ML20236F310

Nonproprietary WCAP-11620, Addl Technical Bases for Eliminating Large Primary Loop Pipe Rupture as Structural Design Basis for Kewaunee

ML20236F310
Person / Time
Site:	Kewaunee
Issue date:	10/31/1987
From:	Kim C, Lee Y, Roarty D WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
Shared Package
ML111751332	List: ML20236F310
References
WCAP-11620, NUDOCS 8711020090
Download: ML20236F310 (26)

Text

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. ADDITIONAL TECHNICAL BASES FOR ELIMINATING LARGE PRIMARY LOOP PIPE.

l;/*. 1 . RUPTURE AS THE STRUC" URAL DESIGN BASIS-

!% A ,'- FOR KEWAUNEE.

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H + f' -October 1987

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.D. H. Roarty' Y. S. Lee 7' C. C. Kim V. B. Bhambri Vehifiedby: 8 .

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Appr6ved by: -M h/ f G ffilusamy, Manager Structural Materials Engineering

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' Approved by: /[f[ N M M

~B'. R. NutyaTh, Manager

g Piping Design and Qualification

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WESTINGHOUSE ELECTRIC CORPORATION  !

.. Generation Technology Systems Division

-g P.O. Box 2728 Pittsburgh, Pennsylvania 15230-2728

.. 1 nu -omano 8711020090 871026-  !

PDR ADOCK 05000305 i P PDR

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,Section '-

Title .

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1. 0. ~

SUMMARY

AND' INTRODUCTION . 4 1 1.11 Summary- '

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' 2 '. 0 FABRICATION AND WELDING- PROCESSES"f0'(THE IRINARY4 LOOP L ; ~ 2-l' 4c i -

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j*: .1l i 3.0 MATERIAL PROPERIIES 3 ,

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4.0 LEAKAGE FLAW DETERMINATE 0NS'- 4-1 ,f .p

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STABILITY ANALYSES

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' 6.0 DISCUSSION AND CONCLUSIONS i

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7. 0 REFERENCES , .. .

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APPENDIX A. -

THE.NRC REQUEST FOR ADDITIONAL INFORMATION A-1 '

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• Title- Page

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Wt Y ,..3-1 * . Lower-Bound and Average Material-Properties.for- 3 l

" A-351ECF8M Used in the Leak-Before-Break-Analyses

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3-2 Plant Specific Material' Properties'(Yield: Strength - PSI) '3  !

, for Six Heats'of A-351 CF8M.Used in Leak-Before-Break .]

y Analysis.of Location 1: )

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Normal Condition (Deadweight + Pressure + Thermal) 4-2 Loabs:for:Kewaunee

. 2 ' Leak Rates for Various Flaw. Sizes at Locations 1, 8, 9 and 10 4-3 i n s pl M';Sl.

LFaulted Condition (Normal + SSE) Loads for Kewaunee 5-2 4 m.

N .E . Including' Steam Generator Upper Support Redesign  !

L i V 5-2 Results of Stability Analyses 5-3  !

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'6-1 Comparison of Flaw Sizes Established by the Margin Criteria 6-3 F' ,l

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13-1i Lower,-Bound' Stress-Strain Curve for A-351 CF8M at 536*F. 3 '4 o ..a s 3-2. Lower-Bound Stress-Strain Curve for-A-351 CF8M>at 599'F- -~ 3- 5 '

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SECTION-1.0 m

SUMMARY

AND INTRODUCTION

• . 1.1' Summary  !

Wisconsin Public Service Corporation (WPSC) submitted a leak-before-break 1

analysis, WCAP-11411, Revision 1, to the NRC to eliminate the large primary pipe breaks from the structural design basis. After completing their review l the NRC transmitted to Kewaunee a request for additional information. l Included in this request was the requirement for WPSC to reverify the LBB analyses in their upcoming steam generator redesign program. The redesigned steam generator upper support resulted in some minor increases in the SSE loadings on the primary pipes. This report represents responses to all of the '

issues included in the NRC request. l The additional materials information is provided. Leak-before-break analyses I were performed using average properties for leak rate calculations and l lower-bound properties for s.tability calculations. Elastic plastic fracture mechanics procedures were applied. The margins of 10 on leakage rate, 2'on I crack size and 1.4 on applied load were met as detailed in the NRC request.  !

It is concluded that leak-before-break conditions are demonstrated for  !

Kewaunee using the criteria and recommendations provided by the NRC. This evaluation used loadings which included the effects of snubber reduction. -The !

conclusions of WCAP-11411, Revision 1, are unchanged. I

)

'1.2 Introduction ,

l I

Wisconsin Public Service Corporation contracted with Westinghouse Electric 1 Corporation to develop a leak-before-break analysis for the Kewaunee nuclear power plant. The leak-before-break analysis is documented in Westinghouse i

, Proprietary Class 2 Report WCAP-11411, Revision 1, (reference 1.1).  !

WCAP-11410, Revision 1, 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 Postulated Primary Loop i m4.aaoman 3_1

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1 Pipe' Ruptures as a. Design Basis. One of-the requests was the consideration of t

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loads from the snubber reduction program.. This' report addresses the NRC ~~

requests (appendix A.).

I Portions of the NRC request can be answered as. independent items; however, those directly involving the calculational methods are best' addressed by- 1

. presenting a reanalysis reflecting compliance with the NRC's request. j '

Specifically, request items 1, 2,;and 3 are. addressed in separate sections!

(2.0, 3.0, and 4.0) while items 4 through 8, with the exception of item 5, are

' addressed in the same section.(5.0). Item 5 is addressed.in the concluding discussion. The material in WCAP-11411, Revision 1, is. referenced extensively ~and, in' genera ~1, will not'be reproduced in this report, j j

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.SE'CTION 2.0 . _

~ FABRICATION'AND WELDING PROCESSES FOR THE. PRIMARY LOOP

(-[ * - The primary loop piping 'and fittings. of Kewaunee are A-351 CF8M' cast stainless steel.- The piping 11s centrifuga11y~ cast while the fittings are statically i

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cast. ;The field welds' feature'a' gas tungstenLarc weld-(GTAW or. TIG) r' cot pass  ;

followed by shielded metal ' arc welding (SMAW) to completion... The shop welds )

are either SMAW or submerged arc (SAW)-with a GTAW root pass. Weld-repairs on-.

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' shop welds would be'either SMAW or GTAW. .The welds have TP 308~ stainless R- . steel chemistry. No solution annealing was performed.- ,

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, SECTI0'N 3.0 4 f MATERIAL PROPERTIESL

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The material properties presented in table 3-1 of WCAP-11411,-Revision.-1, are i

-the ASME Boiler and Pressure Vessel Code Section III (reference 3.2) minimum

properties-at the operating temperatures. However, to perform the reanalyses 1 given in:the next section, elastic plastic analyses are required.

The 1 material properties at; operating temperatures are calculated using the Nuclear.

Sysiems~MaterialsHandbook(reference 3.1). The plant' specific certified f material' test reports were used for location 1. The properties used in the analyses are summarized.in table 3-1.

The lower-bound properties;are used in the stability analyses while the i average properties are used in the leak rate calculations. In reference 3.1, I average properties'dre'obtained by multiplying the lower-bound yield stress by a factor of 1.25 and proceeding with the properties calculations. The i I

lower-bound: stress-strain curves used in the stability evaluations are given .[

in" fig'ures 3-1 and 3-2. I

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For location 1 at defined in reference 1.1, plant specific material properties  !'

were used from the plant certified material-test reports (CMTRs). Table 3-2 summarizes the room temperature, and elevated temperature test results from  ;

the CMTRs of six heats.of straight pipe. Operating temperature data were obtained using an interpolation based on the variation of material properties 4

presented in;the ASME Section'III Code Appendices (reference 3-2). The pipe '

at Location'1, which is in the hot leg, is heat number A-355123456. This heat l and the heats from the other two hot' leg and three cold leg pipes were used to .i obtain a conservative lower bound value for the stability calculations. The actual yield strength for location 1 was higher than the average value of the  ;

six selected heats. Therefom the actual yield strength was conservatively used in the leak rate calculations for location 1.

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' LOWER-BOUND AND AVERAGE MATERIAL PROPERTIES FOR A-351 CF8M i

USED IN THE LEAK-BEFORE-BREAK 'ANALYSESa ,

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' Property. :Temperafurei Yield ~ Stress ! Ultimate Sgrangth Modulus of' Elasticity. j

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Lower Bound 536 :18952 67000 26.031 x 10 6

- Average 536- 6 23690 67000 26.031 x 10 .

C Llower Bound ' 599 23300 -67000- 25.547 x 10 6 Averagec. -599 26600 67000  : 25.547 x'10 6 }

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- b)??These are code. minimum properties.  !

ic) Based on; plant spesific 'CMTRs.

-d). / Temperatures correspond to operating temperatures of hot leg (599),

crossover leg (536) and cold leg (536)

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< A4 PLANT SPECIFIC MATERIAL PROPERTIES (YIELD STRENGTH-PSI):

FORJSIX HEATS OF A-351*CF8M USED:IN-

+ - LEAK-BEFORE-BREAK ANALYSES. OF LOCATION 1 -

' Heat Number. . Room Temperature' Elevated. Temperature (650*F)

A'-3391234 '43000 -24800'.

!' A-3557890" 37900 24200 A-3626789- 43100 P2900.--

A-351567890 39950 24500:.

b A-355123456 - '43950 26200 A-362012345' 44950 -26900 L- c 1 a) Lower. bound. heat used for stability analysis 'l

b) location l', heat used for leak rate analysis.

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SECTION 4.0 LEAKAGE FLAW DETERMINATIONS i The leakage size 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 reference 1.1. However,. ,

in the leak rate calculations of this section the average material properties of table 3-1.are used. Normal loads used in this evaluation are listed in table 4-1. .The leak rates were calculated for series of flaws at load critical and toughness critical-locations 1, 8, 9 and 10 as discussed in reference 1.1. The results are given in table 4-2. The leakage size flaws =

are 4.45 in at location 1, 6.8 in, at location 8, 6.2 in, at location 9 and 7.1 in, at location 10.

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,' I TABLE:4-1 NORMAL. CONDITION-(DEADWEIGHT .+ PRESSURE +' THERMAL) LOADS FOR KEWAUNEE Weld Location'. -Axial'L6ad Fx (kips)"~ BendingMomentMb'(in-kips)( ' -

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2 1453- 5844~ j 3- 1346 11356 -

4- 1670' 2690 1

'5 1673- 1960 ,

'6: 1666 1198 I

.7 1729 5050 b'

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1729- 8729 b ~

9 1788 11467-b 4 10 1424 4358'

.11 1424 3590-12 1420- 3576

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S- LEAK RATES FOR VARIOUS. FLAW SIZES AT LOCATIONS 1, 8, 9 ' AND 10 : .

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Location a> Crack Length (in)' Leak Rate-(opm). .

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'SECTION 5.0- .1 g , . STABIi.I'TYf ANALYSES ]

4' 1 0

Stability analyses were performed a't the load critical and toughness critical locations defined:in reference 1.1. Revised loadings.from the steam generator.

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upper support redesignTanalysisd 'id not change the criticar iocations.1 The: ]

revised.n'rmal'plus"SSE o loads are given in table.5-1. TheLelastic plastic fracture mechanics (EPFM) J-integral analyses for through-wall circumferential-

cracks:in~alcylinder were performed using the procedure in the EPRI fracture L

mechanics handbook (reference 5.1). The. lower-bound material propertie's of .)

section 3.0 were used..

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The results.of the EPFM analyses are-given in. table-5-2. 'The leakage flaws-of- j

-table 4-2.are identified. Theicritical. toughness criteria established in I

. reference 1;1 are unchanged. In. summary local stability is demonstrated by- 'l 4the following_ criteria:

1 J < J;g <

f . y-or.T,pp < Tmat K J.> J7c and J < J max 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 i g, g j

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.where E is.the modulus of elasticity, of is the flow stress taken as the  !

average of the yield and ultimate strength and a is the crack length. In table 5-2 the calculated values are seen to be well below the critical

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toughness values. J was met at all locations.

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Similar analyses were made using the leakage flaws with 1.4 times the normal 1plus'SSE loads. As seen in table 5-1, J Ic is exceeded at one of the four  ;

locations (location 1). However the tearing criteria are met and stability is established, m4.-iman o 5-1

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, .,7 in LTABLE'5  ! FAULTED. CONDITION (NORMAL + SSE) LOADS FOR KEWAUNEE-  :.;..

INCLUDING STEAM' GENERATOR. UPPER SUPPORT REDESIGN

. Weld Location- Axial' Lead Fx-(kips)a B'ending Moment'Mb (in-kips) 1 1541. -23871 2- :1540 6560 q 3' =1405 s12748

-.4: 1684 3846' 5 .1680 ~2718 6- 1673' 1567 -)

7- -1739. 5519 1739; 8 9172' 9 1797- 12757 j 10 1459 6036 1 11 1456' 3994

12. 1449 4235'

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TABLE 5 9 .RESULTS OF STABILITY ANALYSES ,

• . Criticala4  ; Crack- d I J Length- J Location J~c: 2.

-(in-lb/inj;Tmat max 2 (in-lb/in )- (in) app. 2 (in-lb/in ) T app Factor of 2~on Leakage Flaw Size b' i-a,c e ,

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,(hotleg)'

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Factor'of 1.4 on Load b-

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,(crossoverleg) 9 (crossoverleg) 10 (cold. leg) . _

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, a) Lowest values among the loops at the specific locations l b) Normal ~plus SSE loads used as a base c) N.A. - not applicable d) Leakage flaw from table 4-2

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[, SECTION 6.0 DISCUSSION AND' CONCLUSIONS

& First the"NRC. requests given-in appendix A are addressed individually.

L  :

Request (1)L l

,The response to this request is given in section 2.0', - All of. the information , l requ'sted e is3provided. ,

Request (2)

The response to thisl request.is given in~section 3.0. All of the information I requested for performing leakage and stability reanalyses presented in this report:is'provided. In WCAP-11411, Revision-1,' ASME Section III code minimum'

- properties at operating. temperatures were used-throughout. j RequestL(3) I

.- l In this report the lower-bound stress-strain relationships were used for the y .-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.-

.. Request (4)

. Elastic plastic fracture mechanics was used for determining both J and app ,

T,pp in the stability analyses of section 5.0. Thus, the analyses of f section 5.0 comply with this request.

Request (5)

'As.shown in reference 1.1, limit load analyses do not produce limiting flaw

_, sizes andlsuch results have no impact on the governing stability and margin evaluations presented here. The loadings resulting from the steam generator  !

am. ioom.io 6-1 i

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1 i upper support redesign resulted in a negligible' change in the limit load- )

. analyses'and therefore the:results were not repeated in thisLreport. Fracture-(.

stability analyses which account for material toughness are presented both in

-l.;

reference 1.1 and this report. Thus the analyses presented comply with this-  !

a request. '

\

Request 6 l

.i The definition of limiting location for LBB evaluations is clouded by the  !

.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 1

1.4 times normal plus SSE loads. To provide the proper perspective the stable- i flaw sizes for normal plus SSE loads were divided by 2 and are also given in table 6-1. Based on the criteria suggested by. item 6 of appendix A, location '

1 is the limiting location. In addition based on 1.4 times normal plus SSE j loads location 1 is clearly the most limiting location. Finally, the least margin of critical flaw size compared to the leakage flaw-also occurs at location 1.

Thus, for the analyses presented in this repor$ the limiting location is  !

location 1. -

Request 7 i

h 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 i analyses presented comply with this request. l 1

i Request 8 1

The leak-before-break evaluation presented in this report include the revised loadings associated with the redesigned steam generator upper support.

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In conclusion, leak-before-break conditions are demonstrated using the criteria and recommendations provided by the NRC. The conclusions of WCAP-11411, Revision 1 are unchanged.

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COMPARISON;0FcFLAW SIZES ESTABLISHED BY THE MARGIN CRITERIA' j,

Flaw Size (in)~ Stable Flaw

-Stable Flaw .0.5 x Stable- ~(1.4. times Leakage' (normal ~plus. Flaw (normal normal'plus- d l  : Location Flaw' ~ SSE' load) plus'SSE load)- SSE load)

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, SECTION 7.0 REFERENCES l s

• ' 1.1 D. H. Roarty et. al., Technical Bases for Eliminating Large Primary Loop j Pipe Rupture as the Structural Design Basis for Kewaunee, WCAP-11411, j Revision 1, Westinghouse Electric Corporation, April 1987 (Westinghouse Proprietary Class 2) 3.1 Nuclear Systems Materials Handbook, Part I - Structural Materials, Group 1 - High Alloy Steels, Section 4, ERDA Report TID 26666, November 1975 Revision.

3.2 ASME Boiler and Pressure Vessel Code, Division 1,Section III, Appendix I, 1983 Edition. ,

5.1 Kumar, V., et. al., " Advances in Elastic Plastic Fracture Analysis," EPRI '

i Report NP-3607, Project 1237-1, Electric Power Research Institute, August 1984. .

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APPENDIX-A.

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[.; THE NRC REQUEST FOR ADDITIONAL INFORMATION. .- i

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After reviewing-WCAP-11411, Revision 1, the.NRC' submitted..to. Wisconsin'Public j-.. ' Service Corporation a Request for Additional Informationiconsisting.'of eight items. The request is reproduced on the following pages. j

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i REQUEST FOR ADDITIONAL INFORMATION ON ELIMINATION OF POSTULATED PRIMARY. LOOP PIPE RUPTURES AS A DESIGN BASIS .

(1)' The primary loop piping and fittings were fabricated from cast stainless steel. Describe whether the piping and fittings are. centrifugally cast 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-11411, Revision 1. 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 zo88Psi,zes are not small compared with the half-crack ,

length "a". The licensee should use elastic plastic fracture mechanics-(EPFM) instead of LEFH procedures.

(5) Limit load analysis was used to estimate the size of a stable crack.

However, limit load analysis does not account-for material toughness 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 critical locations. 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.

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.(7) ~ The limiting location as discussed in item 6 above~ should be evaluated to (i. ' 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 .

1 4 submittal, the. licensee did not discuss the margin of-1.4 on the applied l load.' The-licensee should include this margin of 1.4 on the applied. load in:the LBB evaluations.)

-(8) The loads used for the LBB analyses in WCAP-11411, Revision 1, were the 1 a loads associated with the current primary loop supports. The licensee i should~ commit to reverifying the LBB analyses in the licensee's upcoming i steam generator support redesign program. j

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