ML20236R929

Nonproprietary Suppl 2 to Verification of Fracture Mechanics Analysis Techniques Used in Support of Technical Justification for Eliminating Large Primary Loop Pipe Rupture as Structural Design Basis for Beaver Valley..

ML20236R929
Person / Time
Site:	Beaver Valley
Issue date:	11/30/1987
From:	Palusamy S, Swamy S, Witt F WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
Shared Package
ML19302D091	List: ML20236R923 ML20236R929 ML20236S073
References
WCAP-11318-S02, WCAP-11318-S2, NUDOCS 8711240117
Download: ML20236R929 (42)

Text

7, WESTINGHOUSE CLASS 3

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WCAP-11318 Supplement 2.

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VERIFICATION OF FRACTURE MECHANICS ANALYSIS TECHNIQUES USED IN SUPPORT I

0F'THE TECHNICAL-JUSTIFICATION FOR j

-ELIMINATING LARGE PRIMARY LOOP PIPE i

RUPTURE AS THE STRUCTURAL DESIGN BASIS l

FOR BEAVER' VALLEY UNIT 1 November 1987 F. J. Witt s

Verified'by:

o Nem y 7. A.) wamy xD:',. ~

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Approved by:

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5. 5. Palusamy, Manager i

Structural Materials Engineering i

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Work-Performed Under Shop Order DPDJ 950 y

WESTINGHOUSE ELECTRIC CORPORATION Generation Technology Systems Division a

P.O. Box 2728

.g Pittsburgh, Pennsylvania 15230-2728 l.

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' TABLE OF CONTENTS p

Section-Title O

Page A,4 s

.T 1-1 l'. 0

SUMMARY

AND INTRODUCTION

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1.~ 1 -

Sumary 1-1 1

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1.2 Introduction 1-2'

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- 2.0 VALIDATION OF THE ELASTIC?i.kSTL: FRACTURE MECHANICS 2-1 ANALYSES OF CIRCUMFERENTIALLY FLAWEG PIPES 2.1 Introduction 2-1 2.2_

The Significance of the Stress-Strain Relationship.

2-1 2.3 A Rationale for Stress-Strain Curve Estimation 2-2 2.4 The Validation Analyses 2-3 2.5

' Application of the Handbook Procedure in Leak-2-7

)

Before-Break Analyses c.

.v

-2.6

= Handbook Procedure Results Based on Mid-Range 2-97 f ~

I Strain' Y,

,r 4

2.7 ~ Relevance of this Section to Ittri 1 of, the j

2-9

,j I

NRC Request r

3.0 AVERAGE PROPERTIES FOR AUSTENITIC S~rAINLESS STEEL' 3-1

)

1 4;0 REFERENCES-

,J

1. 4-1 J'

- 4 l7 APPENDIX A THE SECOND NRC REQUEST FOR ADDITIONAL INFORMATION A-1 p

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_t LIST OF TABLES 1

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Table o7

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!9 2-1 GEOK,ETRICAL DESCRIPTION FOR THE ANALYSES 2-11 p.j 4(

2-?. -

MATERIAL PRCPERTIES FOR THE ANALYSES 2-12

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~ 2-3 LOADINGS FOR THE ANALYSES 2-13 s

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l.IST OF FIGURES 1),

p Figure Title Page

'h 2-14 2-1 Comparlton of [

a

,)a,c.e 2-2 Stress-Strain Curves used in Computer Code Results 2-15 Comparison - SA376 TP316 Material at 600'F 2-3 Stress Strain Curve for Cases 2 and 3 - SA376 TP316 at 653'F 2-16

F-4 Comparison of Ranterg-Osgood Curve (2 Couple Fit Used 2-17 1

in Case 1) with 'Kultilinear Stress Strain Curve Used intheFinitoElemestAnalysis A.

2-5 Cenaarison of Ramberg-Osgood Curve (13 Couple Fit 2-18 UsedinCasat!2and3)WithStressStrainCurveUsed in Finite Element Analysis 2-6 Case 1 - Comparison of J Results Using Handbook Procedure 2-19 I

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'with the Finite Element J Results

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2-7 Case 2 - Comparison of J Results Using Handbook Procedure 2-20 o

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with tne Finite Element J Results i

I 2-8 Caso 3 - Comparison of J Results Using Handbook Procedure 2-21

4, with the Finite Element J Results i.E j{f},

!i 2-9 Comparison of Four Couple Ramberg-Osgood Fit Used in Case 2-22 i

2A with the Stress Strain Curve l

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H LIST OF FIGURES (cont.)

d.

Figure Title Page

'2-10' Comparison of J Results Using Handbook Procedure in 2-23 Case'2A with Finite Element J Results in Case 2

1. 2-11:.

Comparison'of J Results Using Handbook Procedure in 2-24 Case'3A-with Finite Element J Results in Case 1 2-12 Comparison of 4 Couple Ramberg-Osgood Fit.Used in 2-25 Case 1A with the Multilineal Stress-Strain Curve of Case 1-2-13.'

Comparison'of J Results Using Handbook Procedure in 2-26 Case 1A with Finite Element J Results in Case 1 2 Comparison of Mid-Range Strain Fit Ramberg-Osgood Curve 2-27 used is Case 2B with Stress Strain Curve of Case 2 2-15

~ Comparison of'J Results Using Handbook Procedure in Case 2-28 2B Having Mid-Range Strain Fit Ramberg-Osgood Curve with Finite Element J Results of Case 2 i

X

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1 L

SECTION 1.0

SUMMARY

. AND INTRODUCTION i

E,.

)

11.1' Summary Duquesne Light Company submitted a ' leak-before-break analysis, WCAP-11317, to NRC. in support of. their snubber reduction program for Beaver Valley Unit 1.

After. completing their review the NRC transmitted to Duquesne Light Company a l.

request for additional information. Duquesne Light Company contracted with

'. Westinghouse Electric Corporation to respond to the NRC request including the.

H performance of analyses.. The response is documented in WCAP-11317, Supplement w

l 1.

After reviewing the supplement, the NRC submitted an additional request for information which consisted of two items. This Supplement 2 of WCAP-11317 l

is the response to'the latest request for information.

p Item.1 of the NRC request addresses the validity of the J results obtained to h

demonstrate the factor of. 2 on the leakage flaw size.

In response to this concern a study is presented which validates the results presented in c-

'WCAP-11317, Supplement 1.

The procedure used by Westinghouse in fitting a

Ramberg-Csgood curve to the stress strain curve of the material is described.

This procedure is validated by comparison with the results of three finite I

L element. analyses. The procedure is shown'to be either accurate or conservative. An example is presented which shows that fitting the mid-strain

. range (i.e., 2 to 5 percent) of the stress strain curve with a Ramberg-Osgood

+

representation yields unrealistic J results not appropriate for engineering applications.. It is concluded that the J results of WCAP-11317, Supplement 1

(

are either accurate or conservative. No new results are submitted and the prior.resultr are unchanged.

In response to the second NRC concern the methodology for determining average L

properties are further discussed based upon the referenced work developed by Hanford Engineering Development Laboratory.

3 1-1

f' L

l'.2 ~ Introduction I

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 Postulated Primary Loop Pipe Ruptures as a Design Basis. Westinghouse prepared the response which is documented in WCAP-11317, Supplement 1 (reference 1.2). After reviewing the response, the NRC issued a second Request for Additional Information on Elimination of Postulated Primary Loop

Pipe Ruptures as a Design Basis. Two items of concern were listed. This second supplement to WCAP-11317 is the response to the latest NRC request (see

. Appendix-A for a copy of the request).

The first item of the second NRC request is addressed in Section 2.0 and the remaining item in Section'3.0.

e 4

1-2

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SECTION 2.0 h

VALIDATION OF THE ELASTIC-PLASTIC FRACTURE MECHANIC ANALYSES OF CIRCUMFERENTIALLY FLAWED PIPES ea l~

2.1L' Introduction I

. Westinghouse has applied the EPRI Handbook Procedure'(reference 2.1, hereafter

! called the' handbook procedure) of elastic plastic fracture mechanics in 1str.bi.lity evaluations of circumferential1y flawed pipes typical of PWR primary

/ loops.. Such applications were made in.the stability analyses of the Beaver

[.'

N11ey Unit 1. primary loop as given.in reference 1.2.

E*

. Prior to applying the handbook procedure adequate assessments were made to fjustify application of the handbook procedure to stability analyses of circum-L

?ferentially flawed pipe typical of those evaluated for leak-before-break.

LThis activity has been ongoing. Additional assessments have been made to establish the range of practical applicability. Verification results are

'given.in this section sufficient to draw specific conclusions.concerning the handbook' procedure including range of applicability for the type of problems A

of interest.

2.2 '.The Significance of the Stress-Strain Relationship A basic assumption is that finite element analyses yield the most accurate state-of-the-art solution and serve as a benchmark for validation of the handbook procedure. The handbook procedure is in fact an interpolation scheme

. based on finite element results and would be expected to give very accurate results if only interpolation were involved.

However, there is an important aspect of the handbook procedure which is an open issue, that of how to fit a given stress-strain diagram with the required Ramberg-Osgood curve.

This p

. issue is discussed extensively in the remainder of this section.

A Ramberg-Osgood representation of the stress strain relationship is assumed of the form N

h = h + a (h)

(2-1) o o

o 1

2-1 I

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I

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j where o and e. denote stress and strain, respectively. a and N are the Ramberg-Osgood coefficients. Subscript o indicates the stress and strain at yield, Rigorously speaking,[

)a,c.e l

Equation (2-1) represents the stress-strain behavior of the material of interest here (i.e., stainless steel) only to an approximation. As seen

. lator, the method of approximating the stress-strain behavior can have an impact on J-integral results every bit as significant as changing flaw size, loading or geometry.

Frequently, the key to performing an accurate or reasonably accurate analysis is the use of the proper a and N.

This is especially true when the nominal stress is in the elastic plastic regime.

Thus the problem is not with the accuracy of the handbook procedure itself but with the Ramberg-Osgood coefficients. Landes and McCabe (reference 2.2) have evaluated the applicability of the Ramberg-Osgood relationship to the stress-strain behavior of stainless steel and have concluded that e reasonably good fit cannot be obtained over the full strain range.

They suggest a mid-strain fit as perhaps being the best. The impact on J calculations was not addressed. This impact is addressed below.

2.3 A Rationale for Stress-Strain Curve Estimation As a rationale for approaching the problem of determining the Ramberg-Osgood coefficients, there are certain facts which are helpful.

First and foremost, it is generally known that when the nominal stress produces plastic flow the J value increases very dramatically.

Thus an a priori requirement to obtaining fairly accurate results as the elastic plastic regime is entered, is to adequately fit the stress-strain relationship of interest as strain hardening It would seem reasonable, that to maintain accuracy as more occurs.

plasticity occurs, the stress-strain curve of interest must continue to be reasonably described by the Ramberg-Osgood fit.

It is also reasonable to judge that if the strets-strain relationship is not reasonably well fit as 2-2

early plasticity occurs then the J-integral results may not be accurate in f

that stress region and will be questionable at higher plastic regions until such a high strain is obtained for which earlier effects are minimized.

2.4 The Validation Analyses For leak-before-break finite element J-integral analyses Westinghouse uses the computer code L

>]a,c.e results l

have been compared with results of others with very good success. Of interest here a comparison is given in figure 2-1 of the J-integral results presented in the landmark work of reference 2.3 and a more recent analysis using the latest version of (

Ja,c.e

[

aj,c,e In figure 2-1 the comparison of results using the same stress-strain curves is excellent, In this section then, J-integral results obtained using the EPRI handbook procedure will be benchmarked against [

3a,c e results.

As previously noted, finite element results such as presented in figure 2-1 are judged to be state-of-the-art. This should perhaps be temperad by noting that again the' approximation of the stress-strain curve is critical.

For, example,(

)a,c.e To validate the handbook procedure the results of three finite element J-integral analyses are used to benchmark the handbook procedure.

These analyses are also used to develop a methodology for applying the handbook 2-3

f.-

l

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procedure in engineering applications to circumferential cracks in pipes typical of those analyzed in leak-before-break analyses of Westinghouse type PWR primary loop piping systems.

I Geometrical descriptions of the three pipe configurations (referred to as case 1, 2, and 3) are given in table 2-1.

Case 1 is the geometry for the configuration of figure 2-1.

Case 2 and 3 have the same pipe dimensions but different crack lengths. The crack angles indicate the crack :izes are typical of.those analyzed in leak-before-break margin analyses for the larger diameter piping involving a factor of two on leakage flaw. The crack lengths are perhaps most often on the high side of the leakage flaw for which a margin on load is applied.

i The material properties are given in table 2-2, including those for cases discussed later. The stress strain curves for the cases 1 through 3 analyses are given in figures 2-2 and 2-3.

Figure 2-2 comes directly from reference 2.3.

The stress strain curves from both figures were developed using the Nuclear Systems Materials Handbook which is discussed in section 3.0.

Also

• i given in table 2-2 are the Ramberg-Osgood coefficients used in the handbook procedure analyses, including those for cases discussed later.

The procedure used for selecting the stress-strain points (input couples) for fitting the Ramberg-Osgood relationship (equation 2-1) for the validation analyses is as follows.

[

)a,c.e 2-4

The results taken from reference 2.3 represents an early effort with [

Ja,c.e but the multi-linear results of figure 2-1 were, of course, obtained using the same stress-strain input couples as used in reference 2.3.

The objective of the handbook procedure analysis of case 1 is then to obtain results comparable to the finite element results. For a maximum strain limitation of [

ja,c.e j

- for case l'as given k table 2-2, recognizing, of course, that additional points could be obtained by interpolation. The two couples provided an exact fit at the couples. A comparison of the Ramberg-Osgood fit with the stress-strain multi-linear curve is given in figure 2-4.

A reasonable fit is obtained up to [

ja.c.e It should be observed that, in general, a fit couple is on the Ramberg-Osgood curve whereas the input couple is at the same stress level but on the i

stress-strain curve.

Noting that the Case 1 analysis predates the Cases 2 and 3 analyses by at least five years, a directed effort was made in setting up the finite element input for Cases 2 and 3 to well defina the [

]a,c.e Ten couples ' including the proportional limit were used as input. A comparison of the finite element stress strain couples with the stress-strain curve is given in figure 2-5.

The stress-l strain curve is well defined by the finite element input couples.

The same nine strain-hardening couples and four additional couples were used for the l

Ramberg-Osgood fit. The four additional couples [

Ja,c.e The Ramberg-Osgood curve is also given in figure 2-5.

[

I

)a,c.e 2-5 L..

The loadings on the finite element models consisted of an axial forco which was applied first followed by incremental loadings up to the desired axial moment. The current capability for the. handbook procedure as given in reference 2.1 does not include a combined axial force and axial bending moment

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formulation'.

j For cases where the axial stress, o,, is well below yield, [

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1 Ja,c.e The loadings for the three cases are given in table 2-3.

Equivalent moments are also given as well as the maximum monent and maximum stress levels obtained in the finite element analyses.

The stress in

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ksi per 1000 in-kips moment is also given for obtaining intermediate stress levels.

A comparisbn of the Case 1 handbook procedure J results versus moment with those from the finite element analysis is given in figure 2-6.

Overall the comparison is excellent up to a moment of near 40,000 in-kips.

The cor-responding stress level is 29.3 ksi.

(.

ja,c,e The small differences noted up to [

Ja,c.e are inconsequent-tial and.can easily be accounted for in the differences noted in the stress-strain curves of figure 2-4.

As noted previously, the finite-element descrip-tion of the stress-strain curve does not depict the [

Ja,c e In fact the Ramberg-Osgood curve gives a better fit.

This is based on the fact that of a multitude of fittings 2-6

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l i

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of stress-strain curves, [

Ja.c,e This is seen in figure 2-5.

Looking at figure 2-4 and based on strain hardening alone, one might speculate

'I 4

that the finite-element results would slightly exceed the handbook procedure

. results up to around a stress of 30 ksi even if the two methods compared exactly. One would expect the-handbook procedure to produce substantially higher J values as the stress increases above 30 ksi.

[

ja,c.e

. For Case 2, a comparison of J versus moment curves for the finite element and handbook procedure results is given in figure 2-7.

Excellent agreement is noted.'up to a moment of around [.

f ga,c,a I

Case 3 results are given in figure 2-8.

The comparison is excellent over the whole loading regime. - Particularly, the small flaw analysis (Case 3) appears 1

to give a slightly better comparison than the large flaw analysis (case 2).

In conclusion, the handbook procedure is seen to be successfully benchmarked against three finite element analyses.

The pipes analyzed are typical of the larger pipes in the' primary loop of Westinghouse type PWRs. The relative flaw 4

sizes well span the flaw sizes of concern in leak-before-break analyses.

~ Forces are typical and moment loads up to those of interest are evaluated.

1 I

t.

. 2.5 Application of the Handbook Procedure in Leak-Before-Break Analyses

)

In J evaluations of circumferentially flawed pipes of interest in-leak-before-break stability analyses, the handbook procedure has been applied however with some constraints.

2-7 l

a J

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Once a problem is well defined, the first step is to obtain the Ramberg-Osgood coefficients. However there is one restriction.

[

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.]a,c e The casa is designated 2A. Only four couples were used in tSe fit. A comparison of the actual stress-strain curve with the fitted results is shown in figure 2-9.

The adequacy of the fit is judgemental.

However J values for a stress level above [

]a,c e are considered invalid.

The load level defined by the maximum applied stress (in this case [

]a,c.e) defines the cut-off point for acceptable results. A slightly higher stress can be used in conformance with the above restriction.

The J results using this procedure for Case 2A are compared with the Case 2 finite' element results in figure 2-10.

For the axial stress of [

ja,c,e The comparison is excellent up to this level of J.

The same situation as above was run for Case 3 and is designated Case 3A.

The cut-off moment is [

]a,c,e Results are given in figure 2-11.

The value of J at the [

la,c,e It is also seen that at higher moments Case 3A is unconservative for the results i

plotted.

Excellent agreement is seen up to the cut-off point.

Finally Case 1 was reevaluated for a maximum stress level not exceeding

~

[ ]a,c.e ksi.

This case is designated Case 1A.

The Ramberg-Osgood curve is compared with the one used in the finite element analysis in figure 2-12.

2-8

E p

r Interestingly, a, better. fit is obtained in the 20 to 25 ksi range than was obtained in the original case. The cut-off moment is [

]a,c.e l

The J results are compared in figure 2-13. The handbook procedure results are

' conservative throughout the moment loading.

j

- It is thus seen that the handbook procedure with load cut-off as described

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here produces results which. agree very wel1~with finite element results or which are conservative. This procedure is strictly adhered to.

The use of J values above the cut-off load is not acceptable unless confirmed by an independent approach.'

~

2.6 Handbook Procedure Results Based on Mid-Range Strain It is quite easy to obtain a reasonable Ramberg-Osgood fit to the stress-strain curves of interest in the midrange of strain between 2 and 5 percent.

For' example, a Ramberg-Osgood fit of the stress-strain curve of Case 2 in the range of from 2 to 5 percent is shown in fiaure 2-14.

The fit curve [

l.

Ja,c,e This case is designated 28. The J results from the handbook procedure'are compared with the Case 2 finite element results in figure 2-15.

The handbook procedure

{

l results are unacceptable for engineering applications.

This is true even for a' loading stress level in the 2 to 5 percent strain range since the stress 1

level for the finite element results presented go as high as [.

]a,c.e i

2.7 Relevance of This Section to Item 1 of the NRC Reauest Item 1 of the NRC request is given in Appendix A.

The relevanco of the above part of this section to item 1 is discussed.

First it is shown that the handbook procedure produces very accurate or conservative estimates of finite element results if a good Ramberg-Osgood fit of the stress strain curve starting with initial strain hardening is obtained.

2-9

j Since a good fit is generally not obtainable over a large strain range (up to 5' percent), a good or conservative fit early in the strain hardening is necessary if any success is to be obtained in comparison with finite element results using the stress-strain curve of interest.

To assure Ramberg-Osgood l

coefficients within the matrix of the handbook procedure and continuation of accurate or conservative results a load cut-off procedure is used.

The handbook procedure used to obtain the J results of reference 1.2 followed the methodology of this section.

It is therefore concluded that the J results presented in reference 1.2 are either accurate or conservative and that no additional J analyses are required.

Perhaps it should be noted that estimation methods which underestimate J values from finite element analyses well into the elastic plastic regime of ten overestimate J in the low stress regime. For example, the LEFM method with plastic zone correction as noted in item 4 of Appendix A of reference 1.2 is one such method.

It is considered inappropriate te perform extensive evaluations of methods which are not used by Westinghouse such as identified in NUREG-1061, Volume 3 (reference 2.5) and NUREG/CR-4572 (reference 2.6) and with which Westinghouse has limited experience.

In conclusion, the results of reference 1.2 are considered to be acceptably accurate and reevaluations are not necessary.

This is the response to Item 1 of Appendix A.

O 2-10

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GE0 METRICAL DESCRIPTION FOR THE ANALYSES

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.'0UTSIDE

. NOMINAL CRACK CRACK' l-CASE-

- DIAMETER

THICKNESS-TEMPERATURE.

LENGTH ANGLEa

.IN ).

(IN.)

('F)

(IN.)-'

("F)

(

NO.

a,c,e-V

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abased on radius'to middle surface.

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TABLE 2-2

- MATERIAL PROPERTIES FOR,THE ANALYSES.

r MODULUS OF CASE-ELASTICITY.

POISSION'S PROPORTIONAL RAMBERG-OSGOOD COEFFICIENTS NO. -

(psi)

RATI0t LIMIT (psi)

'a N

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aihe flow: stress was taken asL42500 psi IThe flow stress was taken as 40000 psi a

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Figure 2-2 Stress-Strain Curves used in Computer Code Results Comparison -

SA376 TP316 Material at 600*F 2-15 l

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. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - - _ - _ _ _ _ _ _ =.

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Figure 2-3 Stress Strain Curve for Cases 2 and 3 - SA376 TP316 at 653*F 2-16

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Figure 2-4 Comparison of Ramberg-Osgood Curve (2 Couple fit Used in Case

1) with Multilineal Stress Strain Curve used in the Finite Elen.ent Analysis 2-17 i

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m t.'

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Figure 2-5 Comparison of Ramberg-Osgood Curve (13 Couple Fit Used in Cases 2 and 3) With Stress Strain Curve Used in Finite Element Analysis 2-18

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Figure.2-7 Case 2 - Comparison of J Results Using Handbook Procedure with the Finite Element J Results 2-20

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i Figure 2-8 Case 3 - Comparison of J Results Using Handbook Procedure with the Finite Element J Results 2-21

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Figure 2-9 Comparison of Four Couple Ramberg-Osgood Fit Used in Case 2A with the Stress Strain Curve 2-22

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a i

SECTION 3.0 AVERAGE PROPERTIES FOR AUSTENITIC STAINLESS STEEL The stress strain curves at operating temperatures are obtained from the Nuclear Systems Materials Handbook (reference 3.1). The methodology was

. developed by extensive analyses of actual stress strain behaviors from many experimental results. Generally the lower bound properties are used in the stability analyses for leak-before-break evaluations, several of which have been approved by the NRC. The lower bound properties so determined agree very well with the ASME B and PV Code Section III Code minimum properties. To obtain average properties, the procedure of reference 3.1 is to multiply the lower bound yield stress by 1.25 and continue the calculation, the yield stress being involved in determining the proportional limit and all strain levels for stresses exceeding the proportional limit. This procedure of course resulted from the multitude of data evaluations upon which reference 3.1 is based.

The work of reference 3.1 was sponsored by the Energy Research and Development Agency (ERDA) at the Hanford Engineering Development Laboratory (HEDL) and is considered a landmark work.

TheLabove is 'the response to Item 2 of Appendix A.

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3-1

SECTION

4.0 REFERENCES

1.1 D. H.. Roarty et. al., Technical 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).

1.2 F. J. Witt et, al., Additional Information in Support of the Technical Justification for Eliminating Large Primary Loop Pipe Rupture as the Structural Design Basis for Beaver Valley Unit 1, WCAP-11317, Supplement 1, Westinghouse Electric Corporation, September 1987, (Westinghouse Proprietary Class 2).

2.1 V. Kumar, M. D. German, and C. P. Shih, "An Engineering Approach for Elastic-Plastic Fracture Analysis," EPRI Report NP-1931, Project 1237-1, Electric Power Research Institute, July 1981.

2.2 " Toughness of Austenitic Stainless Steel Pipe Welds," EPRI NP-4768 Electric Power Research Institute, Principal Investigations, J. D. Landes

~~

and D. E. McCabe, October 1986.

2.3 S. S. Palusamy and R. J. Hartmann, Mechanistic Fracture Evaluation of Reactor Coolant Pipe Containing a Postulated Circumferential Through-Wall Crack, WCAP-9558, Rev. 2, Westinghouse Electric Corporation, May 1981 (Westinghouse Proprietary Class 2).

2.4 C. Y. Yang and'S. S. Palusamy, "VCE Method of J Determination for a Pressurized Pipe Under Bending", Journal of Pressure Vessel Technology, Vol. 105, February, 1983, pp. 16-22.

2.5 Report of the U.S. Nuclear Regulatory Commission Piping Review Committee

- Evaluation of Potential for Pipe Breaks, NUREG-1061, Volume 3, U.S.

Nuclear Regulatory Commission, November 1984.

4-1 E-------

)

l 2.6 R. Klecker, et. al., NRC Leak-Before-Break (LBB.NRC) Analysis Method for Circumferential1y Through-Wall Cracked Pipes Under Axial Plus Bending Loads, NUREG/CR-4572, BMI-2134, U.S. Nuclear Regulatory Commission, May 1986.

~

3.1 Nuclear Systems Materials Handbook, Part I - Structural Materials, Group 1 - High Alloy Steels, Section 4, ERDA Report TID 26666, November 1975 Revision.

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1 1

APPENDIX A.

.'THE SECOND NRC REQUEST FOR ADDITIONAL INFORMATION 1*:

' After. reviewing WCAP-11317, Supplement-1, the NRC submitted to Duquesne Light 7

- Company'a Request for Additional Information consisting of two items. The request is-reproduced ~on the'following page.

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. REQUEST FOR' ADDITIONAL INFORMATION c ON: ELIMINATION OF: POSTULATED PRIMARY LOOP PIPE RUPTURES f

AS A DESIGN BASIS j

a

,L ll (1)(The'staffhas'performedindependentflaw'stabilitycomputationsbasedon

'~l elastic plastic fracture mechanics (EPFM) procedures using data specific

' to' Beaver. Valley Unit I as provided by the licensee. However, the staffs results disagreed with those provided in table 5-1 in WCAP-11317, l

c Supplement 1, relative to the factor of 2 on the leakage flaw size. The

. licensee ~used. the EPFM procedures.in Reference 5.1.in WCAP-11317,

Supplement 1.

The. staff benchmarked the licensee's procedures with the staff's procedures in NUREG-1061, Volume 3, and concluded that the tlicensee's procedures resulted in higher values of the crack driving force parameter " applied J" as compared with the staff's procedures.

However, the " applied J" values presented in the top half of Table 5-1 in WCAP-11317, Supplement 1 to' demonstrate the factor of 2 on the leakage flaw size were less than those obtained by the staff.. The licensee should verify the~ calculations:and-resubmit the " applied J" values used to demonstrate. the ' factor of 2 on the leakage flaw size.

(2)L In-Section 3.0 in WCAP-11317, Supplement 1, the licensee stated that the average austenitic material properties were determined by multiplying the Code minimum values by a factor of 1.25.

The licensee should provide a brief. justification for this estimation procedure.

1 1^

'" The two items below make up the second NRC request.

S A-2

_ _ _ _ _ _ _ _ _ _