0 l

_ .__ ____ _____ - __ D

~ -_

Q 0

pfe.49.#p < h* i.

0,6, O  % 9's Y IMAGE EVALUATION T </

$<I9 TEST TARGET (MT-3) e[e;f[" sp<g,

/g s\/////o 9) 4

$ %jgf 1.0 Fa m l.I 5[E0

!m EM li!!M M

l.25 1.4 1.6

=- - - 1 =ss 4 150mm -

< 6" - >

• +

r # n3* /i ~ ~ ~ ~ ~ ~ - --

+ As- .

'N, k,b'r/f}fg c 8 or'y,

/

e V.

$++& +,.

o t

n - -. . - - _ _ _ _ _ __

2dl0 .

a

3-

1.0 INTRODUCTION

A Crack brest Verification (CAV) system was installed at I- Plant Hatch Unit 1 in 1988/89. The system contains three crack growth specimens, has electrochemical potential (ECP) measuremont capability and accommodates inputs from Plent I- Katch water chemistry instrumentation. The system is, connected to an existing recire water chemistry sample lins with flow being returned to the RWCU system.

A separate autoclave is provided in the CAV for ECP measurements. Copper / Copper oxide, Silver / Silver Chloride,

,I and Piatinum reference electrodes and Type 304 and 316HG working electrodes are installed in this autoclave. In addition, the ECP autoclave itwelf (Type 316 stainless oteel) is used as a working electrode.

The CAV system also accepts inputs from the ex(4 ting Plant Hatch Dissolved Oxygen Monitor and Conductivity Monitor to allow these primary system water chemistry parameters to be

'Jnaluded in the CAV data base.

The CAV system began operation on November 16, 1989. '

I: Information covering this initial paried of operation was auzmarized in a previous report (1). The present report acvars oparation of the CAV system during fuel cycle 13

only.

l'-0 XESDLTS '

2.1 General '

Pertinent parameters for the thres, specimens included in the CAV system are. summarized in table 1.

Table 1. Crack Growth Test Specimen Details Specimen Material Condition Stress Intensity 3

SS-144 T-304 Sensitized 20 l stainless steel (1200F, 16 hrs) kaiVin E

SS-126 T-316NG Simulated Wold 20

' stainless steel sensitization kaiVin (1200F, 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />)

INC-76 Alloy 25 182 ksiVin l

I

' E NO - Dec 13,91 11:42 P,04 I 2.2 Crack Growth s I The crack Length versus Elapsed Time data for the three crack g:tovth specimens are shown in Figures 1, 2 and 3. ELJ of these three figures is divided into regions representing I normal watbr chemistry (NWC) and hydrogen water chemistry (HWC) operation periods. Note that the key operating parameters c@.anged many times over fuel cycle 13, these I different oberational regions are identified in Appendix A.

2.3 WaterJ,'homistry/EcP i

I The electre. chemical potential (ECP) data are summarized in Figure 4. E r s611d line in Figure 4 represents the data from the Type 304 stainless steel working electrode. The I other symbols represent the data from the ECP autoclave itself. It should bs, noted that this vessel is made from Type 316 stainless steel and is grotmded to the Plant Hatch I primary piping compared to the Type 304 working electrode which is isolated from the plant piping.

I Figure 5 summarizes the hydrogen injection rate into the Plant Hatch Unit 1 primary system, these valuer. represent corrected values which take into account calibration shifts observed by plant personnel and the aubsequont corrections l made in the plant data base.

E The reactor recirc water dissolved oxygen and conductivity E data for this time period are shown in Figures 6 and 7, respectively. Note that these signale are provided to the CAV system from existing Plant Hatch Unit 1 instruments.

3. DISCUSSION 3.1 Effect of Hydrocen Water Chemistry on Crack Growth.

The crack growth data from the welding alloy 182 specimen (Figure 1) show a clear effect of hydrogen injection on l crack growth. Figure 8 is an expanded view of the data from Figure 1 which shows the distinct change in slope which occurs shortly after the start of hydrogen injection in I August 1990 (T = 799 hours0.00925 days <br />0.222 hours <br />0.00132 weeks <br />3.040195e-4 months <br />). The steady state crack growth rate

• drope a factor of =20 beginning shortly af ter the start of hydrogen injection.

I 3 *The range on growth rate shown in a l figures represents a i 3 sigma interval about the mean value. In statistical terms l3 this means that there $s a *99.9% confidence that the actual value falls within this interval.

I I -

I

• Figure 9 shows the data frc~ th6 two stainless steel specimens covering this sat. time paried. Here there is no I distinct difference between the NWC (i.e 200 part/ billion s

oxygenated water) s.,d HWC (Hydrogen Water Chemistry) periods.

However, the growth rate, even in the NWC environner t is

-g very low in both stainless steels and is, in fact, near the

. limits of detectabi) tty of the potential drop technology.

E yor exampia, the growth rates represented in rigure o i

' correcpond to less than 1 mil of measured crack inxtension 1 over the 800 hour0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br /> duration of the initial NWC region (i.e. 1 l til in 800 hours0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br /> is =11 mil / year). Existing SCC models (GENE PLEDGE) would predict a growth rate of about 32 ril/ year depending on the value of conductivity assumed. It is, I therefore, somewhat unexpected to see growth rates this low for these two materials.

I Figure 10 is an expanded view of another region of .the data from Figure 1 covering a time period =2400 hours later when hydrogen injection is stopped. While interruptions in I hydrogen injection have-occurred, the specimens at this point in time have accumulated over 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br /> of HWC exposure. The nominal growth rate for this alloy 182 material under HWC conditions has now dropped another facter

-l of =10 to a nominal 2 mil / year value. Thts suggests thot for this material, while there is an immediate decrease in SCC gro.ith rate as soon as HWC begins, additional decreases g occur the longer HWC is maintained.

The data from the two stainless specimens in this same time I region was examined and found to be inconclusive in terms of any detectable differences in crack growth rates due to the HWC-to-NWC transition.

An example of another HWC/NWC transition is shown in Figures 11, 12 and 13. Here the response of the three materials is l seen in the March / June 01 time frame where the plant operated under NWC conditions for over a month. 3!WC resumed for about one weak, was suspended for =0 weeks and then reestablished again for 6 weeks.

-l:

Once again, the alloy 182 crack growth (Figure 11) tracks the changes in water chemistry almost immediately. Distinct

.I growth ratesinobserved decreases slope are seen o ch time NWC is initiatod. The unde- Wng term NWC are still less that those observed durin .nitial NWC exposure suggesting that there is some linger ng benefit of exposure to HWC.

I I +

,y . . . . . . . . , . . . . . _ . . .. . . . . . . . . . . _ . .

_ _ . . _ ~ . . . . . . . ,

l TEL No, Dec 13 91 11:43 P.06-

)

f ,

L  :

' Extensive GENP, laboratory experienct with alloy.182 crack L '

growth specimens has shown that the potential drop toch ique tends to underpredict crack growth, in some cases by as much as a. factor of 2. This is due to the interdendritic nature of-the alloy 182 fracture surface and the inherently uneven,

- - multiplanar geometry. This geometry leaves patches of unbroken anterial behind the primary crack front which

.evidentlyfcontinue to conduct current thereby-producing a

. potential drop reading normally associated with a shorter

-crack. Therefore,-it is likely-that the'true NWC growth rates in tha; alloy 182 are even greater than those

-I calculated in these figures.-If this is the case, then the- s absolute amount of crack growth mitigated by NWC is likely

-to be even greater.than the values calculated in the preser.:

figures would:suggest.

The Type 304 and 316NG stainless steel data (Figure 12 and

13) are still exhibiting very low growth rates both in NWC

I:

and HWC However, there now appears to be a slope difference between-the NWC and HWC regions are very low and the-variance on,-but once again the slopen verythe rates large.

I ICP Considerations.

E' . Electrochemical' Potential (ECP) is the primary criterion 15

'used-to assess the degree to which HWC protection is-

g. maintained. The EPRI' guidelines'specify that the ECP be

-3 maintatined at -250 av-5HE or. lower for full HWC protection.

iThe Plant Hatch Unit 1 CAV system uses a Type 304 stainless steel working electrode and a copper oxide reference-i electrode as the primary means for making this measurement.

Also included in the CAV ECP electrode-complement is a-platinua reference electrode which-allows the EcP to be Lindependently: checked.- The:ECP vessel itself is'also used as

' a working-electrode to allow an ECP measurement to be made which. represents the grounded recirc piping system itself.

ii Table 2;isfe' summary of-CAV ECP measurements made over Fuel-

' Cycle'13. The 304 stainless steel /platinua values were-calculated based upon an assumed value in the recirc system

I

.of 100 part/ billion hydrngen. This-value is not-actually measured at Plant Natch but.a 100 ppb value'is reasonable J

-based.upon. experience at other BWRs. Also shown in table 1-y 1

is the vessel ECP referenced to the copper oxide electrode l and'the hydrogen injection rate associated-with the Jindividual readings.

LI!

I

I

' TEL No. Dec 13 91 la:M P.07 Table 2. Plant Hatch Unit 1, Fuel C)cle 13, ECP Results (all values av8HE**)

Test T304/Cu Hours T304/Pt* Vessel /Cu Hydrogen I

Injection (sef a)-

500 +78 N/A +71 900 -175 -202 0(NWC)

-208 16 1200 -371 -402 -401 1700 22

-477 -491 -424 I 6100 8750

-466

-191

-397

-298

-409

-312 16 16 16 Replaced copper oxide ret t 9049 I 9550 10000 10251

-310

-213

-291-

-312

-262

-317

-251

-123 16 12

-195 16

• Calculated for an assumed 100 ppb hydrogen level.

• • SHE = Standard Hydrogen Electrode I

There in Figureresults, and the more comprehensive plot of these data 4, indicats

-I that full protection was achieved at 16 sefm until late in the fuel cycle when the vessel- (i.e.

ground) reading drifted out of protection. This is I consistent with previous experience at other BWRs which indicates that late in the fuel cycle, more hydrogen must be injected to maintain the ECP levels previously achieved earlier in the cycle at lower levels.

Table 3 represents a summary of the entire fuel cycle in terms of CAV availability and amount of time on HWC.

I'- Table 3. Plant Hatch Unit 1, Fuel Cycle 13, CAV/HWC Operating Summary.

.l-m fotal durs. tion, fuel cycle 13 (June 1, 1990 *:o September 18, 1991) 11376 hours Total time CAV on line 4866 hours0.0563 days <br />1.352 hours <br />0.00805 weeks <br />0.00185 months <br /> Total time CAV&HWC on line 4691 hours0.0543 days <br />1.303 hours <br />0.00776 weeks <br />0.00178 months <br /> HWC Availability 4691 / 11376 = 41%

I

, TEL No. Dec 13 91 11: 45 P.08-L g.- -

I 4.0 stDO(ARY E The CAV system at Plant Hatch Unit 1 has provided data which E support the following conclusions:

I 1.-Inplementation of hydrogen water chemistry (HWC) has resulted in significant decreases in stress corrosion crack growth in alloy 182 from rates as high as 138 mil / year prior to HWC to very low growth rates after long periods of time-f on HWC.

2. When HWC is suspended, the alloy 182 growth rates I increase again, although not to their former pre-HWC values.

These new values are on the order of 19 mil / year.

I 3. over the last several thousand hours of the fuel cycle, the alloy 182 post-HWC growth rates are much lower than those seen in the pre-HWC period. Ho' 7 var, they do appear to I be increasing with time. This may be an indication of a residual benefit to the long exposure period to HWC conditions.

l 4. The growth rates measured in either the sensitized Type 304 stainless steel or the simulated weld sensitized Type 316 NG stainless steel were very low and ,therefore, I displayed significant variability. It was not possible to detect significant differences in growth rate between the HWC and normal water chemistry (NWC) conditions. This may be I due to the-excellent water chemistry control (low water conductivity) seen during the current fuel cycle.

I S. The ECP levels measured during the current fuel cycle, at hydrogen injection levels of 16 scfm or-greater, were sufficient to achieve full protection until late in the fuel cycle. This was true for the isolated Type 304 stainless I- steel electrode as well as the grounded Type 316 stainless steel ECP vessel.

I' 6. Although the HWC system was on line 41% of the time, the alloy 182 crack growth data, showed significant reductions in crack growth. This suggests that a substantial amount of j- crack propogation was avoided even though HWC was only on line for part of the operating time.

5.0 REFERENCE 8

). Hale, " Plant Hatch Unit 1, CAV Progress Report #1",

42 E Report SASR-91-04, January 1991.

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6000 h000 8000 segg 10000 z3000 HOURS Figure 1.Stress PlantIntensity Hatch Unit 1 CAV, Cra@ Length Versus Time Data, Fuel Cycle 13 25 kst/in. , Alicy 182, Specimen IIUC-76, 4

M m m M ' -

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0 1000 2000 3000 4000 5000 6000 7000 0000 3000 10000 11000 f-HOURS -

i

(

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c Figure 2. Plant Hatch Unit I CAY, Crar.k length Versus Time Data, Fuel- Cycle

, Type 13 304 Stainless Steel (sensitized), Specimen SS-144 Stress Intensity 20 ksi/in.

g .. .

g- g .g g _g . .m g

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o Figt M 3.Specimen Plant Hatch Unit 1 CAV, Crack Length Versus Time Data, Fesel Cycle 13 SS-126, Stress Intensity 20 ksi/in.

ed

, Type 316MG Stainless Steel,

a TEL No. Dec 13.91 11: 47 P.12 f les s9 vs Cu E isa -

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a reca geee ssee seen som ireee HOURS I Figure 4. Plant Hatch Unit 1 CAV, Electrochemical Potential (ECP) Data, Fuel Cycle 13.

.n_

.g .g g m'. m g- M -E E' E 50 m

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0 2000 4000 6000 8000 10000 12000 HOURS Figure 5. Plant Hatch Unit 1, Hydrogen Addition Rates, Fuel Cycle 13.

M.'M ;M.- M. M M - 'M . M M M 'M M M. M. .

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0 2000 4000 6000 8000 10C09 12000 C.

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Figure 6. Plant Hatch Unit 1 CAV, Dissolved Oxygen Data, Fuel Cycle 13 3

3 M M M M M M M M M M M M M M M m -W

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o Figure 7.

Plant Hatch' Unit 1 CAV, Conductivity Data, Fuel Cycle 13.

~ -

- - ---- -=- -

TEL No.

Dec 13 91 11:49 '.16 g

I I ,

.882 '

I da/dt - 135/138 mil / year HWC n .977 - \

E .

w I'

F da/dt = 15 5/25 mil / year

@ .s72 - K _

W

.J

'I x U

C Cr U .867 -

da/dt = 187/196 mil / year I ,

.es2 ' ' ' ' ' ' ' '

o '

100 gee sea 400 sea see 700 sea sea lace g HOURS I

I Figure 8. Plant Hatch Unit 1 CAV, Expanded View of Alloy 182 Crack Length Versus Time Data For initial Application of Hydrogen Water Chemistry.

I ~15-

4 . - - - - - . .. .

7 erp. n ao s.s.

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see toes saae itse i -

HOAS 1<

Type 304 S.S.

.P42 da/at - 441 - + st mtyr.ar 1 da/dt = 0.34*l.64 mil / year

., s f. .*'

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a res see see see inee itse ties HOURS Figure 9. Plant Hatch Unit 1 CAV, Expanded View of Type 304 and 316HG Stainless Steel Crack Length versus Time Data For Initial Application of Hydrogen Water Chamistry.

66 60 9 .

ves 60eva aa.:)v 7.ao I

I I a = '

I da/dt = 18/19 mil / year l

n .BBS -

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.886 -

i gl i i da/dt = 0 21/3 3 nul/ year

~g: ....

2500 3000 3500 4000 ,

4500 5000 HOURS I

3 .

I

'I- Figure 10. Plant Hatch Unit 1 CAV, Expanded View of Alloy 182 Crack Length Versus Time Data For Time Period After Resumption of Normal Water Chemistry, October / November 1990. ,

I .

~

l.

I

., E E E

,, u s - a u -

1 o A 4 4 4 4 3 4 i i I l l 1 i

~

da/dt = 8.46-6.2 mD/ year ,._a.

• y; '+

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da/dt = 46.1-49.6 m!!/ year b

i s

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is

.;gure 11. Plant Hatch Unit 1 CAV, Expanded Vlev of Alloy 182 Crack Len7th Versus Time Data For Time Period After Resumption of Normal Water Chemistry, March / June 1991.

I I

4 4 4 M 4 4 5 e 2 A c g 4 4 a 4 4 4 4 4

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, da/dt = 0,62-148 mil / year da/dt = 0.M-4.1 mu/ year

,743 *

. i . .

5998 8598 Fees- 73pe eget 0599 HOURS B

u Figure 12. Plant !!atch Unit 1 CAV, Expanded View of Type 304 I .

Stainless Steel Crack Lan Time Period After Resumptmon Chemistry, March / June 1991.

g Versus of Normal Time Data For Water D'

I

p ,

g go, Dec 13 91 11:51 P.21 A

I I

E I E

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i da/dt = 0.34-1.36 mu/ year de/dt = 3.1-7.3 mil / year I .,,, . .

HOURS I

Figure 13. Plant Hatch Unit 1 CAV, Expanded. View of Type 316HG Stainless Steel Crack Length Versus Time sI Data For Time Period After Resumption of Normal 4 Water Chemistry, March / June 1991 Appendix A, Fuel cycle 13, operating History.

Region Start Stop

-I (Test (Test Remarks

, Hours) Hours)

I' N/A 6/1/90 6/29/90 Plant startup to begin Fuel cycle 13, Normal Water j Chamistry (WWC) operation 1 6/29/90 8/1/90 Start CAV syatem, operation (0) (798) on NWC 2 8/1/90 8/9/90 started hydrogen addition (799) (984) 8 16 SCFM.

3 8/9/90 8/15/90 started Eine addition, (985) (1128) hydrogen increased to 22 SCFM 4 8/15/90 8/27/90 continued Zinc, hydrogen to (1129) (1418) 18 SCFM 5 8/27/90 8/31/90 Isolated ECP vessel to '

(1419) (1516) replace reference electrode 6 8/31/90 9/12/90 continued Zinc, hydrogen (1517) (1812) dropped to 16 8CFM 7 9/12/90 9/14/90 Continued Zinc, returned to (1813) (1844) MWC 8 9/14/90 9/15/90 Continued Zinc addition of (1845) (1869) hydregen resume,d S 8 SCFM 9

9/15/90 9/21/90 Continued Zinc, returned to (1970) (2023) NWC I 10 9/21/90 (2024) 9/27/90 (2160)

Continued Zinc, addition of hydrogen resumed 8 12 SCFM

,E 11 9/27/90 E 10/4/90 Continued Zinc, addition of (2161) (2332) hydrogen increased to 16 SCFM I

I I

' TEL No. 5ec13.9111152 P.23 Appendix A, (continued) i {

.12 10/4/C0 10/22/90 continued Zinc, returned to  !

I- (2333) (2762) MC, two startups during I

interval 13 10/22/90 11/7/90 Continued Zinc addition of

, (2763) (3119) hydrogen resume,d e 16 sCFM I 14 11/7/90 (3150) 12/6/90 (3852)

Continued Zinc, zeturned to MC I 14a 12/6/90 (3953) 12/7/90 (3864)

Special 14 hour1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> hydrogen injection test I 15 12/7/90 (3865) 1/16/91 (4823)

Resumed W C operation 16 1/16/91 1/26/91 CAV Cut of Service (4824) (5058) 17 1/26/91 2/12/91 Continued WC operation (5059) (5473) 18 2/12/91 2/25/91 CAV out Of Service (5474) (5791) 19 2/25/91 2/27/91 Continued WC operation (5792) (5836) 20 2/27/91 3/7/91 CAV Out of Service I 21 (5837) 3/7/91 (6025) 3/12/91 (6026) Resumed addition of hydrogen

-(6149) 0 16 SCFM 22 3/12/91 3/20/91 Resumed W C operation (6150) (6340) 23 3/20/91 4/4/91 CAV Out Of Service (6341) (6703) -

24 4/4/91 4/15/91 Resumed W C operation (6704) (6963) 25 4/15/91 4/21/91 Resumed addition of hydrogen (696'4) (7116) t 16 SCFM

,l I

I _22 L _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

'em - TEL No.

g. Dec 13,91 11:53 P.24

\

Appendix A, 26 (continued) 4/21/91 5/4/i1 (7117) (7416) Rasumed WC operation

'27 5/4/91 (7417) 6/12/91 (8364) Resumed 9 16 SCFM addition of hydrogen 28 6/12/91 6/14/91 (8365) (8400) Plant shutdown 29 6/14/91 6/17/91 (8401) (8466) Rasumod W C operation 30 6/17/91 6/20/91 (8467) (8539) Resumed addition of hydrogon 31 0 16 SCFM 6/20/91 t>/21/91 .

(8540) (8565). Resumed M C operation 32 6/21/91 6/26/91 (8566) Resumed 33 (8682) 9 16 SCFM addition of hydrogen 6/26/91 6/26/91 l8683) (8692) Resumed WC operation 34 6/26/91 7/1/91 (8693) (8799) Resumed addition of hydrogen I 35 7/1/91 (8800) 7/11/91 9 16 SCFM j (9049) Resumed e 8 scFM addition of hydrogen 36 B 7/11/91 7/16/91 (9050) (9174) CAV out of service I 37 7/16/91 (9175) 8/9/91 (9750) Resumed addition of hydrogen 0 16 SCFM I 38 8/9/91 (9751) 8/13/91 (9845) Plant shutdown 39 8/13/91 8/26/91 (9846) (10143) Resumed addition of hydrogen 40 9 12 SCFM 8/26/91 8/27/91 (10144) (10167) Resumed WC operation I

I E

-=>-

- -- E

^ ^

,, ~TEL'No. ,

Dec 13.91'11:53 5,25 I ,

1 Appendix A, (continued)

,l. 41 8/27/91 9/10/91 Resumed addition of hydrogen (10168) (10517) 9 16 SCFM

'l d2 9/10/91 (10518) 9/18/91 (10656)

CAV out of service

• 43 9/18/91 Plant shutdown to begin (10696) refuel outage I l I

I I

I I

I lI I

I I

I

.I l _

-u-v'Ci' = - - - . , _ _ . _ _ _ _ _ _ _ .