ML20070M607

Design Input Calculation for NSM-ON-52966

ML20070M607
Person / Time
Site:	Oconee
Issue date:	12/07/1993
From:	Donaldson D DUKE POWER CO.
To:
Shared Package
ML15261A430	List: ML20070M597 ML20070M607
References
OSC-5556, NUDOCS 9405020219
Download: ML20070M607 (20)

Text

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borm oion m7-n) FORM 101.1 REVISION 14 l

CERTIFIC. WON OF ENGINEERING CALCULATION l

Ocor.: Nuclear Station Unit 5 STATION AND UNIT NUMBER TITLE OF CALCULATION Desian InDut Calculation for NSM-0N-52966 CALCULATION NUMBER OSC-5556 l ORIGINALLY CONSISTING OF:

PAGES 1 THROUGH I8 TOTAL ATTACHMENTS One None TOTAL MICROFICHE ATTACHMENTS TOTAL VOLUMES 1 TYPEICALCULATION/ ANALYSIS YESO NOId TYPE I REVIEW FREQUENCY NA THESE ENGINEERING CALCULATIONS COVER OA CONDITION 01 ITEMS. IN ACCORDANCE WITH ESTABLISHED PROCEDURES, THE QUALITY HAS BEEN ASSURED AND l CERTIFY THAT THE ABOVE CALCULATION HAS BEE IGINATED, CHECKED OR APPROVED AS NOTED BELOW:

ORIGINATED BY N? bM DATE uh0N 3 CHECKED BY DATE II- IIo D APPROVED BY # DATE M'M-U ISSUED TO DOCUMENT C TROL 2CC DATE Q -Ol' D RECEIVED BY DOCUMENT CONTROL lb DATE 17-I 7/ D MICROFICHE ATTACHMENT LIST: 0 Yes I /

2lLNo SEE FORM 101.4 REV CALCULATION PAGES(VOL) ATTACHMENTS (VOL) VOLUMES ORIG O CHKD APPR REVISED DELETED ADOFL REVISED l

DELETED ADDED DELETED ADDED DATE DATE DATE hpD 1

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9405020219 940224 PDR P ADDCK 05000269 PDR

i Calculation No o S c. - 5 5 5 6 Originated By: Q cLA w ,,O M Date: II f fO[9 3 Sheet 1 of lg i Form 101.2 Ravinon 0 26164 (R9-89) i REVISION DOCUMENTATION SHEET l

Review Revision Fregaency Revision Description Number Changed (Yes/No) l l

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l Calculation No: 5 - 555 G (ALd MTs o4 originated By: . h Date: _llllolq3 Sheet 2.of gg ,

i CONTENTS N/A Documentation of NSM Design Inputs and Verification Methods (Power Systems) Sheet N /A Design Input Source Document Form (Power l Systems) Sheet l

N l A Power Systems NSM Engineering Checklist - Sheet l X Documentation of NSM Design Inputs and Design Verification Method *

(Control Systems) Shoot 13 ' 6 X Design Input Source Document Form (Control Systems) Sheet I'

\( Control Systems NSM Engineering Checklist Sheet b$ ~ l 52 N / A Documentation of NSM Design Inputs and Design '/erification Method j (Instrumentation) Sheet l N/A Design Input Source Document Form (Instrumentation) Sheet i NI,lA Instrumentation NSM Engineering Checklist Sheet N/ A Documentation of NSM Design Inputs and i

Design Verification Method (Lighting, l

Communications and Heat Tracing) Sheet M/ A Design Input Source Document Form (Lighting, Communications, and Heat l Tracing) Sheet l b{fbLighting,CommunicationsandHeat Tracing NSM Engineering Checklist Sheet i

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Calculation No 6( ' 5 560 b'I '

l Originated By: - 2 0 d^ s(Dates lll1G[43 l Sheet 3 of it ELECTRICAL DISCIPLINE DOCUMENTATION OF NSM DESIGN INPUTS  ;

AND DESIGN VERIFICATION METHOD I i

Lighting, l

Communications,

) Power sf Control Heat Tracing, Systems A Systems - Instrumentation and Tank j Heating I Originator: Dates !Ifl0 f 9 3-l- Checked: Date: Il ~ I l8 ~ 93 Approved: Date M'/b8

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DESIGN INPUTS l ANSI N45.2.ll(1974) requires the documentation of design. inputs used in the design of a station modification. Therefore, the following topics have been adapted from ANSI N45.2.ll(1974) to serve as a guide for describing the design inputs applicable to the electrical and instrumentation portions of a station modification. The related paragraph (a) of ANSI N45.2.ll are identified by the number (s) in parentheses that follow the design input topic. In addressing these design input topics, the following guidelines should be used

i )( If the NSM modifies an existing system / equipment and does not change the design basis or require new design bases or criteria, then the design inputs should be described from the perspective of the modification. '

If the NSM adds a new system or a significant new function to an existing system, then the design input should be described from the perspective of the system being added or modified.

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calculation Np c 5 5 5 6 cal 1 PbeTied Originated By: M Sheet 4 of (g M Dates h l lo l c(3 ELECTRICAL DISCIPLINE DOCUMENTATION OF NSM DESIGN INPUTS AND DESIGN VERIFICATION METHOD

1. State the QA condition of the design being implemented by this portion of the modification and its basis.

QA-1 because of control interfaces with the on-site emergency power sources (Keowee Hydro Units) and the emergency underground power path (Breakers ACB-3 and ACB-4)

2. Identify the codes, standards and/or regulatory requirements that initiated this modification or that are unique in implementing the design of this modification. (3)

The postulated ccenario, which this portion of the NSM addresses, was identified during the sing' e failure analysis of the Keowee Emergency Power System and involves a single failure concern as outlined in the resulting PIP-4-092-0538 and LER 269-92-16.

3. Describe the basis function of the system and/or equipment affected by this modification including the various plant operating modes or events for which it is required to function (e.g.,. normal operation, LOCA,' MSLB, LOOP, fire, security). ( 1, 13, 15, 16)

Refer to Attachment 1 for the basic function and equipment affected by the ALI portion of this modification. The circuitry and logic added by the ALI portion of this mod. is required to be operational during normal operation, LOCA, MSLB and LOOP and during a SSF/ West Penetration Room Event.

4. Describe the performance requirements for the system and/or equipment affected by this portion system output).

of the modification (e.g., capacity, ratings, (2, 13, 16) and The contact and timer outputs of the devices utilized to generate the logic described in Attachment 1 are fully capable of the pilot duty requirements of the closing circuitry of breakers ACB-3 and 4. Also, the timing range and tolerances of timers 62-3C and 62-4C are acceptable to perform the function as described. These conclusions are based on published manufacturer's information i t

5. Mdbspr ye]p,ggey,gggions under which the equipment affected by this modification is required to function (e.g. , seismic, vibra' tion, environmental, and process). (4, 5, 6, 8, 9, 27)

All components, either installed by this portion of the. modification (or directly affected by it) are located in mild environment areas and are required to correctly function during seismic events.

1

Calculation N - S 5 5 (- (A L.1 p rcT4od originated By btCcCbLDate: Mllo N 3 Sheet 5 of l8 ELECTRICAL DISCIPLINE DOCUMENTATION OF NSM DESIGN INPUTS AND DESIGN VERIFICATION METHOD 6.-Describe any special functional or physical interface requirements for systems or equipment affected by this modification (e.g., non-standard power supply requirements, special mounting / orientation requirements). (7)

None

7. Describa any special location, layout, or arrangement requirements related to this portion of the modification. (14)

None

8. Describe the redundancy, diversity, and/or separation requirements for the systems or equipment affected by the modification.

1. Redundancy - Separate, independent logic arrangemen(18)for ts breakers ACB-3 and ACB-4 closing circuits.

2. Diversity - None

3. Separation - Where encountered, sapt ration between safety channels and individual components providtd rcr established criteria.

9. Describe any design feature (s) incorjs*zated in this portion of the modification to specifically accoun*. for the failure mode of the system / equipment af fected by this moditf cation. (19)

As described in Attachment 1, this portion of the modification provides logic to mitigate the consequences of a failure (fault) within breaker ACB-1 or ACB-2.

Therefore, an additional failure, postulated within the logic provided by this portion of the mod., is outside of design basis. See Item 1 under Section 8 above j and Section 11 below. '

lo. Describe any design feature (s) incorporated in the modification as a result of special system and/or equipment testing requirements. (20) i l

None '

11. Describe any other important factors considered or decisions made in the design of this portion of the modification.

Separate and redundant logic arrangements have been provided in the closing circuits of ACB-3 and 4 to assure that under the postulated single failure conditions (addressed in PIP-4-092-0538), the unaffected underground path breaker will automatically close. Although one common device is used in both of these logic arrangements (namely LOR 86T contacts) the overall result addresses the postulated breaker fault scenario and complies with established ONS single failure criteria.

The two second time delay, as explained in Attachment 1, is based on generally

accepted industry practices, relating to automatic bus transfers, where a one second time delay is considered sufficient time for residual voltage to decay (on a de-energized bus) to such levels that the bus may be safely re-energized without synchronization problems.

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Calculation Nc 6C.- 5 5 5 6 C A LI M'w) l Originated By:pJ:)d O w 0

• w Date: Illlof 93 Sheet 6 of 18 DESIGN VERIFICATION METHOD ANSI N45.2.ll(1974) requires that the particular' design verification method (s) to be used for a station modification be documented. Design verification is -

1 defined as the process of reviewing, confirming, or substantiating the design  !

by one or more methods to provide assurance that the design meets the specified design inputs. Acceptable design verification methods include but are not limited tot 1) design reviews,.2)-alternate calculations, or 3) qualification testing (Ref. ANSI N45.2.ll, Section 6.3). _

t Indicate the design verification method (s) to be used for this portion of the l NSM by marking the appropriaNe blank (s).

)( _ Design Review (Same as " Checking / Inspecting")

I Alternate Calculation Qualification Testing *(includes equipment / system prototype testing or inplant testing)

Other

! SPECIFY Note: If qualification testing is used as a design verification method, the appropriate design documents describing the test such.as Test Acceptance Criteria or a qualification testing specification shall be generated, s

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Calculation Not o c.- 555 6

! Originated By: v .

Date Ik ,l0 f93 Sheet 7 of g 8 i l

l DESIGN INPUT SOURCE DOCUMENTS DOCUMENT' REVISION DESCRIPTION i

! P@ -4.- eq2. o 53 8 0 9@ A h keccoes 6M G1LE FAtlve E 4MA LYst s

LER. - 2(A- u- t 6 O L E R. hot. .\v- /= ksocoe s SING,LE FAILUe s Ade1LV SIS I

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Calculation No: o sc- 5 5 5 c (ALI M80N)

Originated By:M JLo A M Date s liholCC5 Sheet 8 of lg ELECTRICAL DISCIPLINE  !

NSM ENGINEERING CHECKLIST - CONTROL SYSTEMS, I CONTROL EQUIPMENT AND ASSOCIATED MONITORING NSM NUMBER: er4- 52A 66 ( ALL fbgDoN)

The Electrical Discipline NSM Engineering Checklist is provided as a tool.to ~;

identify key technical considerations that may apply to a particular NSM. '

This checklist will also serve to support the documentation of design inputs.

This checklist should be completed using.one of the following guidelines. i Indicate which guideline applies to this NSM by marking the appropriate blank.

)[ If the NSM modifies an existing systems' equipment and does not change the design basis or require new design bases or criteria, then the checklist should be answered from ihe perspective of the modification.

If the NSM adds a new system or a sign.ficant new function to an existing system, then the checklist shauld be answered from the perspective of the system being addcA or modified.

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Calculation N SC - 565% CALL @@ONh Originated By h Dats: ll llol q'3 Sheetct of lg A. General

1. QA condition (s) of this portion of the NSM G A-t

2. Is this design / equipment required to' function for any of the following conditions:

%El M

a. Normal Operation Y

b. Loss of Coolant Accident (LOCA)

c. Main Steamline Break (MSLB) N

d. Loss of Offsite Power (LOOP) Y

e. Station Blackout Y

f. Earthquake (Seismic) N

g. SSF Event (Fire, Security, sj and Flood - (OES, only)) A

h. ATWS Y

i. Control Room Evacuation I

3. Has the Appendix R/ Fire Protection III E U/.h Review been initiated (EDP 9.02 &

DC-1.04) ? Su6uilTEb tO N TO RtJOVE R par x ACNE . /EN(:

3.

4. Have the following plant security aspects of this NSM been reviewed?

a. Changes to vital or protected area barriers Y

b. Security lighting Y

c. Revisions to yard equipment or structures M

d. Revisions to site buildings Y

e. Changes to the vital equipment control circuits N

5. Does the scope of this modification require the application of ALARA i

principles?

N

calculation No uo c. - 5 55 6 (A U 90*'O # }

Originated By: o m O M Dates 11ll014 3 Sheet 10 of l 8 4

A. General (cont'd) 111 Hg gfg

6. Has the FSAR been reviewed concerning this NSM7 h[

a. Are changes required? >(

b. Is the proposed update provided (EDP 3.2)7 )(

7. Has the system descriptions (s)/ design basis documents affected by this NSM been review 7 )k (K<ome. Gv). r D*0 a.'Are changes required? )k

b. Is the proposed update provided (EDP 3.2)? )k B. Control Systems

1. Is SSS/ ASP isolation required? )[

Provided? )[

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2. Have control Voltage Limitations such as Max / Min Values, Uninter-ruptible, Momentarily Interrup- gj tible Blackout been considered? A

3. Have the setpoints for automatic control, interlocks, trip, etc.

been established and documented? )(

4. (SEE. A Lt Pc5CDe4 Are control componentoF t45% make/

contact 9Eol.tE54.)

break rating sufficient for circuit? h(

Note: DC rating is usually less than AC rating.

5. Are non-QA components in QAl cir-cuits shunt tripped (MNS Only)? )(

6. Are control Power Transformers /

Power Supplies loaded within recommended limits?

y A,

7. Is duplicate non-safety equipment designed for alternate use to provide for equal wear? )(

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t Calculation No c. 55 5 6 CALI PbmTmd) l Originated Bys'AO Dates \1 l 16l 4 3 Sheet ll of fg '

B. Control Systems (cont'd) 1El HQ Efg

8. Have Human Factors considerations, I including appropriate operator Readouts near controls, Standard Switch Conventions, proper i Labeling, Identical Nameplates l at multiple control locations i

been appropriately applied to the components and documents affected sj l by this modification (EDP 3.17)? A

9. Have controls been analyzed for Sneak Circuits (circuit compo-nents evaluated for possible v unintentional current paths)? A l

10. Have controls been analyzed for relay race problems? )(

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11. Are components applied in a manner i

to minimize the consequences of a failure and provide the opportunity for detection prior to operation? e

12. Have controls been reviewed for effects of loss of power / return of power? N

13. Are there any special testing (,

requiraments noted? A (refer to Section B26)?

Have provisions been made for routine testing (examples: jacks, isolating switches, indication, signal conditioning devices (i.e., resistors, shorting blocks, etc.)]? )[.

14. Is coil monitoring required and implemented? )(

15. Are reset functions required and gj implemented? A

16. Have the locations of all local remote control stations been inves-tigated to provide an acceptable environment? )[

17. Are Duke's standard control wiring sizes adequate? X

18. Are redundancy, diversity and sepa-ration requirements addressed? D('

(~7 At 6 C ALC LL4Tlo AL)

I Calculation No Lo c - 5556 (AL1 Pbeen) l Originated By: .

. .. O p h Date ll( to /q 3 !

Sheet 17 of lg B. Control Systems (cont'd) XE1 ILQ Q

19. Are there specific requirements or criteria for local / remote, auto / manual control? )( 1

20. Is compatibility with existing I wiring and insulation maintained? h[

21. Have circuits been designed to allow installation with least sj tmpact on unit / plant availability? A

22. Does this modification involve Solenoid / Air Operated Valvis? )<

If Yes, answer the followings

a. Are solenoid valves and their respective control circuits separately fused from other solenoid valves on the same breaker?

b. Are solenoid valves wired with appropriate voltage (125 VDC or 120 VAC)?

c. Are solenoid valve control cir-cuits designed to require manual reset on ESF signal reset 7

d. Have all loss of air and/or power failure mode requirements been met?

e. Are all control interlocks identified? ,

f. Are the required limit switches available for response time testing? __

g. Has Plant Computer position indication been requested (examples status, graphic display, response time)?

h. Has High Temperature Wire on solenoid valve (Valcor 526, V709000-39, etc.) with internal blocks been specified?

Calculation No c - 5 55 6 CA'-l WF'o ^D Originated By: Dates lll 't6 l 4 3 Sheet 13 of if B. Control Systems (cont'd) Igg gg gfg

23. Does this modification involve motor operated valves 7 h[

If Yes, answer the followings

a. Are all MOV control requirements identified in Engineering Cri-teria CO-4.02 met (examples anti-hammer)?

b. Have limitorque. valves been reviewed for limit switch heater requirements? (Limit seques were not qualified with heater energized.)-

-c. Are extended torque switch by-pass requirements met? (See NRC IE Bulletin 85-03 for re-quirements.)

d. Have MOV vendor limit / torque position requirements been met?

e. Are overloads wired according to Engineering Criteria CO-4.017

f. Has Plant Computer posit' ion indication been requested (examples status, graphic display, response time)7

g. Are power disconnects required to assure position?

h. Have all control interlocks been identified and properly wired?

1. Are stem-mounted limit switches available for cross train inter-Jocks?

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i i calculation Ng C. - 55 5 6 (Alt Obstra eN)

Originated By: U M W d Dates ll l10 l 4 3 Sheet l4 of 19 B. Control Svetems (cont'd) Igg gg gfg

24. Does this modification involve heaters, pumps or fans? )(

l If Yes, answer the followings

a. Have emergency trip requirements been met (examples: pressure, temperature, level)?

b. Have bearing wear monitoring and insulation protection requirements been met (examples: thermocouples, vibration, high current)?

c. Are motor overloads alarmed or flashed as appropriate?

d. Are all control interlocks iden-tified?

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e. Have Plant Computer points been requested (examples: equipment run time, response time test, status indication)?

' f. Are controls designed to prevent unsafe or unwarranted restarts of equipment on the return of power?

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g. Have appropriate sequencer con-tacts been requested?

25. Are containment penetration circuits g, affected? A If Yes, answer the following questions:

a. Are redundant overcurrent protec-l tion devices specified of correct size to protect the penetration?

b. Is the correct penetration type selected for circuit current /

instrument application (see DC 16.01 - 16.06)7 i

Calculation Not o c.- 5556 CAtt Gbunen].

originated By: y OA 4 &.0 Dates ll\)olq3 Sheet 15 of g g I

B. Control Systems (cont'd). XM gg Q l 26. Are there interfaces between analog

[ voltage or current loops and analog y l to digital conversion devices (A/D)? A ,

a. If so, will the digital equivalent  !

l '1 of the analog signal be affected-by any potential spike (s) created by' opening or closing the analog loop? k

b. Will this erroneous signal have an .

effect~on the alarm / control circuits  !

or program?' 'k- ~!

C. Centrol Eauiement

1. Have the following requirements been considered - Reg. Guide 1.97, Fire i

Protection, Containment Pressure Con-- '

trol, Hydrogen Mitigation, Crane Drop Zones, Attachments to Block Walla? .N

2. Do Equipment Min / Max Environmental Ratings / Qualification envelope the expected actual environment (examples ' temperature,' pressure, l humidity, radiation, chemical I spray, flooding, freezing)7 N

3. _tation Has required been receiv,ed7( qualificat na geg en- -OtA A ., Y

4. MIs ,6.amw any special WEquipment m -A(Protection required such as Space Heaters, Blowers, Cooling, Heat Tracing, gj Shielding, Limited Access?

- A.

5. Has. equipment accessibility been considered? Access provided.for All Plant Operating Conditions (operating, installation, mainte- gj nance, testing). A

6. If the equipment is QA condition 1 safety-related, has the seismic qualification documentation been reviewed and approved? Y

7. If the equipment M EQI QA Condition 1, does it require seismic anchoring? Y,

, ,,yr-- . - , , . - , . . , , , - - - y -,- .- , r

Calculation No sc- 5556 cal 1 R@eND originated By: m -

- .0 h w at., ggiio(q3 Sheet I 6 of 18 C. Control Eculoment (cont'd) 1E1 Efg HQ

8. Have any special equipment qualifi-cation requirements beyond EQMM been documented? (Consider replacement parts or main components.) )( f

9. Are equipment response times adequate to satisfy required functions? )(

10. Has the purchase of spara parts or special tools been considered for specialized equipment or due to any impending availability problems?

11. Have cables that require special g, purchases been identified? A

12. Have special equipment restrictions been considered (examples: Alumi-num, Teflon or cable jackets gj inside Reactor Bldg.)? A

13. Have all new manufacturing drawings /

information been sent to appropriate manufacturer's/ correspondence /NSM .sj files? A

14. Has adequate allowance for growth been considered in the design and rating of-equipment? )(

15. Does the manufacturer's equipment internal circuit design meet require- v ments for the application? ^

16. Have all required manufacturer's drawings been received, approved, gj and transmitted? A,

17. Has the required number of computer j program documentation sets / i instruction books been ordered, received and transmitted? )(

)

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i calculation No O Df. - 55 5 6 (4 4.1 PoRTso N)

Originated By: h 0Jhw Dates ll[ tts( q 3 Sheet l7 of g g C. Control Eauipment (cont'd) 1E1 EQ. M[&

18. Will the following Environmental Qualification documentation be affected/ required due to addition / deletion / modification of QA condition 1 control equipment (Project Manual, Section 1000.00)7- >[ l

a. EQ Test Report / Analysis Summary h# l N

(DEPM Document 1002-01) l

b. 10CFR50.49 EQ Review and ff-verification calculation? X (DEPM Document 1002-02)-

-l

c. EQ Licensing Submittal  !

(DEPM Document 1002-03 & 1002-04) Y l T

d. Environmental Qualification Master- sf List (EQML)? A l (DEPM Document 1002-05) I

e. Environmental Qualification gj Maintenance Manual (EQMM) A '

Sections?

(DEPH Document 1002-06)-

D. Monitorino i

1. Have instrument shielding / grounding requirements been met? hl,

2. Have Httman Factors considerations, including labeling, scaling, and other operator interface considera-tions been appropriately applied to the components and documents affected by this modification (EDP 3.17)? h

3. Have instrument accuracies, ranges, and response time requirements been i D(

met?

4. Have the loop accuracy calculations been completed (revised) for new (modified) instrument loops? (Loop accuracy calculations are normally required for all safety-related and technical specification related instrument loops or for any other instrument loop for which there is a regulatory requirement on o accuracy.) X t

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. . - - - . . .. .- .~. = ~ - -

c. 5556 (All EbET[oN Calculation No >

Originated By L(O OLA G Dates l\l 'lolCG Sheetl8 of IS ' .

D. Monitorina (cont'd)- XE1 HQ HihL

5. Have instrument loop design require-ments such as Device Compatibility, Signal' Level, Analog signals to Digital or PLC interface, Power Supplies, 2 or 4 Wire,-Over/Under Loading, Voltage Fluctuation,. Square Root -Extractors if Required, Range, Display, Human Factors been considered? __)(_,

6. Havelsetpoints been selected andi documented 7(~ TIME MLAy) X-

7. Have' bypass (1.47 panel).and moni- - g):

tor light requirements been met? A

8. Have all Loop. Functions-been-established.(exampless' analog /.

digital' control, analog monitoring, q!

digital' alarms & status)? . 'A-

9. Have Regulatory 1.97 Requirements been met (examples parameters monitored, readout requirements, redundancy / diversity, qualifica- .sj tion)? A ,

10. Is Heat Tracing required? D[

11. Are monitored conditions alarmed for l

off-normal conditions? )( }

12. Are any special calibration and  !

maintenance requirements for sj instruments specified? __ A -j-

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13. Have alarm limits for Plant Computer Analog Points been specified? )(

d a er- th= aquipment.added by this modification require a new installa-tion specification or a revision to an existing installation specification? -

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c>5c - 5 55 6 ATTAc.RM ENT .1.

PA(_iE i cfi NSM-ON-52966 (AL1 PORTION) PROJECT DESCRIPTION This modification provides logic in the controls of various Keowee devices, which, when implemented, will preclude postulated scenarios from adversely affecting the Keowee generators ability to function as the emergency on-site sources to the three Oconee units.

This portion of the NSM therefore addresses the following item:

1. Single failure concerns relative to differential protective relays zone overlap when a failure within one of the overhead generator breakers (ACB-1 or ACB-2)is postulated.

A failure within one of the breakers noted, when the affected Keowee unit is also the one selected as the " underground path" unit will result in both emergency power paths " locked out" and unavailable. An interim solution to this problem is that of maintaining the overhead breaker, on the selected underground path unit, isolated (breaker tripped with its respective disconnects open) thus, making one of the Keowee units unavailable for system purposes.

The logic provided by this modification which addresses this concern will result in the underground breaker (not previously selected) to automatically close when indication of the postulated breaker fault occurs.

This is accomplished by providing automatic closing logic in each underground path breaker (ACB-3 and ACB-4) such that they will close when the following conditions are satisfied.

A Main step-up transformer Lock-Out Relay 86T tripped ; and B. The opposite Keowee units Emergency Lock-Out Relay 86E tripped: and C. Either channel of emergency start to the respective Keowee  ;

unit actuated. l l

Once satisfied, the close signal to the open underground path breaker is delayed for two seconds to preclude the highly unlikely possibility of the open breaker rapidly closing with no synchronization supervision present.

Please note that the time delay has been provided as a precautionary measure and is not required nor is its function considered to be within design basis.

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