ML20214H129

Structural Evaluation of Vacuum Breakers (Mark I Containment Program),Nine Mile Point Unit 1 Nuclear Generating Station, Supplementary Technical Evaluation Rept

ML20214H129
Person / Time
Site:	Nine Mile Point
Issue date:	08/01/1986
From:	Carfagno S, Con V, Triolo S CALSPAN CORP.
To:	NRC
Shared Package
ML17055C677	List: ML20214H129
References
CON-NRC-03-81-130, CON-NRC-3-81-130 TAC-07943, TAC-7943, TER-C5506-331, TER-C5506-331-S01, TER-C5506-331-S1, NUDOCS 8608070246
Download: ML20214H129 (21)

Text

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ATTACHMENT TO SAFETY EVALUATION SUPPLEMENTARY TECHNICAL EVALUATION REPORT NRC DOCKET NO. 50-220 FRC PROJECT C5506 1

NRC TAC NO. 07943 FRC ASSIGNMENT 12 N RC CONTRACT NO. N RC-03-81-130 FRC TASK 331 STRUCTURAL EVALUATION OF THE VACUUM BREAKERS (MARK I CONTAINMENT PROGRAM)

NIAGARA MOHAWK POWER CORPORATION NINE MILE POINT UNIT 1 NUCLEAR GENERATING STATION TER-C5506-331 Prepared for l Nuclear Regulatory Commission FRC Group Leader V. N. Con Washington, D.C. 20555 NRC Lead Engineer: H. Shaw o

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.

ratus, product or process disclosed in this report, or represents that its use by auch third party would not infringe privately owned rights.

Prepared by: Reviewed by: Approved by:

hEUM PWincipal uthor T Yv Ya r (k .$kf tepartment Dir clo Date: 8!/!8'b Date: @!Iffb - Date:- Ol b i ,

% ppt FRANKLIN RESEARCH CENTER 010 DIVISION OF ARVIN/CALSPAN 30tn a SAC 8 ff9f tf t, PMsLA00 LPM 4A PA 19103

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TER-5506-331 CONTENTS Section Title Pace 1 INTRODUCTION . . . . . . . . . . . . . 1

. 1.1 Generic Background. . . . . . . . . . . 1 1.2 Vacuum Breaker Function . . . . . . . . . 2 2 EVALUATION CRITERIA. . . . . . . . . . . . 9 3 DESIGN LOADS . . . . . . . . . . . . . 10 4 STRESS EVALUATION . . . . . . . . . . . . 11 5 PLANT-SPECIFIC REVIEW: NINE !!ILE POINT UNIT 1 . . . . . 15 5.1 Background Information. . . . . . . . . . 15 5.2 Stress Analysis Results . . . . . . . . . 15

6 CONCLUSIONS. . . . . . . . . . . . . . 17 j 7 REFERENCES . . . . . . . . . . . . . . 18 d

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FOREWORD

, This Technical Evaluation Report was prepared by Franklin Research Center under a contract with the U.S. Nuclear Regulatory Comission (Office of Nuclear Reactor Regulation, 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 the NRC.

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1. INTRODUCTION 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 I

chugging and condensation phases of hydrodynamic loadings. To resolve this 1 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.

l 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 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

-used in the plant-unique analysis (PUA) reports of 16 plants. As a part of i

this review, the structural analysis of the vacuum breakers has been reviewed 4

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 Nine Mile Point Unit 1.

1.1 GENERIC BACKGROUND i

In 1980, the Mark I owners and the NRC became aware of the vacuum breaker i

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 l 83-08 [2], requesting commitments from affected utilities to provide I

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TER-5506-331 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 4

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.

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1.2 VACWM 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 j 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

,- capability to remain functional.

A vacuum breaker is a check valve installed between the wetwell and the i

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 g drywell is depressurized slowly.

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

e 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.

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. Table 1. Vacuum Breaker Types and Affected Plants F

- Vacuum Breaker Plant GPE 18 In (Internal) Brown Ferry Units 1, 2, and 3 J .- Pilgrim Unit 1 L- Brunswick Units 1 and 2 Cooper Fhtch Units 1 and 2 .

Peach Bottom Units 2 and 3 Duane Arnold r- Fermi Unit 2 GPE 24 in (Internal) Hope Creek i

AM 18 in (Internal) Monticello Quad Cities Units 1 and 2

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v AM 18 in (External) Dresden Units 2 and 3 y Millstone Unit 1 Oyster Creek Vermont Yankee AM 18 in (External) FitzPatrick Nine Mile Point Unit 1 I

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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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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 [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 suppression system, which was capable of predicting pressure transients at specified locations in the vent system. With this dynamic model and the full-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 addressed by the NRC [6].

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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 ASMI Codes (4).

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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 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.

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S. PLANT-SPECIFIC REVIEW: NINE MILE POINT UNIT 1

5.1 BACKGROUND

INFORMATION i

o Vacuum breaker type: fkI'inAtwood-Morrill(external) o There are three wetwell to drywell vaccum breakers [7].

o Vacuum breakers are located on 30-in external pipes connecting the main vent line and the wetwell.

5.2 STRESS ANALYSIS RESULTS An evaluation was performed of the adequacy of the vacuum breakers at Nine Mile Point Unit 1 under the chugging transient. This evaluation was .

based on the calculation of valve closing impact velocities, which was generically developed in Reference 8. A plant-unique evaluation of the valve

. closing impact velocities at Nine Mile Point Unit I revealed that the vacuum break'ers would not actuate during the chugging transients [9). Therefore, no modifications to the vacuum breakers were required at this plant.

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6. CONCLUSIONS A review has been conducted to determine the structural int 6grity of the vacuum breakers at Nine Mile Point Unit 1. The design loads associa.ted with the hydrodynamic phenomena have been reviewed and addressed by the N!!C in Reference 6. This review covered only the structural analysis of the vacuum 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 results of the Licensee's evaluation indicated that the vacuum breakers at Nine Mile Point Unit I will not actuate during the chugging transient. Therefore, no modifications are necessary; the existing design is structurally adequate.

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7. REFERDJCES

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

" 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 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

" 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 i, Valve Dynamics"

+ December 24, 1984

7. " Plant Unique Analysis Report of the Torus Attached Piping for Nine Mile Point Unit 1 Nuclear Generating Station" TR-5320-2

- Niagara Mohawk Power Corporation April 1984

8. " Mark I Vacuum Breaker Improved Valve Dynaanic Model-Model Developmental Validation"

. C.D.I. Tech Note 02-31 Continuum Dyanmics, Inc., Princeton, New Jersey October 1982

9. T. E. Lempges Letter to D. B. Vassallo (NRC)

Subject:

Nine Mile Point Unit 1 Mark I Vacuum Breaker Modifications, Niagara Mohawk Power Corporation July 22, 1983