ML20070M597

USQ Review of NSM-52966 Part AL1, 'Modify Keowee Acbs 3 & 4 to Automatically Close During Postulated Single Failure to Acbs 1 & 2.'

ML20070M597
Person / Time
Site:	Oconee
Issue date:	11/02/1993
From:	DUKE POWER CO.
To:
Shared Package
ML15261A430	List: ML20070M597 ML20070M607
References
OSC-5600, NUDOCS 9405020213
Download: ML20070M597 (7)

Text

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i ownbim- l FORM 101.1 l REVISION 14 I

CERTIFICATION OF ENGINEERING CALCULATION STATION AND UNIT NUMBER Oconee Nuclear Station, Units' 1,2,3 TITLE OF CALCULATION USO Review of NSM 52966 Part All,

• Modify Keowee ACBs 3 & 4 to Automatically Close During Postulated Single Failure to ACBs 1 & 2 "

CALCULAT!ON NUMBER OSC 5600 _,

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ORIGINALLY CONSISTING OF:

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PAGES 1 THROUGH -- 4 TOTAL ATTACHMENTS-- - ' O TOTAL MICROFICHE ATTACHMENTS O TOTAL VOLUMES 1 TYPE 1 CALCULATION / ANALYSIS YES O NO @

TYPE I REVIEW FREQUENCY -

THESE ENGINEERING CALCULATIONS COVER OA CONDITION 1 ITEMS. IN ACCORDANCE WITH ESTABLISHED PROCEDURES, THE QUALITY HAS BEEN ASSURED AND i CERTIFY THAT THE ABOVE CALCULATION HAS BEEN ORIGINATED, ECKED OR APPROVED AS NOTED BELOW:

ORIGINATED BY DATE //- / - 9 3 CHECKED BY d)

- - y DATE // Y 9 3 APPROVED BY TA $m*8g. DATE //-2.-73 3 SUED TO DOCUMENT CONTROL DATE RECEIVED BY DOCUMENT CONTROL DATE MICROFICHE ATTACHMENT LIST: OYES 3NO SEE FORM 101.4 REV. CALCULATION PAGES (VOU ATTACHMENTS (VOU VOLUMES ORio CHKD APfH ISSUE NO. DATE REVISED DELETED ADDED REVISED DELETED ADDED DELETED ADDED DATE DATE DATE REC'D DATE i

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PURPOSE 4

j- Tho purpose of this evaluation is to determine if;any unreviewed are involved with NSM ON-52966'Part'AL1, l

SafGty questions (USQ) ~

j " Modify Keowee ACBs 3 & 4'to Automatically close During Postulated i Single Failure to ACBs 1 & 2". The criteria of-10CFR50.59 a(2)'will i be used to make this determination. ~ This evaluation is QA Condition 1 because it determines the presence;or absence of'a USQ.

d I- DESCRIPTION:

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This modification will change Keowee' . logic to prevent- a certain l

from adversely impacting the ability' ofi the

[ Postulated scenarioKsowee hydro units to supply emergency power to the Oconee nucl units. This modification addresses the single failure'of ACB-1 or

2 rendering both the overhead path :and underground unit. '

j uncvailable. For more information see Reference 5.

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,! 8AFET1r REVIEW The purpose of the Keowee Emergency Power System is to supply a j

reliable source of emergency power to the Oconee Nuclear Station This. modification ' is being j during a design basis. event (DBE).

i implemented.to preclude a single failure of ACB 1 orrespectively) '

2 (overhead j paths _ air circuit breakers for Keowee Units l'& 2, from propagating into an event'that could deprive ONS of its onsite j

amargency power source during a DBE. It was ' postulated that. a i-failure within either ACB-1 or 2, when the affected Keowee unit is

• also selected to the underground path would. result in both-power paths being locked out. As an example, if Keowee Units.1'& 2 were-i i

generating to the grid (ACB-1 & 2 closed) with Unit i selected to.- '

j the underground path (ACB-3 underground the following tielogic breaker sequenceclosed),.and woulda fault occurred inside ACB-1, transpire: Generator dif ferential relay'87G picks up and . initiates l

l L lan 86E Emergency Lockout Relay which trips and ' locks out Keowee Step-up Transformer No.. 1 i Unit 1. Concurrently, the Main

' differential relay (87T) detects the fault and operates Lockout

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l Relay 86T to trip ALL breakers connected to the transformer (ACB- -,

L 1,2,5,6 and PCB-8, 9). Thus, Keowee Unit 2 is separated from the l j

overhead path, and both the overhead path and the underground unit 1

are unavailable ~ to ONS. This modification will change the operating l

}' logic such that the underground breaker not selected (ACB-4.in the previous example).will automatically close upon indication of the j

i- postulated breaker fault. ACB-3 & 4 will be provided with automatic l i

closing logic to initiate closure if all the following conditions I' exist: (1) Main Step-up Transformer Lockout Relay 86T is. tripped, (2) the other Keowee units Emergency Lockout Relay 86Elis tripped, i

and (3) either. channel of Emergency start to the respective'.Keowee E unit is actuated. Once these three conditions are satisfied, a two second' time delay is provided to protect.against the unlikely event-l of the open breaker rapidly closing with no synchronization.

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&M) Date //-i-43 j eupervision present. The time delay is installed solely as a I

precautionary measure. These changes will remove the possibility of i a single failure fault on the overhead pathway ACBs causing a loss '

of both emergency power paths. (References 1, 2, 3, 5) 1 This modification will require addition and installation of type M 4

l and solid state timing relays, type M relay contact blocks, nodules. These new devices will be Cutler Hammer brand,

" QA Condition 1, safety related components..The need for additional cabling is expected to be minimal. The new devices will' be l

seismically mounted and located within the mild Keowee environment.

[ References 5]

This modification makes changes to the Keowee emergency power l l

system to preclude a single failure of ACB-1 or 2 from rendering t

both the overhead path and the underground unit unavailable. This modification has no adverse effect on the ability of the Keowee Units to satisfy their design requirements of achieving rated speed

' and voltage within 23 seconds of receipt of an emergency start I signal. This modification does not degrade the function of any probability or safety system. There is no increase in the 4

J consequences of any previously analyzed accidents, and no new failure modes introduced. Both Appendix R and seismic reviews of I this modification have been performed. The final design for Part  !

l AL1 is complete. (References 4, 5, 6]

! U80 EVALUATION j May the modification:

1 l 1. Increase the probability of an accident evaluated in the 8AR7 No. The Keowee Hydro units provide the main source of emergency power for the Oconee Nuclear units, but they are not

• accident initiators. The FSAR Loss of Electric Power accident l

assumes two types of events: (1) Loss of load (unit trip) and

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(2) Loss of all system and station power. These changes to the control logic do not increase the likelihood of either. All

• replacement equipment will be QA condition 1 and seismically mounted.

I 2. Increase the consequences of an accident evaluated in SAR?

No. The changes to the Keowee operating logic per this j

modification will not adversely af fect the ability to mitigate LOOP, LOCA, and LOCA/ LOOP accidents as described in the FSAR.

The loss of all station power accident analysis assumptions 4

j are still valid. This modification has no adverse impact on

' the ability of the Keowee Units to satisfy their design requirements of achieving rated speed and voltage within 23 seconds of receipt of an emergency start signal.

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3. Create the possibility for an accident of a different type than any evaluated in the SAR7 No. This modification simply changes the Keowee control logic to remove the possibility of certain postulated events from i causing a loss of emergency power to the Oconee nuclear units.

The Keowee emergency power systems will remain operable and available to mitigate accidents. No new failure modes are i postulated.

probability of a malfunction of equipment 1

4. Increase the important to safety evaluated in the SAR7 No. This modification removes a potential single failure of ACB-1 or 2 that could have rendered the Keowee overhead path and the underground unit unavailable. No function of any  !

safety related or emergency power systems / components will be l degraded as a result of this modification. I

5. Increase the consequences of a malfunction of equipment J important to safety evaluated in the SAR7 1 No. No safety related equipment will be adversely affected

6. Create the possibility for a malfunction of a different type than any evaluated in the SAR7 No. This modification will permanently correct a potential failure mode associated with existing breaker control logic.

No new failure modes are postulated.

Will the modification:

7. Reduce the margin of safety as defined in the basis for any Technical Specification?

are adversely affected, so No. No safety margins or design of safety as defined limitsin the bases to any Technical reduced as a result of this Specifications are not modification.

CONCLUSION Based on the preceding discussion, this modification involves no safety concerns or USQs. No FSAR changes or Technical specification changes are necessary. [ Reference 5]

SUMMARY

FOR 10CFR50.59 ANNUAL RErfdT NSM ON-52966 Part AL1, will change Keowee breaker logic to prevent certain postulated scenarios from adversely impacting the ability

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OSC-5600 j Pg 4 of 4 By YAf Date/N-t3 of the Keowee hydro units to supply emergency power to the Oconee nuclear units. This modification prevents a single failure of ACB-1 '

or 2 from rendering both the overhead path and the underground unit unavailable. There is no adverse impact on the function of any safety system, no increase in the probability or consequences of any previously analyzed accidents, and no new failure modes associated with this modification. No FSAR changes or Technical Specification changes are necessary.

REFERENCES

[1] Oconee Final Safety Analysis Report, Sections 6.3.3.3, 6.3.3.4, 7.1.2.2, 8.1, 8.2, 8.3, 8.4, 15.8, 15.14, Table 8-3, Figure 8-6, 1992 Update

[2] Oconee Technical Specifications, Sections 3,7, 4.6, 5-18-93 Update I

[3] Keowee Emergency Power Design Basis Document, Rev 1A, dated -

6-21-93

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[4] Personal communication between Dave Donaldson (EE) and Ed '

Price (MNE) on 11-1-93 to discuss overall modification design and verifying:

- the mod will remove a potential single failure fault

- Appendix'R review has been performed

- the final design for AL1 is complete (5) NSM-ON-52966 AL1 Portion, Project Description

[6] Personal communication between Warren Bright (EE) and Ed Price (MNE) on 11-1-93 verifying Part AL1 of this modification has been evaluated for seismic concerns.

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666 '/I70 Design Bases / Objectives

> q l DESIGN BASIS: + o i Interlocks have been provided to ensure the availability of the underground emergency power path if a postulated fault (single failure) were to occur within the overhead breaker (ACB-1 or ACB-2) of the Keowee Unit which has been previously selected and aligned to the underground feeder.

These interlocks function to automatically close the non-selected underground path breaker (ACB-3 or ACB-4) after a preset time delay when the following conditions concurrently exist:

1) The main stepup transformer lock-out relay 86T tripped,

2) The opposite unit's emergency lock-out relay 86E-1 or 86E-2 tripped, and

3) An emergency start signal from either channel of KE0 VEE EMERGENCY START LOGIC.

Test Acceptance Criteria Test / Measurement Reforence Document Acceptable Value including Tolerance O

M/MRN PERNS REVISED REV;SIONDATE:l0NDATE AND IMPLEMENTAi PRINT EDITION PERMANENT LIM 11ED AS A IS A llSED THIS NOT BE  !

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Keowee Hydro Station Units 1&2 DB/ TAC for Auto-Closure of Non-Selected Underground Path Breaker DSN/Dato INS /Date hfl'21"M

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TEST OBJECTIVES:

To demonstrate that if a fault were to occur within the overhead breaker of the Keowee Unit selected to the underground path (which results in the above listed interlocks being satisfied) the nonselected underground breaker will automatically close after a 2 second time delay.

NOTE: As noted in Reference Document OSC-5556 the two (2) second time delay relay is added to the logic as a precautionary measure for postulated events not within design basis.

Test Acceptance Criteria Test / Measurement Reference Document Acceptable Value including Tolerance l l Knowee Hydro Station Underground Path Keowee Emergency Power System Breakers ACB-3 & ACB-4 Design Basis Documents Maximum Times 2 seconds t .2 seca.

Accomplish Autcmatic OSS-0254.00-00-2005 Breaker closures of & Tech spec 3.7 the non-selected Surveillance Requirements

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' DB/ TAC for Auto-Closure of Non-Selected Underground Path Breaker DSN/Date . Id2*N INS /Date- D CHK/Date N/fl' '21 INS /Dateb '#MI APP /DateY .il IZAd31NS/Date NA A_ //UO No l Rewsons DSN CHK APR DTE C/E ELE M/N DWG No. KTC-0-0114-0001-002 Rev mA l

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