ML20204G392

Structural Evaluation of Vacuum Breakers (Mark I Containment Program),Edwin I Hatch Nuclear Plant Units 1 & 2, Supplementary Technical Evaluation Rept

ML20204G392
Person / Time
Site:	Hatch
Issue date:	08/01/1986
From:	Con V, Shaw H, Triolo S CALSPAN CORP.
To:	NRC
Shared Package
ML20204G396	List: ML20204G392 ML20205R213 ML20236F615 ML20245A498
References
CON-NRC-03-81-130, CON-NRC-3-81-130 GL-83-08, GL-83-8, TAC-57156, TAC-57157, TER-C5506-329, NUDOCS 8608070241
Download: ML20204G392 (23)

Text

y :,. . . . .:.- ~ . . . . ..~...:...-..._.......~...........:.........., -

=

1 l

l FRANKLIN RESEARCH CENTER  :

1 i

DIVISION OF ARVIN/CALSPAN l

)

i i \ l 6

i I

( .

TECHNICAL REPORT l

4 20TH lh RACE STREETS PHil.ADELPHIA. PA 19103 TWX 710-6701889 TEL (215) 448-1000 1A_

. a .a . . c. . .w.

.+.

. . . . : . - .~ . .. . .

r l

[ -

SUPPLEMENTARY i

TECHNICAL EVALUATION REPORT )

l NRC DOCKET NO. 50-321, 50-366 FRC PROJECT C5506 ,

1 FRC ASS'GNMENT 12 )

N RC TAC NO. --

FRC TASK 329 NRC CONTR ACT NO. NRC-03-81 130 I

i STRUCTURAL EVALUATION OF THE VACUUM BREAKERS (MARK I CONTAINMENT PROGRAM) 1

)

GEORGIA POWER COMPANY EDWIN I. HATCH NUCLEAR PLANT UNITS 1 AND 2 TER-C5506-329 II Prepared for Nuclear Regulatory Commission FRC Group Leader: V. N. Con NRC Lead Engineer: H. Shaw Washington, D.C. 20555

~

I' August 1, 1986 This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, or any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for any third party's use, or the results of such use, of any information, appa-I. ratus, product or process disclosed in this report, or represents that its use by such third party would not inf ringe privately owned rights.

I Reviewed by: Approved by:

sW Prepared by:

I  % %b Princi' pal Author

_v. L s#

' Department cto I" I "' Dir[b

~

Date: S!!!Plo Date: 8,fI,b Date:

FRANKLIN RESEARCH CENTiiR

[ DIVISION OF ARVIN/CALSPAN sotn & R Act STPittl.PHILADSLPMIA.PA 19105 I

pe .-'<., ,- _,..;o... - . - . s.s . t _ .

~

TER-C5506-329 l~

E .

e ll CONTENTS I'

Section Title Page 1 INTRODUCTION . . . . . . . .

. . . . . . 1 1.1 Generic Background. . . . . . . . . . . 1 Iq ., 1.2 Vacuum Breaker Function . . . . . . . . . 2 2 EVALUATION CRITERIA. . . . . . . . . . . . 9 .

1 1

i 3 DESIGN LOADS . . . . . . . . . . . . . 10 l 4 STRESS EVALUATION . . . . . . . . . . . . 11 5 PLANT-SPECIFIC REVIEW: HATCH UNITS 1 AND 2. . . . . . 15

,. 5.1 Background Information. . . . . . . . . . 15 5.2 Stress Analysis Results . . . . . . . . . 15

m. 6 CONCLUSIONS. . . . . . . . . . . . . . 18 7 7 REFERENCES . . . . . . . . . . . . . . 19

+

9 J.

l J

iii

> v. .

TER-C5506-329 I

FOREWORD This Technical Evaluation Report was prepared by Franklin Research Center under a contract with the U.S. Nuclear Regulatory Commission (Office of Nuclear Reactor Regulation, Division of Operating Reactors) for technical assistance in support of NRC operating reactor licensing actions. The 4 technical evaluation was conducted in accordance with criteria established by the NRC.

[

[

t

[

Ii L

L l

V

~

[ TER-C5506-329 l.l ,

1. INTRODUCTION In a latter state of the generic resolution of the suppression pool I. dynamic load definition of the Mark I Containment Long-Term Program, a potential failure mode of the vacuum breakers was identified during the clugging and condensation phases of hydrodynamic loadings. To resolve this issue, two vacuum breaker owner groups were formed, one for those with General Precision Engineering (GPE) vacuum breakers, the other for those with Atwood-Morrill (AM) vacuum breakers.

The issue was not part of the original scope of the Mark I Containment Long-Term Program as described in NUREG-0661 (1]. However, vacuum breakers have the function of maintaining containment integrity and, therefore, are subject to Nuclear Regulatory Commission (NRC) review. In a generic letter dated February 3, 1983 (2), the NRC requested all affected plants either to submit the results of the plant-unique calculations which formed the bases for ,

modifications to the vacuum breakers or to provide the justification for the as-built acceptability of the vacuum breakers.

Franklin Research Center (FRC) has been retained by the NRC to evaluate the acceptability of the structural analysis techniques and design criteria

, used in the plant-unique analysis (PUA) reports of 16 plants. As a part of this review, the structural analysis of the vacuum breakers has been reviewed and documented in this report.

. The first part of this report (Sections 1 through 4) consists of generic

, information that is applicable to all affected plants. The second part of the report (Sections 5 and 6) provides a plant-specific review, which pertains to Hatch Units 1 and 2.

1.1 GENERIC BACKGROUND In 1980, the Mark I owners and the NRC became aware of the vacuum breaker damage during full-scale test facility testing and of the potential for damage during actual LOCAs. Two vacuum breaker owner groups, General Precicion Engineering (GPE) and Atwood-Morrill (AM), were formed to develop action plan for resolving this issue. In February 1983, the NRC issued Generic Letter 83-08 (2), requesting commitments from affected utilities to provide

}

L. . . .. ._ m. .

TER-C5506-329 l 1

analytical results. The licensees responded to the NRC request by developing appropriate force functions simulating the anticipated hydrodynamic loads, and then performing stress analyses that used these loads. With respect to loading, the NRC has reviewed and issued a staff position as indicated in Section 3. FRC's function is to review the stress analysis submitted by a

~

licensee.

1.2 VACUUM BREAKER FUNCTION During steam condensation tests on BWR Mark I containments, the wetwell-to-drywell vacuum breakers cycled repeatedly during the transient phase of steam blowdown. This load was not included in the original load combinations r used in the design of the vacuum breakers. Consequently, the repeated impact of the pallet cn the valve seat and body created stresses that may impair its capability to remain functional.

A vacuum breaker is a check valve insta'. led between the wetwell and the

, drywell. Its primary function is to prevent the formation of a negative pressure on the drywell containment during rapid condensation of steam in the drywell and in the final stages of a LOCA. The vacuum breaker maintains a wetwell pressure less than or equal to the drywell pressure by permitting air flow from the wetwell to the drywell when the wetwell is pressurized and the

, drywell is depressurized slowly.

A vacuum breaker can be internally or externally mounted. Figures 1 and 2 illustrate locations of vacuum breakers.

Schematics of typical GPE and AM vacuum breakers are illustrated in Figures 3 and 4.

A typical pressure differential vacuum breaker during a LOCA is provided in Figure 5.  ;

Table 1 lists the various vacuum breaker types and the plants affected by them.

n j

_2_

l

- ~ - ~ ~

. . T~

e. .

TER-C5506- 329 9

, r' i

IN TERN AL.

vacuum SREAKEA WETWEL.L AIRSPACE. -

MAIM VEN

/ 1 '

4

[ i .

I cy N w RIN(a MILACEA

[' \ \' _

I r

, \ -

i 5 <

m== l m- /

i CCWNCCMERS

L "'

l SUPPREsticN . . Tomun l

![

?

~ c' i"

r.

1

, Figure 1. Internal Vacuum Breaker

nr * . . . e. .

t TER-C5506-329 4

F-

, , , External Vactnrn Breaker

.1 m  :

- k  !

WetWell M@I TO Dr7We Main ven

- - Ring Header I. r p .

1 m, m-

, DOWncomers j

)

l I

j ... ..

Torus W

• Suppression Pool 4

4 Figure 2. External Vacuum Breaker l

'14

. i- , . ,,.

' l TER-C5506-329

{I .

I~

l I

I I

WAC'.itm tasARER WALL e

[ / I

[ .. ,,..

Q.;gpfe-

, \

J.%;.: .

'. Y SE AT Alloc

', l [

===( == -..( v AC'.*um tatARER f 6 PALLEY ,

g / N pALLg? O 7

f 's (CL st3 * .

== '%

• P05tt!OND *

. '%== *

. m 4 3 / t e .f PALLET $*CP 4Aust? LATC11 St;C LDCAT10N to PLActs) 8 t.

g I

Figure 3. GPE Vacuum Breaker y,- -

TER-C5506-329 1

._  ?.! '/2 _

I F- _

_ 7 #A4" _'

• e "5 gm q COUNTERWE4M P

/

l ccvNrtswE4W ,

lev tR. 8.

l l

)

iL" l

[- ,

< A* -

~

- g ,.

4*dE ,n-

. msc.

or ..

w -.

s l s e / 1 o,

,, s ( -

LATERAL DSC. k f  ? , SCOf SEATfA(E ,Y f! g

- \

~

t*,

s ourur

- ~

y b- 6 pt.ANc E t &

a NLt.T .

- mi \ $_8 1 cisc

- i e

n. , ,.

. s,g

.I. -

m

~

9 scar f  ?

Figure 4. Atwood-Morrill Vacuum Breaker TER-C5506-329 F

g,

+ve WW - Wetwell

,; DW - Drywe11 e

~

t r $

o.

0 D Chugging Drywe11

[ g d 0 Condenaation

,y

. .. '.. . . . . . . . . . . . , { ,

Depreasuri ation 3 Drywell

[.7 , f. Pressurization i

E

-ve

s. Time + .

W

[

Figure 5. Typical DW/WW Vacuum Breaker Pressure Differential Due to LOCA

y i '

- ,- i;. ". s . a..... ' . . . , .. _ , ,

~

TER-C5506-329 1

Table 1. Vacuum Breaker Types and Affected Plants I

[.

Vacuum Breaker Plant f.s, GPE 18 In (Internal) Brown Ferry Units.1, 2, and 3 f Pilgrim Unit 1 Brunswick Units 1 and 2 Cooper Hatch Units 1 and 2

[: Peach Bottom Units 2 and 3 Duane Arnold

[ Fermi Unit 2 GPE 24 in (Internal) Hope Creek AM 18 in (Internal) Monticello Quad Cities Units 1 and 2 AM 18 in (External) Dresden Units 2 and 3 (g< Millstone Unit 1 Oyster Creek Vermont Yankee

~ AM 18 in (External) FitzPatrick Nine Mile Point Unit i 1

}

e s

m.

e uk

.. , . - _ ..'.s ..._/,_.... - ._ ..

TER-C5506-329

2. EVALUATION CRITERIA l

1

-, To evaluate the design of the vacuum breakers, the affected licensees follow the general requirements of NUREG-0661 [1] and those of " Mark I Containment Program Structural Acceptance Criteria Plant Unique Analysis Application Guide" [3]. Specifically, the requirements of the ASME Boiler and Pressure Vessel Code,Section III, Subsection NC for Class 2 Components,1977 Edition, including the summer 1977 addenda [4], have been used to evaluate the structural integrity of the vacuum breakers.

[

[

L 7

o

[:

L L

O I -

l

_9-

J TER-C5506-329

3. DESIGN LOADS

, The loads acting on the Mark I structures and on the vacuum breaker are based upon the Mark I Program Load Definition Report (S] and the NRC Acceptance Criteria (1). The loads acting on the vacuum breaker include gravity, seismic, and hydrodynamic loads. The hydrodynamic forcing functions were developed by Continuum Dynamics, Inc, (CDI). CDI used a dynamic model of a Mark I pressure suppression system, which was capable of predicting pressure transients at specified locations in the vent system. With this dynamic model and the full-e scale test facility data, load definition resulting in pressure differential across the vacuum breaker disc was quantified as a function of time. This issue has been reviewed and ad::ressed by the NRC [6).

[

[ .

L L

[

f

. - .m ,s.<.s_ .- .

w' -

l TER-C5506-329 i

4. STRESS EVALUATION 7- To determine structural integrity of the vacuum breaker, the licensees a have employed standard analytical techniques, the including finite element method, to calculate stresses of critical components of the vacuum breaker 7

under various design loadings. Loads resulting from the hydrodynamic phenomenon were compared with those values specified in the ASME Codes (4].

, For illustration purposes, a schematic drawing of the moving parts of all components other than the actual disc of the Atwood-Morrill valve and of the corresponding finite element model are shown in Figures 6 and 7, respectively.

The model in Figure 7 was used to investigate the dynamic response following 7 .

Impact.

A typical model for stress analysis of the vacuum breaker disc is shown in Figure 8. Loading inputs to this model are the displacement time histories that were obtained from the impact model analysis.

4 4

4 l i S. l l

b l

1

W- --

TER-C5506-329 p ..

Bearing Supports Counterweight -

[ -

C b/

r Counterweight Arm

{ \ Disc Arm I J

N-

[ -

. *IE ""

Counterweight

' Arm Bolts

- Counterweight Arm Connector m.

I 3

Figure 6. Detailed Valve Internal Model

+

TER-C5506-329 COUNTERifEIGHT N

NTERifEICliT

- SH. AFT

[

DISC ARM E

I..'

COUNTERhTIGHT AFJ< CONNECTOR P

L L.

Figure 7- Finite Element Model of Valve Internals

PW TER-C5506-329 r

l I

,e J --

- _ i i i  !

i i I i i i INSIDE DISC SURFACE i l

Il .  !

- . 1

[

HUB CONTROL POINT L: l i

t

/

2 i  ! '

f i s, i '

l \

g j t M M N

Ti T ,

/ a B /

.. %_ , RIM CONTROL POINT

- / l } OUTSIDE DISC SURFACE l 1

1

?

l -

u r

W r

- Figure 8. Valve Detailed Disc Model Geometry l

+

~

g;; ~ - .:. t

_ TER-C5506-329

5. PLANT-SPECIFIC REVIEW: HATCH UNITS 1 AND 2 i

5.1 BACKGROUND

INFORMATION o Vacuum breaker type: 18-in GPE (internal) o Vacuum breaker characteristics: Table 2 o Vacuum breakers are located on six of the eight vent header / vent

. line intersections within the wetwell. There are two vacuum breakers at each location.

5.2 STRESS ANALYSIS RESULTS

{

g-A finite element model of the vacuum breaker was developed using the i ANSYS computer program. The stress levels for vacuum breaker critical components were calculated for various pallet impact velocities (Table 3).

The plant-unique impact velocities for Hatch Units 1 and 2 were predicted

using an analytical model of the vacuum breaker / vent system fluid dynamics

[7]. The design impact velocity for Hatch Unit I was calculated to be 1.26 rad /sec, and the design impact velocity for Unit 2 was 0.12 rad /sec [8).

Since vacuum breaker stresses are directly proportional to the pa'let impact velocity, the design impact velocities for Hatch Units 1 and 2 weris used to scale the stresses in Table 3 to determine vacuum breaker component stresses for this plant. It can be seen from Table 3 that none of the compcnents will exceed the ASME allowable stresses for the design impact velocities at the Hatch plant. Therefore, no modification of the vacuum breakers is necessary.

E J

u.

z.

%.b

a .n . . .. . _.J. m . . _. . :. . m .. ..

e..

~~

TER-C5506-329

~

Table 2. Vacuum Breaker Characteristics for Hatch Units 1 and 2 4

Vacuum breaker type 18 in GPE Internal System moment of intertia (Ib-in-s 2) 20.08 System moment arm (in) 10.86

~

Disc moment arm (in) 11.468 System weight (Ib) 49.84

. Disc area (in 2) 375.83

,- System rest angle (rad) 0.06109 seat angle trac) 0.05236 Body angle (rad) 1.391 Seat coefficient restitution 0.6 Body coefficient restitution 0.6 Magnetic latch set pressure (psi) 0.25 g+m" e

[

P b

l

g> -

TER-C5506-329 Table 3. Stress Levels by Component for 18-Inch GPE Vacuum Breaker Stress (ksi) for

[.

t' Various Pallet Impact Velocities Existing ASME Allowable

• 3.0 4.5 9.3 Component Material Stress (ksi) (rad /sec)

Pallet SA-516 Gr 70 35.0 21.6 32.4 67.0 Hinge Arm SA-516 Gr 70 35.0 11.8 17.7 36.6 Hinge Shaft SA-320 BS 30.0 19.1 28.6 59.2 Hinge Arm Stud SA-320 BB 30.0 12.5 18.8 38.8

[ *ASME Section III NC3520

[

[

l. .:

d L

L L

s.

,O' 1

l_ .

p .

L-

n. TER-C5506-329 I

p. 6. CONCLUSIONS A review has been conducted to determine the structural integrity of the l

vacuum breakers at the Hatch Units 1 and 2. The design loads associated with the hydrodynamic phenomenT have been reviewed and addressed by the NRC in Reference 6. This review covered only the structural analysis of the vacuum i breaker, and the following conclusion is drawn from the review:

?>

o The analytical methods used to evaluate stresses of critical

~-

components have been reviewed and judged to be adequate: the stress results indicate that all vacuum breaker components are within ASME allowable limits. Therefore, the existing vacuum breaker design at Hatch Units 1 and 2 is structurally adequate.

=

j b

.o.

1

'}

?

4 4

t I

6 m

w w

W 65

~' ~- -

2 - - . . .

. , . . _ . .

L TER-C5506-329

& 7. REFERENCES 3, 1. NUREG-0661

" Safety Evaluation Report, Mark I Containment Long-Term Program a Resolution of Generic Technical Activity A-7," Office of Nuclear Reactor Pegulation, USNRC July 1980

2. D. G. Eisenhut "USNRC Generic Letter 83-80, Modification of Vacuum Breakers on Mark I Containment" February 2, 1983

[

L

3. NEDO-24583-1

" Mark I Containment Program Structural Acceptance Criteria Plant Unique Analysis Application Guide," General Electric Co., San Jose, CA October 1979

i. American Society of Mechanical Engineers Boiler and Pressure Vessel Code,Section III, Division 1, " Nuclear Power

[ Plant Components," New York, 1977 Edition and Addenda up to Summer IS77

5. NEDO-21888 Revision 2

" Mark I Containment Program Load Definition Report," General Electric

[? -

Co., San Jose, CA November 1981

6. D. B. Vassallo, NRC Letter with Attachment to H. C. Pfefferlen, BWR Licensing Programs, GE ,

e " Evaluation of Model for Predicting Drywell to Wetwell Vacuum Breaker j j Valve Dynamics" l December 24, 1984 1

7. " Mark I Vacuum Breaker Improved Dynamic Model," C.D.I. Tech Note No. 82-31

- Continuum Dynamics, Inc., Princeton, New Jersey Septembr 1982

~

8. L. T. Gucwa Letter with Attachments to J. F. Stolz (NRC)

Subject:

Wetwell/Drywell Vacuum Breakers on Mark I Containments Georgia Power June 9, 1983 k

L.

L

_