ML17348B321

LER 91-011-00:on 911011,Appendix R Safe Shutdown Analysis Design Inadequacy Identified Due to Failure to Recognize Potential for Spurious Actuation of Auxiliary Relay.Manual Action List in Safe Shutdown Analysis revised.W/911218 Ltr

ML17348B321
Person / Time
Site:	Turkey Point
Issue date:	12/18/1991
From:	Plunkett T, Dawn Powell FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-91-341, LER-91-011, LER-91-11, NUDOCS 9201090114
Download: ML17348B321 (8)

Text

I REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9201090114 DOC.DATE: 91/12/18 NOTARIZED: NO DOCKET FACIL:50-250 Turkey Point Plant, Unit 3, Florida Power and Light C 05000250 AUTH. NAME AUTHOR AFFILIATION POWELL,D.R; Florida Power 6 Light Co.

PLUNKETT,T.F. Florida Power & Light Co.

RECIP.NAME - RECIPIENT AFFILIATION

SUBJECT:

LER 91-011-00:on 911011,Appendix R Safe Shutdown Analysis design inadequacy identified due to failure to recognize potential for spurious actuation of auxiliary relay. Manual Action List in Safe Shutdown Analysis revised.W/911218 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL ) SIZE

'TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES' RECIPIENT COPIES RECIPIENT COPIES D ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR' ENCL PD2-2 LA 1 1 PD2-2 PD 1 D AULUCK,R 1 1 INTERNAL: ACNW 2 2 AEOD/DOA 1 1 AEOD/DS P/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DET/ECMB 9H 1 1 NRR/DET/EMEB 7E 1 1 NRR/DLPQ/LHFB10 1 1 NRR/DLPQ/LPEB10 1 '1 NRR/DOEA/OEAB 1 1 NRR/DREP/PRPB11 2 2 NRR/DST/SELB 1 1 NRR/DST/SICB8H3 1 '1 8D'PLB8D1 1 1 NRR/DST/SRXB 8E 1 1 1 1 RES/DSIR/EIB 1 1 F112 FILE 01 1 1" EXTERNAL EGGG BRYCE i J ~ H 3 3 L ST LOBBY WARD 1 1 NRC PDR" 1 1 NSIC MURPHY,G.A 1 1 NSIC POORE,W. 1 1 NUDOCS FULL TXT 1 1 D

D D

NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM PI-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

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P.. Box 029100, Miami, FL, 33102-9100 APL

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L-91-341 10 CFR 50.73 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Gentlemen:

Re: Turkey Point Units 3 Docket No. 50-250 Reportable Event: 91-011-00 Date of Event: October 11, 1991 10 CFR 50 A endix R Safe Shutdown Anal sis Desi n Inade uac The attached Licensee Event Report 250-91-011-00 is being provided in accordance with the requirements of 10 CFR 50.73(a)(2)(ii) to provide notification of the subject event.

Very truly yours, T. F. Plunkett

.Vice President Turkey Point Nuclear I

TFP/CLM/clm Attachment cc: Stewart D. Ebneter, Regional Administrator, Region II, USNRC Senior Resident Inspector, USNRC, Turkey Point Plant 0.r r)>3 v4

~.1 AOOCK Qr 1(.)oi.) ':.red F Lr:=.'n FPL Group company

LICENSEE 'EVENT"REPORT'LER)

FACILITY NAME ll) DOCKET NUMBER {2) PAGE l3)

TURKEY POINT UNIT 3 05000250 '

oF 4 TITLE l4) 10 CFR 50 A endix R Safe Shutdown Anal sis Design Inade uac EVENT DATE l5) LER NUMBER 6 RPT DATE l7) OTHER FACILITIES INV. <8)

MON DAY YR eSEQ I Rl MON DAY YR-FACILITY NAMES DOCKET t lS) 10 91 91 '011 00 12 18 91 TURKEY "POINT UNIT '4 05000251 OPERATING MODE PO'HER LEVEL l10) l>) 1 45 10 CFR'0.73 a ' ii L'ICENSFE CONTACT FOR THIS LER (12)

David R. Powell, Licensing Superintendent TELEPHONE NUMBER 305-246-6559 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT l13)

CAUSE SYSTEM COMPONENT NPRDS? CAUSE MANUFACTURER NPRDS?

COMPONFNT EXPECTED MONTH DAY SUPPLEMENTAL REPORT EXPECTED,l1,4) WO,gl ~  ;."- YES Q QUBMISS ION ~,

DATE l15) l1f yes, cceylete EXPECTED SUBMISSION DATE)

ABSTRACT l16)

On October 11, 1991, at: 0700"EDT,-,Florida-.;Power;,and Light 'identified an Appendix R Safe Shutdown Analysis design inadequacy at Turkey Point.

Originally considered 'not'eportable, further review resulted in the decision to report 'the condition 'as one n'ot 'covered by procedures. .As described in the Turkey Point Appendix R,Alternate Shutdown analysis, our design and procedures are required to be able to shut down the plant for a fire which'.may'-,occur in the control room or the =cable spreading room. Additionally, a .loss of offsite power is assumed to occur. The procedure for control. room evacuation directs the removal of power from the safeguards relay 'racks,,but"this'ction may. not prevent a spurious .short from occurring on,the:output side of a safeguards relay. The resulting spurious actuation of a, safeguards auxiliary relay, coupled with disabling of the Emergency Diesel Generator (EDG) lo'ad sequencer,:will result in.4zipping of .the ZDG output breaker. .This scenario applies to the 3B;and the 4B"EDGs. The Manual Action List in the Safe Shutdown Analysis, and the Off-Normal Operating Procedure" for control room evacuation, have both'"been *revised to require the removal- of f'uses which .will prevent the. spurious .

actuation of the. auxiliary relay.

LICENSEE QENT REPORT (LER) TEXT QVJIEUATIOE FACILITY NAME DOCKET NUMBER LER NUMBER PAGE NO.

TURKEY POINT UNIT 3 05000250 91-011-00 02 OF 04 EVENT DESCRIPTION On October 11, 1991, at 0700 EDT, with Unit 3 in Mode 1 at 45 percent power and Unit 4 in Mode 6 (Refueling), a system engineer (non-licensed utility personnel) identified a potential design inadequacy with the Turkey Point 10 CFR 50 Appendix R Safe Shutdown analysis. A Nonconformance Report (NCR) was generated to determine scenario was valid, and, if if the postulated spurious so, what corrective actions were necessary. Two suggested corrective actions were offered; one hardware modification, and one procedure enhancement.

The NCR disposition stated that the postulated scenario was valid, and provided two corrective actions, both procedural. The corrective actions were implemented by the time the NCR disposition was approved. In. addition, the disposition stated that there was no plant operability concern resulting from the NCR. On that basis, the condition was originally deemed to be not reportable; In response to concerns raised by the resident inspector, the 10 CFR 50 Appendix R requirements, the Turkey Point Safe Shutdown Analysis, and the facility Upgraded Final Safety Analysis Report were further examined. On November 21, 1991, at 1438, the condition was determined to be one not covered by the plant's operating and emergency procedures at the time the NCR was generated, and therefore reportable under 10 CFR 50.72(b)(1), and under 10 CFR

50. 73 (a) (2) .

10 CFR 50 Appendix R Alternate Shutdown criteria require that design and procedures be able to shut down the plant, for a fire which may occur in the control room. Additionally, a loss of offsite power is assumed to occur.

The following discussion describes the relays and components for Unit 3 Train B. The scenario described also applies to Unit 4 Train B. The B Trains are the "protected" trains for the Appendix R Safe Shutdown analysis.

Accoz'ding to Turkey Point's current Safe Shutdown Analysis, circuit 3E24Z is protected by removing power from the Safeguards [JE] relay

[RLY] racks. This is reflected in procedure O-ONOP-105, Control Room Evacuation, in Attachment 7, Step 6.

This action will not prevent a possible spurious actuation from occurring on the output side of the safeguards relays. One of theses relays (9524/3A) is associated with the 3B EDG. A spurious short of relay SI23X contacts 2-6'ill result in actuation of relay 9524/3A.

This relay actuation, coupled with disabling of the EDG load sequencer per O-ONOP-105, will result in tripping of the 3B EDG output breaker [52].

The condition was reported pursuant to 10 CFR 50.72 (b) (1) (ii) at 1530 on November 21, 1991.

LICENSEE ENT REPORT (LER) TEXT tlTINUATION FACILITY NAME DOCKET NUMBER LER NOMBER PAGE NO:

TURKEY POINT UNIT 3 05000250 91-011-00 03 OF 04 II. EVENT CAUSE The cause of this condition was design inadequacy. The Appendix R Safe Shutdown Analysis design'eview for Plant Change/Modification 87-264 failed to recognize the potential for this possible spurious scenario; therefore, mitigating manual actions were not included in the Safe Shutdown Analysis Manual Action List.

III. EIGHT SAFETY ANALYSIS The EDG output breaker circuitry has been designed to trip the breaker upon receipt of a Safety Injection (SI) signal. If an SI signal is received while the EDG is responding to a Loss of Offsite Power (LOOP), or during periodic testing with the EDG paralleled to the grid, the EDG output breaker trips automatically, without tripping the EDG. The objective of this feature is to re-strip the busses and allow loading of the Safeguards equipment, for the "LOOP followed by SI" event, and to separate the EDG from the grid, for the "parallel testing followed by SI" event.

Although the postulated scenario is a valid spurious actuation scenario, there are at least two concurrent events required to trip the EDG output breaker; (1) fire in the control room safeguards rack, and (2) failure of the 12 conductor cable 3E24Z/B 3C23B-3QR45 by shorting conductors 1 and Pl. The probability of this scenario exists only during an Alternate Shutdown condition, and even then is considered highly unlikely.

The design basis for this Appendix R fire scenario renders the EDG output breaker unusable; however, the design basis also allows the use of manual action to achieve and maintain hot standby conditions.

Any of several manual actions, such as removal of the fuses on the trip portion of the EDG breaker circuit, tripping of the SI auxiliary relays breaker, or removal of the fuses that power the SI auxiliary relays, would allow closure of the EDG output breaker.

Since the postulated scenario would result in obvious symptoms, e.g., loss of lighting, operators would be reasonably expected to recognize the symptoms and take manual actions. In addition, the control room is manned around the clock, and fire extinguishers are available in the control room. These mitigating factors provide added insurance against the postulated scenario. Thus the health and safety of the public was not materially affected.

Nevertheless, the choice. of action is important, and therefore the optimum corrective action warrants inclusion in the control room evacuation procedure. Removal of the fuses that power the SI auxiliary relays, including 9524/3A, does not affect anyandequipment hence is or functions that are required for Alternate Shutdown, considered the optimum manual action.

I ICENSEEEMT REPORT (LER) TEXT QFZINUATION FACILITY NAME DOCKET NOMBER LER NUMBER >> PAGE No.

TURKEY POINT UNIT 3 05000250 91-011-00 04 OF 04 IV. CORRECTXVE ACTIONS Procedure 0-ONOP-105 was revised with an On The Spot Change (OTSC) on October 11, 1991, to. include steps to remove fuses FU-1(+) and FU-1(-), thereby de-energizing the SI auxiliary relays during control room evacuation. The OTSC was reviewed and approved by. the E'lant. Nuclear Safety .,Committee on October 15, 1991.

,2. '-,.Change .Recpxest Notice CRN-, M-5490 ~as.:issued to correct the

'-.-:Appendix R Safe Shutdown. Analysis Manual..Action List by adding steps to-pull fuses ZV-1(+) and FU-1(-). The CRN was approved on Oct.ober'll, '1991.

3; " 'The feeder .cable routing to the SI auxi'liary relays has also been reviewed to verify that other possible cable to cable failures" will .not result'n the energization of the SI

-, auxiliary,.relays.

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V'. ADDXTXONAX, XNFORMATXON Licensee Event Report 50-250/89-09 described another Appendix R design izadequacy"," involving the operation of, valves supplying water

-:.to-.the:suction.';of the -;charging imps.:

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