ML20214H115

Structural Evaluation of Vacuum Breakers (Mark I Containment Program),Quad Cities Station Units 1 & 2, Supplementary Technical Evaluation Rept

ML20214H115
Person / Time
Site:	Quad Cities
Issue date:	07/17/1986
From:	Carfagno S, Con V, Triolo S CALSPAN CORP.
To:	Shaw H NRC
Shared Package
ML20214H117	List: ML20214H115 ML20214X090 ML20214X111
References
CON-NRC-03-81-130, CON-NRC-3-81-130 TER-C5506-325, TER-C5506-325-S01, TER-C5506-325-S1, NUDOCS 8607220468
Download: ML20214H115 (23)

Text

.

ATTACHMEtiT TO SAFETY EVALUATI0ft

~

SUPPLEMENTARY TECHNICAL EVALUATION REPORT NRC DOCKET NO. 50-254, 50-265 FRC PROJECT C5506 NRC TAC NO. -- FRC ASSIGNMENT 12 A N RC CONTRACT NO. NRC43-81-130 FRC TASK 325

] STRUCTURAL EVALUATION OF TlE VACUUM BREAKERS (MARK I CONTAINMENT PROGRAM) d COMMONWEALTH EDISON COMPANY QUAD CITIES STATION UNITS 1 AND 2 m

TER-C5506-325 7

1.

Prepared for Nuclear Regulatory Commission FRC Group Leader: V. N. Con Washington, D.C. 20555 NRC Lead Engineer: H. Shaw July 17, 1986 This report was prepared as an account of work sponsored by an agency of the United States n, 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-ratus, product or process disclosed in this report, or represents that its use by such third

, , party would not infringe privately owned rights.

i Prepared by: Reviewed by: Approved by:

. Y= Maet.- b M/~

W

~PrirSipal hor " Department Di[ectors Date: 7[ ,

M Date: N 'b Date: 7 ' N ~~ b 1

FRANKLIN RESEARCH CENTER DIVISION OF ARVIN/CALSPAN 20th & RACE STREtt$ PHILADELPHIA.PA 19101 A

%07220Yli8

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TER-C5506-325 l

,f I.

CONTENTS Section Title Page 1 INTRODUCTION . . . . . . . . . . . . . 1 1.1 Generic Background. . . . . . . . . . . 1 1.2 Vacuum Breaker Function . . . . . . . . . 2 2 EVALUATION CRITERIA. . . . . . . . . . . . 9

.s 3 DESIGN LOADS . . . . . . . . . . . . . 10

. 4 STRESS EVALUATION . . . . . . . . . . . . 11 5 PLANT-SPECIFIC REVIEW: QUAD CITIES UNITS 1 AND 2 . . . . 15

^ '

5.1 Background Information. . . . . . . . . . 15

~

5.2 Stress Analysis Results . . . . . . . . . 15 W

6 CONCLUSIONS. . . . . . . . . . . . . . 18 7 REFERENCES . . . . . . . . . . . . . . 19 A

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TER-C5506-325 3

FOREWORD t

This Technical Evaluation Report was prepared by Franklin Research Center

.i under a contract with the U.S. Nuclear Regulatory Commission (Office of Nuclear Reactor Regulat2on, Division of Operating Reactors) for technical assistance in support of NRC operating reactor licensing actions. The technical evaluation was conducted in accordance with criteria established by

,o the NRC.

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TER-C5506-325

l. INTRODUCTION i

In a latter state of the generic resolution of the suppression pool dynamic load definition of the Mark I Containment Long-Term Program, a potential failure mode of the vacuum breakers was identified during the chugging 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, p

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 -

T have the function of maintaining containment integrity and, therefore, are

} subject to Nuclear Regulatory Commission (NRC) review. In a generic letter o

dated February 2, 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 q 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 y

and documented in this report.

- The first part of this report (Sections 1 through 4) consists of generic m 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 Quad Cities plant.

1 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 Precision 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 f

_1_

TER-C5506-325

! analytical results. The licensees responded to the NRC request by developing I

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-7 to-drywell vacuum breakers cycled repeatedly during the transient phase of steam blowdown. This load was not included in the original load combinations ,

used in the design of the vacuum breakers. Consequently, the repeated impact of the pallet on the valve seat and body created stresses that may impair its m

f capability to remain functional, a*

A vacuum breaker is a check valve nstalled 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

[g1 drywell is depressurized slowly.

A vacuum breaker can be internally or externally mounted. Figures 1 and

,1 F

d 2 illustrate locations of vacuum breakers.

~

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

I 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.

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i INTRANAL

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

I TER-C5506-325 Table 1. Vacuum Breaker Types and Affected Plants i

i Vacuum Breaker Plant f

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'[ GPE 18 In (Internal) Brown Ferry Units 1, 2, and 3 Pilgrim Unit 1 Brunswick Units 1 and 2 Cooper q

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Hatch Units 1 and 2 -

Peach Bottom Units 2 and 3 Duane Arnold t Fermi Unit 2 he

'T 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

.o Millstone Unit 1 Oyster Creek

~' Vermont Yankee

,, AM 18 in (External) FitzPatrick Nine Mile Point Unit 1 a

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i-TER-C5506-325

2. EVALUATION CRITERIA 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.

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P TER-C5506-325 f 3. DESIGN LOADS

{ The loads acting on the Mark I structures and on the vacuum breaker are i

based upon the Mark I Program Load Definition Report (5) 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 f, . ,

suppression system, which was capable of predicting pressure transients at specified locations in the vent system. With this dynamic model and the full-I scale test facility data, load definition resulting in pressure differential across the vacuum breaker disc was quantified as a function of time. This l' issue has been reviewed and addressed by the NRC (6). .

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[ TER-C5506-325

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

A typical model for stress analysis of the vacuum breaker disc is shown f

in Figure 8. Loading inputs to this model are the displacement time histories that were obtained from the impact model analysis.

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Counterweight -

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! TER-C5506-325

! 5. PLANT-SPECIFIC REVIEW: QUAD CITIES UNITS 1 AND 2 '

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5.1 BACKGROUND

INFORMATION s 1 ,

o Vacuum breaker type: 18-in Atwood and Morrill (Internal) o Vacuum breakers are mounted on the spherical junction of the vent header and vent line. ,

o There are two vacuum breakers on six of the eight vent line/ vent header junctions.

o Vacuum breaker valves have been modified by changing tha cast

- aluminum discs to wrought aluminum discs with stainless steel posts, r .

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5.2 STRESS ANALYSIS RESULTS y After the modification to wrought aluminum discs, the vacuum breakers at' >

d, the Quad Cities plant were analyzed using an ANSYS finite element computer model. The stress results for various vacuum breaker components are summarized in Table 2. These results show a potential overstressed cond'ition in the shaft and the weight lever. Consequently, the vacuum breakers were furthat modified by upgrading the shaft and weight lever materials to a higher strength material. As can be seen in Table 2, the replacement material (ASTM A-564 Gr. 630 age hardened at 1100*F) has an allowable stress of 70 ksi compared with a calculated stress of 31.90 ksi (membrane plus bending) for the weight lever and 49.24 ksi for the shaft. The allowable strest criteria were a based en the ASME Boiler and Pressure Vessel Code,Section III, Subsection NC

, for Class 2 components, 1977, and the Summer 1977 Addenda. Following this analysis, the load evaluation was refined [7] and lower loads (in terms of ',

i pallet impact velocities) than had originally been calculated were predicted.

The Licensee conducted its structural analysis based on an impact velocity of f 4.631 radians /sec, whereas the refined load evaluation predicts a ma/imum impact velocity of 3.09 radians /sec. Since stress is proportional to impact velocity, the Licensee's results are conservative with respect to the refined loading criteria.

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Table 2. Stresses in Vacuum Breaker Components (Cont.)

catcus.ates erness atunenste sroess tuset

1. AT88848 Srt?IfifAT304.. ._. ..

(Est) F0st sol.Ts, ALldhsAeLE

• 2sg REISAGE s FART WAME #ATERIAL e e, (ass) (assi rest says, noramenet.e -g l pe.se 7e.e

>* neeese n-a,3. or. of ses 325 we t severs 33, e stecommend .

mist lots 33, 354 59.se Replacement seye tshaft -

Oloc Ave, lever Connector)

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TER-C5506-325 t

i 6. CONCLUSIONS.

A review has been conducted to determine the structural integrity of the I-vacuum breakers at Quad Cities Units 1 and 2. The design loads associated with the hydrodynamic phenomena have been reviewed and addressed by the NRC in Reference 6. This review covered only the structural analysis of the vacuum breaker, an'd the following conclusion is deswn from the review:

o The analytical methods used to evaluate stresses of critical ,

components have been reviewed and judged to be adequate; the structural analysis indicated a potential overstress condition in the 2 shaft and weight lever. Consequently, these components were replaced with those of a higher strength material. Predicted stresses are

- within allowable limits for the modified vacuum breaker. Therefore, .

with the upgrading of the shaft and weight lever, the vacuum breakers at the Quad Cities plant are structurally adequate.

D.

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i TER-C5506-325

7. REFERENCES

1. NUREG-0661

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

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

~

February 2,1983

3. NEDO-24583-1 a " Mark I Containment Program Structural Acceptance Criteria Plant Unique Analysis Application Guide," General Electric Co., San Jose, CA .

October 1979

4. American Society of Mechanical Engineers g-g Boiler and Pressure Vessel Code,Section III, Division 1, " Nuclear Power Plant Components," New York, 1977 Edition and Addenda up to Summer 1977

5. NEDO-21888 Revision 2 h " 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

" Evaluation of Model for Predicting Drywell to Wetwell Vacuum Breaker Valve Dynamics"

[. '

December 24, 1984 l 7. " Improved Dynamic Vacuum Breaker "alv Response for the Quad Cities Units IJ 1 and 2, Revision 1," C.D.I. Technical Note 82-7

~

Continuum Dynamics, Inc. , Princeton, liew Jersey September 1982

8. B. Rybak P Letter with Attachment to H. P. Denton (NRC)

Subject:

Modification of Vacuum Breakers on Mark I Containment - Generic Letter 83-08 July 12, 1983

.s. e November 26, 1986 Dennis L. Farrar The staff's technical assistance contractor, Franklin Research Center (FRC),

has reviewed the results.of the stress analysis to verify that the vacuum breaker stresses are within the ASME code allowable values for the materials used. Their Technical Evaluation Report is appended to our Safety Evaluation which is enclosed for your information.

Based on our review, NRC staff concludes that the analyses performed to predict the drywell vacuum breaker impact velocities and resulting j stresses were perfonred using acceptable methodology and that the vacuum breakers will not be subjected to excessive stress as a result of LOCA chugging and condensation oscillation loads.

This completes our resiew of Multiplant Action Item D-20 for Quad Cities Power Station. If you have any questions concerning our review, please contact the NRC Quad Cities Power Station Project Manager.

Sincerely, Original signed by John A. Zwolinski, Director BWR Project Directorate #1 Division of PWR Licensing

Enclosure:

Safety Evaluation cc w/ enclosure:

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JZwolinski QC File l DBL:BWD#1 DBL:BWD# DRL:BWD#1 CJamerso( TRotella:ac J7wolinski 11/ 6 /86 11/17/86 11/g6/86

--, - .. -