ML20012A321

Nonpropietary Rev 1,Suppl 2 to Reconciliation of Fatigue Crack Growth Results for South Texas Project Unit 1 Surge Line.

ML20012A321
Person / Time
Site:	South Texas
Issue date:	02/28/1990
From:	Coslow B, Tilda Liu, Witt F WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
Shared Package
ML19293A180	List: ML20012A300 ML20012A307 ML20012A321
References
WCAP-12087-R01-S02, WCAP-12087-R1-S2, WCAP-12087-S02, WCAP-12087-S2, NUDOCS 9003090228
Download: ML20012A321 (13)

Text

WESTINGHOUSE CLASS 3 i

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,  : WCAP-12087:

Rev. 1, Supp. 2-1.-

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RECONCILIATION OF FATIGUE CRACK GROWTH LESULTS FOR THE SOUTH TEXAS PROJECT UNIT 1 SURGE LINE February, 1990 F. J. Witt B. J. Coslow T. H. Liu L. M. Valasek

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Approved by: [ a< msA

5. A. Swamy V / 5. 5. YaTus Wy, Manager Structural Materials-

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Engineering Work Performed Under Shop Order HHSP961 l'

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I WESTINGHOUSE ELECTRIC CORPORATION Nuclear and Advanced Technology Division P.O. Box 2728 Pittsburgh, Pennsylvania 15230-2728 I- . e 1990 Westinghouse Electric Corp. ,

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TABLE OF CONTENTS Section Title Page

. EXECUTIVE

SUMMARY

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1.0 INTRODUCTION

1 2.0 DESIGN TRANSIENTS 3

3.0 STRESS ANALYSIS ,

3 4.0 RE-EVALUATION OF FATIGUE CRACK GROWTH 5 -

5.0 DISCUSSION AND CONCLUSIONS 5

6.0- REFERENCES f

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LIST OF TABLES' 4

. Table Title Page Heatup/Cooldown Transients for Past Operation 6 1 --

'of Unit 1 2' RCP Start /Stop Transients for Past Operation 7 of Unit 1 Worst Case Fatigue Crack Grovith Results for an 8

-3 laitial Crack 10% of the Wall, South Texas Project Unit 1

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EXECUTIVE

SUMMARY

Thermal stratification was evaluated for the surge line of South Texas Project Units 1 and 2 on the basis that each unit had a single vertical rigid support ir c a surge line configuration. However, Unit 1 operated for almost two years with two rigid supports in the surge line configuration, a difference which impacts the fatigue crack growth as originally obtained. This supplementary report to the original evaluation reconciles the original fatigue crack growth with the fact that Unit 1 operated two years with the two rigid supports-in the surge line configuration.

The operating history of Unit 1 for the first two years was reviewed and thermal stratification transients were determined for that period. Stress analyses were performed for these transients. Conformance to ASME code.

criteria was assessed. Fatigue crack growth analyses were performed which

, accounted for the first-two years of operation followed by the remaining service life.

.The ASME code criteria were mat. It was determined that the NRC recommended allowable of 60% of the wall for end-of-service fatigue crack depth was met by a large margin.. These results for Unit 1 also envelope Unit- 2 which had two rigid supports prior to criticality. Furthermore the. original leak-before-t break analysis of the thermal stratification evaluation is not impacted by the-initial years of service of Unit 1.

The major finding of this report is that the prior leak-before-break related l

conclusions regarding. thermal' stratification'as applicable to South Texas Project. Units 1 and 2 remain valid and are unchanged.

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1.0 INTRODUCTION

Fatigue crack growth results due to thermal stratification were presented for.

South Texas Project Units 1 and 2 in WCAP 12067, Revision 1 (Reference 1). It

.was demonstrated that the fatigue crack growth met by a large margin the NRC recommended allowable of 60% of the wall for the end-of-service fatigue crack depth (Reference 2). These evaluations were made for the one vertical rigid support configuration currently typical of both units. However Unit 1 operated for about two years with two rigid supports in its surge line configuration. This mode of operation impacts the fatigue crack growth evaluation as-originally presented in WCAP 12067, Revision 1.

The objective of this supplement to WCAP 12067, Revision 1 is to reconcile fatigue crack growth analyses of that report with the service-to-date and anticipated service of Unit 1. The initial service conditions of Unit 1 were reviewed and appropriate thermal stratification transients were determined.

Stress analyses were performed for these transients. ASME code evaluationt.

were made. Fatigue crack growth evaluations were performed appropriate for Unit 1. The impact on the original evaluations are discussed and conclusions are drawn.

2.0 DESIGN TRANSIENTS

.In this section the methods used to update the surge line design transients for past operation of South Texas Unit 1 are discussed. Specifica1',j, the design transients developed in this section are intended to conservatively represent those experienced by the Unit 1 surge line prior to removal of rigid support HL 5001 (see Section 3.0 for discussion of rigid supports).

Section 1.0 of WCAP 12067, Revision 1 (Reference 1) presents the methods used to update design transients for evaluation of thermal stratification for the surge lines at South Texas Units 1 and 2. That evaluation was based on a single rigid support in the surge line. The transients developed in this section were used to reconcile the evaluation of Reference 1 to account for approximately two years of Unit 1 operation with two rigid supports. ,

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For Unit

• H?Hficant operating history has occurred since hot functional .;

testtng 9 a n y 1987. This operating history was reviewed for its effect on the design transients previously developed for Unit 2. Operating logs were j reviewed to determine maximum estimated temperature differences between the  !

pressurizer and the reactor coolant loop (RCL) hot leg during past heatups and cooldowns on Unit 1. Based on this information, a set of updated design j transients was developed for Unit 1 to represent the effect of past heatups and cooldowns.

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ja,c.e For future operation at Unit 1, the transients presented in tables 1-3 and 1-4 of WCAP 12067~(Reference 1) are considered.

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3.0 STRESS ANALYSIS

.The pressurizer surge piping layout of South Texas Project Unit 1 is identical to that of South Texas Project Unit 2. The original surge line support configurations of both units consisted of two vertical rigid supports (HL 5001 and HL 5004); however rigid support HL 5001 of Unit 2 was removed prior to criticality. Rigid support HL 5001 of Unit I was removed after about two years of operation such that the surge line support configurations of both units are now identical, t

A plant specific structural analysis was performed for the Unit 1 surge line to determine the effects of thermal stratification for its original support system '

based on the transients developed in Section 2.0. The local stresses due to the

-non-linear portion of the radial temperature distribution in the pipe cross-section were recalculated for the transients and stratification delta Ts developed in tables 1 and 2.

Fatigue usage factors were calculated for the combined effects of operations prior to the removal of the support and future operations (with system delta T limits of 320'F maximum) with one support acting. The evaluations were performed at the surge line RCL hot leg nozzle safe-end (nozzle to pipe weld) and-the first long radius elbow from the RCL hot leg nozzle. The total fatigue usage factors calculated at both locations were less than one and hence meet ASME Section III fatigue requirements as stated in subsection NB-3600. Additionally, pipe stresses were shown to satisfy ASME Section III limits.

4.0 RE-EVALUATION OF FATIGUE CRACK GROWTH Fatigue crack growth results were presented in WCAP-12067, Rev. 1 (Reference 1) for forty year service of the pressurizer surge lines of South Texas Project Units 1 and 2 including consideration of thermal stratification. The maximum wall penetration met by a large margin the NRC recommended allowable of 60% of the wall thickness for end-of-service fatigue crack depth (Reference 2). The analyses were based on a one rigid support configuration. However Unit I had a two rigid support configuration for the initial two years of service. The impact of the initial operation of Unit 1 on the fatigue crack growth assessment presented in Reference 1 is discussed below.

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~The initial operating history of South Texas Project Unit I was reviewed and thermal transients appropriate to the pressurizer surge line with two rigid supports were developed in Section 2.0. Stress analyses were performed as discussed in Section 3.0 to account for these transients in updating the fatigue crack growth calculations for Unit 1.

The same approach was used for the South Texas Project Unit 1 fatigue crack growth re-evaluation as was for the original fatigue growth analyses as described in Reference 1. Specifically, the evaluations of Section 3.0 of this supplement provides the stresses for the original support configuration. Section 2.0 of Reference 1 provided the stresses for the modified support configuration.

Fatigue crack growth calculations were made with the initial two years having the original two rigid support configuration and the additional thirty-eight years having the one rigid support configuration. For conservatism the one-support configuration was actually evaluated for forty year service. The fatigue crack growth evnluations were made at the most critical locations as discussed in Reference.l.

-The results are presented in Table 3. The results again met the NRC recommended allowable by a large margin. These results envelope Unit 2 for its short time of operation with two rigid supports prior to criticality.

In conc 1"sion, anticipated fatigue crack growth is reasonably small for the South Texas Project Unit 1 pressurizer surge line for full service life including the presence of thermal stratification. Leakage caused by fatigue crack growth would not be expected.

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L 5.0- DISCUSSION AND CONCLUSIONS

. The thermal stratification transients associated with the two rigid support configuration of the pressurizer surge line of the South Texas Project Unit 1.

.during its first two years of operation have been determined. Stress analyses for the supoort configuration and transients were performed. ASME code criteria were shown to be met. Fatigue crack growth analyses were performed which accounted for the two years of service with the two rigid support configuration and the remaining time with the one support configuration. The fatigue crack growth met the NRC recommended allowable by a large margin. The results envelope Unit 2 fatigue crack growth.

The leak-before-break analysis of WCAP-12067, Revision 1 is not impacted by the first two years of service of Unit 1.

In summary, the conclusions of WCAP-12067, Revision 1 regarding leak-before-break remain valid and are unchanged.

6.0 REFERENCES

1. R. L. Brice-Nash et al, Evaluation of Thermal Stratification for the South Texas Units 1 and 2 Pressurizer Surge Line, WCAP-12067, Revision 1, January,1989 [ PROPRIETARY)

2. Letter: N. Prasad Kadambi, NRC Division of PWR Licensing to J. H.

Goldberg, Houston Lighting and Power Compan:r, Docket Nos. 50-498 and 50-499, Subject-South Texas Project Units 1 and 2, Alternative Pipe Break Criteria, July 10, 1986.

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TABLE 1 HEATUP/COOLDOWN TRANSIENTS FOR PAST-OPERATION OF UNIT 1-HEATUP C00LDOWN

. TRANSIENT SYSTEM' TRANSIENT SYSTEM-CYCLES. DELTA T ('F) CYCLES DELTAT('F)

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• System delta T for these transients is above any previously considered in Reference 1.

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TABLE 2

.-RCP START /STOP TRANSIENTS FOR PAST OPERATION OF UNIT 1-

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r4 A11 'of these transients are postulated to'have occurred before removal of the rigid support during the February 1989 outage.

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TABLE 3 WORST CASE FATIGUE CRACK GROWTH RESULTS FOR AN INITI AL CRACK 10% OF THE WALL, SOUTH TEXAS PROJECT UNIT 1 Location Position Initial Initial Final (40 yr) Final Flaw Size Flaw Size Flaw Size Flaw Size (in) (% of Wall) (in) (% of Wall)

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