ML18046A894

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Forwards Revised Technical Evaluation Rept on SEP Topic VII-1.A.Evaluation Supports Findings of NRC Safety Evaluation Recommending Mods to Reactor Protection Sys
ML18046A894
Person / Time
Site: Palisades 
Issue date: 08/28/1981
From: Crutchfield D
Office of Nuclear Reactor Regulation
To: Hoffman D
CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
References
TASK-07-01.A, TASK-7-1.A, TASK-RR LSO5-81-08-082, LSO5-81-8-82, NUDOCS 8109030054
Download: ML18046A894 (14)
v • d • e


Text

August 28, 1981 Docket No. 50-255 LS05 08-082 Mr. David P. Hoffman Nuclear Licensing Administrator Consumers Power Company 1945 W Parn~ll Road Jackson, Michigan 49001

Dear Mr. Hoffman:

SUBJECT:

SEP TOPIC VII-1.A, ISOLATION OF REACTOR PROTECTION SYSTEM FROM_ NON-SAFETY SYSTEMS, INCLUDING QUALIFICATION OF ISOLA-TION DEVICES, SAFETY EVALUATION FOR PALISADES is a revised Technical Evaluation Report on this topic.

The report has been modiff ed to reflect the infonnation provided in your letter of June 29, 1981. is a copy of our revised safety evaluation report that is base~ on Enclosure 1.

  • This evaluation supports the findings of the staff safety evaluation of Topic VII-1.A and recommends modifica-tions _to the Reactor Protection System.

The need to actually implement these changes will be determined during the integrated safe~y 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.

Enclosures:

As stated Sincerely, Dennis M. Crutchfield, Chief Operating Reactors Branch No. 5.

Division of Licensing

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Mr. David P. Hoffman

' cc M. I. Miller, Esquire Isham, Lincoln & Beal~

Suite 4200 One First National Plaza Chicago, Illinois 60670 Palisades Plant ATTN:

Mr. Robert Montross Plant Manager Covert, Michigan 49043

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U. S. Environmental Protection Agency Federal Activities Branch Regfon V Office ATTN:

EIS COORDINATOR 230 South Dearborn Street Chicago, Illinois 60604 Charles Bechhoefer, Esq., Chairman Atomic Safety and Licensing Board Panel U. S. Nuclear Regulatory Commission Washington, D. C *. 20555 Dr. George C. Anderson Department of Oceanog*raphy.

University of Washington Seattle, Washington 98195 Dr. M. Stanley Livingston 1005 Calle Largo Santa Fe, New Mexico 87501 Resident Inspector c/o U. S. NRC Palisades Plant Route 2, P. O. Box 155 Covert, Michigan 49043

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SEP TECHNICAL EVALUAtION TOPIC V.II-1.A ISOLATION OF REACTOR PROTECTION SYSTEM FROM NON-SAFETY SYSTEMS FINAL DRAFT.

PALISADES PLANT Docket No. 50-255 July 1981

  • Enclosure l 0490J

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7-16-81

1.0 2.0 3.0 4.0 5.0 6.0 CONTENTS INTRODUCTION CRITERIA SYSTEM DESCRIPTION.......... ~**********~*-~***********~~..*... ~

EVALUATION REFERENCES

SUMMARY

APPENDIX A--NRC SAFETY TOPICS RELATED TO THIS REPORT 2

5 6

7

8.

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1.0 INTRODUCTION

. SEP TECHNICAL EVALUATION TOPIC. VIl-1.A

  • ISOLATION OF REACTOR PROTECTION SYSTEM FROM NON~SAFETY. SYSTEMS PALISADES The objective of this review is to determine if non-safety systems which are electrically connected to the Reactor Protection System (RPS) are properly isolated from the RPS and if the isdlation devices or techniques used meet turrent licensing criteria. The qualification of safety-related equipment is not within the scope of this review.

Non-safety systems gen~rally receive cont~ol signal~ from ~PS sensor

.current loops.. The non-safety circuits are required to have isolation devices to ensure electrical independence of the RPS channels. Operating*

experie~ce ~as shown that so~e of the earJier isolation devices or arrange-ments at operating plants may not meet current licensing criteria.

2.0 CRITERIA

. General Design Criterion 24 (GDC 24), entitled, "Separation of Protec-ti~n and Contrbl Systems," requires that:

The ~rotection system shall be separated from control sys-tems to the extent that failure of any single control system component or channel, or failure or removal from service of any single protection system component or channel which is common to the control and protection systems, leaves intact a system that sati_sfies all.reliability, redundancy, and..

  • independence requirements of the protection system.

Inter-connection of the protection and control systems shall be limited so as.to assure thAt safety is not signifjcantly

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Nuclear Power Generating Stations, 11 Section 4.7.2, states:

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The transmission of signals from protection system equipment for control system use shall be through isolation devices

. which shall be classified as part -0f the protection system and shall meet all the requirements of this document.

No credible failure _at the output of an isolation device shall prevent the associated protecti9n system ~~annel *fro~ ~eet~

ing the minimum performance requirements specified in the

_design bases *.

Examples of credible.failures include short circuits, open circuits, grounds, and the application of the maximum cred-ible AC or DC potential.

A failure in an isolation device is evaluated in the same manner as a failure of other equip~

. ment in ~he protection system.2

. 3.0 SYSTEM DESCRIPTION The reacto~protection system (RPS) includes the sensor instrumenta-tion, amplifiers, logic, and other eq~ipment necessary to monitor select~d nu~lear steam supply syst~m conditions and to reliably effect a rapid reac~'

tor shutdown ~f any one*or a combination of conditions deviates from a

  • preselected o*perat i ng _range *. The syste'm functions to protect the reactor' core.

The fciur'RPS trip paths consist of redundant sensors, bistables, and

~elays operating through coincidence logic to maintain power to~ or re~ove it fro~, the ~ontrol rod drive (CRD} clutches.* Four independent and separ~

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. '**..... ate measurement chann~ls normally monitor each safety parameter *.

  • Indiv.idual ch~nnel trips occur wh~n. the measurement reaches_ a p~eselected value.

Two-

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.o~t.:.of"-t our channeT tri.p log1c' provides trip signals to one-out-of-six

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matrix logic units, each of which causes a direct trip of the contactors *in the.a-c sup~ly to the CRD clutch power supplies.

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The RPS is derived from the following inputs: 3 *..

(1) *High rate-cif-change of power*

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(2) _High power level

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Lo~ reactor coolant flow

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High pressurizer pressure (S)

Thermal margin/low-pressure (6)

Loss of load (1)

Low steam generator water levels (8)

Low. steam generator pressure levels'

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Manua 1 trip (10) High containment pressure.

4. 0 EVALUATION Four basic types of isolation devices are used betw-een the safety circuits ~nd the non-safety devices.

Devices used for isolation ire optical isolators, thermistors, resistors, and operational amplifiers; which are described. in ~he following paragraphs *

4. 1 Thermistor Isolation. Tennecomp Systems drawings4 show that isolation for.the RPS analog signals to the data logger is achieved by 1-K ohm thermistors.

The following RPS analog signals. have this type of*

isolation:

a.

Steam generators A and B pressure (channel A only).

b.

Primary coolant flow (channel A onlj).

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Steam generator.s A and B water _1eve1 ( channe 1. A only) *

d.

Primari coolant loops 1 and 2 outlet temperature (channel A only) *

e.

Primary coolant loops l and 2 inlet ~emperature (channel A only).

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Neutron flux safety (channels A through D).

The above R~S analog signals in~~t to the'RPS logic system and to the Tennecomp data lcigging system.

The data logging system is loc~ted in the field remote station {FRS) in the plant feedwater purity room.

RPS analog signals connect to input ~onditioning cards in the FRS.

intra-cabinet assembly.

The input conditioning cards include two 1-K ohm positive temperature coefficient thermistors and zener diodes for isolation.

Reference 5 describes the protection provided by the input condition-

.. ing card~ against high voltage surges ~nd o~erload~. It also analyzes the result of two or more input~ tied together.as a result of a multiplexer relay failure.

The analysis does not e~aluate the effect of open and shorted circuits or maximum credible AC and DC potential on the output of the isolation device; Moreover, IEEE Standard 279-1971 states that the isolation device shall be classified as a ~art of the ~rotective system ~nd shall meet all the requirements of the standard. There is no indication that the i~put conditioning cards have been de~igned and qualified to Class lE ~equirements. Qualification of these units should be addressed during the integrated assesment *

. 4.2 lsolation by Resistors and Optical Isolators. Refefence 5 and

.the Tennecom.p drawing6 shows.the isolation of di.gital RPS sig~als in the data logger is by 36K ohm input resistci~s and optical isolators. The RPS ciigital output signals to the data logger are by relay contact *. These signals are:

a.

Reactor control rod drive, clutch power relays b~

Reactor trip

c.

Pressurizer pressure high (chan~els A through D)

d.

Reac.tor core neutron flux (channels A through D)

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e.

Reactor power rate change (channels A through D)

f.

Thermal margin (channels A through DY

g.

Steam generator A and B pressure (channels A through ~)

h.*

Steam generator A and B water level (channels A through D)

i.

Primary coolant flow, loop 1 (chann~ls A through D)

j.

Reactor load, turbine trip (channels A through D)

Relay contact isolation is an acceptable means of isolation between RPS functions and control and non-safety equipment.

4.3 Resistor Isolation to Computers.

Sketch VII-1.A.1 5 identifies four RPS analog signals to the ~lant computer. These funttions are:

a.

Neutron flux start up rate (channel 3)

  • b.

Primary flow (channel A)

c.

Steam generator A pressure (channel B) fl.

  • d~

Steam generator B pressure (channel B)

Reference 5, page 5 inditates the 100 ohm resistors were not intended as isolation devices for RPS inputs to the Fischer &.porter plant computer and with the exception of the neutron flux start up.rate signal, the inputs.

are not in compliance with Section 2 of this repor~.

4.4. Isolation by Operational Amplifier. Operational amplifie.r.s, Model A709C, are used as isolation buffers in the neutron flux start up*

rate channels tq the Fischer & Porter comput~r. They are also used.in the*

neutron flux safety channels to the Tennecomp auto loggef as well as to recorders, remote meters and auxiliary circuits. 7 5

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The Model A709C operational amplifier is a relatively low input impedance amplifier and was not designed to be used as an isolation buffer. Qualification as class lE eq~ipment under Reg. Guide l.S98 should be addressed at the integrated assessment.

5.0

SUMMARY

Based on current licensing criteria and reyiew guidelines, the plant reactor protection system*complies to all cur~ent licensing criteria listed in Section 2.0 of this report except for the follo~ing:

1.

The isolation devices used to isolate the RPS analog sig~als from the Tennecomp data logger, with the exception of neutron flux safety channels, do not meet IEEE 279-1971 par 4.7.2 requirements.

2.

There are no isolation devices between the RPS primary flow and steam generator pressure channels and the Fischer and Porter plant computer.

3~

Use of Model A709C 6perational amplifier as an isolation buffer device as defined in IEEE 279-1971 is. questiona,ble and requires further evaluation as class lE equipment.

6. 0.REFERENCES l~

General. Design Criterion 24~ "Separation df Protection and Control Systems," of Appendix A, "General Design Criteria for Nuclear Pow~r Plants," 10 CFR Part 50, "Domestic Licensir:ig of Production and Utili-zation Facilities.h 2 *.

IEEE Standard:279-1971, "Criteria for ~rotection Systems for Nucle'r Power Generating Stations."*

3.

Appendix A to the operating license DPR20, Technical Specifications for the Palisades Plant,.Consumer Power Company, Docket 50-255.

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4.

Tennecomp Systems Drawing 161~002815, Rev. C and 114-002815, Rev.

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-5.

LetterR. A.* Vincent to D.:*M. Crutchfield, Docket 50-255 DPR0-20, Palisades Plant--SEP Topic VII-lA, Electrical, Instrumentation and Control Portions *of the Isolation of the RPS from Non-Safety Systems, including Qualification of Isolation Devices.

June 29, 1981.

6.

Tennecomp Systems Drawing 161-002811, Rev. B 7 *. *Combustion Engineering Drawings 2966-E-2821, Jl47-1121, 2966-E-2858, 2966-D-3196, 2966-D-3198, 2966-E-2846 and 2966-0-3106.

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U.S. Atomic Energy Commission Regulatory Guide 1.89, Qualification of Class l~ Equipme~t for Nuclear Power Plants.

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Report, "Systematic Evaluation Program,.Review of NRC Safety Topic VII-1.A, Associated with the Electrical, Instrumeritation and Control Portion of the RPS from Non-Safety Systems, including Qualifi~

tation of Isolation De~ice for the Palisades Nuclear Power Plant~" By San Ramon Operations, 1183-4167 dated October 1980 *

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APPENDIX A NRC SAFETY TOPIC_S RELATED TO THIS REPORT

1.

Ill-I Classification of Structures, Components and Systems.

2.

Vl-10.A Testing of Reactor Trip Systems and Engineered Safety F~a tures, Including Response Time Testing.

3.

VII-2 ESF System Control Logic and Design

4.

VII-3 Systems Required for Safe Shutdown

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SYSTEMATIC EVALUAT.ION PROGRAM TOPIC VII-1.A PALISADES TOPIC:

VII-1.A, ISOLATION. OF REACTOR PROTECTION SYSTEM FRON NON-SAFETY SYSTEMS, INCLUDING QUALIFICATION OF ISOLATION DEVICES I.

INTRODUCTION Non-safety systems generally receive control signals from the reactor protection system (RPS) sensor current loops.

The non-safety circuits are required to have isolation devices to insure the independence of the RPS channels.

Requirements for the design and qualification of isolation devices are quite specific. Recent operating experience has shown that some of the earlier isolation devices or arrangements at o~erating plants may not be effecti~e. The objective of our review was to verify that operating reactors*have RPS designs which provide effective and qualified isolation of non-safety systems from safety systems to assure that safety systems will function as required.

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II.

REVIEW CRITERIA The review criteria are presented in Section 2 of EG&G Report 0490J, "Isolation of Reactor Protection System fron Nein-Safety Systems."

  • . II I.

RELATED SAFETY TOPICS AND INTERFACES The scop~ of review for this topic was limited to avoid duplication of effort since some aspects of the review were performed under related topics.

Th~ related topics and the subject matter are identified below:

Each of the related topic reports contain the acceptance criteria and

  • review guidance for *its s~bject matter.

V1:::7.C.l VIII-1.A.

IX-6 Independence of Onsite Sources Degraded Grid*

Fire Protection

. There a re no safety to pi cs dependent on the present topic i nforma.tion

  • because proper isolation has.been assumed.

IV.

REVI.EW GUIDELINES The review guidelines are presented in Section 3 of R_eport:0490J.

V.

EVALUATION

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Based on current licensing criteria.and review guidelines, the plant

  • _reactor protection system complies to all current licensing critetia listed in Section 2.0 of EG&G Report 0490J except for the following:

1.. The isolation devices used to isolate the RPS analog signals from the Tennecomp data logger, with the exceptirin of neutron flux safety channels, do not meet IEEE 279-1971.par 4.7.2 requirements;

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There are no isolation devices between the RPS primary flow and.

steam generator pressure channels and the Fischer and Porter plant computer.

3.

Use of Model A709C operational amplifier as an isolation buffer device as defined in IEEE 279-1971 is questionable and requires further evaluation as Class lE equipment.*

V1.

CONCLUSION The staff's position is that suitably qualiffed isolators should be

  • provided for these channels or that the acceptability of the present design be justified by the licensee.

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