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LER 98-002-00:on 980310,ESF Actuation Occurred Due to Failure of Alternate Feeder Breaker Position Switch.Will Continue Testing & Visual Insps on Addl Breaker Position Switches & Will Revise Applicable Maint Instructions
	ML18039A314
Person / Time
Site:	Browns Ferry
Issue date:	04/09/1998
From:	Morrison G; TENNESSEE VALLEY AUTHORITY
To:	;
Shared Package
ML18039A313	List: ML18039A312; ML18039A314;
References
	LER-98-002, LER-98-2, NUDOCS 9804150349
	Download: ML18039A314 (10)
	v • d • e

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150.0104 (4.96) EXPIRES 04I30/SS ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY INFORMATION COLLECTION REQUFSTI 60.0 HRS. REPORTED LESSONS LICENSEE EVENT REPORT (LER) LEARNED ARE INCORPORATED INTO THE UCENSING PROCESS AND FED BACK To INDUSTRY. FORWARD COMMENTS REGARDING BVRDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (T.e F331, U.S.

(See reverse for. required number of NUCLEAR REGVLATORY COMMISSION, WASHINGTON, DC 2066&%01, AND To THE PAPERWORK REDUCTION PROJECT 13160%1041, OFRCE OF digits/characters for each block] MANAGEMENTAND BUDGET. WASHINGTON. DC 20603.

FACIUTY NAME ffI DOCKET NUMBER 12). PAGE l31 Browns Ferry Unit 3 05000296 1OF5 Engineered Safety Features Actuation As a Result of a Switch Failure EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED IB)

MONTH OAY YEAR YEAR SEOVENTIAL REVISION MONTH DAY YEAR FACIUTY NAME DOCKET NUMBER NUMBER NUMBER FACILITYNAME DOCKET NUMBER 03 10 1998 1998 002 00 04 09 98 OPERATING THIS REPORT IS SUBMITTED PURSUA NT TO THE REQUIREMENTS OF 10 CFR 5: (Check one or morel MODE (9) 20. 2201 (b) 20.2203 (a) (2) (v) 50.73(a)(2)(i) 50.73(a)(2)(viii),

POWER 20.2203(a)(1) 20.2203(a) (3)(I) 50.73(a)(2)(ii) 50.73(a) (2)(x)

LEVEL (10) 100 20.2203(a) (2)(i) 20.2203(a) (3)(ii) 50.73(a) (2) (iii) 73.71 20.2203(a)(2)(ii) 20.2203(a) (4) X 50.73(a)(2)(iv) OTHER 20.2203(a) (2) (iii) 50.36(c) (1) 50.73(a) (2) (v) Specify in Abstract below 20.2203(a)(2)(iv) 50.36(c)(2) 50.73(a)(2)(vii) or in NRC Form 366A LICENSEE CONTACT FOR THIS LER (12I TELEPHONE NUMBER (Include AIee Code)

G.M. Morrison, Industry Affairs Specialist (256) 729-7534 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE. SYSTEM COMPONENT MANUFACTURER REPORTABLE TO CAUSE SYSTEM COMPONENT MANVFACTURER REPORTABLE h

NPRDS TO NPRDS A ED '33. G080 NA SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH OAY YEAR YES No SUBMISSION DATE (15)

(If yes, complete EXPECTED SUBMISSION DATE). X ABSTRACT (Umit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)

On March 10, 1998, Surveillance Instruction (Sl) 3-SI-4.9.A.4.b(ll), 4KV Shutdown Board Undervoltage Start of Diesel Generator Division II Test, was in progress. At approximately 1059 hours0.0123 days 0.294 hours 0.00175 weeks 4.029495e-4 months CST Operations personnel attempted to manually transfer 480V Shutdown Board 3B to its alternate supply in accordance with normal operating procedures. During the performance of the board transfer, the 480V Shutdown Board 3B alternate feeder breaker did not close as expected. This resulted in the momentary de-energization of 480V Shutdown Board 3B and all of its associated loads, including Reactor Protection System (RPS) bus B. The Primary Containment Isolation System groups associated with RPS bus B isolated as expected. Standby Gas Treatment System Trains A, B, and C and Control Room Emergency Ventilation System Train A automatically started as expected. The immediate cause of this event was the failure of the 480V Shutdown Board 3B alternate feeder breaker position switch to close. A mispositioned wire interfered with the proper operation of the switch close contacts. The most probable root cause of the. wire being mispositioned, was improper wire routing and/or improper removal or installation of the switch cover which caused the wire to interfere with the switch contacts. Corrective actions include continuity testing and visual inspections on additional breaker position switches to verify proper switch operation, and revision of the maintenance instruction(s) applicable to GE type SB-1 switches to include appropriate wire routing guidance.

TVA is submitting this report pursuant to 10 CFR 50.73(a)(2)(iv) as an event or condition that resulted in a manual or automatic actuation of any engineered safety feature.

9804i50349 980409 PDR ADQCK OSQ00296 8 PDR ten~ rvnIYI ooo I4.Vol

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NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION I4-96)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME 1 DOCKET LER NUMBER 6 PAGE 3 YEAR SEQUENTIAL REVISION NUMBER 2OF5 Btowns Ferry Unit 3 05000296 1998 002 00 TEXT fifmore space is required, use additional copies of NRC Form 366AI (17)

I. PLANT CONDITIONS At the time the event occurred, Units 2 and 3 were in the Run Mode at 100 percent power. Unit 1 was shutdown Bnd defueled.

11 ~ DESCRIPTION OF EVENT A. Event:

On March 10, 1998 surveillance instruction (Sl) 3-SI-4.9.A.4.b(ll), 4KV Shutdown Board Undervoltage Start of Diesel Generator Division II Test, was in progress. This test is performed to verify that an undervoltage condition on a 4KV Shutdown Board [ED) will start the associated diesel as required by Technical Specification Section 4.9.A.4.b. Prior to establishing an undervoltage condition on 4KV Shutdown Board 3EC, the Sl provides for the transfer of loads normally supplied by the 4KV Shutdown Board to an alternate power supply to minimize the impact of the test on plant operations.

At approximately 1059 hours0.0123 days 0.294 hours 0.00175 weeks 4.029495e-4 months operations personnel attempted to manually transfer 480V Shutdown Board 3B to its alternate supply in accordance with normal operating procedures. During the performance of the board transfer, the 480V Shutdown Board 3B alternate feeder breaker did not close as expected. The normal feeder breaker was immediately reclosed. This resulted in the momentary de-energization of 480V Shutdown Board 3B and all of its associated loads, including Reactor Protection System (RPS)[JC] motor-generator set 3B. Upon the'loss of power to RPS bus 3B, Unit 3 received a RPS half-scram and Primary Containment Isolation System (PCIS)[JM) groups 2, 3, 6 and 8 isolated as expected. Standby Gas Treatment System [BH) Trains A, B, and C and Control Room Emergency Ventilation System [Vl] Train A automatically started as expected. Operations personnel immediately recognized the failure of the 480V Shutdown Board to transfer as the cause of the engineered safety features actuation. Operator response to the event proceeded in accordance with the plant abnormal operating instruction for loss of one RPS bus. Recovery from the event was completed at 1300 hours0.015 days 0.361 hours 0.00215 weeks 4.9465e-4 months when all components were returned to the state which existed prior to the beginning of the Sl.

On March 10, 1998, at 1348 hours0.0156 days 0.374 hours 0.00223 weeks 5.12914e-4 months (CST), TVA made a four-hour non-emergency notification to the NRC via the Emergency Notification System pursuant to 10 CFR 50.72(b)(2)(ii).

This report is submitted pursuant to 10 CFR 50.73(a)(2)(iv) as an event or condition which resulted in a manual or automatic actuation of any engineered safety feature.

B. Ino erable Structures Com onents or S stems that Contributed to the Event:

None.

C. Dates and A roximate Times of Ma or Occurrences:

May 10, 1998 1059 hours0.0123 days 0.294 hours 0.00175 weeks 4.029495e-4 months CST While performing a transfer of 480V Shutdown Board 3B to its alternate supply, the alternate feeder breaker fails to close. The deenergization of 480V Shutdown Board 3B results in a loss of power to RPS bus 3B.

NRC FORM 366 I4ISEI

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NRC FORM 366A U.s. NUCLEAR REGULATORY COMMISSION I4-SS) s LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME 1 DOCKET LER NUMBER 6 PAGE 3 YEAR SEQUENTIAL REVISION NUMBER 3 OF 5 Browns Ferry Unit 3 05000296 1998 002 00 TEXT (Il more space is required, use addirional copies of hfRC Form 366A/ I17I C. Dates and A roximate Times of Ma or Occurrences continued:

PCIS Groups 2, 3, 6 and 8 isolate as expected and SBGT Trains A,

-B, and C and CREV Train A autostart.

March 10, 1998 1300 hours0.015 days 0.361 hours 0.00215 weeks 4.9465e-4 months CST. Recovery from the event is completed. All components were returned to their pre-event status.

March 10, 1998 1348 hours0.0156 days 0.374 hours 0.00223 weeks 5.12914e-4 months CST A four-hour non-emergency report is made to the NRC pursuant to 10 CFR 50.72(b)(2)(ii) .

D. Other S stems or Seconda Functions Affected:

None.

E. Method of Discove Loss of RPS B was received in the Unit 3 control room at 1059 hours0.0123 days 0.294 hours 0.00175 weeks 4.029495e-4 months CST.

F. O erator Actions:

.No operator actions contributed to occurrence of this'event. Operator actions in response to the event were proper and in accordance with plant instructions.

G. Safet .S stem Res onse:

All safety systems responded as expected.

III. CAUSE OF, THE EVENT A. Immediate Cause:

The immediate cause of this event was the failure of the 480V Shutdown Board 3B alternate feeder breaker position switch to close. A mispositioned wire interfered with the proper operation of the switch close contacts; B. Root Cause 'e The most probable root cause of the wire being mispositioned, was improper wire routing and/or improper removal or installation of the switch cover which caused the wire to interfere with the contacts.

C. Contributin Factors:

None.

'NRC FORM 366 I4-95)

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NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-96]

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME 1 DOCKET LER NUMBER 6 PAGE 3 YEAR SEQUENTIAL REVISION NUMBER 4OF5 Browns Ferry Unit. 3 05000296 1998 002 00 TEXT llfmore space is required, use additional copies of NRC Form 366A/ (17I IV. ANALYSIS OF THE EVENT The event was uncomplicated operationally. The half-scram event occurred on Unit 3 and involved the Unit 3 RPS bus 3B. A full scram was not initiated because RPS bus 3A remained energized throughout the event. The only.

impact of this event on Units 1 and 2 were Refuel Zone isolations and the autostart of the SGT and CREV systems which are the expected responses to the loss of RPS bus 3B. Operations personnel immediately recognized the cause of the.ESF actuation and took appropriate actions in accordance with plant procedures. Proper communications and coordination took place between the Operations personnel in the Units 1, 2, and 3 control rooms.

All initiations and actuations/isolations were consistent with and to be expected with the loss of RPS bus 3B.

V. ASSESSMENT OF THE SAFETY CONSEQUENCES There were no actual or potential safety consequences associated with this event. The 480V Shutdown Board alternate feeder breaker position switch which failed does not perform a safety function. The failure of this switch would not have prevented the 480V Shutdown Board from performing its safety function. This event did not adversely affect the safety of plant personnel or the public.

VI. CORRECTIVE ACTIONS A. Immediate Corrective Actions:

The wiring interference with the 480V Shutdown Board 3B alternate feeder breaker, position switch was corrected and proper operation of the switch was verified.

B. Corrective Actions to Prevent Recurrence:

Continuity testing and visual inspections will be performed on a sample of breaker position switches on the remaining 480V Shutdown Boards to verify proper breaker position switch operation. Testing and inspections of additional switches may be performed based on the sample results.'he maintenance instruction(s) applicable to GE type SB-1 switches will be revised to ensure appropriate wire routing guidance is incorporated.

VII ADDITIONALINFORMATION

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A. Failed Com onents:

Troubleshooting revealed that a wire was interfering with the proper operation of the alternate feeder breaker position switch closing contacts. The switch is a General Electric (GE) [G080] control and instrument switch, type SB-1. The type SB-1 switches are multi-stage rotary switches with cam-operated contacts. Each stage consists of a insulating barrier carrying one or two moving contacts and two or three cams on the operating shaft which move the contacts. The switch is provided with a protective cover which is removable for access to the switch terminals and contacts.

'TVA does not consider these corrective actions regulatory commitments. The completion of these items will be tracked in TVA's Corrective Action Pro ram.

NRc FQRM 366 I4-95I

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NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-9SI LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME 1 DOCKET LER NUMBER 6 PAGE 3 YEAR SEQUENTIAL REVISIOI4 NUMBER 5OF5 Browns Ferry Unit 3 05000296 1998 002 00 TEXT fffmore spece is required, use edditionel copies of NRC Form 366A/ (17)

A. Failed Com onents continued:

Inspection of switch revealed a wire which was landed on the ¹2C switch terminal was in close proximity to the ¹2 moveable contact. The moveable contact was observed to move the wire out of the way when the switch was operated with the cover removed. However, with the cover installed sufficient interference was present to prevent contact closure. No maintenance or modification history was discovered relevant to condition of the switch. It was concluded that the most probable root cause of the event was improper wire routing and/or removal or replacement of the switch cover which caused the wire to interfere with the contacts. The absence of maintenance or modification history prevented the evaluation of human performance issues.

Figure 1:shows the, wire impact point with moveable contact ¹2.

B. Previous Similar Events:

No previous LERs have resulted from GE type SB-1 switch failures at Browns Ferry.

VIII. COMMITMENTS None.

Figure 1 Wire Interference With Alternate Feeder Breaker Position Switch Moveable Contact

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