ML18033B582

LER 90-004-01:on 901020,unplanned ESF Actuation Occurred & RWCU Sys Inboard Isolation Valve Found Closed.Caused by Failure of Control Room Alarm to Reflash.Failed Relay & Blown Fuse replaced.W/901217 Ltr

ML18033B582
Person / Time
Site:	Browns Ferry
Issue date:	12/17/1990
From:	Bynum J, Ridgell E TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-004, LER-90-4, NUDOCS 9012210158
Download: ML18033B582 (12)

Text

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ACCESSION NBR:9012210158 DOC.DATE: 90/12/17 NOTARIZED: NO DOCKET FACIL:50-296 Browns Ferry Nuclear Power Station, Unit 3, Tennessee 05000296 AUTH. NAME AUTHOR AFFILIATION RIDGELL,E.M. Tennessee Valley Authority BYNUM,J.R. Tennessee Valley Authority RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 90-004-01:on 901020,unplanned ESF actuation occurred &

RWCU sys inboard isolation valve found closed. Caused by D failure of control room alarm to reflash.Failed relay &

blown fuse replaced.W/901217 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL SIZE:

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

NOTES:1 Copy each to: S. Black,B.WILSON 05000296 D

RECIPIENT RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL D KREBS,M. 1 1 HEBDON,F 1 1 ROSS,T. 1 1 INTERNAL: ACNW AEOD/DOA 2,

1 2

1 ACRS AEOD/DSP/TPAB 2

1 2

1 AEOD/ROAB/DSP 2 2 NRR/DET/ECMB 9H 1 1 NRR/DET/EMEB 7E 1 1 NRR/DLPQ/LHFB11 1 1 NOTES'OPIES NRR/DL'PQ/LPEB10 NRR/DREP/PRPBll NRR/DST/SICB 7E NRR/DST/SRXB 8E 1

2 1

1 1

2 1

1 NRR/DOEA/OEAB NRR/DST/SELB 8D

-REG 02 1

1 1

1 1

1 1

1 RES/DSIR/EIB .1 GN2 FILE 1 1 EXTERNAL: EG&G BRYCE,J.H 3 3 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MAYS,G 1 1 R NSIC MURPHYiG A 1 1 NUDOCS FULL TXT 1 1 5 5 D

D D

NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROO5,1 Pl-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 38 ENCL 38

i' TENNESSEE VALL'EY AUTHORITY

'6N 38A Lookout Place 1101 Market Street Chattanooga, Tennessee 37402-'2801 U.S'. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555

Dear Sir:

TVA BROWNS'ERRY NUCLEAR PLANT (BFN) UNIT 2 DOCKET NO. 50-296 FACILITY OPERATING, LICENSE DPR-33 REPORTABLE OCCURRENCE REPORT BFRO-50-296/90004, Rl The enclosed report provides details concerning an unplanned engineered safety feature actuation. This report is submitted, in accordance with 10 CFR 50.73(a)(2)('iv) and is provided to supplement the report issued on November'9, 1990.

Very truly yours, TENNESSEE VALLEY AUTHORITY J. g Baw~w J. R. Bynum Vice President Nuclear Operations Enclosures cc (Encl'osures):

INPO Records Center Suite 1500 1100 Circle 75 Parkway Atlanta,, Georgia 30339 NRC:Resident Inspector, BFN Regional Administration U'.S. Nuclear Regulatory Commission 101 Marietta 'Street, Suite 2900 Atlanta, Georgia 30323 Thierry M. Ross U.S. Nuclear Regulatory Commission One White Fl'int, North 11555 Rockville Pike Rockville, Maryland 20852 9012210158 901217 PDR ADOCK 0 000296 PDR An Equal Opportunity Employer +8

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NRC (6-89)

Form 366 U. UCLEAR REGULATORY COHHISSION LICENSEE EVENT REPORT (LER) t Approved OHB No. 3150-0104 Expires 4/30/92 FACILITY NAHE (1) )DOCKET NUHBER (2)

B wn r 4 TITLE (4) 1 V NT D HB R

( SEQUENTIAL ( REVISION/ i i / FACILITY NAHES (DOCKET NUHBER(S)

NTH D Y H N N Y I I I I I I I I I I 12 17 90 OPERATING I ITHIS REPORT IS SUBHITTED PURSUANT TO THE REQUIREHENTS OF 10 CFR 5:

HODE I I n r f IZ0.405(c) )~f50.73(a)(2)(iv) [73.71(b)

POWER I (20.405(a)( l)(i ) i50.36(c)(1) [50.73(a)(2)(v) (73.71(c)

LEVEL I )20.405(a)( 1)(ii) (50.36(c)(2) t50.73(a)(2)(vii) [OTHER (Specify in

)20.405(a)( l)(iii) I I50.73(a)(2)(i) )50.73(a)(2)(viii)(A) t Abstract below and in (20.405(a)( 1)(iv) [50.73(a)(2)(ii) )50.73(a)(2)(viii)(B) ( Text, NRC Form 366A)

NAHE I AREA CODE I Er . i '1 ni r ml' i in N N F I D 8 I I IREPORTABLEI I I I IREPORTABLEI A Y H T N I I I I I I I I P HNT P T P T 14 I I SUBHISSION I I I Y f ABSTRACT (Limit to 1400. spaces, i.e., approximately fifteen single-space typewritten lines) (16)

On October 20, 1990 at 0253 hours0.00293 days <br />0.0703 hours <br />4.183201e-4 weeks <br />9.62665e-5 months <br />, an unplanned actuation of an engineered safety feature (ESF) occurred. Operations personnel were transferring the 3B 480 volt Reactor Motor Operated Valve (RMOV) board to its alternate power supply. During the transfer the reactor water cleanup system inboard isolation valve (3-FCV-69-1) was found to be closed due to a primary containment isolation system (PCIS) actuation.

The PCIS, actuation of 3-FCV-69-1 was not anticipated in association with the deenergization of RPS bus 3B.

Investigations revealed that 3-FCV-69-1 closed due to a blown fuse in conjunction wi.th the deenergization of RPS bus 3B.= The blown fuse was a result of a coil failure on a relay. Under normal conditions, the blown fuse would have resulted in a control room annunciation. However, the fus'e failure annunciator was sealed in due to modifications related hold orders and was not equipped with a reflash capability.

The root cause of this event was a non-fault tolerant system since the annunciator is not designed to reflash on multiple failures.

The immediate corrective action was to replace the failed relay and the blown fuse.

Additional corrective actions include installation of reflash capabilities on annunciators with multiple inputs.

NRC Form 366(6-89)

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NRC Form 366A U.NUCLEAR REGULATORY COMMISSION Approved OMB No. 3150-0104 (6-89) Expires 4/30/92 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACIL'ITY NAME '(1) IOOCKET NUMBER (2)

I I I I SEQUENTIAL I IREVISIONI I I I I I I I I I Br wn F r i TEXT (If more space is required, use additional Form 366A's) (17) t' t NRC On, October 20, 1990 at 0253 hours0.00293 days <br />0.0703 hours <br />4.183201e-4 weeks <br />9.62665e-5 months <br />, Operations personnel were transferring the 3B 480 volt Reactor Motor Operated Valve (RMOV) board to its alternate power supply per approved plant procedures. During the transfer the 3B Reactor Protection System (RPS) bus. [JC] deenergized . This was an expected occurrence since 'the 3B RPS bus was on its alternate transformer supply and a board transfer under these circumstances results in a trip of RPS undervoltage circuit protectors 301 and 302.

The deenergized RPS bus resulted in the closure of two reactor water cleanup (RWCU) system [AD] isolation valves, (3-FCV-69-2 and 3-FCV-69-12). Although 3-FCV-69-12 receives a primary containment isolation system (PCIS) actuation signal, it is not considered to be a primary containment isolation valve. These valve closures were anticipated occurrences for the planned activities. In addition, the RWCU inboard isolation valve (3-FCV-69-1) was found to be closed due to a PCIS 'group 3 isolation. The closure of this valve was not anticipated in associated with the deenergization of the 3B RPS bus.

Investigations revealed that 3-FCV-69-1 closed due to a blown fuse in conjunction with the 3B RPS bus deenergization. The fuse had blown when the coil on a General Electric (GE) relay, Model: HFA, shorted. Under normal conditions, the blown fuse would have resulted in a control room annunciation for fuse failure. However, the fuse failure annunciator was sealed in due to modifications related hold orders on systems not related to the RWCU system.

The fuse 'failure annunciator is fed by multiple signals and is not equipped with reflash capability. No event occurred prior to the transfer of the power source which would have led the operators to believe additional faults had occurred which could have affected the PCIS.

BFN Unit 3 was shutdown and defueled at the time of this event and no fuel handling or other operations over the spent fuel were in progress. This event resulted in an unplanned actuation of an ESF and is reportable in accordance with 10 CFR 50.73(a)(2)(iv).

v t The RWCU inboard isolation valve (3-FCV-69-1) provides the ability to isolate the RWCU system, piping during abnormal events such as line breaks associated with the RWCU system. This valve is part of the dual valve arrangement used to ensure the isolation capability of lines penetrating the primary containment.

During this event, the 'PCIS operated as designed to isolate the RWCU system.

NRC Form 366(6-09)

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orm pp rove oe (6-89) Expires 4/30/92 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) [DOCKET NUM8ER (2) i SEQUENTIAL i i REVISIONS ) i )

I Y I I I I r wn F (If more space is required, use additional NRC Form 366A's) (17) 4'EXT The fuse failure annunciator is designed to alarm on the failure of any fuse within the alarm logic of the panel. However, this annunciator was sealed in due to previous hold orders which were issued to perform plant modifications.

Also, the fuse failure annunciator is not designed with a reflash capability to inform operations personnel of additional fuse failures once the alarm is sealed in. The inability of the panel to re-alarm on multiple failures will not affect

,safe operation of the plant since the associated inputs to this alarm are designed to fail safe on loss of power.

At this time BFN Unit 3's shutdown, defueled, and a significant number of modifications are being performed. The 'hold orders associated with the fuse failure annunciator resul'ted in a masking of the blown fuse. Based on the masking of this annunciator, there was no event which could have led the operators to believe additional failures had occurred.

These conditions would not have occurred if Unit 3 was operational. The BFN alarm response -procedure requires an immediate response to a fuse failure alarm. Also,, it would not be possible to perform the same number of modifications, concurrently, under operational conditions. Therefore, events similar to this event would not be expected to occur after refueling or during operations at BFN.

This specific event could not have occurred at BFN Unit 2. The Unit 2 alarm response procedure (ARP) was revised based on control room design review (CRDR) recommended modifications to the annunciator panels. These modifications provided a specific annunciator for the RWCU isolation logic. The ARP associated with this annunciator provides a detailed description of the RWCU isolation. logic in contrast to the general fuse failure alarm presently provided for Unit 3.

There were no safety consequences or implications resulting from this event.

All of the associated ESF systems reacted, as designed, to maintain Unit 3 in a I safe condition. Therefore, this event had no safety significance.

v t The root cause of this event was a non-fault tolerant system in which errors were not detectable [GU] ~

Investigation determined that Unit 3 plant conditions at the time of the event were such that the annunciator was illuminated due to other fuses, in the annunciation logic, being pulled as a result of modifications hold orders. In addition, the alarm is not designed with reflash capabilities to annunciate when additional failures occurred.

NRC Form 366(6-89)

Qi ,<Qi NR 0 Form 366 A U.S CLEAR REGULATORY COHNISSION Approved OMB No. 3150-0104 (6-09) Expires 4/30/92 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY WANE (1) iOOCKET NUHBER (2)

I I I. I SEQUENTIAL I IREVISIONI I I,I' I I I I I TEXT (If more space is required, use additional NRC Form 366A's) (17) v The immediate corrective action was to replace the failed relay and blown fuse.

'This was. completed by maintenance perso'nnel on October 21', 1990. The long-'term corrective action is to install reflash capabilities for annunciators with multiple inputs. These actions will be completed for Units 1 and 3 prior to the

-startup of each unit and for Unit 2 during the cycle 6 refueling outage. The corrective actions discussed above were previously identified by the control room design review group and are scheduled for completion which TVA committed to by letter dated 12/28/89.

v t No pr'evious similar events.

mmt t No additional commitments.

Energy Industry Identification System EIIS Codes .are Identified in the Text as [XZ]

NRC Form 366(6-89)

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