ML20043G332

Nonproprietary Suppl 3 to WCAP-12247, Supplementary Assessment of Leak-Before-Break for Pressurizer Surge Lines of Unit 1.

ML20043G332
Person / Time
Site:	Comanche Peak
Issue date:	06/30/1990
From:	Palusamy S, Schmertz J WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
Shared Package
ML19298E149	List: ML20043G313 ML20043G323 ML20043G332
References
WCAP-12247-S03, WCAP-12247-S3, NUDOCS 9006200162
Download: ML20043G332 (22)

Text

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i WESTINGHOUSE CLASS 3 ,

.WCAP 12247 )

Supplement 3 )

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A SUPPLEMENTARY ASSESSMENT OF LEAK-BEFORE-BREAK FOR THE PRESSURIZER SURGE LINE OF COMANCHE PEAK UNIT 1 June 1990 D. C. Showmick  !

S. A. Swamy J

.. l Verified by: 3.2., C l b i

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1 Ji/U. Schmert2 L. '

Approved by: If /w m res

/ 5. 5. Palusaig y Nanager Structural Mechanics and Diagnostic Technology Work Performed Under Shop Order JTGP2920E q

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m WESTINGHOUSE ELECTRIC CORPORATION 1

Nuclear and Advanced Technology Division n.-

• P.O. Box 2728 Pittsburgh, Pennsylvania 15230-2728 i

e 1990 Westinghouse Electric Corp.

9006200162 900615 PDR ADOCK 05000445 P PDC.- f

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1 This nonproprietary report bears a Westinghouse copyright notice. The NRC is permitted to make the number of copies of this report necessary for its internal use and such additional copies which are necessary in order to have one copy available for public viewing in the appropriate docket files in the public document room in Washington, D. C. and in local public document rooms as may be required by NRC regulations if the number of copies submitted is insufficient for this purpose. The NRC is not authorized to make copies for the personal use of members of the public who make use of the NRC public

' document rooms. Copies of this report or portions thereof made by the NRC must include the copyright notice.

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.- TABLE OF CONTENTS Section Title Page-

SUMMARY

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1.0 BACKGROUND

AND INTRODUCTION 1 1.1 Background 1 )

1.2 Introduction 2 4

2.0 LEAK-BEFORE-BREAK ASSESSMENT FOR ADDITIONAL 3 l FAULTED LOADINGS  !

.I 2.1 Introduction 3 2.2 Loading Conditions 3

• 2.3 Loads' 3 i 2.4 Leak Rate Calculations 4 l 2.5 Stability Evaluations 4 2.5 Margins 4 1

1 3.0 DISCUSSION AND CONCLUSIONS 4 .l

4.0 REFERENCES

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I APPENDIX A - NRC REQUEST FOR ADDITIONAL INFORMATION A-1 l

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g LIST OF TABLES Table Title Page-1 Types of Loading 6 i l

2 Normal and Faulted Loading Cases for Leak-Before-Break 7 l

Evaluations 3 Associated Load Cases for Analyses 8 ,

4 Summary of Loads and Stresses at the Critical Location 9 .

5 Load Cases, Location and Temperatures Considered ior 10 Leak-Before-Break Evaluations -l

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[ 6 Leakage Flaw Sizes, Critical Flaw Sizes and Margins 11 I

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LIST OF FIGURES-  !

Figure Title Page Sketch of Analysis Model for Comanche Peak Unit 1 1 12 Pressurizer Surge Line Showing Node Points, Critical Locations, Weld Locations and Types of Welds 2 Critical Flaw Size Prediction including Application of Z Factor 13 n

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SUMMARY

.- Thermal stratification effects on the Comanche Peak Unit 1 pressurizer surge line were addressed and leak-before-break was established in Westinghouse topical report WCAP-12248. The NRC reviewed and concurred with the conclusions of WCAP-12248.

In May,1990, the NRC suggested that. additional margins for leak-before-break be demonstrated by evaluating the surge line for higher temperature differences under faulted conditions. Specifically, the NRC requested that the faulted loading conditions should include pressure, deadweight, thermal expansion'(including thermal stratification with a differential temperature of 320'F) and Safe Shutdown Earthquake loads for flaw stability analysis. The

- corresponding leakage size flaw should be based on case "B" in Table 5-7 of WCAP-12248 (also i'ncluded in Table 2 of this report) to demonstrate margins'on, flaw size. As suggested by .the NRC additional margins have been demonstrated l in this report for the higher temperature difference of 320'F in combination with pressure, deadweight and SSE. A margin of a factor of 2 on flaw size is established even for this loading combination which has a low probability of occurrence.

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1.0 BACKGROUND

AND INTRODUCTION t . . -

1.1 Background The pressurizer of a Westinghouse type pressurized water reactor mair.tains and

! controls pressure in the reactor coolant system (RCS) via the pressuriter surge line which connects to a hot leg of the primary loop. The pressure is maintained such that boiling is suppressed and departure from nucleate boiling is prevented.

The pressurizer vessel contains steam and water at saturated conditions with the steam-water interface level between 25 and 60% liquid volume depending on the plant operating conditions. From the time the steam bubble is initially

- drawn during the heatup operation to hot standby conditions, the level is maintained at approximately 25%. During power ascension, the level is increased to approximately 60%.

." Thermal stratification in the pressurizer surge line is the direct result of e

the difference in densities between the pressurizer water and the generally

. cool er hot leg water. The lighter pressurizer water tends to float on the cooler heavier hot leg water. The potential for stratification is increased as the difference in temperature between the pressurizer and the hot leg increases and as the insurge or outsurge flow rates decrease.

At power, when the difference in temperature'between the pressurizer and the hot leg is relatively small (less than 50'F) the extent and effects of stratification have been observed to be smal_1. However, during certain modes of plant heatup and cooldown, this difference in temperature can be as large as 320'F end-to-end, in which case the effects of stratification must be accounted for.

Thermal stratification was addressed for Comanche Peak Unit 1 in WCAP-12248, (Reference 1). Fatigue usage factors, striping and fatigue crack growth were evaluated for the service conditions of Comanche Peak Unit 1. Leak-before-

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break was also established for Comanche Peak Unit 1 in WCAP-12248.

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- . TV Electric submitted WCAP-12248 to_the Nuclear Regulatory Commission (NRC).

The NRC reviewed and accepted the conclusions of WCAP-12248. At the request  !

- of the NRC, additional information and clarification were provided in WCAP-12248 Supplements 1 and 2 (references 2 and 3).

l In May 1990, the NRC suggested that additional margins for leak-before-break be demonstrated by evaluating the surge line for higher temperature differences under faulted conditions. A 320'F temperature difference in combination with pressure, deadweight and Safe Shutdown Earthquake (SSE) conditions is provided herein to satisfy the NRC request. The NRC request is included in Appendix A. This report addresses item 3 of the request.

1.2 Introduction Additional leak-before-break evaluations are presented herein to address higher temperature differences under faulted conditions as a supplement to the l

evaluations previously performed in References 1, 2 and 3.

e Information found in references 1, 2 and 3 required for the evaluations in this report is, in general, not repeated. 4 Accordingly, leak-before-break evaluations are presented at the critical location associated with higher system temperature and faulted conditions.

The system temperature difference is 320'F in combination with pressure, deadweight and Safe Shutdown Earthquake (SSE).

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2.0 LEAK-BEFORE-BREAK ASSESSMENT FOR ADDITIONAL FAULTED LOADINGS 2.1 Introduction The methodology, material properties and margins established in WCAP-12248 (Reference 1) are unchanged for this evaluation. New scenarios for stratification are presented which address the new faulted condition. Loads are established for the new faulted condition and the critical location is

dentifie'd. Leak rates and stability evaluations are presented. Conclusions are drawn.

2.2 Loading Conditions The loading states in Table 5-6 of Reference 1 are given in Table 1 of this report supplemented by the new faulted condition (320*f stratification in combination with SSE). From Table 1, various normal and faulted loading cases

, can be combined for leak-before-break evaluations. The combinations which have either previously been evaluateo in Table 5-7 of Reference 1 or are evaluated in this report are given in Table 2. The new faulted load case is Case G.

In Case G an SSE is assumed to occur with a stratification delta T of 320*F.

Considering the coincidence of SSE and maximum stratified delta T, Case G is judged to be a low probability event. The combination of Case B with Case G is also judged to be a low probability event.

With Cases A and B being normal conditions and Cases E, F and G being faulted conditions, the various load cases are given in Table 3. The first four cases were evaluated in Reference 1. Case S/G is evaluated herein.

i 2.3 Loads l

The loading components for Cases A through F were provided in Reference 2 and are reproduced here in Table 4. The additional loadings for Case G were

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-evaluated and are also summarized in Table 4.

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f O  ; 2.4 Leak Rate Calculations

[ ;. The load cases and temperatures considered for the leak-before-break evaluations are given in Table 5.

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The leakage size flaws-(flaws giving a leakage of 10 gpm) are summari:ed in Table 6 for all the loading cases.

2.5 Stability Evaluations The stability evaluations were performed using the procedures of SRP 3.6.3-(Reference 4). This procedure uses the limit load methodology with a correction factor (Z-Factor) related to the typ'e of weld. In Figure 1, the weld at Node 1010 is GTAW; thus by Reference 4 the Z-Factor is 1. The critical flaw sizes at Node 1010 are also given in Table 6.

• 2.6 Margins

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The margins (critical f. law length divided by leakage flaw length) are also

. given in Table 6. Margins are 2 or more in all cases, a In summary, leak-befora-break criteria are satisfied at the critical location (Node 1010) for the 320'F temperature difference in combination with pressure, deadweight and SSE.

3.0 O!SCUSSION AND CONCLUSIONS As suggested by the NRC, additional margins have been demonstrated for the higher temperature difference of 320'F in combination with pressure, deadweight and SSE.

i The conclusions of WCAP-12248 (Reference 1) and WCAP-12248, Supplements 1 & 2

, (References 2 & 3) are reaffirmed.

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4.0 REFERENCES

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1. R. L Brice-Nash et. al., " Evaluation of Thermal Stratification for the Comanche Peak Unit 1 Pressurizer Surge Line," WCAP-12248, April, 1989.

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2. E. L. Cranford, et. al., " Additional Information in Support of the l Thermal Stratification for Comanche Peak Unit 1 Pressurizer Surge Line,"

WCAP-12248, Supplement 1, September, 1989.

3. E. L. Cranford, et. al., " Additional Information in Support of the i Evaluation of Thermal Stratification for the Comanche Peak Unit 1 Pressurizer Surge Line," WCAP-12248, Supplement 2, October, 1989.

4. Standard Review Plan; Public Comment Solicited; 3.6.3 Leak-Before-Break Evaluation Procedures; Federal Register /Vol. 52, No. 167/ Friday, August 1

28, 1987/ Notices, pp. 32626-32633.

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TABLE 1 TYPES Of LOADINGS ,

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Dead Weight (DW)

Normal Operating Thermal Expansion (TH)

Safe Shutdown Earthquake and Seismic Anchor Motion (SSE)a

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TABLE 2 NORMAL AND FAULTED LOADING CASES FOR LEAK-BEFORE-BREAK EVALVATIONS CASE A:- This is the normal operating case at 653'F consisting of the algebraic sum of the loading components due to P, DW and TH, )

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CASE D: This is the faulted operating case at 653'F consisting of l the absolute sum (overy component lea'd is taken as  :

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. CASE F: )

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TABLE 3 ASSOCIATED LOAD CASES FOR ANALYSES A/D This is the here-to-fore standard leak-before-break evaluation.  !

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B/F 4,

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TABLE 4

SUMMARY

OF LOADS AND STRESSES AT THE CRITICAL LOCATION Force Stress Moment Stress Total Node Case F (1bs) op (psi) M(in-lbs) eg(psi) Stress (psi) 8 7293 11751 1010 A 222878 4458 1069639 1010 ( I"'"

1010 0 240526 4811 3436696 23433 28244 1010 (

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aDimensions: 0.0. = 14 in.. minimum wall thickneis a 1.249 in, b

Stratification AT is ( lC -

cStratification AT is 320'F me .e.o o to g

h TABLE 5 LOAD CASES, LOCATION AND TEMPERATURES CONSIDERED FOR LEAK-BEFORE-BREAK EVALUATIONS Temperature ('F)

Case Node Leak Rate Stability A/D 1010 653 653 -

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'. TABLE 6 LEAKAGE FLAW SIZES. CRITICAL FLAW SIZES AND MARGINS Location of Smallest Critical Flaw Lead Critical Flaw Size Size Based On Leakage Case Based on IWB-3640 Calc. !WB-3640" (in) Flaw (in) Margin A/D 1010 12.4 4.60 2.7 a.c.e 1010 a,c.e 1010 1010 1010 a GTAW Weld l

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NORN SIM W W APSYS N30E PCIN3 L

Figure 1. Sketch of Analysis Model for C:manche Peak Unit 1 Pressurizer Surge Line Showing Node Points, Critical Locations, Weld Locations ano Types of holds e4ui,coneo in 12 i

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Figure 2. Critical Flaw Size' Prediction including Application of Z-Factor 44l24eM119010

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APPENDlX A NRC REQUEST FOR ADDITIONAL INFORMATION ,

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NRC REQUEST FOR ADDITIONAL INFORMATION

[ The staff's review of the Comanche Peak Unit 1 pressurizer surge line thermal stratification issue as related to NRC Bulletin 88-11 and the " leak-before-break" methodology permitted by General Design Criterion 4 was documented in Supplement 23 to the Safety Evaluation Report (NUREG-0797). Since the issuance of Supplement 23, there have been instances at other PWRs where the temperature difference between the pressurizer and the hot leg exceeded the 320'F value utilized in the Westinghouse analysis (WCAP-12248). Such occurrences may invalidate the thermal stratification loads defined in WCAP-12248 and the conclusions contained in Supplement 23. In order to assure that the Comanche Peak Unit 1 pressurizer surge line meets the requirements of General Design Criterion 4 and NRC Bulletin 88-11, you are requested to provide responses by June 15, 1990 to the information requests detailed below:

1) Describe the measures in place that will prevent the pressurizer to

, hot leg temperature difference from exceeding the value assumed in i WCAP,-12248 during all modes of plant operation.

2) If the pressurizer to hot leg temperature difference cannot be maintained below the 320'F value used in WCAP-12248 at all times, provide an analysis of the effects of this potential excess on the thermal stratification loads defined in WCAP-12248 and verify continued compliance with Section 111 of the ASME Boiler and Pressure Vessel Code.

3) The assumptions used in the " leak-before-break" analysis should be consistent with the assumptions used to show compliance with the ASME Section 111 Code. The " Leak-Before-Break" analysis should include the loading resulting from the combination of pressure, deadweight, thermal expansion (including thermal stratification with a differential temperature of 320'F), and safe shutdown earthquake loads. The corresponding leakage flaw size for this loading in the T . analysis should be based on " Case B" in Table 5-7 of WCAP-12248.

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