ML20214H094
| ML20214H094 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 07/14/1986 |
| From: | Carfagno S, Con V, Triolo S CALSPAN CORP. |
| To: | NRC |
| Shared Package | |
| ML20214H099 | List: |
| References | |
| CON-NRC-03-81-130, CON-NRC-3-81-130 TAC-07950, TAC-7950, TER-C5506-320, TER-C5506-320-S01, TER-C5506-320-S1, NUDOCS 8607170230 | |
| Download: ML20214H094 (22) | |
Text
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SUPPLEMENTARY TECHNICAL EVALUATION REPORT NRC DOCKET NO. 50-271 FRC PROJECT C5506 NRC TAC NO. 07950 FRC ASSIGNMENT 12 I
NRC CONTRACT NO. NRC-0341-130 FRC TASK 320
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STRUCTURAL EVALUATION OF THE VACUUM BREAKERS (MARK I CONTAINMENT PROGRAM)
't,j VERMONT YANKEE NUCLEAR POWER CORPORATION VERMONT YANKEE NUCLEAR STATION
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TER-C5506-320
.i Prepared for Nuclear Regulatory Commisslor FRC Group Leader:
V. N. Con Washington, D.C. 20555 NRC Lead Engineer:
H. Shaw
,.7 July 14, 1986
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,a 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
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responsibility for any third party's use, or the resulta 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.
Prepared by:
Reviewed by:
Approved by:
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Date: 7 Date:
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FRANKLIN RESEARCH CENTER DIVISION OF ARVIN/CALSPAN 30th & WACE 57setts.PMnActLpMIA.PA 19105 glo?tW4l$'
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CONTENTS Section Title Page 1
INTRODUCTION 1
1.1 Generic Background.
1 1.2 Vacuum Breaker Function 2
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2 EVALUATION CRITERIA.
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DESIGN LOADS 10 I'!
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4 STRESS EVALUATION 11 tu 5
PLANT-SPECIFIC REVIEW: VERMONT YANKEE.
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5.1 Background Information.
15 5.2 Stress Analysis Results 15 i{rr 6
CONCLUSIONS.
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' REFERENCES.
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1 t.3 TER-C5506-320 FOREWORD
't This Technical Evaluation Report was prepared by Franklin Research Center l
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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INTRODUCTION t
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
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chugging and condensation phases of hydrodynamic loadings. To resolve this issue, two vacuum breaker owner groups were formed, one for those with General r
Precistion Engineering (GPE) vacuum breakers, the other for those with Atwood-Morrill (AM) vacuum breakers.
1 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 l.
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
- d as-built acceptability of'the vacuum breakers.
i 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 j
and documented in this report.
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i 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
- p report (Sections 5 and 6) provides a plant-specific review, which pertains to Vermont Yankee.
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1.1 GENERIC BACKGROUND
'l 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
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analytical results. The licensees responded to the NRC request by developing l
appropriate force functions simulating the anticipated hydrodynamic loads, and j
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 4i licensee.
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1.2 VACUUM BREAKER FUNCTION
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During steam condensation tests on BWR Mark I containments, the wetwell-
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to-drywell vacuum breakers cycled repeatedly during the transient phase of steam blowdown. This load was not included in the original load combinations
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7 used in the design of the vacuum breakers. Consequently, the repeated impact i
Li of the pallet on the valve seat and body created stresses that may impair its f
capability to remain functional.
7 A vacuum breaker is a check valve installed between the wetwell and the drywell.
Its primary function is to prevent the formation of a negative y
pressure on the drywell containment during rapid condensation of steam in the drywell and in the final stages of a LOCA. The vacuum breake'r 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.
jJ A vacuum breaker can be internally or externally mounted. Figures 1 and 2 illustrate locations of vacuum breakers.
Schematics of typical GPE and AM vacuuni breakers are illustrated in Figures 3 and 4.
A typical pressure differential vacuum breaker during a LOCA is provided l
in Figure 5.
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Table 1 lists the various vacuum breaker types and the _ plants affected by them.
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Internal Vacuum Breaker 4
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Atwood-Morrill Vacuum Breaker i
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Typical DW/WW Vacuum Breaker Pressure Differential Due to LOCA
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Vacuum Breaker Types and Affected Plants Vacuum Breaker Plant
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GPE 18 In (Internal)
Brown Ferry Units 1, 2, and 3 Pilgrim Unit 1 Brunswick Units 1 and 2 Cooper
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Hatch Units 1 and 2 Peach Bottom Units 2 and 3 Duane Arnold
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Fermi Unit 2
,l GPE 24 in (Internal)
Hope Creek 4
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Monticello Quad Cities Units 1 and 2 f
AM 18 in'(External)
Dresden Units'2 and 3 L
Millstone Unit 1 Oyster Creek Vermont Yankee AM 18 in (External)
'FitzPatrick Nine Mile Point Unit 1 1
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TER-C5506-320
'o 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 addend'a (4), have been used to evaluate the i
structural integrity of the vacuum breakers.
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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 bretker disc was quantified as a function of time. This issue has been reviewed and addressed by the NRC (6].
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STPESS EVALUATION *
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To determine structural integrity of the vacuum breaker, the licensees i !
have employed standard analytical techniques, including the finite element method, to calculate stresses of critical components of the vacuum breaker j{
under various design loadings. Loads resulting from the hydrodynamic j
phenomenon were compared with those values specified in the ASME Code.4 (4].
)i For illustration purposes, a schematic drawing of the moving parts of all components other than the actual disc of the Atwood-Norrill valve and of the
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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 4
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in Figure 8.
Loading inputs to this model are the displacement time histories i
that were obtained from the impact model analysis.
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Detailed valve Internal Model
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Finite Element Model of Valve Internals
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Valve Detailed Disc Model Geometry
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5.
PLANT-SPECIFIC REVIEW: VERMONT YANKEE PLANT
5.1 BACKGROUND
INFORMATION o
Vacuum breaker type:
18-inch Atwood-Morrill (external) o Vacuum breakers are located on two 18-inch external lines connecting the wetwell and the drywell o
In 1980, the valve disc material was changed from a cast aluminum disc to a tougher wrought aluminum disc material for improved resistance to cyclic loading.
2 5.2 ANALYSIS RESULTS 1
A Vermont Yankee unique report [7] was prepared in which a model of the vacuum breaker having the characteristics outlined in Table 2 was evaluated.
m The report concluded that the vacuum breakers would not actuate during d
chugging transients. As stated in Reference 8, since the vacuum breakers do not actuate during chugging transients, no additional analysis was performed j
by the Licensee.
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Table 2.
Vacuum Breaker Characteristics for the Vermont Yankee Plant Vacuum breaker type 18-in A&M External 2
System moment of inertia (1b-in-s )
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System moment arm (in) 3.586 i
Disc moment arm (in) 11.375 l
System weight (1b) 106.1 2
Disc area (in )
283.5 t,
System rest angle (rad) 0.4124 t'
Seat angle (rad) 0.53 II Body angle (rad) 1.32 Seat coefficient restitution 0.8 Body coefficient restitution 0.6 l
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CONCLUSIONS ii A review has been conducted to determine the structural integrity of the j
vacuum breakers of the Vermont Yankee plant. The design loads associated with
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the hydrodynamic phenomena have been reviewed and addressed by the NRC in a
l Reference 6.
Any revisions to the Licensee's loading transients which may result from the NRC's evaluation and their effect on vacuum breaker component t ('
stress levels have not been addressed in this report. This review covered i
only the structural analysis of the vacuum breaker, and the following conclusion is drawn from the review.
o The vacuum breaker will not actuate during the chugging transients.
Therefore, the existing design is structurally adequate and no
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modifications are required.
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REFERENCES 1.
" Safety Evaluation Report, Mark I Containment Long-Term Progrdm Resolution of Generic Technical Activity A-7," Office of Nuclear Reactor Regulation, USNRC July 1980 2.
D. G. Eisenhut J
"USNRC Generic Letter 83-80, Modification of Vacuum Breakers on Mark I
[
Containment" February 2, 1983 3.
" Mark I Containment Program Structural Acceptance Criteria Plant Unique Analysis Application Guide," General Electric Co., San Jose, CA October 1979 j
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 a
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 J
Valve Dynamics" December 24, 1984
't 7.
CDI Tech Note 82-20, " Improved Dynamic Vacuum Breaker Valve Response for J
Vermont Yankee," Revision 0, Continuum Dynamics, Inc. May 11, 1983 8.
J. B. Sinclair Letter with Attachments to D. B. Vassallo (NRC)
Subject:
Request for Additional Information Mark I Containment Long-Term l
Program
(
Vermont Yankee Nuclear Power Corporation, June 17, 1983
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