ML20009A615
| ML20009A615 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 07/08/1981 |
| From: | Crutchfield D Office of Nuclear Reactor Regulation |
| To: | Counsil W NORTHEAST NUCLEAR ENERGY CO. |
| References | |
| TASK-05-11.A, TASK-5-11.A, TASK-RR LSO5-81-07-012, LSO5-81-7-12, NUDOCS 8107130378 | |
| Download: ML20009A615 (11) | |
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Docket No.50-24S e
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2 JUL 10198W L Mr.,W. G. Counsil Vice President
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Nuclear Engineering and Operations essa Northeast Nuclear Energy Company Po't Office Box 270 9
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s Hartford, Connecticut 06101 co to
Dear fir. Counsil:
SUBJECT:
SEP TOPIC V-ll.A. REQUIREMENTS FOR ISOLATION OF HIGH AND LOW PRESSURE SYSTEMS, SAFETY EVALUATION FOR !!ILLSTONE UNIT 1 Enc 1csure 's is the final version of our contractor's technical evaluation of SEP Topic V-ll.A.
This report replaces the report fomarded by ray letter dated January 13, 1981 and has been revised to reflect the conments contained in your letter of May 8,1981. is the staff's safety evaluation for this topic.
is based upon Enclosure 1.
As a result of our safety evaluation of Topic V-ll.A, we are propcsing modifications to the RWCU inboard suction isolation valve control circuitry.
The need to actually implement these changes will be determined during the integrated plant safety assessment.
This topic assessment may be revised in the future if your facility design is changed or if NRC criteria relating to this topic are modified before the integrated assessment is completed.
Sincerely,,
Dennis M. Crutchfield, Chief Operating Reactors Branch No. 5 Division of Licensing
Enclosures:
As stated M
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.cc William H. Cuddy, Esquire Cc.necticut Energy Agency Day, Berry & Howard AT'N: Assistant Director LCounselors at. Law Research. and Policy One Can'stitution Plaza' Development Hartford, Connecticut 06103 Departaent of Planning aad
., Energy Policy?
Natural Resources' Defense Council 920 Grand Street, 91715th Street, N. W.
. Hartford, Connecticut 06106 hashington, D. C.
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Northeast Nuciear Energy Company ATTN: Superintendent Millstcne Plant P. 0. Box 128 Waterford, Connecticut 06385 Mr. Janes R.' Himmelwright Northeast Utilities Service Coapany
-P. 0. Box 270 Hartford, Connecticut 06101 Resident Inspector c/o.U. S.'NRC P. O. Box Drawer KK Niantic, Connecticut 06357 4
Waterford Public Library Rope Ferry Roac, Route 156 Waterford, Connecticut 06385 First Selectman of the Town of Waterford Hall of Records 200 Boston Post Road Waterford, Connacticut 06385 i
John F. Opeka Systens Superintendent Northeast Utili;ies Service Coapany 1
P. O. Box 270 Hartf ord, Connecticut 06101 U. S. Environmental Protection Agency Region 1 Office ATTN: EIS COORDINATOR JFK Federal Building j
Boston, Massachusetts 02203
V (Enclosure 1) 1 l
l 0146J
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i SEP TECHNICAL EVALUATION REPORT ELECTRICAL, INSTRUMENTATION, AND CONTROL FEATURES FOR ISOLATION OF HIGH AND LOW PRESSURE SYSTEMS FINAL DRAFT MILLSTONE NUCLEAR STATION, UNIT 1 Docket No. 50-245
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June 1981 I
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CONTENTS a
l.0 INTRODUCTION
i.
1 2.0 CRITERIA 1
2.1 Residual Heat Removal (RHR) System.....,.......
1 2
2.2 Emergency Core Cooling System 2.3 Other Systems
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3.0 DISCUSSION AND EVALUATION.... t'.
3 3.1 ReactorWaterClean-Upjystem' 3
3.2 Low Pretsure Coolant Injection System 3
4 3.3 ' Core Spray System 4.0
SUMMARY
4 4
5.0 REFERENCES
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' ELECTRICAL,' INSTRUMENTATION,!AND CONTROL FEATURES FOR
~ ISOLATION OF HIGH AND LOW PRESSURE SYSTEMS
-MILLSTONE NUCLEAR: STATION, UNIT 1
. l.0 INTRODUCTION-The purpose-of this review is to determine if the electrical;
' instrumentation, and control (El&C) features used to isolate systems with a lower pressure rating than the reactor coolant-primary system 4
are in compliance with current licensing requirements as outlined in
~
'SEP Topic.V-llA.- Current guidance for isolation of high_.and low pres-sure systems is contained in Branch Technical Position (BTP) EICSB-3,
- BTP RSB-5-1, and.the Standard Review' Plant (SRP), Section 6.3.
2.0 CRITERIA 1
2.1 Residual Heat Removal (RHR) Systems.
Isolation requirements for RHR systems contained in BTP RSB-5-1 are:
'(1) The suction side must be provided with the following isolation features:
(a). Two power-operated valves in series with posi-tion indicated in the control room.
(b)
The valves must have independent and diverse interlocks to prevent opening if the reactor coolant system (RCS) pressure is above the design pressure of the RHR system.
(c) The valves must have independent and diverse interlocks to ensure at least one valve closes 1
upon an increase in RCS pressure above the design pressure of the RHR system.
(2) The discharge side must be provided with one of the following features:
(a).The_ valves, position indicators, and interlocks described in (1)(a) through (1)(c) above.
-(b) One or more check valves in series with a i
normally-closed power-operated valve which has I
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its position; indicated'in the' control room; If this valve is used for an Emergency Core
Cooling System (ECCS) function, the valve me3t' open-upon receipt of a safety injection signal
'(SIS) when RCS pressure has decreased belcw RHR system design pressure.
-(c) Three check valves in series.
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.. s (d) Two check valvest in series,,provided that'both
... may be periodically checked for leak tightness and are checked at least annually.
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2.2 Emergency Core Cooling System.
Isolation requirements for ECCS are contained in SRP 6.3.
Isolation of ECCS to prevent overpres-surization must meet one of t following features:
(1) One or more check valves in series with a normally-closed motor-operated valve (MOV) which is to be opened upon receipt of a SIS wnen RCS pressure is less than the ECCS design pressure (2)- Three check valves in series (3) Two check valves in series, prov,ided that both may be periodically checked for leak tightness and are checked at least annually.
2.3 Other Systems. All other low pressure systems interf acing with the RCS must meet the following isolation requirements from STP EICSB-3:
i (1) At least two valves in series must be provided to isolate the system when RCS pressure is above the system design pressure and valve position should be provided in the control room (2) For. systems with two MOVs, each M0V should have independent and diverse interlocks to prevent opening until RCS pressure is below the system design pressure and should automatically close when RCS pressure increases above system design pressure (3)
For systems with one check valve and a M0V, the MOV should be interlocked to prevent opening if RCS pressure is above system design pressure and should automatically close whenever RCS pressure exceeds system design pressure.
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3.0 DISCUSSION AND' EVALUATION
There are three systems at Millstone 1,'with d.irect interface to the RCS pressure boundary, which have a design pressure-rating for.all or part d( the system which.'is lower than the RCS design pressure.
These systems are the Reactor Water Clean-Up (RWCU) system, Low Pres-
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sure. Coolant Injectica-(LPCI)' system, and Core. Spray (CS) system.
4 3.1 Reactor Water Clean-Uo System.
The RWCU system takes suction on the RCS, cools the water by circulation through regenerative and non-regenerative heat exchangers,- and lowers the water pressure by the use of a pressure control valve. After passing through the low pres-sure filter and clean-up portions of the system, the water is pumped at high pressure'through the regenerative heat exchanger and back to the reactor via the feed line.
The suction side of the system has three motor-operated isolation valves, an inboard valve, a pump suction valve, and a pump bypass valve.
Isolation on the discharge side is provided by a MOV and a check valve. The MOVs cannot open if the pressure in the low pressure portions of the system is higher than its designed pressure. They will automatically close on high RWCU system tempera-i ture, high RWCU system pressure, low reactor level, or loss of control power. However, the interlocks for these valves all use the same
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s'nsors and relays. Each M0V nas_ position indication in the control e
room.
Isolation provisions of the RWCU system do not meet the current licensing criteria since the interlocks for the isolation valves are
- not independent as required by BTP EICSB-3.
3.2 Low Pressure Coolant Injection System.
The LPCI system takes suction on-the supp'ression pool (or condensate storage tank) and dis-charges into the reactor vessel. The discharge of each loop has two normally-closed MOVs which cannot be opened unless a LPCI system initi-ation signal is present and the RCS pressure is below the design pres-sure of the system. The valves will automatically close if either the LPCI system signal-or RCS pressure increases above' the LPCI system L
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Each valve has position indication in t.$ control I
room. The LPCI system is in 'conformance with isolation pr_,/isions of current licensing requirements.
3.3 Core Soray System. The CS system consists o'fitwo loops
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-taking suction on'the suppression pool and dischargingiinto the reactor.
vessel through!two MOVs (one normally opem the other:no'rmally closed)
.e and a testable (air-operated) check valve per loop. All three valve p'titions are indicated in the cqatrol ~ room. The normally-closed MOV wiis only open upon a CS system in,itiation signal when RCS pressure has decreased below CS system design pressure.. The M0V will automatically close upon clearing the initiation signal or increasing RCS pressure above CS system design pressufe. Therefore, the CS system meets the isolation criteria of current licensing requirements.
4.0
SUMMARY
Millstone 1 has three systems with lower design pressure ratings than the RCS which are directly connected.to the RCS. The LPCI and CS systems meet current licensing criteria contained in SRP 6.3 for isola-j tion of high and low pressure systems. The RWCU system is not in com-j pliance with BTP EICSB-3 since the isolation valve interlocks are not independent.
5.0 REFERENCES
1.
NUREG-075/087, Branch Technical Positions EICSB-3, RSB-5-1; Stan-dard Review Plan 6.3.
2.
Millstone 1 Piping and Instrumentation Drawings 25202-26008,
-29119, -29128, and 29133.
3.
Millstone 1 Electrical Drawings 25202-31001-684, -684A, -685,
-686, -687, -745, -746, -773, -798, -858, -859, -863, -864, -868, and -869.
4
4.
Final Safety Analysis Report, Millstone Nuclear Station, Unit 1.
5.
Letter, Northeast Utilities (Counsil) to NRR (Crutchfield), dated May 8, 1981.
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TOPIC: V-ll. A REQUIREMENTS FOR ISOLATION OF HIGH AND LOW PRESSURE SYSTEMS 1.
_ INTRODUCTION Several systems that have a relatively low design pressure are connect-ed to the reactor coolant pressure boundary. The valves that form the interface between the high and low pressure systems must have suffici-ent redundan;y and interlocks to assure that the low pressure systems are not subjected to coolant pressures that exceed design limits. The problem is complicated since under certain operating modes (e.g.,
shutdown cooling and ECCS injection) these valves must open to assure adequate reactor safety.
II.
REVIEW CRITERIA The review criteria are presented in Section 2 of EG&G Report 0146J, "Flectrical, Instrumentation and Control Features for Isolation of High and Low Pressure Systems."
.III.
RELATED SAFETY TOPICS AND INTERFACES The scope of review for this topic was limited to avoid duplication of effort since some aspect" of the review were performed under related topics. The related topics and the, subject matter are identified be-low. Each of the related topic reports contain the criteria and review guidance for its subject matter.
V-10.B RHR Reliability VI-4 Containment Isolation Topic V-ll.B is dependent on the present topic information for completion.
IV.
REVIEW GUIDELINES The review guidelines are presented in Section 7.3 of the Standard Review Plan.
V.
EVALUATION As noted in EG&G R-QQ/t 0146J, Millstone Unit 1 has three systems with a lower design pressure rating than the reactor coolant system (RCS) that are directly connected to the RCS.
These systems are the Reactor Water Clean-up (RWCU) System, the Low Pressure Coolant Injection (LPCI) System, 1
and the Core Spray (CS) System.
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4 The LPCI'and CS systems meet current licensing criteria.- The RWCU does not have independent interlocks on the suction valves.
VI.
CONCLUSIONS
.4-s Because of the severe consequences.of a LOCA 'outside of containment the,. staff proposes that an indepeh' dent high pressure interlock be installed on the RWCU inboard suction isolation valve.
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