ML20247G983

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App 5B, Structural Evaluation of Steam Line Break for Steam Generator Internals, to CESSAR Sys 80+ Std Design
ML20247G983
Person / Time
Site: 05200002, 05000470
Issue date: 03/30/1989
From:
ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY
To:
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ML20247G537 List:
References
NUDOCS 8904040358
Download: ML20247G983 (9)


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iO APPENDIX 5B STRUCTURAL EVALUATION OF STEAM LINE BREAK FOR STEAM GENERATOR INTERNALS O

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O APPENDIX 5B STRUCTURAL EVALUATION OF STEAM LINE BREAK FOR STEAM GENERATOR INTERNALS i I

ABSTRACT This report documents the structural adequacy of combustion Engineering's (C-E's) System 80+ ALWR steam generator internals D to withstand a steam line rupture.

The steam generator separator deck, shroud and tubes are subjected to a hypothetical steam line break accident. The lD resulting stresses in the structures are compared to ASME Boiler  !

and Pressure Vessel Code,Section III allowables to determine the adequacy of the structure.

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EFFECTIVE PAGE LISTING APPENDIE 5B I

Table of Contents j ZAgt Amendment Abstract D j i D 11 D Text Pace Amendment 5B-1 D 5B-2 D j Tables O 5B-1 Amendment D

SB-2 D 1

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TABLE OF CONTENTS APPENDIX 5B l

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l; Section Subiect Pace No.

1.0 INTRODUCTION

SB-1 2.0 ANALYSIS SB-1 I

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2.1 DISCUSSION SB-1 2.1.1 HYDRODYNAMIC ANALYSIS 5B-1 D'

2.1.2 STRUCTURAL EVALUATION 5B-1

2.2 CONCLUSION

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3.0 REFERENCES

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O LIST OF TABLES APPENDIX 5B Table Subiect 5B-1 Peak Pressure Loads SB-2 Comparison of SYSTEM 80 Margins to Anticipated D SYSTEM 80+ ALWR Margins O

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1.0 INTRODUCTION

The hydraulic loadings on the steam generator internals resulting from the rupture of one 28.0 inch I.D. main steam line nozzle are calculated using the CEFLASH computer code to perform the hydrodynamic analysis of the steam generator blowdown during the accident. The structural analysis of the System 80+ ALWR steam generator internal parts which are significantly loaded by the Main Steam Line Break (MSLB) accident, as established by the D above CEFLASH analysis, is accomplished by adjusting the stresses calculated for the System 80 steam generator by the differences in pressure loadings and size of the parts. The results of these adjustments show the expected margins of safety for the System 80+ ALWR steam generator to be smaller than the margins for the System 80 steam generator. However, the expected stress levels are still much less than the allowed stress levels defined by the ASME Code,Section III.

2.0 ANALYSIS 2.1 DISCUSSION

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2.1.1 HYDRODYNAMIC ANALYSIS 9 The hydrodynamic analysis to establish hydraulic pressure loads on the steam generator internals is performed using the CEFLASH computer code. Details of this analysis are given in Reference

1. The analysis is done for the 15% and 0% power conditions.

Pressure loadings for the MSLB accident are given in Table SB-1.

The basic assumptions for the MSLB hydrodynamic analysis are:

A. Rupture of one 28.0 inch steam outlet nozzle.

B. A break opening time of .0094 seconds for the rupture of the steam line.

C. A Moody critical flow correlation with a discharge coefficient of 1.0.

2.1.2 STRUCTURAL EVALUATION The structural evaluation of the System 80+ ALWR steam generator internals is based on the structural analysis of the system 80 steam generator internals presented in References 2 and 3. The following internal parts are considered to be significantly loaded by the MSLB accident and are evaluated.

1. Separator Deck G 2.

3.

Shroud Tubes Amendment D 5B-1 September 30, 1988

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The basis of evaluation and comparison is the margin of allowable l stress for the System 80 and System 80+ ALWR steam generators. j The margin is calculated as the percentage of remaining allowable j stress, or:

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IAllowable Stress - Calculated Stress 1 X 100 Allowable Stress The allowable stress is the elastic allowable stress as defined in the ASME Code,Section III. The margins for the System 80+

ALWR steam generator are based on adjustments of the calculated System 80 stresses by the ratios of hydraulic pressure loading ,

and part size. A comparison of the margins is given in Tablo SB-2. Materials for the parts of the System 80+ ALWR generator are the same as materials for the System 80 generator, except for the tubing. The tube differential pressure is conservatively considered to be 2250 psi during the MSLB event. This is based on the operating pressure with the assumption that the secondary pressure has decayed to zero.

2.2 CONCLUSION

S The results of the evaluation, which are given in Table 5B-2, show that the anticipated margins of the parts for the System 80+

ALWR steam generator are smaller than the calculated margins for the System 80 steam generator. However, the smallest anticipated margin for the System 80+ ALWR generator is 60.0% for the shroud.

Therefore, the separator deck, tubes, and shroud are considered to be adequately designed to withstand a hypothetical Main Steam Line Break accident.

3.0 REFERENCES

1. Combustion Engineering Calculation, ST-801, Loads for Steam Line Break, July 1988.
2. System 80, CESSAR FSAR, Appendix SB, Amendment No. 7, March 31, 1982.
3. Combustion Engineering Report No. CENC-1479, Analytical ,

Report for Arizona Public Service Company, Palo Verde Unit '

No. 3 Steam Generators, August, 1981.

4. ASME Boiler and Pressure Vessel Code, Section III for Nuclear Vessels.

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PZAE_ PRESSURE _ LOADS 0% and 15% Power AP Time Location (nsi) (sec) Direction l

Separator Deck 28.5 .10 Upward Upper Shroud 29.9 .30 Tension Lower Shroud 35.6 .40 Tension '

Tube Bend Region 26.6 .10 Upward D j s -

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COMPARISON OF SYSTEM 80 MARGINS TO ANTICIPATED SYSTEM 80+ ALWR MARGINS Allowable Anticipated Stress Stresa System 80 System 80+ ALWR Part CateqorY (ksil Margin (%) Marcin (%)

Separator Deck PM+PB 73.5 90.7 84.0 0 Stiffener PM+PB 73.5 87.8 80.0 Tubes PM 56.0 68.2 68.2 Shroud PM 49.0 90.8 60.0 O

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