ML20246H265

Nonproprietary Addl Info in Support of Evaluation of Thermal Stratification for Beaver Valley Unit 2 Pressurizer Surge Line

ML20246H265
Person / Time
Site:	Beaver Valley
Issue date:	08/31/1989
From:	Cranford E WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
Shared Package
ML19292J513	List: ML20246H255 ML20246H260 ML20246H265
References
WCAP-12094-S02, WCAP-12094-S2, NUDOCS 8909010202
Download: ML20246H265 (31)

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WCAP-12094.

. Supplement 2 k

ADDITIONAL INFORMATION IN SUPPORT OF THE EVALUATION OF THERMAL STRATIFICATION FOR THE BEAVER VALLEY UNIT 2 PRESSURIZER SURGE LINE E. L. Cranford K. C. Chang M. A. Gray R. L. Brice-Nash August 1989 Verified by:

Verified By:

I L

T. H. Liu F.@,Witt Approved by:

Approved by:

./

fM R. B.~ Patel, Manager

5. ST Palusamyf Manager Systems Structural Structural Materials Analysis Engineering WESTINGHOUSE ELECTRIC CORPORATION Nuclear and Advanced Technology Division P.O. Box 2728 Pittsburgh, Pennsylvania 15230-2728 a

~

unswees to

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n _-

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(

L FOREWORD This supplement addresses specific questions presented by the Nuclear Regulatory Commission during their audit of 88-11 issues at Beaver Valley Unit

"~

2.

The questions were presented to Duquesne Light Company in Docket No.

. 50-412, dated June 28, 1989.

The questions and their respective responses are provided on the following pages.

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wwma ie 5

e.

4 TABLE OF CONTENTS

)

Section Title Page 1.0 ISSUES AND RESPONSES ON SECTION 1.0 1

2.0 ISSUES AND RESPONSES ON SECTION 2.0 5

3.0l ISSUES AND RESPONSES ON SECTION 3.0 13 ERRATA 24

>h l

3872s/081689 10 i

k 1.0 ISSUES AND RESPONSES ON SECTION 1.0

~

ISSUE 1:

Need to review document SSDC 1.3 which defines thermal design transients for BV-2.

How was this updated to reflect a)

The monitoring data? b) From which plants? c) Was a combination of plants used or was one plant (worst case) only?

RESPONSE

SSDC 1.3 was not updated to incorporate surge line data.

The monitoring data from Beaver Valley Unit 2 was used in conjunction with data from plants A, B, and C pressurizer surge lines to create an enveloping transient set with stratification for heatup and cooldown transients.

The new heatup and cooldown transients per WCAP-12093 with stratification replaced the SSDC 1.3 heatup and cooldown transients.

The balance of the normal and upset transients defined in SSDC 1.3 was used in the surge line evaluation except that the transients were assumed to cause thermal stratification [

Ja,c.e It should be noted that some of the transients defined in SSDC 1.3 assume no insurge or outsurge and are therefore not considered to cause thermal stratification.

The combination of transients defined in WCAP-12093 are considered to conservatively envelope all four plants monitored.

ISSUE 2:

Delta T

=T

-T Why this does not agree for Strat PRESS RCS some events of tables 1-4, 1-5?

RESPONSE

The pressurizer and reactor coolant hot leg temperatures defined in the surge line transients reflect the approximate system delta T and not the pipe delta T.

Delta T in tables 1-4 Strat and 1-5 are pipe delta T and not system delta T.

e 3872s/0616E910 g

ISSUE 3:

What is the % difference or actual values for the pipe myt's at critical locations between analytical values and HFT?

RESPONSE

See response to section 2.0, Response No. 4 ISSUE 4:

The licensee reported that "An additional conclusion from the heat transfer and stress analysis is that the steady state stratification stresses at points of maximum stress envelopes the peak transient stress, even in the case of a step change temperature." What is the justification for this?

RESPONSE

Westinghouse performed analyses to show that the thermal shock effects due to an instantaneous change in fluid temperature, when considering thermal stratification, are less severe than the total effects of steady state thermal stratification.

The analyses show that during the initial insurge of cooler fluid local axial stresses reach a maximum about {

Ja,c.e into the transient.

This corresponds to the time when the through-wall temperature difference is at a maximum.

The global bending of the pipe during this time has not yet been established since the bulk of the pipe material is still at some initial uniform temperature. As the pipe approaches thermal equilibrium the through wall temperature difference gets smaller. At the same time the global bending effects accelerate and produce global bending stresses.

In the thermal equilibrium condition, the global bending stresses, when combined with the local stratification stresses, produce higher total stresses than the thermal shock stresses alone.

i I

l 3872s/081689 10 2

_N

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ISSUE 5:

In reference to figures 1-33, 1-34, and 1-35 a) Where is l-location 17 b)

Is this the worst case?

If yes, justify.

RESPONSE

The locations referred to in figures 1-33,1-34, 1-35 and 1-36 represent monitoring locations on the corresponding surge lines

~

(figures 1-6 through 1-9).

Location 1 for figure 1-33 shows the only location monitored with top and bottom mounted temperature detectors, see figure 1-6, RTD location A.

The monitoring results for location 1 for figures 1-34, 1-35, and 1-36 do show the worst case thermal activity for those plants.

The corresponding pipe locations where these readings were taken are shown in the figt,res 1.5-1, 1.5-2 and 1.5-3 attached. The determination of worst case is a combination of [

ja c.e It can not be stated that location 1 for Beaver Valley Unit 2 is the worst case, since it was the only location where pipe delta T could be observed.

However, location 1 is in the general

~

vicinity where the highest pipe delta T's are expected.

~

ISSUE 6:

Fig. 1-35.

Why data for plant "B" were used instead of BV-2 data?

RESPONSE

Figure 1-35 was intended to show'the method used to determine the number and relative magnitude of fatigue significant events.

This method was applied to all the monitoring data to determine the number of fatigue significant events each plant experienced per heatup and cooldown.

The Beaver Valley Unit 2 data were also evaluated in this manner.

ISSUE 7:

Section "F" page 1-12.

What is the justification / basis for this?

RESPONSE

The basis for the final cycles and stratification ranges are the monitoring data shown in tables 1-15 and 1-16, and historical data shown in table 1-17.

The process shown in section F (page 1-12) is simply the reconstruction of the observed data with conservatism added to yield a design basis [

)"'C transient set.

1872s/081C 10 3

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ISSUE 8:

Figures 1-37, 1-38.

How was this factor derived?

J

~ '

RESPONSE

Figures 1-37 and 1-38 were developed to show graphically the comparison between the design transients assumed and the actual

~

transients observed.

They represent the results of a fictitious evaluation that was supposed to show only the relative severity of the design transients as compared to the actual transients experienced by the sampled plants.

[

J,c.e Then a a

simplified fatigue calculation was performed and the results shown in figures 1-37 and 1-38.

ISSUE 9:

Explain tables 1-14, 1-15, 1-16, 1-17, 1-18 a) How was this data derived and used? b) How do they relate to BV-2?

a) Table 1-14 is an example showing the approximate r.iagnitudes of each

RESPONSE

significant cycle shown in figure 1-35; [

3a,c,e Table 1-15 shows the data used to determine the design distribution of the strength of stratification factors.

This table shews the intervals used to group the strength of stratification factors and to determine their relative distribution.

[

3a,c e l

Table 1-16 shows the data used to determine the number of cycles of stratification events for one heatup for design purposes.

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)a.c.e 3872s/De t68910 4

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Table 1-17 was developed from historical data collected from plants A & B.

{

ja.c.e Table 1-18 shows the striping transients used in the design evaluation.

[

3a,c.e b) The basis for tables 1-14 through 1-16 was actual monitoring data, including Beaver Valley Unit 1.

Beaver Valley Unit 2 monitoring data was used in the development of [

)a,c.e 2.0 ISSUES AND RESPONSES ON SECTION 2.0 ISSUE 1:

Figure 2-3 (Page 2-21) What is the significance of this model and how does this relate to BV-27

RESPONSE

The Figure 2-3 shows the layout and supports of a typical surge line.

The model was used to verify the suitability of using an i

equivalent linear temperature profile and the ANSYS computer code to perform the structural analysis of the surge line under stratified conditions.

Once it was demonstrated that the ANSYS code is suitable for the application, it was used for the Beaver j

Valley Unit 2 analysis.

9 l

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3

ISSUE 2:

Figure 2-4 What about the case of top-to-bottom Delta T = 320'F.

RESPONSE

Figure 2-4 describes the temperature profiles in the verifica~

tion analysis using the typical surge line layout of figure 2-3.

These temperature profiles were not used in the Beaver

~

Valley Unit 2 surge line analysis. A aT,,

of 320'F was used in the Beaver Valley Unit 2 surge line analysis as indicated in Tables 1-4 (page 1-20) and Section 2.1.3 (page 2-5).

ISSUE 3:

Need to review cases of thermal stratification which have been obtained by interpolation from the 11 cases run.

RESPONSE

Moment values for all individual transient cases, obtained by interpolation from 11 cases, are included in the input decks to WECEVAL.

The methodology used to obtain these moments is provided in the documentation.

The 11 cases provide sufficient data to evaluate all the transients defined in tables 1-4 and

~

1-5.

~

ISSUE 4:

. Provide maximum values and locations for a)

Displacements calculated vs. measured b)

Reaction values c)

Stresses for ASME III equations 9, 10, 11, 12, 13, 14.

Need to ses comparison with/without stratification.

RESPONSE

Maximum values and locations:

a.

Displacements Node 182 of figure 2-22 corresponds to the approximate lanyard location where the comparison is made.

Measurements provided at lanyard location were:

Vert. displacement = -2.4 inches for Pipe delta T = 180*F Vert. disp. = -2.5 inches for Pipe delta T = 200*F un.w ne ic 6

+/

t t!

w.

L

' Analysis results:;(node 182'in model-lanyard location)'

Corresp. vert disp.=~-2.5 inches for Strat.-Case 2,' delta T-

~

= 182'F 9

Max vert. disp. = -4.1 inches for Strat Case 1, delta 1

'T

= 320'F

- strat.

b.

Reactions Maximum reactions from anelysis.for pipe delta T = 320 F, at ends of model:

Hot leg: 1FX = 7.6 K PZR:

FX =

7.6 K FY =-10.0 K FY = 10.0 K-FZ = 8.1 K FZ =

-8.1 K MX = 4175 IN-K MX = -1104 IN-K MY = 836.IN-K MY = -741 IN-K MZ'=-3038 IN-K MZ =

283 IN-K n.::

c.

ASME III Stresses y.

1)

-Without stratification: One case run in the strati-fication analysis was a normal operating condition without stratification. This case was used to benchmark the ANSYS model. For all stresses without stratification, see BV-2 stress report.

2) With stratification:

Eq. 9:

Not affected by stratification; existing analyses unchanged Eq. 10:

['

ja,c,e Eq. 10 values are calculated for all combinations-in elastic plastic analysis to determine penalty u

factor, Ke,

.ws.mssm no 7

_ _ - _ = _ _ _ _ _ _ _ _ _ _ _

[ p..;

5.4 L Eq. 11,14:

Actual' maximum values of these stress equations are not' checked against,a specific allowable stress, but are reflected in the final usage factor

~"_.

values.

Maximum usage factor of [

~

)a.c.e l

Eq. 12:

Maximum value was calculated at [

3a,c.e.and is-54.1 ksi.

Corresponding allowable stress 3S,= 55.5 ksi.

Eq. 13:

Values of.Eq.13 from existing analyses are not affected by thermal stratification loading where-no gross structural discontinuity is present.

Therefore, Eq. 13 was only recalculated at [

3a,c.e Maximum-value calculated'is =-33.6 ksi. Corresponding allowable stress 3S, = 48.6 ksi.

l

' ISSUE 5:

How was the worst case (enveloped case) determined for fi'im-coefficients and fluid velocities?

RESPONSE

Film coefficients were calculated for a~ wide range of fluid velocities.

[

3a,c,e The value used also corresponded well with the known fluid velocities during the period evaluated..

ISSUE 6:

Need to review results of the flow model test which were used to establish the boundary conditions for striping effects.

RESPONSE

Thermal striping was examined during 1/5 scale water model flow tests performed for the Liquid Metal Fast Breeder Reactor-primary pipe' loop (reference 2.1).

These tests were performed

[

by Westinghouse at the test facility in Waltz Mills, Pa.

In l..

order to measure striping, thermocouple were positioned at 5 locations in the hot leg piping system (three in the small diameter pipe and two in the large diameter pipe).

Thermocouple

. un,amo 8

.4

'.i

.o l

locations ~were selected [.

']a,c.e Figure 2.6-1 shows the

. test setap'and location of thermocouple.- The inside diameters of.the 1crge and small pipes were 6-1/2 and 4 inches, respectively.. Figure 2-59 of WCAP-12093 shows the test pipe size with circumferential position of. thermocouple.

The thermocouple extend [

3a,c e into the fluid.

A tctal of [

']a,c.e tests were performed and evaluated. The [

3a,c.e were' reported in the test results and are shown in table 2.6-1.

Three parameters were measured during the flow water tests which establish boundary conditions for striping. They are: frequency of fluctuations, duration of-striping, and amplitude of delta fluid temperature.

The frequency of temperature fluctuations from these test results were reported to be in the'. range of [

]a,c.e As shown in table 2.6-1,'the [

ja,c e Table 2.6-1 also prc'vides the ['

ja.c.e

'3672s/082289-10 g

=

O ISSUE 7:

Figure 2-62, 2-63.

Were these F.E. models based on specific BV-2 input data or envelope parameters were used? If envelope parameters were used, what was the basis for that?

~

RESPONSE

The generic striping analysis was applicable to the Beaver Valley Unit 2 pressurizer surge line analyses.

However, the finite element analysis listed in figure 2-62 and 2-63 of j

WCAP-12093 was for a typical surge line.

[

l j

r i

e r Ja,c.e ISSUE 8:

Table 2-4 shows Delta T = 260*F.

What about Delta T = 320*F?

RESPONSE

Westinghouse analyses show [

Ja,c.e; therefore, stresses for the 320 F case can be determined from the 260*F case.

s.

3872s/081689 10 10

LISSUE 9:'

. Table 2-5, 2-6.. How are these values utilized in question 4c

?above? Explain.

RESPONSE

l Tables 2-5'and 2-6 show-stresses calculated from finite element

~

models [.

Ja,c.e' Values were obtained:for each trans'ient: load case by superposition of-stresses.due to.the.various loadings.. Actual stress--for a given g

loading was obtained using ratios based on specific'. load case parameters.

[

3a,c.e Load-case pressure and delta T are obtained from the transient definition.

[

Ja,c.e This is more fully described in the calculation packages..

ISSUE 10:

. Figure 2-45.

How were the five local stresses locations (for.

temperature gradient) and the eleven thermal transient load cases incorporated in this analysis? a) enveloped? b) ' actual cases c) applicability to BV-2?

4

RESPONSE

Local stresses in the RCL nozzle were determined using a location 1 profile per Figure 2-28. The RCL nozzle analysis

]

utilized specific moment loadings for all transient load cases.

J Moments at the nozzle for each load case were determined, as for all.other points, by interpolation from the 11 cases run in the j

global analysis.

[~

ja.c.e i

i yy j

. x n,eonin e ie 1

I

(

Ja.c,e The finite element model'

'was shown to be applicable' for Beaver. Valley Unit 2.inLthe calculations with: respect to geometry.. The transient load cases-were consistent with the reference. set of stratification transients defined'for Beaver Valley Unit 2.

ISSUE 11:

Figure 2-59. How were these results modified to be used for

~ larger diameter and thicker wall pipes?-

' RESPONSE:

The flow model. test results are used to obtain frequency and' duration parameters which are'used in the striping evaluation.

The frequency'and duration parameters are considered to be functions of the flow rate and buoyancy forces between the hot and cold water interface, and not pipe diameter and wall' thickness.

[

Ja,c e The total calculated usage factor for striping has been increased by 8

'50 percent to account for any uncertainty in the selection of frequency or other variables.

Section 2.0 -

References:

2.1'W. S. Woodward, " Fatigue of LMFBR Piping Due to Flow Stratification",

ASME Paper 83-PVP-59.

I O

e nn.mim in 12

y

+

,y

<?

s'

/

3.0LISSUES-AND R.ESPONSES ON

SECTION 3.d 1

~

j 701 i

' ISSUE'1; Which'are the fivefcases-used? -How were these determined:to be the worst case?

N RESPONSE:.

~In the-plant-specific analysis,-[-

s y

I 1

. l h

Ja c.e-The five worst cases selected.in the fatigue anaiysis are the in-line component in

.each profile region with the. highest C and K stress indices

~

' defined by the ASME Code.- At SD bends. K indices for.buttwelds-

'were conservatively applied.to add conse~rvatism.

ISSUE.2:

Need to discuss the superposition technique on the' stress component basis. How were.the " appropriate factors to account for= specific. transients and load cases" determined?

RESPONSE

For a given load condition, the total stress in the pipe is' determined by superposition of stresses due to pressure, moment and local stratification effects.

The stresses in the finite element model due to each of these types of loading were first determined for nominal values of load and stored on computer tapes.

[

3a c.e

.u e

3872s/081689 10 g

g, l

g Scale' factors were then developed for each load condition based on actual' pressure, moment.and stratification loading for each condition and stress indices for the component being evaluated.

'~

[-

Ja.c e C and C2 are determined from ASME y

Code Subsection NB-3681 for the component being evaluated.

The total stress at each node point in the finite element model is then determined by superposition of the individual contributions as follows:

[

3a,c.e The finite element model stresses on tape are the six stress components at each node point in the model.

36/2s/081689 10

}4 J

m, p

g-f After determining the total stress components for'each load condition defined in Tables 1-4 and 1-5, program WECEVAL j

proceeds with'the-fatigue evaluation according to NB-3222.4..:In the evaluation, peak effects are conservatively considered by' applying the maximum peak' stress iiidex' from.NB-3681 (K), K '

2 K ).f r the component being evaluated to the total stress.

3

ISSUE 3:

For which cases a)

~ASME.III code stress indices were used?

b)

F.E. stress' concentration effects were utilized?

RESPONSE

a) ASME B&PV Code Section'III stress indices were used for all cases except [

]a,c.e b) [

]a,c.e evaluation used the results of finite element analyses for secondary stresses in lieu of Code stress indices.

ISSUE 4:

Which 17 sections were evaluated for the usage factors? How was, it determined that these are the worst cases? What are the values?

RESPONSE

The mesh of the finite element model is such that 17' cross sectional cuts are defined by the element boundaries and node points in the circumferential direction (see attached Figere 3.4-1).

Thus, the 17 sections virtually comprise the entire model.

The values of stress at each section for each loading are contained on computer tapes used in the evaluation.

Usage factors were calculated at selected node points in the finite element model on the pipe wall surface, corresponding to-the analysir sections. These node points were selected based on

~

review of the local stress profiles and previous analysis results where maximun usage factors were calculated.

[

3a,c.e The maximum usage factor was then reported f or the glot;ai location.

3anseisse to 15

-_--_-_____2____-.

l j

.b

, e,I l

0 ISSVE 5:

-At which location and for which load cases' ASME III NB-3600-3 equation 10 was' exceeded? khatwasthevalue?l

]

RESPONSEi ASME Equation 10 is calculated by WECEVAL forrevery combination

-at each cross section evaluated' at each global-location to determine the. elastic plastic penalty factor's, Ke.

The values of Ke.are sto. red on' tape to be used in the' subsequent usage factor calculation.

The various locations for.which Eq.10 'was exceeded can be obtained by detailed review of.the computer. runs.

In the whole of the analysis,.Eq. 10 is assumed to be exceeded at all points-and Eq. 12 and 13 are addressed as appropriate.

Due to the nature of the thermal stratification loading, Eq._12' stress is the more critical for qualification.

ISSUE 6:

At which location and for which load case ASME III NB-3600 equations 12 and 13 is maximum? What is the value?

" ~

. RESPONSE:

ASME Equation 12 is maximum at [

Ja,c e and is 54.1'ksi. Corresponding allowable 3S,= 55.5 ksi.

This is due to the range between [

3a.c,e ASME Equation 13 was only affected by thermal stratification at

[

Ja,c e The maximum value recalculated at [

]., c. e 33.'6 ksi.

Corresponding allowable 3S,= 48.6 a

is ksi. This is due to the range between [

3a,c,e

,e p

l i

5672s/031989 10 16 i

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i TABLE 2.11-1 FLOW RATES AND RICHARDSON NUMBERS FOR WATER H0 DEL FLOW TESTS Cold Water Flow Rate Pipe Section (GPM)

Rii 4.0 inch I.D.

1 6.5 inch I.D.

e 1

e s

0 1672s/081689 10

}g

1

1

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sno i

taco L

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P 1

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F 10 986 1

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b a,c.e i

l l

l 0

Fi;ure 1.5-3.

Plant C Pressurizer Surge Line Monitoring Locations 3872s/06I689 10 21

6 ViaT1 CAL AUS - L3f"%-

1 I

7 y

4" t0 LOCAfl0S e lets 37 3r*

vtE l

[r,ftCALSUS.19.8*

(

TT arr nr e Ji

(

()

(>.

i VtRTICAL AUS.1Lif"2 UTLif gg 3 WERTICAL AUS - tLIS"% r 3 RfACTOR 8 ttr ie v

WIMit

~

n7r L.CAfi. 8 J-nrr I_

.t etu view b

figure 2.5-1.

Water Model of LMFBR Primary Hot Leg 3672s/C8168910 g

a,c.e 9

Figure 3.4-1.

Fatigue Calculation Locations an.,oe tais io 23

n-4

'd s-ERRATA' The following pages contained typographical errors.

The corrections are shown with vertical lines on the right hand border.

'f e

i I

24

}

a n uosia.io

f '

• 3s

'A.,

2 l

TABLE-1 -)

L

SUMMARY

OF PLANT MONITORING TRANSIENTS i

1 WITH STRENGTH OF STRATIFICATION (RSS)

)

j a

[-

. )a,c.e :

(

)a,c.e Beaver Valley l

Observed Observed:

Observed

' Cycles

'RSS-(1).

Cycles RSS(1).

Cycles-

'RSS;(1) a,c.e-OBSERVED-TRANSIENTS GROUPED BY STRENGTH OF STRATIFICATION (RSS) INTERVALS No. Observed

% of RSS Cycles Total a,c.e l

Note:

The No. of groups is reduced by combining the intervals.70 < x

<.8 and.60 < x <.70

% of total = 3.4% for the interval-

.60 <fx'<.80-h mwoeinn io 1-32

m.

j fS:dh 1

W 3

TABLE:1-15 (cont.)'

4,

SUMMARY

OF PLANT. MONITORING TRANSIENTS'

'WITH STRENGTH OF STRATIFICATION (RSS)-

'4.

RSS J

% of Transients-a,c,e RELATIVE NUMBER OF CYCLES OF STRENGTH OF: STRATIFICATION (RNSSj)

AFTER GROUPING.

RSSj RNSSj,

Strength'of

'2' Transients (2).

j.

. Stratification (1) a,c.e-L Nomenclature:

l(1) Strength of Stratification (RSS)

(2). Relative Number of Cycles of Strength of Stratification:(RNSS)

a.

1-33

___A

m-7 :

L-I TABLE 1-16 i

SUMMARY

OF MONITORED TRANSIENT CYCLES (ONE HEATUP) j 0

Plant No. of Cycles a,c.e i

l l

J j

1 Avg. Monitored. Cycles:

15.75 = x; Selected No of Design Cycles:

36.5 (added 30% to observed maximum number of cycles, plant A)

DESIGN DISTRIBUTION APPLIED TO MAX NUMBER OF TRANSIENTS EXCEPTED MULTIPLIED BY 200 HEATUP OR C00LDOWN CYCLES j

l l

No. of Transients RSS i

a,c,e 1

I 1

I l

1 I

a 3872s/081689 10

}.34