ML20235J480
| ML20235J480 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 09/30/1987 |
| From: | Kim C, Lee Y, Witt F WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML19304B526 | List: |
| References | |
| WCAP-11318-S01, WCAP-11318-S1, NUDOCS 8710010461 | |
| Download: ML20235J480 (23) | |
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WEST 3NGHOUSE CLASS 3 '<
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1.' CAP-11318 Supplement 1
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i ADDITIONAL INFORMATION IN SUPPORT 'i 0F THE TECHNICAL JUSTIFICATION FOR 1 ELIMINATING LARGE' PRIMARY. LOOP PIPE RUPTURE AS THE STRUCTURAL DESIGN BASIS FOR BEAVER VALLEY UNIT 1 -l September 1987 F. J. Witt Y. S. Lee C. C..Kim T. H..Liu Verified by: Md D. H. Roarty U Approved by: hM
/ 5. 5. falusaniy, Manager Structural Materials Engineering-Approved by: / N244//pf B.'R. MutyaTa, ht/ nager Piping Design and Qualification
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' WESTINGHOUSE ELECTRIC CORPORATION.
Generation Technology Systems Division P.O. Box 2728 Pittsburgh, Pennsylvania 15230-2728 -
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TABLE'0F' CONTENTS Section 1 Title Page 1.0
SUMMARY
AND INTRODUCTION 1-1 1.1 Summary' 1-1 1.2 Introduction 1-1 2.0 FABRICATION AND WELDING PROCESSES-FOR THE PRIMARY LOOP 1 3.0 MATERIAL PROPERTIES 3-1.
4.0 LEAKAGE FLAW DETERMINATIONS 4 ..!
5.0 STABILITY ANALYSES 5-l' 6.0 DISCUSSION AND CONCLUSIONS 6-1
7.0 REFERENCES
7-1 APPENDIX A - THE NRC REQUEST FOR ADDITIONAL INFORMATION A-1
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LIST OF TABLES- 1
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Table Title Page 3-l' Lower-Bound and Average Material Properties.for. 3-2 SA351 CF8M lised in the Leak-Before-Break Analyses 1
4-1 Leak-Rates for Various Flaw Sizes at ,4-2 Locations 1, 5,'10 and 11 j i
5-1 Results of Stability' Analyses 5-2 6-1 Comparison of Flaw' Sizes Established by the Three Criteria 6-3 i
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- LIST OF FIGURES Figures Title Page 3-1 Lower-Bound Stress-Strain Curve for' SA351 CF8M at 547'F 3-3 3-2 Lower-Bound Stress-Strain Curve for SA351 CF8M at 614*F 3-4 S
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SECTION 1.0 1
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SUMMARY
AND INTRODUCTION $
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1.1 Summary I Duquesne Light Company submitted a leak-before-break analysis. WCAP-11317, to-I NRC in support of their snubber reduction program for Beaver Valley Unit 1. j 1
After completing their review the NRC transmitted to Duquesne Light Company a request for additional information. Duquesne Light Company contracted with Westinghouse Electric Corporation to respond to the NRC request including the performance of analyses. This report represents the response.
Additional materials information is provided. Leak-before-break analyses were performed using average properties for leak-rate calculations and lower-bound properties for stability calculations. Elastic plastic fracture mechanics procedures were applied. The margin criteria of 10 on leakage rate, 2 on crack size and 1.4 on load were met as detailed in the NRC request.
It is concluded that leak-before-break conditions are demonstrated for Beaver Valley Unit 1 primary loop using the criteria and recommendations provided by the NRC. The conclusions of WCAP-11317 are unchanged.
1.2 Introduction Duquesne Light Company contracted with Westinghouse Electric Corporation to develop a leak-before-break analysis for the Beaver Valley Unit i nuclear power plant for licensing support in their snubber reduction program. The leak-before-break analysis is documented in Westinghouse Proprietary Class 2 Report WCAP-11317 (reference 1.1). WCAP-11318 is the associated Westinghouse Class 3 report. During the regulatory review process, the Nuclear' Regulatory Commission (NRC) issued a Request for Additional Information on Elimination of
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Postulated Primary Loop Pipe Ruptures as a Design Basis. This report addresses the NRC request. The NRC document is given in appendix A.
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0' Portions of the NRC request.can be ' answered as-independent' items; however, these directly~inv'olving the calculational methods are best addressed by presenting a reanalysis reflecting the NRC's request.- Specifically, request --
. items 1, 2, and 3 are addressed in separate. sections while items 4_ through 7, with the exception of _ item 5, are addressed'in.'the same section. Item 5.is- ~
addressed'in the concluding discussion. The material in WCAP-11317 is.
referenced extensively;and,.in general.:will not be reproduced in.this report.
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SECTION 2.0 FABRICATION'AND WELDING PROCESSES FOR THE PRIMARY LOOP i The primary loop piping and fittings of Beaver Valley Unit 1 are SA351 CF8M cast stainless steel. The piping is centrifuga11y cast while the fittings are statically cast. The field welds feature a gas tungsten arc weld (GTAW or TIG) root pass followed by shielded metal are welding (SMAW) to completion.
The shop welds are either SMAW or submerged arc (SAW) with a GTAW root pass.
Weld repairs on shop welds would be either SMAW or GTAW. The welds have TP ;
308 stainless steel chemistry. No solution annealing was performed.
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.. 'SECTION 3.0 -
MATERIAL PROPERTIES The material properties presented in table 3-1 of WCAP-11317 are the ASME' Boiler and Pressure Vessel Code Section III minimum properties 1at the operating temperatures. However, to perform the reanalyses given in the next section, elastic plastic analyses 'are required. The mate'ialr properties at operating temperatures are calculated using the Nuclear Systems Materials Handbook (reference 3.1). The properties used in the analyses are summarized in table 3-1.
The lower-bound properties are involved in the stability analyses while the average properties are used in the leak rate calculations. In reference 3.1, average properties are obtained by multiplying the lower-bound yield stress by a factor of 1.25 and proceeding with the properties calculations. The lower-bound stress-strain curves used in the stability evaluations are given in figures 3-1 and 3-2.
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' TABLE 3-1
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LOWER-BOUND AND AVERAGE MATERIAL PROPERTIES FOR SA351 CF8M 1 a
USED IN THE' LEAK-BEFORE-BREAK ANALYSES )
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froperty Temperature Yield Stress UltimateSt5ength.ModulusofElasticity Type ('F)- (psi) (psi) (psi) 1 6
L Lower Bound 547 18903 67000 25.946 x 10 )
Average 547 23629 67000 25.946 x 10 6 Lower Bound 614 18603 67000. 25.432 x 106 -
Average 614 23254 67000 25.432 x 10 6 a) Poisson's ratio used is 0.3.
b) These are code minimum properties.
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Figure 3-1: Lower Bound Stress-Strain Curve for SA351 CF8M at 547*F 2621s-090947.10 3-3
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. O for SA351 CF8M at 614*F an.-amano 3-4
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~ SECT 10N 4.0'
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LEAKAGE FLAW DETERMINATIONS:
. The leakage flaw is ' defined as 'the flaw size' which produces a leak rate of 10 gpm under normal operating' loadings. The method of determining the leakage
.through a flaw is described in section 5.0 of referenceJ1.1.- However, in the leak' rate analyses of this section the average materia 11 properties of table 1 are used. The leak rates were calculated for series of flaws at load critical and toughness critical locations 1, 5,10 and 11 as' discussed in-reference 1.1. The results are given in table 4-1. The leakage flaws are 5.2 in. at location 1, 7.5 in, at location 5, 4.5 at location.10 and 7.1 at location 11. ,
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TABLE.4-l' .:j LEAK RATES FOR VARIOUS FLAW SIZES AT LOCATIONS 1- 5, 10'AND 11' ,
Location- Crack Length (in) Leak' Rat'e'-(gpm) b,c.e r- 4 -
1-15.2" 10.0-5 ,
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a) Leakage flaws are underlined. l j
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SECTION 5.0 STABILITY ANALYSES Stability analyses were performed at the load critical and toughness critical locations defined in reference 1.1. The elastic plastic fracture mechanics (EPFM) J-integral analyses for through-wall circumferential cracks in a cylinder were performed using the procedure in the EPRI fracture mechanics !
handbook (reference 5.1). The lower-bound material properties of section 3.0 were used.
i The results of the EPFM analyses are given in table 5-1. The critical toughness criteria established in reference 1.1 are unchanged. The normal plus SSE loads are given in table 3-1 of reference 1.1.
Two margin conditions were evaluated. First, the leakage flaw was doubled and EPFM analyses were performed for normal plus SSE loadings. The applied tearing modulus was calculated from the EPFM results using dJ E T,pp = 3, q f
where E is the modulus of elasticity and of is the flow stress taken as the average of the yield and ultimate strength. In table 5-1 the calculated values are seen to be well below the critical toughness values. J gc is exceeded only at one location, location 5.
Similar analyses were made using the leakage flaws with the normal plus SSE loads increased by a factor of 1.4. As seen in table 5-1, J Ic is exceeded at three of the four locations. However the tearing criteria are well met and stability is established.
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l TABLE 5-1 j RESULTS OF STABILITY ANALYSES i
. l Criticala Crack J
Ic J Length J <
max app 2 2 2 T I Location (in-lb/in ) Tmat (in-lb/in ) (in) (in-lb/in ) app Factor of 2 on Leakage Flaw Size b l t
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1 (hotleg) 5 (crossoverleg) 10 (crossoverleg) 11 (cold leg) -
Factor of 1,4 on Load b f
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i a) Values are lowest among the loops at the specific locations b) Normal plus SSE loads used as a base N.A. - not applicable c) ;
d) Leakage flaw
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SECTION 6.0
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DISCUSSION AND CONCLUSIONS 1
First the NRC requests given in appendix A are addressed individually i
Request (1)
The response to this request is given in section 2.0. All the information requested are provided. ,
Request (2)
The response to this request is given in section 3.0. All the information requested for performing the reanalyses for leakage and stability are provided. In WCAP-11317, ASME Section III code minimum properties at operating temperatures were used throughout.
Request (3)
In this report the lower-bound stress-strain relationships were used for the stability evaluations; however, the average properties were used to establish the leakage flaws. Thus, the analyses of sections 4.0 and 5.0 comply with this request.
Recuest (4)
Elastic plastic fracture mechanics was used for determining both J,pp and T,pp in the stability analyses of section 5.0. Thus, the analyses of section 5.0 comply with this request.
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. As shown in reference 1.1, limit load analyses do not produce limiting flaw 4 sizes and such results have no impact on the governing stability and margin j evaluations presented here. Fracture stability analysrs which account for j material toughness are presented both in reference 1.1 and this report. Thus I the analyses presented comply with this request.
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- I The definition of limiting location for LBB evaluations is clouded by the I three tiered margin evaluations which are performed. In table 6-1 the leakage '
flaws are listed along with stable flaw sizes for normal plus SSE loads and l 1.4 times normal plus SSE loads. To provide the proper perspective the stable j
flaw sizes for normal plus SSE loads were divided by 2 and are also given in j table 6-1. Based on the suggestion of item 6 of appendix A, location 11 is i the limiting location closely followed by location 1. Based on 1.4 times )
normal plus SSE loads location 1 is clearly the critical location followed by location 10. The least margin of critical flaw size compared to the leakage l flaw occurs at location 5.
It appears that two limiting locations are required, one based on normal plus SSE loads and one based on 1.4 times normal plus SSE loads. Thus, for this I study, the limiting locations are location 11 (based on normal plus SSE loads) and location 1 (based on 1.4 times normal plus SSE loads). i i
The limiting locations are defined in a positive response to item 6. .
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The margin of 1.4 on normal plus SSE loads for the leakage flaws was established in section 5.0. Similarly, the margin of 2 on the leakage flaw sizes for normal plus SSE loads was established in section 5.0. Thus the f
analyses presented comply with this request. j l
In conclusion, leak-before-break conditions are demonstrated using the criteria and recommendations provided by the NRC. The conclusions of WCAP-11317 are unchanged.
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- TABLE-6-1 COMPARISON OF FLAW SIZES ESTABLISHED BY THE THREE CRITERIA (
i 9 s Flaw Size.(in) Stable Flaw Stable Flaw 0.5 x1 Stable -(1.4 factor Leakage: '(normal plus Flaw (normal on normal plus
- Location Flaw SSE load) plus SSE load) SSE load)
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1 5.20 5 7.50 10 4.50 11 7.1 4
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REFERENCES-e- 1.1.D. H. Roarty et. al., Yechnical Justification for Eliminating Large-Primary Loop Pipe. Rupture as the Structural Design Basis:for. Beaver
' Valley Unit 1, WCAP-11317,. Westinghouse Electric Corporation, March 1987 (Westinghouse Proprietary Class 2)-
3.1- Nuclear Systems Materia'Is Handbook, Part I - Structural Materials,' Group 1 - High Alloy Steels, Section 4, ERDA Report TID 26666, November 1975 Revision.
5.1 Kumar, V., German, M. D. and Shih, C. P. "An Engineering Approach for Elastic-Plastic Fracture Analysis," EPRI Report NP-1931, Project 1237-1, Electric Power Research Institute,-July 1981.
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.- APPENDIX'A THE NRC REQUEST FOR ADDITIONAL INFORMATION_
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After reviewing WCAP-11317, the-NRC submitted to Duquesne Light. Company a -1 Request for Additional Information consisting.of sever i'. ems. The request is' reproduced on the.following page.
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REQUEST FOR ADDITIONAL INFORMATION I ON ELIMINATION OF POSTULATED PRIMARY LOOP PIPE RUPTURES --I AS A DESIGN BASIS d 1 s >
(1) The primary loop piping and fittings were fabricated from cast stainless '
steel. Describe whether the piping and fittings are centrifugally cast 1 stainless steel or statically cast stainless steel. Also, identify the welding process of the primary loop and indicate if solution annealing was performed.
(2) The material properties were presented in table 3-1 in Westinghouse report WCAP-11317. Describe whether the properties are plant specific data from ,
certified material test reports (CMTRs) or Section III Code-minimum values, !
at room temperature or operating temperature. Provide the elastic modulus, yield strength, ultimate strength, and stress strain curve, at the limiting location and at the operating temperature, that would be used in the leak-before-break (LBB) analyses.
(3) It appears that the same stress-strain relationship was used in the fracture stability and leakage calculations. The licensee should use the lower-bound stress-strain relationship for the stability evaluation and the average stress-strain relationship for the leakage evaluation.
(4) Linear elastic fracture mechanics (LEFM) was used for the fracture stability analysis. However, from the calculated fracture mechanics parameter J-integral "J it appears that the associated Irwin plane-stress plastic zoREPsi,zes are not small compared with the half-crack '
length "a". The licensee should use elastic plastic fracture mechanics (EPFM) instead of LEFM procedures. Similarly, the tearing modulus "T "
should be evaluated based on EPFM procedures. app q 1
(5) Limit load analysis was used to estimate the size of a stable crack. j However, limit load analysis does not account for material toughness i limitations. In particular, low toughness thermally-aged cast stainless steel is involved in the present evaluation. The licensee should use a fracture stability analysis which accounts for material toughness.
(6) Since the primary loop was fabricated from materials having various toughness properties, load critical and toughness critical locations were discussed. However, the LBB evaluation margins should be demonstrated for the limiting location having the least favorable combination of stress and material properties. The limiting location may be defined from a fracture stability evaluation of the load critical and toughness eritical location,s. Since the primary loop piping is of a similar size, the location with the smallest stable crack size under a combination of normal (pressure, deadweight, and thermal) and safe shutdown earthquake (SSE) '
loads, independent of leakage, is the limiting location for LBB evaluations.
(7) The limiting location as discussed in item 6 above should be evaluated to demonstrate that the LBB margins are satisfied. Specifically, the margins are 10 on the leakage rate, 2 on the crack size, and 1.4 on the applied load, as discussed in detail in NUREG-1061, Volume 3. (Note that in the submittal, the licensee did not discuss the margin of 1.4 on the applied load. The licensee should include this margin of 1.4 on the applied load in the LBB evaluations.)
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