ML20031C924
| ML20031C924 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 10/05/1981 |
| From: | Crutchfield D Office of Nuclear Reactor Regulation |
| To: | Kay J YANKEE ATOMIC ELECTRIC CO. |
| References | |
| TASK-07-01.A, TASK-7-1.A, TASK-RR LSO5-81-10-003, LSO5-81-10-3, NUDOCS 8110090132 | |
| Download: ML20031C924 (19) | |
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n, October 5, 1931 Docket No. 50-29 A
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Mr. James A. Kay 007 0
Yankee Atomic Electric Company
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1981 % 7, Senior Engineer - Licensing
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Dear Mr. Kay:
SUBJECT:
SEP TOPIC VII-1.A, ISOLATION OF REACTOR PROTECTION SYSTEM FROM NON-SAFETY SYSTEMS, INCLUDING QUALIFICATION OF ISOLA-TION DEVICES, DRAFT SAFETY EVALUATION FOR YANKEE R0WE is our contractor's draft Technical Evaluation Report on this topic. is a copy of our draft safety evaluation report that is based on Enclosure 1.
This evaluation supports the findings of the staff safety evaluation of Topic VII-1. A and recorrrnends modifications to the Reactor Protection System. Please infom us if your as-built facility differs from the licensing basis assumed in our assessment within 30 days of receipx. of this letter.
The need to actually implement these changes will be detennined during the integrated 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 4
Division of Licensing f
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Enclosures:
As stated cc w/ enclosures:
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.c Mr. James A. Kay cc Fr. James E. Tribble, President Yankee A.tomic Electric Company 25 Research Drive k'estborough, Massachusetts 01581 Greenfield Community College 1 College Drive Greenfield, Massachusetts 01301 Chairman Board of Selectmen Town of Rowe Rowe, Massachusetts 01367 Energy Facilities Siting Council 14th Floor One Ashburton Place
' Boston, Massachusetts 02108 U. S. Environmental Protection Ager.cy Region 1 Office ATTN: Regional Radiation Representative JFK Federal Building Boston, Massachusetts 02203 Resident Inspcctor sf*
Yankee Rowe Nuclear Power Station c/o U.S. NRC Post Office Box 28 Monroe Bridge, Massachusetts 01350 f
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0506J SIP TECHNICAL EVALUATION TOPIC VII-1.A ISOLATION OF REACTOR PROTECTION SYSTEM FROM NON-SAFETY SYSTEMS YANKEE R0WE Docket No. 50-29 August 1981 D. J. Morken EG&G Idaho, Inc.
Draft 8-27-d1
4 CONTENTS 1.' O I N TR O D UC T I O N....................................................
1 2.0 CRITERIA........................................................
1 3.0 DISCUSSION AND EVALUATION.......................................
2 3.1 General...................................................
2 3.1.1 Manual Reactor Trip...............................
3 3.1.2
. Nuclear Instrumentation...........................
3 3.1.3 Main Coolant Flow.................................
5 3.1.4 Main Coolant Pump Current.........................
6 3.1.5 Low Pressurizer Pressure..........................
6 3.1.6 Low Main Coolant Pressure.........................
7 3.1.7 High Pressurizer Water Level......................
8 3.1.8 Low Stean. Generator Water Leve l...................
9 3.1.9 Turbine Trip......................................
9 3.1.10 Generator Trip....................................
9 4.0
SUMMARY
10 5.0. REFERENCES......................................................
11 6.0 APPE NDI X A--NRC SAFETY TOPICS RELATED TO THIS REPORT............
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F SEP TECHNICAL EVALUATION TOPIC VII-1.A ISOLATION 0E REACTOR PROTECTION SYSTEM FROM NON-SAFETY SYSTEMS YANKEE R0WE
1.0 INTRODUCTION
The objective of this review is to determine if non-safety systems wnich are electrically connected to tne Reactor Protection System (RPS) are properly isolated from the RPS and if tne isolation devices or techniques used meet current licensing criteria. Tne qualification of safety-related equipment is not within the scope of this review.
Non-safety systems generally receive control signals from RPS sensor current loops.
The non-safety circuits are required to have isolation devices to ensure electrical independence of the RPS cnannels.
Operating experience has showr. that some of tne earlier isolation devices or arrange-ments at operating plants may not meet current licensing criteria.
2.0 CRITERIA General Design Criterion 24 (GuC 24), entitled, " Separation of Protec-tion and Control Systems'," requires that:
The protection system shall be separated from control sys-tems to tne extent that failure of any single control system component or channel, or f ailure or removal from service of any single protection system component or channel whicn is common to the control and protection systems, leaves intact a system that satisfies all reliaoility, reaundancy, and inoependence requirements of the protection system.
Inter-connection of tne protection and control systems shall be limitedsgastoassurethatsafetyisnotsignificantly impaired IEEE-Standard 279-1971, entitled, " Criteria for Protection Systems for Nuclear Power Generating Stations," Section 4.7.2, states:
1
The transmission of signals from protection system equip-ment for control system use shall be tnrougn isolation devices whicn shall oe classified as part of the protection system and shall meet all the requirements of this docu-ment. No crediDie failure at the output of an 1 solation device shall prevent tne associated protection system chan-nel from meeting the minimum performance requirements speci-fied in tne design bases.
Examples of credible failures include short circuits, open circuits, grounds, and the application of tne maximum cred-iole AC or DC potential. A failure in an isolation device is evaluated in tne same manner as a failure of other equip-ment in the protection system.2 3.0 DISCUSSION AND EVALUATION 3.1 General.
The Reactor Protection System (RPS) includes tne sensors, amplifiers, logic and other equipment essential to tne monitoring of selected nuclear power plant conditions.
It must reliably effect a rapid snutdown of the reactor if any one or a comoination of parameters ceviates beyond pre-selected values to mitigate the consequences of a postulated desigt sasis event.
The RPS parameters and their logic cnannels as identified in the Yan<ee 3
Rowe Technical Specification are as follows:
No. of Parameter Channels Trip Logic Manual Trip 3
1 out of 3 Powe: and Intermediate Range Nuclear Instrumentation 6
2 out of 6 Intermediate and Hign Start-up Rate Nuclear Instrumentation 2
1 out of 2 Source Range Nuclear Instrumentation E
1 out of 2 Low Main Coolant Flow 4
2 out of 4 2
Main Coolant Pump Current
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2 out of 4 System A 4
Systera B 4
2 out of 4 Low Pressurizer Pressure 1
1 out of 1 Low Main Coolant Pressure 1
1 out of I High Pressurizer Water Level 1
1 out of 1 Low Steam Generator Water Level 4
2 out of 4 Turbine Trip 1
1 out of 1 Generator Trip 1
1 out of 1 3.1.1 Manual Reactor Trip.4 Three scram switches are arranged in a one-out-of-tnree configuration. Tne output of eacn switch goes directly to tne trip coil circuitry of the two trip coils of the rod scram circuit breakers. Additional contacts go to the auxiliary scram relay whicn actu-ates automatic plant functions upon a scram signal.
Evaluation. The manual scram logic circuitry uses switch and relay contacts wnicn crovide adequate isolation from control and non-safety systems.
3.1.2 Nuclear Instrumentation.5 The RPS nuclear instrumentation system includes the source range monitors (cnannels 1 and 2), tne inter-mediate range ano start-up monitors (channels 3, 4 ana 5) and the power and intermediate range monitors (cnannels 3, 4, 5, 6, 7 and 8).
The source range monitors use SF3 pr portional counters. The counter outputs feed pulse integrators wnich output direct current signals to log microammeters. Outputs from the log mic-oammeters go to start-up rate (SUR) meters, test panels, source range instrumentation on the main control board and to SUR Distable magnetic amplifiers. Tne oatput of either b w staole is selected througn a source range scram cutout switen.
Tne resul-tant signal is connected to the output of the interm @ iata range SUR oistables, channels 3 and 4.
The signal tnen feeds tne memory oistaole in the alarm and scram panel and inputs to tne two scram Duses, A and 8, through a resistor divider network. Relay contacts from the permissive 3
logic isolate the intermediate range signal from the, source range below a preset reactor power level. A decade selector switch permits monitoring the output of the log microammeters on a two pen recorder on the main control board.
Isolation of the recorder from the log microammeter is by a resistor in series with the recorder input.
The intermediate range nuclear instrumentation channels 3 and 4 serve a cual purpose. They provide startup rate protection as well as interme-diate end power range level protection.
(Channel 5 of the intermediate range monitors is not used in the start up rate system).6 The sensors are compensated ion chambers. The output signals from these chambers feed log microammeters for startup rate protection as well is power range level
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magnetic amplifiers. The output logic from the log microammeters is the same as for the source range instrumentation described above, initiating a reactor scram upon sensing a high reactor startup rate.
The power range nuclear instrumentation, channels 6, 7 and 8, use uncompensated ion chambers to sense power level. Additional monitoring and plant protection is prosided by the power level signals from the inter-mediate range channels 3, 4 and 5 as noted above. Each of the six ion r
chambers provides a current signal to a linear magnetic amplifier. The outputs of the linear magnetic amplifiers feed power range instruments on the main control panel and may be selected by the decade selector switch for monitoring on a two pen recorder.
Isolation of the recorder from the linear magnetic amplifier is by a 13.1 Kohm resistor. The linear magnetic amplifiers also provide input signals to level trip magnetic amplifiers for scram signals. The three outputs from the intermediate range bistable amplifier are transmitted to a resistor coincidence circuit in the inter-mediate range panel. The output of the coiacidence circuit provides a signal to scram bus B.
The output signals from the three power range chan-nels are also connected by a resistor coincidence circuit in the alarm and scram panel with a scram signal to scram bus B.
This logic provides the two-out-of-six scram logic for the intermediate and power range nuclear instrumentation systems.
4
The intermediate range auxiliary panel also contains,the necessary switches for testing and calibrating the individual power monitoring cnannels.
The startup and power range panel contains relays for annunciators, indicators, rod stop signal circuit and the BF counter hign voltage dis-3 connect. A power range scram switen selects coincidence vs single channel scram logic. The permissive circuitry operates by relay action but may be bypassed by a manual switch on tne start-up and power rar.ge panel.
Power to tne nuclear instrumentation systems is from a single circuit on the vital bus.
Individual 5,ower supplies are isolated from tne vital bus circuit by fuses.
Evaluation. Use of switch contacts and relays for annunciators, indi-cator lights and permissive circuitry provides adequate isolation of these functions of the nuclear instrumentation from control ano non safety sys-tems.- Tne isolation of the microammeters r,r the linear magnetic amplifiers from the indicating meters and tne two pen recorder do'es not meet current licensing criteria.
3.1.3 Main Coolant Flow.7 Low main coolant flow, a four channel system, is monitored oy delta pressure transmitters across the input and output legs of the four steam generator loops. A bourdon tuDe type trans-mitter (MC-FD-8,10,11, and 12) senses tne flow in tne steam generator loop and transmits a signal proportional to flow through a flow test panel to a linear magnetic amplifier. The signal is demodulated and amplified by the magnetic amplifier and feeds a remote indicating meter, a process
.ecorder and a bistable magnetic amplifier whicn acutates a relay for annun-ciations and low flow signals.
The output of the four cnannel bistacle I
amplifiers are also connected through a resistor network to a common shut-down, loss of flow, bistaole amplifier.
The resistor network establisnes a two out-of-four scram logic for the system. Tne signal from the snutdown bistaole is fed througn contacts of the parmissive relay in tne start-up and power range panel, tnen to a scram oistaole amplifier in tne alarm and scram l
-panel whicn feeds scram buses A and 5.
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The main coolant flow circuitry requires 90 V
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.These voltages are supplied from fou ' regulated pcwer supplias fed from the vitalbus.~Eachpowersupplyisindividuallyprotectedbkfuses.
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Evaluation. The isolation between tne linear magnetic amplifier odt s
put and the process recorders and the indicating meters ji by shunt alld "
.a series resistors which does not meet. current licensing sc'andards.
'e' 3.1.4 Main Coolant Pump Current.6,8 Low main coolant flow is also k
determined by monitoring main coolant pump current.
Four current trans-
- formersforeachpumparedividedintotworedundanttripchannels. Two transformers monitor pnases A and B for logic channel 1 and pnases A and C for logic channel 2.
Output from each current transf ormer feeds an over current (0C) relay and an under current (VC) relay.
Outputs of the OC and
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UC relays for each cnannel pass through a logic matrix which develops a two-out-of-four trip function wnich feeds a time delay relay. Tne output signal of the time delay relay for each subsystem is connected through contacts of the permissive circuit ta the control rod trip relays. Pump status alarms are provided by relay contact in the logic matrix. A manual disconnect switch is provided for each current transformers and test switches for eacn OC and UC relay permits on line testing of tne system.
m Power for channel 1 logic is from 125V DC battery bank No. I and for channel 2 logic from 125V DC battery bank No. 3.
s Evaluation. Adequate isolation is maintained Detween channels and a
from control and non-safety systems.
3.1.5 Low Pressurizer Pressure.9 Tne pressurizer pressure protec-tion system is a single cnannel system.
Sensor PR-PD-6 is a courdon tube transmitter. The sensor signal output is from a diffe:ential transformer.
This signal passes througn a test circuit to a ' lear magnetic amplifier wnere the signal is demodulated and amplified. The output of the linear magnetic amplifier feeds six bistable magnetic amplifiers (H, P, R, S, T and U), a remote meter and a process recorder.
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Contacts of the relays operate tne pressurizer heater contepilNe,sprayvalvePR-MOV-191,reliefvalve50V-90,reliefvalve N~
MOV-512 and; annunciators. Bistablegmagnetic arrplifier N provides an on-off 4
output to thgala'rm t.nd scram pt.nel where a b.istable inagnetic amplifier drives the@ar'id B scram buses; f
Powerto\\(hesystemsisfr6mpowersupplyno.3fedfromthevital Input to the pressurizer.y(' essure systen is isolated by fuses.
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I-f' Evaluit' ion..Controlfunctiodfassociatedwiththepressurizerpressure cynnelareactuatedfddmrelaycontactswhichprovideadeouateisolation f(6mtheRPSsystem. The< isolation between the linear magnetic amplifier an,d,the,remcQmeter and the recorder is oy snunt and series resistors which do's n n 5eet current licensing standards.
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3.1.6 Low Main Coolant Pressure.10 Tne main coolant pressure pro-r tpction system is a single cnar.nel system. Sensor MC-PD-9 is a bourdon t'ube transmitter. Tne sensor signal output is from a-differential trans-former, tnrough a test circuit tS a linear magnetic amplifier wrere the t
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signal is demodulated and amplified. The output of tne linear magnetic
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control of the charging pumps and five oistacle magnetic amplifiers (not identified). Four of tne five bistacle amplifiers feed relays. The con-I tacts of these relays actuate the high and low annunciator alarms, safety injection nigh pressure pumps and valves, the low pressure safety' injection pumps and motor operated relief valve PR-M0V-191. The fi#th bistable ampli-i fier provides an on-off output to the alarm and scram panel where a bistable magnetic amplifier drives the A and B scram buses.
/ower to the system is from power supply no. 4 fed from the vital bus.
Input to the main coolant pressure system is isolated by fuses.
i Evaluation.
Isolation between the RPS main coolant pressure system and the annunciators and safety injection system function is oy relay con-tact.
Isolation between tne linear magnetic amplifier and tne remote meter 7
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and recorder is by_snunt and series resistors which does not meet current-licensing standards. There is no isolation device oetwasn tne linear magnetic _ amplifier and the cnarging pump preamplifier control.
3.1.7 High Pressurizer Water Level. I The pre:surizer water level system is a two enannel system. Channel 1, monitoring water level witn sensor PR-LD-6, is a narrow range (NR) system and is used for control.
Channel 2,. monitoring water' level with sensor PR-LD-8, is a wide range (WR) system and supplies the reactor protection.
Sensor PR-LD-8 is a bourdon tuce transmitter._ The sensor output signal is from a differential trans-former wnich inputs to a test circuit'tnen to a linear magnetic amplifier wnere the signal is demodulated and amplified. The output of tne linear magnetic amplifier' goes to a remote meter, a process recorder, and two bistable amplifiers (FF and EE). Bistable EE drives a relay wnose contacts feed the low alarm annunciator.
BistaDie amplifier FF provides an on-off output to the alarm and scram panel where a bistable magnetic amplifier
-drives the A and B scram buses.
Channel 1 is similar to channel 2 except it does~not supply a scram function.
The linear amplifier drives control relays tnrougn bistable magnetic amplifiers, a remate meter,#a process recorder and the charging pump speed contiol system.
Outputofthewiderangelinearamplifiermayalsobeappliedtotne NR level amplifier through a selector switcn on the WR/NR select panel to be used as a narrow range signal if the narrow range sensor becomes defective.
Power to cnannel 1_is from power supply no. 4 anc to cnannel no. 2 from supply No.
Both power supplies are fed from a common circuit from the vital cus. Fuses provide isolation between the power supplies and the monitoring channels.
Evaluation. The RPS WR channel is totally separate and isalated frca j
the NR channel except when it is selected to drive tne NR cnannel due to failure of the NR transmitter.
In that circumstance there is no isolation s
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between tne two systems. The isolation between tne linear amplifier of
- either channel and the remote meters and process recoroer's is oy snunt and series resistors which does not meet current licensing standards.
3.. l.8 Low Steam Generator Water Level.12 Tne steam generator water level system is a four channel system.
Four delta pressure transmitters, one for each steam generator, supply the level signals to four trip relay panels. Output contacts from tne trip relays are configured in a two-out-of-four logic..The~ trip signal from the two-out-of-four logic is connected through cor, tacts of the permissive circuit to a bistable amplifier in the alarm and scram panel. Output of the bistable amplifier feeds the A and B scram buses.
Each trip relay includes a power supply, test switch, contact outputs for Hi/Lo scram alarm and scram system instrument cneck alarm.
Poser for the trip relays is frcm tne vital cus.
Each trip relay is separately fused.
Power for the two-out-of-four relay logic is from tne intermediat range auxiliary panel power supply.
e Evaluation. The steam generator water level RPS channels cre ade-quately isolatea from ccntrol and non-safety functions.
"4 3.1.9 Turbine Trip.13 Tne turbine trip system consists of two channels, eacn actua;ed oy limit switenes on the turoine control and throttle vai'ies.13 Conta ts of tnese switenes connect to time delay on drop out relays, Contacts of the time delay relays feed indicating lignts.
j Other contacts feed the control rod scram trip breakers.
Power for tne tur-bine trip circuits is from nattery No. 2.
Evaluation. The turbine trip system is adequately isolated from con-trol and non-safety functicos.
i 3.1.10 Generater Trip.I4 Reactor trip is initiated from ten separ-ate generator trip relay functions. The ten functions arb grouped accord-
-ing to functicn to actuate four auxiliary relay 8/ GX, 87VX, 56X and 87TS-IX.
Outputs of the auxiliary relays are connected to ouses to initiate various l
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plant siiutaown functions upon generator trip signals. Two separate buses
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from the four auxiliary relays feed the rod scram breakers through conta:ts of the ommissive circuits. One-bus goes to the trip coil of rod control breaker No.1, the oth3r to the trip coil on' rod control breaker No. 2.
Evaluation. The generator trip RPS circuits' are adequately isolated from control and non-safety func.tions by relay contacts on the auxiliary relays.
4.0
SUMMARY
Based on current licensing cr'iteria and review guidelines, the plant
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reactor protection system complies to all current licensing criteria listed in Section 2 of this report except for the following:
1.
The isolation between the remote meters, the process recorders and the following RPS circuits does not meet current licensing requirements:
- sdO Nuclear Instrumentation Systems low Main Coolant Flow Systems Low PIessurizer Pressure Systems Low Main Coolant Pressure Systems High Pressurizer Water Level 2.
There is no isolation between the Low Main Coolant Pressure System and the charging pump speed control circuits.
3.
There is no isolation between the High Pressurizer Water Level wide range channel and the charging pump speed control circuits when the wide range system is used to drive the narrow range channel.
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-y 5.0. REFERENCE _S_
[
1.
General Design Criterion 24, " Separation of Protection and Ccatrol Systems," of Appenaix A,~" General Design Criteria of Neclear Power Plants," 10 CFR Part 50, " Domestic Licensing of Production and Utili-zation Facilities."
2.
IEEE Standard 279-1971, " Criteria for Protection Systems for Nuclear Power Generating Stations."
3.
Yankee Nuclear Power Station Technical Specifications, Appendix "A" to OPR-3.
4.
3 tone and Webster Engineering Drawing 9699-FE-2G-Rev. 14 and JEstinghouse drawing 517F069-Rev. 13.
5.
New England Power and Service Company drawings YED-31-Rev. I and YED-32-Rev. l.
Westinghouse drawings 508F220 sheets 1 & 2-Rev. 8,
' 517F069-Rev.13, 60lJ890-Rev. 6, 60lJ897-Rev. 7 ~ and 60lJ898-Rev. 6.
6.
Yankee Nuclear Power Station, Vol. 1, Original for FSAR, updated through January 1978. Docket 50-29-Al.
7.
Westinghouse drawi gs 60lJ883-Rev. 6, 508F220-Rev. 8, 60lJ897-Rev. 7 anc New England Power and Service Co. drawing YED-31-Rev.1.
8.
Tecnnical Report on " Anticipated Transcients without Reactor Trip for the Yankee Nuclear Powar Station." October 1, 1974.
9.
Westinghouse drawings 60lJ881-Rev. 5 and 601J897-Rev. 7.
- 10. Westingnouse drawings 60lJ880-Rev. 6 and 60lJ897-Rev. 7.
11.
Westinghouse drawings 60lJ882-Rev. 6 and 60lJa97-Rev. 7.
12.
New England Power and Service Company drawings YED-50-Rev. 4, YE0-31-Rev. 1 and Westingnouse drawing 60lJ897-Rev. 7.
- 13. Letter J. A. Kay to 0. M. Crutchfield, "RAI for SEP Topics VII-l.A and VII-2," dated August 7, 1981.
- 14. ' Stone and Webster drawing 9699-FE-2G-Rev.14, and Yankee Nuclear Power Station License application, FSAR, Volume I, January 3,1974.
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' APPENDIX A NRC SAFETY TOPICS RELATED TO THIS REPORT-1.
111-1.
' Classification of Structures, Components anc Systems.
2.
VI-10.A
' Testing of R3 actor Trip Systems and Engineered S'afety Features, including Response Time Testing.
3.-
VII-2 E3F System Control Logic and Design.
4.
VII-3 Systems Required for Safe Snutdown 3 9
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4 4
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- ~e 12
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Enclosura 2 SYSTEt1ATIC EVALUATION PROGRAti TOPIC VII-1.A YANKEE _R0WE JTOPIC:
VII-1.A,' ISOLATION OF REACTOR PROTECTION SYSTEM FROM NON-SAFETY SYSTEMS, INCLUDING QUALIFICATION OF ISOLATION DEVICES I.
INTRODUCTION J ~
-Non-safety systems generally receive control signals from the reactor protection system (RPS) sensor current loops. The non-safety circuits are recuired to ha've isolation devices to ensure the independence of the RPS channels.
Requirements for the design and aualification of isolation devices are quite specific.
Recent operating experience has shown that scme of the earlier isolation devices or arrangements at
- operating plants may not be effective. The objective of our review was to verify that operating reactors have RPS designs which provide effective and qualified isolation of non-safety systems fror., safety systems to assure that safety systems will function as required.
II.
REVIEW CRITERIA
~
u The review criteria presented in Section 2 of EG&G Report 0506J, " Isola-tion of the Reactor Protection System from Non-Safety Systems."
III.
RELEATED SAFETY TOPICS AND INTERFACES The scope of review for tl 's topic was limited to avoid duplication of effort since some aspects of the review were performed under related topics. The related topics and the subject matter are identified below.
Each of the related topic reports conthin the acceptance criteria and re-view guidance for its subject matter.
VI-7.C.1 Independence of Onsite Sources VIII-1.A Degraded Grid '
IX-6 Fire Protection There are no safety topics dependent on the present topic information because proper isolation has been assumed.
IV.
REVIEW GUIDELINES n
The review guidelines are presented in Section 3 of Report 0506J.
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V.
EVALUATION Sections 3.1.2, 3.1.3, 3.1.5, 3.1.6, and 3.1.7 of EG&G Report 0506J, note that Yankee Rowe does not satisfy current licensing criteria. With regard to the deficiencies noted in Section:
a) 3.1.2, several isolation problems exist within the Nuclear Instrumen-tation system. One problem is that a single channel (one of two) is used to feed both scram channels. Thus the logic is not a true one-out-of-two, but a one out of one doubled.
The second problem is that non-safety monitors and recorders are not isolated from the safety channels by isolators that meet the require-ments of IEEE Std. 279-1971.
Because resistors are used for this isolation function, the staff is concerned about the cdequacy of protection provided to the safety equipment feem short circuits, on the non-safety wiring (both wire to wire,tage that might be placed open circuits, and the maximum credible vol l
and wire to ground).
l Furthermore, the testability of the isolators is questioned and there is no indication that these circuits are subject to either Technical l
Specifications or Appendix B requirements.
l h) 3.1.3 and 3.1.5, resistors are used for isolation.
This concern has been discussed the preceeding paragraph.
1 c)' 3.1.5 and 3.1.6, in addition to the problem of using resistors, redundant channels are fed from a common power source. Thus a i
single failure in this power system may disable all of the instru'-
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ments necessary for safe shutdown.
d) 3.1.6 also, presents an examhle of using a single channel for tripping redundant channels.
In this case, however, no safety credit is taken for this trip.
i l
VI.
CONCLUSION The present design should be upgraded by substituting qualified isolafors in the circuits identified above where any of the following conditions are met:
- 1) Redundant channels could be connected to a defective circuit by ope:ation of a switch, or l
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- 2) The wiring to the non-safety recorders and indicators does not satisfy the separation criteria of Regulatory Guide 1.75. '
In addition the source range logic should be modified to a true one-out-of-two unless it can be demonstrated that the startup rate trip is not required and the use of common power supplies should be evaluated under SEP Topic VII-3.
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