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|NDIANA & MICHIGAN ELECTRIC COMPANYP. O. BO X 18BOWLING GREEN ST ATIONN EW Y ORK, N. Y.10004

June 22, 1983AEP:NRC:0761A

Donald C. Cook Nuclear Plant Unit Nos. I and 2Docket Nos. 50-315 and 50-316License Nos. DPR-58 and DPR-74INADEQUATE CORE COOLING INSTRUMENTATION (GENERIC LETTER NO. 82-28)

Mr. Darrell G. Eisenhut, DirectorDivision of LicensingU.S. Nuclear Regulatory CommissionWashington, D.C. 20555

Lear Mr. Eisenhut:

This letter and its Attachments provide a response to yourletter of December 10, 1982 (Generic Letter No. 82-28), regardingInadequate Core Cooling (ICC) instrumentation systems. In particular,Generic Letter No. 82-28 requested three items of information to helpcomplete the NRC's review of the subject systems at the Donald C. CookNuclear Plant. .

Item 1 of your letter requested that we submit the design forthe Reactor Vessel Level Instrumentation System (RVLIS) and schedulesfor ics engineering, procurement, and installation. Attachment I tothis letter provides the requested information for our Westinghouse (W)RVLIS.

Item 2 of your letter requested that we' review the status ofall ICC instrumentation system coc ponents' conforrance to NUREG-0737Item II.F.2, and submit a report on such status. This information isincluded in Attachments 1 and 2 to this letter for the RVLIS and thesubcooling margin monitor, respectively. Attachmenc 3 providesinformation on the current incore thermocouple system and our plans toupgrade the system to NUREG-0737 requirements.

Item 3 of your letter requested that we present a schedulefor implementation of ICC instrumentation system improvements forreview by the assigned NRC Project Manager. Where applicable, this

fO08306270312 830622PDR ADOCK 05000315 l'p PDR

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.Mr. DIrrall G. Eiecnhut 2 AEP:NRC:0761A

information is contained in the Attachments to this letter. We arewilling to discuss these improvements with members of the NRC staff attheir convenience.

As requested by Generic Letter No. 82-28, the informationcontained in this letter and its Attachments is affirmed in accordancewith 10 CFR 50.54(f) .

Very truly yours,

WRFH/os R. F. Hering

Vice Presidentcc: John E. Dolan - Columbus

R. S. HunterM. P. AlexichR. W. JurgensenW. G. Smith, Jr. - BridgmanR. C. CallenG. CharnoffNRC Resident Inspector at Cook Plant - Bridgman

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STATE OF NEW YORK ))

COUNTY OF NEW YORK)

R. F. Hering, being duly sworn, deposes and says that he is aVice President of Licensee Indiana & Michigan Electric Company, that hehas read the foregoing response to Generic Letter No. 82-28 (AEP:NRC:0761A),and knows the contents thereof; and that said contents are true to thebest of his knowledge and belief.

T/C/

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- Subscribed end sworn to before me this c7o? day of @ w g , 19 PJ .

NA /E wcv

(Notary Public)

WILLIAM J. PROCHASKANotary Pub'ic, Sta'e cf New York

No. 43-4536690Qualified m Rahmcnd County

Ceri.saa e e .. n f4ew fork Count .Comminkn Empires March 30,19

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. ATTACHMENT NO. 1 TO AEP:NRC:0761AREACTOR VESSEL LEVEL INSTilUMENTATION SYSTEM

'DONALD C. COOK NUCLEAR PLANT UNIT NOS. 1 AND 2

Int.oduction

Genetic Letter No. 82-28 requested two items of informationwith regard to the Donald C. Cook Nuclear Plant Reactor Vessel LevelInstrumentation System (RVLIS). More specifically, the subject letterrequested that we identify the RVLIS design and. submit schedules forits engineering, procurement, and installation. We were also requestedto report on the status of RVLIS conformance to NUREG-0737.

This Attachment provides the requested information. TheRVLIS derign is first identified, and then RVLIS conformance toNUREG-0737 Item II.F.2 and Appendix B of NUREG-0737 is outlined.Additional information regarding the location of RVLIS equipment andthe use of hydraulic isolators and sensors in the impulse lines, asrequested on page 4 of the checklist attached to Generic Letter No.82-28, is also included herein.

Where applicable, reference is made to one or more documentswhich we understand are either in the NRC's possession or to betrancmitted directly to the NRC by W in the future. To the best of our

! knowledge, documents already submitted to the NRC are still valid inresponse to NUREG-0737 documentation requirements. The list ofreferences is provided at the end of this Attachment. Some RVLISinformation has also been provided in the form of notes for ease ofreference. The notes are also provided at the end of this Attachment.

RVLIS Design

The RVLIS design selected for the Donald C. Cook NuclearPlant is the W differential pressure (d/p) syetem. This system has

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been previously described in References (1), (2), and (3). With theexception of those items identified in Note (iii), this system has beenphysically installed in both Units of the Donald C. Cook Nuclear Plant.We understand that the RVLIS cannot be operated until the task analysisportion of the Control Room Design Review is completed and NRC approvalof the RVLIS is granted. It is anticipated, however, that theadditional RVLIS work will be completed without causing further delayof RVLIS operation.

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_RVLIS Conformance to NUREG-0737 Itest II.F.2.

This section addresses the nine items of documentation identifiedon NUREG-0737 pages II.F.2-3 and II.F.2-4. For each item of requireddocumentation identified in NUREG-0737, the information requested bythe checklist attached to Generic Letter No. 82-28 is provided. Asnoted above, references and notes are contained at the end of thisAttachment.

Item (1)(a): References: (1) through (3) .

Deviations: Functionally none.Schedule: Note (i).

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Item (1)(b): References: (1) through (3) .Deviations: Note (ii).Schedule: Note (ii).

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Item (1)(c): Not applicable to RVLIS. No modificationsplanned.

Item (2): References: (1) through (7) .Deviations: Functionally none.Se!edule: Note (1) .

Item (3): References: (4) through (7).Deviations: None.Schedule: Note (1) .

Item (4): References: (2), (3), (8), and (10)through (13).

Deviations: None.Schedule: Note (1), except for

Reference (13).'

Item (5): References: (1) through (3).t Deviations: None.| Schedule: Note (1) .

* Note: Documentation of Item (5) isapplicable to display function only.

j Item (6): References: Note (iii).'

Deviations: Note (iii) .Schedule: Note (iii).

Item (7): Reference: (9).Deviations: None.Schedule: Note (i).

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Item (8): Reference: Note (iv).Deviations: None anticipated.Schedule: Note (iv).

Item (9): See Note (1).,

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RVLIS Conformance to NUREG-0737 Appendix B[

As requested by the checklist attached to Generic Letter No.82-28, RVLIS conformance to the first nine items of NUREG-0737 AppendixB is outlined below. Since the checklist did not address Appendix BItems 10 through 18, it is assumed that NRC approval of the generic }[d/p system connotes approval of these items.

Item (1): See References (10) through (13). No deviations.Item (2): See Reference (8). No deviations.Item (3): The instrumentation ie energized from Class IE

i power source.! Item (4): One channel operable prior to an accident.

Item (5): Quality Assurance per 10 CFR 50, Appendix B.- Item (6): Continuous indication is provided.

Item (7): Recording of instrument outputs is provided (singletrain).

. Item (8): See Reference (1) .Item (9): Isolation devices are utilized.

Additional Information

Page 4 of the checklist attached to Generic Letter No. 82-28

requested additional information from users of the }[ d/p system. Inresponse to the three questions contained therein, the following

| information is provided.

(1) The effect of instrument uncertainties on themeasurement of level has been described in References(2) and (3) . See also Note (ii).

(2) Differential pressure transmitters are located outsidecontainment. '

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(3) Hydraulic isolators and sensors are included in theimpulse lines.

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NOTES

(1) No further work is currently planned.

(ii) W indicated, via letter No. AEP-83-522, that the existinginstrumentation used by RVLIS does not functionally deviatefrom NUREG-0737 Item II.F.2 requirements. However, the W1etter transmitted additional docucantation which stated thatthe interfacing of wide range pressure transmitters, asoriginally designed by W, is still under study and as such is .

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not recommended. In document No. NS-EPR-2586, which }[' *

. attached to the above referenced letter, concern wasexpressed about post-accident environmental effects on

i in-containment wide range pressure transmitters andsubsequent effects on RVLIS accuracy. Since the wide range ;

transmitters in use at the Donald C. Cook Nuclear Plant havebeen qualified for use in accordante with the DOR Guidelin2s(except for aging and a surveillance / maintenance / replacementprogram), this situation is presently under discussion withW. Therefore, with the possible exception of the wide range

; pressure transmitter, the description of existinginstrumentation documented in Reference (1) through (3) isstill applicable. We will resolve the wide range preseuretransmitter application with 1[ and will, if any changes tothe RVLIS description are necessary, prepare a schedule forthe NRC.

(iii) Work is continuing on the items previously identified in our,

' 'submittal letter No. AEP:NRC:0398H, dated November 9,1982(e.g., implementing calibration correction f actors, reviewingthe environmental qualification of system cable routing, andobtaining equipment qualification reports from W) . Inaddition, the panel recorder for the Donald C. Cook NuclearPlant Unit No. 1 RVLIS remains to be installed. Weunderstand that the RVLIS cannot be operated until the taskanalysis portion of the Control Room Design Review iscompleted and NRC approval of the RVLIS is granted. It isanticipated, however, that the additional RVLIS work will becompleted without causing further delay of RVLIS operation.

l . (iv) We will incorporate the Westinghouse Owners Group EmergencyResponse Guidelines (ERGS) in the Donald C. Cook NuclearPlant operating instructions, as previously explained in ourresponse to Generic Letter No. 82-33 (AEP:NRC:0773, datedApril 15, 1983). It is anticipated that this work will be.

completed without causing further delay of RVLIS operation.

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REFERENCES

(1) Letter No. AEP:NRC:0398D, dated March 31, 1981, R. S. Hunter(I&MECo) to H. R. Denton (NRC). Refer to " Summary Report,Westinghouse Reactor Vessel Level Instrumentation System for '

Monitoring Inadequate Core Cooling (7300 System), December, 1980."Refer also to Letter No. NS-TMA-2357, dated December 23, 1980, T.M. Anderson (W) to D. G. Eisenh':t (NRC).

(2) Letter No. AEP:NRC:0398F, dated September 17, 1981, R. S. Hunter(I&MECo) to H. R. Denton (NRC) .

(3) Letter No. AEP:NRC:0398G, dated November 20, 1981, G. P. Maloney,

( (I&MECo) to H. R. Denton (NRC).|' (4) Letter No. NS-EPR-2579, dated March 19, 1982 E. P. Rahe (W) to L.

E. Phillips (NRC).

(5) Letter No. NS-EPR-2526, dated December 9,1981, E. P. Rahe (jd) toL. E. Phillips (NRC).

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| (6) Letter No. NS-EPR-2542, dated January 13, 1982, E. P. Rahe (W) toL. E. Phillips (NRC).I

(7) Letter No. SED-SA-0081, dated June 28, 1982, E. P. Rahe (W) to L.E. Phillips (NRC).

(8) Letter No. NS-EPR-2597, dated May 14, 1982, E. P . Raha (]d) to D.M. Crutchfield (NRC).

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(9) Westinghouse Owners Group Emergency Response Guidelines, Volumes|

| 1, 2, and 3. Transmitted to the NRC via letters No. OG-64, datedNovember 30, 1981, and No. OG-83, dated January 4,1983.

-**(10) Letters No. NS-EPR-2513 and No. NS-EPR-2600, transmitted to theNRC on September 30, 1981, and May 19, 1982, respectively, from E.P. Rahe (W) . See equipment Qualification Data Package No. ESE-3,D/P Transmitters -- Qualification Group A. Note: We understandthat W, in the future, will reference these transmittersspecifically to the RVLIS.

**(11) Equipment Qualification Data Package No. ESE '3, 7300 ProcesaElectronics. Transmitted to the NRC via Letter No. NS-TMA-2380,dated Janucry 28, 1981, from T. M. Anderson (W), and by Letter No.NS-EPR-2482 dated August 3,1982, from E. P. Rahe (W) . Note: Weunderstand that W, in the future, will reference the processelectronics specifically to the RVLIS.

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**(12) Equipment Qualification Data Packages ESE-42 (Strap -on RTDs),ESE-48 (High Volume Pressure Sensor), and ESE-49 (HydraulicIsolator) . Submitted to the NRC via NS-EPR-2725, dated February28, 1983, from E. P. Rahe (W).

(13) Equipment Qualification Data Package No. ESE-50 (Entire RVLISPackage). Note: We understand that W will transmit this packageto the NRC by June 30, 1983.

**Note: P4ferences (10) through (12) were submitted as supplements to

the environmental qualification topical reports WCAP-8587(non-proprietary) and WCAP-8687 (proprietary).

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ATTACHMENT NO. 2 TO AEP:NRC:0761ASUBC00 LING MARGIN MONITOR

DONALD C. COOK NUCLEAR PLANT UNIT NOS. 1 AND 2 -

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Introduction

Generic Letter No. 82-28 requested that the Donald C. Cookj Nuclear Plant subcooling margin monitor (SMM) be reviewed for| conformance to NUREG-0737 Item II.F.2. This Attachment provides the

results of that review.

Information on the Babcock & Wilcox (B&W) saturation meterand the P250 Plant computer is provided first. Then a response ispresented to the nine items of required documentation identified onNUREG-0737, pages II.F.2-3 and II.F.2-4. Finally, conformance toNUREG-0737, Appendix B requirements are outlined.

Reactor Coolant Margin to Saturation Meter

The B&W saturation meter is a device which is connected toreactor coolant temperature and pressure signals and displays the,

'margin to saturation temperature or to saturation pressure. The meterprovides an on-line aid to the operator to help him assure that an

i adequate saturation margin is maintained at all times.(

Pressure signals f rom Loop 1 and Loop 2 hot legs as well as athird signal, which is the lower of the two, are fed to the P1/P2/P3inputs of the meter. Seven individual and the highest of eighttemperature signals from the vide range reactor coolant RTDs and sevenindividual and the highest of eight temperature signals from eight ofthe incore thermocouples (two per reactor quadrant) provide a tntal of

|sixteen temperature inputs.

The front panel display has four switches. The switchlabelled P1/P2/P3 selects one of the three pressure sources describedabove. The meter determines the saturation temperature of the selectedpressure. An eight position rotary switch in conjunction with the"INCORE/RTD" toggle switch selects one of the sixteen temperature

l inputs. The meter finds the saturation pressure for this temperature.| The derived saturation temperature is compared with the selected

temperature, and the derived saturation pressure is compared with theselected pressure. Thus, saturation margins for both temperature andpressure are determined. Margin to saturation temperature is displayed

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on the digital panel meter. Margin to saturation pressure can bemomentarily displayed using the spring-loaded "T-sat /P-sat" to3Sleswitch.

The alsrm circuitry examines all of the input temperaturemargins to derived saturation temperature. If any of these margins is

less than the setpoint temperature margin, an alarm will agnunciate onthe, Reactor Coolant Panel. The setpoint can be set from 0 F to199 F by a thumbwheel switch located at the equipment rack. Note -

that the alarm function is contingent on the selected pressure.

A test display module is provided for use in calibrating theanalog portion of the saturation meter.

Table 1 provides additional information on the subcooling

meter.

Plant Computer Subcooling Program

The P250 computer will calculate the subcooling of thereactor coolant in degrees Fahrenheit. There are five calculatedvalues which are available for analog or digital trending on the P250computer output devices. The calculations are based on the two widerange pressure inputs f rom Loops 1 and 2, eight thermocouple inputs(two per quadrant), and eight RID wide range temperature inputs (twoper Loop).

From these inputs, calculated values are obtained forsaturation temperature based on lower system pressure, and die marginto saturation temperature based on: (1) the hottest RTD, (2) thehottest thermocouple, (3) the average of the RTDs, with the hottest andcoldest RTDs excluded, and (4) the average of the thermocouples, with

| the hottest and coldest thermocouples excluded.

The computer checks each temperature input signal as afunction of its deviation from its associated average. Signals which

deviate by more than a specified amount are determined to beunreliable. Nevertheless, all inputs are used for calculationalpurposes because a hot spot could exist in the core as a result of flowtiockage. There are two alarm conditions which will annunciate andcause a message to be printed on the trend typewriter. The message

| includes all input and calculated values. The first alarm results from| a saturation margin less than the setpoin . The second results from an

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Table 2 provides additional information on the P250 Plantcomputer. It should be noted that it is our intention to retain the

' P250 subcooling program as a back-up display / alarm to calculatesubcooling margin.

Subcooling Margin Monitor Conformance to NUREG-0737 Itam II.F.2'

This section addresses the nine items of documentationidentified on NUREG-0737, pages II.F.2-3 and II.F.2-4. For each itemof required documentation identified in NUREG-0737, the informationrequested by the checklist attached to Generic Letter No. 82-28 isprovided.

Item (1)(a): Not appliccble.

Item (1)(b): References: This Attachment.Deviations: Not Applicable.Schedule: Completed herewith.

Item (1)(c): Not applicable.

Item (2): References: Item 2.1.3.b of Attachment6 to our letter dated

- January 10, 1980(AEP:NRC:0334).

Deviations: None.Schedule: Complete.

Item (3): Not applicable.

Item (4): References: Item 2.1.3.b of Attachment| to our letter dated MarchL 10,1980 (AEP:NRC:0334B).

Deviations: Yes.Schedule: See following section on

conformance to NUREG-0737Appendix B.

Iten (5): References: Item 2.1.3.b of our letterdated December 19, 1979(AEP:NRC:0253B), updatedper this Attachment.

. Deviations: None.| Schedule: Completed herewith.-

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Item (7): Not applicable.

Item (8): References: See Reference for Item (2)above. See also Item d ofAttachment 1 to letter No.

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AEP:NRC:0773, dated April,

15, 1983.Deviations: None.Schedule: Item IV of Attachment 3 to

Letter No. AEP:NRC:0773,dated April 15, 1983.

Item (9): References: Item IV of Attachment 3 toLetter No. AEP:NRC:0773,

'dated April 15, 1983.

Deviations: Not applicable.Schedule: Not applicable.

Subcooling Margin lionitor Conformance to NUREG-0737. Appendix B

As requested by the checklist attached to Generic Letter No.82-28, SMM conformance to the first nine items of NUREG-0737 Appendix Bis outlined below.

Item (1): See Attachments 1, 2, and 4 to letter No.AEP:NRC:0775C, dated May 20, 1983. These,

| Attachments identify deviations and thei proposed schedule for completion ofI environmental qualification for wide range

reactor coolant temperature RTDs (NTR-110,120, 130, 140, 210, 220, 230, 240) andpressure transmitters (NPS-121, 122).

Item (2): See Notes (i) and (ii). No deviations.l

Item (3): See Note (ii). No deviations.

Item (4): See Technical Specifications 3.3.3.8 (Unit 1)

and 3.3.3.6 (Unit 2) . No deviations.

Item (5): 10 CFR 50, Appendix B. No deviations.

Item (6): See this Attachment and Note (iii). Nodeviations.

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| Item (7): See this Attachment and Note (iii). No -deviations.

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Item (8): See Note (iv). No deviations.

Item (9): See Item 2.1.3.b of Attachment to letter No.AEP:NRC:0334B, dated March 10, 1980. Nodeviations.

NOTES

(i) A review of the design of the Donald C. Cook Nuclear Plantsaturation monitoring systems has shown that no singlefailure within the accident monitoring instrumentation,auxiliary supporting feetures, or power sources, will preventthe operator from determining margin to subcooling. Thereare at least two physically and electrically separatedchannels for reactor coolant tempcrature and pressureinformation available in the Control Room.

(ii) The wide range reactor coolant temperature and pressure-channels, including their isolation devices, are energizedfrom Class IE power sources. The B&W subcooling meter andits associated input signal conditioning, isolation, andselection logic modules are also energized from a Class IEpower source.

(iii) Reactor coolant temperature and pressure are continuouslyrecorded. Subcooling margia is continuously displayed by theB&W subcooling meter.

(iv) Subcooling margin display, wide range reactor coolanttemperature' recorders, and wide range reactor coolantpressure recorder and indicator are all specificallyidentified on the control panels.

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TABLE 1Subcooling Meter Infounation

Display

Information displayed: Margin to saturation temperature orsaturation pressure.

Display Type: Digital, Continuous, Single.Location: Control Room.Alarms and overall uncertainty: See letter No. AEP:NRC:0346,

datgdJanuary 29, 19 80.,FRange of display: 35 F superheat to 200subcooled;O to 500 psi margin.

Calculator:

Type: Dedicated digital.Single calculator.Selection logic: Highest temperature; lowest pressure.Calculational technique: Steam Tables

Input:

Temperature: RTDs and thermocouples.Number of sensors and locations: See (*) below.Range of Temperature sensors: RTDs -- 0 F to 70g F;

thermocouples -- 0 F to 2500 F.Pressure: Wide range reactor coolant system.Number of sensors and locations: 2 RCS Loops 1 & 2.Range of pressure sensors: 0 to 3000 psi.

I Uncertainty of temperature and; pressure sensors: See letter No. AEP:NRC:0346, dated| January 29, 1980.

| Qualifications: RTDs -- See (**) below; thermocouples --control grade; pressure -- See (**) below.

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| Back-up Capability:

Availability of Temp. and Press.: In Control Room --recorders and indicators.

Availability of Steam Tables: Pasted to Control Room panel.Trainingsof Operators: Yes.Procedures: Yes.

(*) Sensors selected are 4 hot leg RTDs, 4 cold leg RTDs, and 8 coreexit thermocouples which are input to the calculator through hi-

| select devices.

| (**) See letters No. AEP:NRC:0578B, dated June 11, 1982, and No.l AEP:NRC:0775C, dated May 20, 1983.

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TABLE 2PRODAC Computer Information

Display:

Information displayed: T - T(sat); temperature; pressure..

Display type: Digital, automatic on alarm or ondemand (temperatures and pressuresavailable for trend, with updatedvalues every 4 seconds; T - T(sat)margin available for trend, withupdated values every 64 seconds),single but back-up for output.

Location: Control Room.Alarms and overall uncertainty: See letter No. AEP:NRC:0346,

dated January 29, 1980.,

Range of display: Adjustable.

Calculator:

Type: Process Cosputer.Availability: Approximately 95%.Single calculator.

Selection logic: Highest temperature; lower pressures.~ Calculational technique: Functional fit agrees with steam

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tables to 1 part in 1000.

Input

See Table 1 of this submittal for pertinent information.Back-up Capability

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Availability of Temp. & Press.: Procedures and saturationI

curves.Availability of Steam Tables: Pasted to Control Room panel.Training of operators: Yes,Procedures: Yes.

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|ATTACHNENT NO. 3 TO AEP:NRC:0761A !

INCORE THERMOCOUPLE SYSTEM

DONALD C. COOK NUCLEAR PLANT UNIT NOS. 1 AND 2_, !

|

Introduction,

Primary indication of ICC conditions at the Donald C. Cook

Nuclear Plant will be provided by the RVLIS and the subcooling marginmonitor. These systems are described in Attachments 1 and 2 to this

letter, respectively. The incore thermocouples, on the other hand,represent a supplemental or back-up instrumentation system for ICCindication purposes. For this reason, we do not believe that theincore thermocouple system should be classified as a Class IE system.A program has been undertaken, however, to perform studies in anattempt to upgrade the incore thermocouple system to NUREG-0737requirements.

This Attachment presents a description of the currentlyinstalled thermocouple system, a status report with regard to systemupgrade to NUREG-0737 requirements, and the presently planned

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implementation schedule. Due to the ongoing nature of the program, |responses in the form of the checklist attached to Generic Letter No. i

82-28 are not being provided at this time.

Current Syetem Design Description

The current'incore thermocouple system is a standard Esystem, provided as original equipment with the Donald C. Cook NuclearPlant.

Each Unit was provided with sixty-five incore thermocouples! which are routed through reactor vessel head incore columns (13

thermocouples per column) . The thermocouples are type "K"chromel-alumel, ungrounded junction,1/8" in diameter, supplied with aThermo-Electric mating connector, type "KK" at the top. Eachtharmocouple is enclosed in a 3/16" inside diameter guide tube which

| extends from the instrument column to the bottom of the reactor upperj internals.

Thermocouple extension wire runs from the Thermo-Electricmating connectors to another set of Maelin mating connectors in thedisconnect boards (disconnect boards are points at which all instrumentand electrical cables to the reactor head are disconnected prior tolifting the head). Thermocouple extension wire runs from the

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disconnect boards to two Whittaker thermocouple reference junction i

boxes located inside containment.

The junction boxes are heated to 160 F and permit,

transition from chromel-alumel thermocouple wiring to copper fieldwiring. Each junction box also contains three platinum ResistanceTemperature Detectors (RIDS). Two RTDs in each junction box areconnected to the Plant computer for monitoring junction referencetemperature. The third RID in each junction box is a spare.,

Primary thermocouple readout capabigity is prgvided by theP250 Plant computer, which has a range of 160 F to 2500 F. Thecomputer prints the temperature values on the printer, or displays themon the console, upon request.

Back-up readout capability is provided by a HoneywellPrecision Indicator mounted in the Flux Mapping Control Console. Thisinstrument is supplied with a double-range mgasuring gircuit whichpermitg measurement within the ranges of 100 F to 400 F or 400 F

' to 700 F. Selection of a single thermocouple to be monitored is madevia use of non-locking key switches on the front of the indicator. Theswitch must be manually held in position (lef t or right) to monitor thedesired thermocouple. The switch returns to neutral (center) positionwhen released.. Since the thermocouple input signal to the indicator isin parallel with the Plant computer, a contact closure signal informsthe computer when any thermocouple is being monitored.

Furthermore, thermocouple signals are sent to the' TechnicalSupport Center Computer, and eight thermocouple signals are input tothe subcooling margin' monitor.

The Donald C. Cook Nuclear Plant operators are trained to usethis thermocouple system.

System Upgrade Status Report

Because of the high failure rate of Unit No. 1 incorethermocouples, we have undertaken a program with three Nuclear SteamSupply System (NSSS) vendors to either repair or replace the incorethermocouple system. A goal of this program is to upgrade the systemto conform as closely as possible to NUREG-0737 requirements.Currently planned improvements are as follows:

(1) Replacement of existing incore thermocouples, if required.We have been notified by the NSSS vendors that no knownqualified incore thermocouple systems have been installed atother nuclear generating stations. Furthermore,

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only limited experience exists where incore thermocoupleshave been recovered and replaced for a W Pressurized Water-

Reactor. State of the art technology is still in adevelopmental stage, and at this time a successful incorethermocouple replacement program cannot be guaranteed.

lI (2) Replacement of connectors and cabling.

l (3) Replacement and/or relocatior of junction boxes outside!

containment, or replacement of junction boxes insidecontainment.

| (4) Separation of thermocouples by columns into two independentgroups, and routing of each group's cabling separate from theother, to the extent possible. It is noted that separationcriteria deviations will be necessary in the vicinity of the

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reactor vessel head.

(5) Termination of two incore thermocouples from each group in| the reactor vessel head to monitor fluid temperature there.l

(6) Use of independent Class IE power sources.

(7) Provisions for independent indication for each group in theControl Room.

| (8) Testing and calibration to be conducted after completion ofinstallation.

We note that these planned modifications may be subject tochange as a result of the ongoing review process.

Upgrade-Implementation Schedule

| Barring unforeseen complications, repair or replacement ofl the incore thermocouple system should commence for Unit No. 1 during a

1984-1985 refueling outage. Following this upgrade, a report will be'

made to the NRC stating our progress and experience. Thereafter a planwill be presented for Unit No. 2.

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