ML18039A310

LER 98-001-00:on 980308,ESF Actuations Occurred When 2B RPS Bus Was Transferred to de-energized Source.Caused by Failure of Preparing Clearance to Exercise Proper Attention. 2B RPS Bus Restored to Transformer Source

ML18039A310
Person / Time
Site:	Browns Ferry
Issue date:	04/07/1998
From:	Root C TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML18039A309	List: ML18039A308 ML18039A310
References
LER-98-001-02, LER-98-1-2, NUDOCS 9804140094
Download: ML18039A310 (8)

Text

NRC FORM 366 U.s. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 (4-96) EXPIRES 04/30IQ 8 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY INFORMATION COLLEC'TION REGUESTI 50.0 HRS. REPORTED LESSONS LlCENSEE EVENT REPORT (LER) LEARNED ARE INCORPORATED INTO THE'CENSING PROCESS AND FED BACK TO INDUSTRY FORWARD COMMENTS REGARDINO BVROEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (T.d F33), U.S.

(See reverse for required number of NUCLEAR REGULATORY COMMISSION, WASHINGTON, OC 205554)001, AND TO THE PAPFRWORK REDUCTION PROJECT (3150%104), OFFICE OF digits/characters for each block) MANAGEMENTAND BVDGET. WASHINGTON, DC 20503.

FACIUTY NAME (1) DOCKET NVMSER (2) PAGE (3)

Browns Ferry Nuclear (BFN) Plant Unit 2 05000260 1OF4 TITLE(4) Engineered safety feature (ESF) actuations when the 2B reactor protection system bus was transferred to a de-energized source because of inattention-to-detail in the preparation of a clearance EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR SEOVENTIAL REVISION MONTH DAY YEAR FACIUTY NAME DOCKET NUMBER NUMBER NUMBER 03 08 1998 1998 001 00 04 07 1998 OPERATING THIS REPORT IS SUBMITTED PURSUAN T TO THE REOUIREMENTS OF 10 CFR II: (Check ono or more MODE (el N . 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) (il 20.2203(a)(3) (iil 50.73(a)(2)(iii) 73.71 20.2203(al(2)(ii) 20.2203(a)(4) 50.73(a) (2) (iv) OTHER 20.2203(a)(2)(iii) 50.36(c)(1) 50.73(a) (2) (v) Specify (n Abstract be)ow 20.2203(a) (2)(iv) 50. 3 6(c)(2) 50.73(a) (2) (vii) or (n NRC Fo(m 366A LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER (Inc(udo Area Code)

Clarence M. Root, Industry Affairs Specialist (205) 729-7547 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TO CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE NPRDS TO NPRDS N/A N/A SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH OAY YEAR YES X NO SUBMISSION DATE (15)

(If yes, complete EXPECTED SUBMISSION DATE).

ABSTRACT (Limit to 1400 spaces, i.e., approximately I 5 single. spaced typewritten lines) (16)

On March 8, 1998, at 2056 Central Standard Time (CST), with Unit 2 and Unit 3 operating at 100 percent power and Unit 1 shutdown and defueled, Unit 2 received a channel 2B reactor protection system (RPS) half-scram, primary containment isolation systems groups 2, 3, 6 and 8.isolations, initiation of the standby gas treatment system and initiation of control room emergency ventilation train A because power was lost to RPS bus 2B. The RPS bus was de-energized when Assistant Unit Operators placing a clearance to support work on the RPS motor generator set, placed the NORMAL/ALTERNATEcontrol switch to the NORMAL position as specified on the clearance sheet. The normal source of power to the RPS bus was not available because the 2B RPS motor-generator set had been removed from service for its semi-annual inspection and preventive maintenance. The root cause of this event was the failure of the Shift Support Tagging (SST) Unit Operator (UO) preparing the clearance to exercise, proper attention to detail to ensure the tagged position for the 2B RPS NORMAL/ALTERNATEswitch was listed as ALTERNATE on the clearance component position sheet.

Appropriate personnel corrective actions have been taken with the SST UO who prepared the clearance and with the Shift Support Supervisor (SSS) for his failure to properly verify that the switch position was correct. Also, for a six-week period, a second SST UO will be required to review any clearance written by the SST UO involved in this event, prior to his presenting the clearance to the SSS for review. This report is submitted in accordance with 10 CFR 50.73(a)(2)(iv) as an event or condition that resulted in an automatic actuation of an engineered safety feature.

LER 296/95004 involved loss of an RPS bus when a 480 volt shutdown board was transferred to a de-energized alternate supply.

9804i40094 '))80407 050002(5)0 PDR ADQCK S PDR

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMiSSioN APPROVED BY OMB NO. 3150-0104 (4.95) EXPIRES 04/30/98 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY INFORMATION COLLECTION AEOVESTI 60 0 HAS. REPORTED LESSONS LICENSEE EVENT REPORT (LER) LEARNED ARE INCORPORATED INTO THE UCENSINO PROCESS AND FED SACK TO INDUSTRY FORWARD COMMENTS REOARDINO BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT SRANCH IT.S F33I, U.S.

(See reverse for required number of NUCLEAR REOVLATORY COMMISSION, WASHINOTON. DC 2066641001. AND digits/characters for each block) TO THE PAPEAWORK REDUCTION PROJECT 131SO<104L OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON. DC 20603.

FACIUTY NAME ill DOCKET NVMSER 121 PAOE l3)

Browns Ferry Nuclear (BFN) Plant Unit 2 05000260 2.OF 4 PLANT CONDITION(S)

At the time this event occurred, Unit 2 and Unit 3 were operating at 100 percent power. Unit 1 was shutdown and defueled.

DESCRIPTION OF EVENT A. Event:

On March 8, 1998, at 2056 hours0.0238 days <br />0.571 hours <br />0.0034 weeks <br />7.82308e-4 months <br /> Central Standard Time (CST), Unit 2 received a channel 28 reactor protection system (RPS) [JC] half-scram when power was lost to the 28 RPS bus. The loss of power resulted in primary containment isolation system (PCIS) [JM] groups 2, 3, 6, and 8 isolations, initiation. of all three trains of the standby gas treatment (SG I) system [BH], and initiation of control room emergency.

ventilation (CREV) system [VI ] train A.

Prior to the event, the 28 RPS bus had been transferred to its alternate source of power. by the Unit Supervisor [utility, licensed), and the 28 RPS Motor Generator (MG) set removed from service for its semi-annual inspection and preventive maintenance. The Shift Support Tagging (SST) Unit Operator (UO)

[utility,.licensed] prepared a clearance to support work on the 28 RPS MG set, listing the tagged position on the clearance component position sheet. for the bus NORMAUALTERNATEcontrol switch as NORMAL, instead of ALTERNATE. The Shift Support Supervisor (SSS) [utility, nonlicensed] reviewing the clearance

.failed to identify that the 28 RPS MG set was being tagged and that the NORMAUALTERNATEcontrol switch should be listed as ALTERNATE. While the Assistant Unit Operators (AUOs) [utility, nonlicensed]

were'placing the clearance to support work on the 28 RPS MG set, they placed the bus NORMAL/ALTERNATEcontrol switch to NORMAL, the position specified on the clearance sheet. This action caused the 28 RPS bus to be transferred to the de-energized normal source and resulted in the half-scram,.PCIS isolations, and the SGT system and CREV initiation signals. The affected systems were restored to normal within 25 minutes.

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

None C. Dates and A roximate Times of Ma or Occurrences:

March 8, 1998 2008 hours0.0232 days <br />0.558 hours <br />0.00332 weeks <br />7.64044e-4 months <br />, CST Operations held a pre-job briefing for the pending transfer of the 28 RPS bus from NORMALto ALTERNATE in accordance with the operating instruction.

2022 hours0.0234 days <br />0.562 hours <br />0.00334 weeks <br />7.69371e-4 months <br />, CST Operations transferred the 28 RPS bus from its NORMAL to its ALTERNATE source and shutdown the 28 RPS MG set.

2040 hours0.0236 days <br />0.567 hours <br />0.00337 weeks <br />7.7622e-4 months <br />, CST The Unit Supervisor authorized placement of a clearance on 28 RPS MG set for semi-annual inspection and preventive maintenance.

2056 hours0.0238 days <br />0.571 hours <br />0.0034 weeks <br />7.82308e-4 months <br />, CST Received a 28 RPS half-scram and associated isolations; SGT and CREV systems initiated.

NRC FORM 366 (4-95I

lb wt

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4.95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME 1I DOCKET LER NUMBER 6 PAGE 3 YEAR SEQUENTIAL REVISION NUMBER 3 OF 4 Browns Ferry Nuclear (BFN) Plant Unit 2 05000260 199 - 001 - 00 8

TEXT (ll more spaceis required, use addidonal copies ol NRC Form 366A/ I17I 2105 hours0.0244 days <br />0.585 hours <br />0.00348 weeks <br />8.009525e-4 months <br />, CST AUOs reported to the control room that they had placed the 28 RPS NORMAL/ALTERNATEcontrol switch to the NORMAL position, causing the loss of the 28 RPS bus.

2111 hours0.0244 days <br />0.586 hours <br />0.00349 weeks <br />8.032355e-4 months <br />, CST A Unit Supervisor restored the 28 RPS'bus to its transformer source.

2121 hours0.0245 days <br />0.589 hours <br />0.00351 weeks <br />8.070405e-4 months <br />, CST All systems returned to normal.

2314 hours0.0268 days <br />0.643 hours <br />0.00383 weeks <br />8.80477e-4 months <br />, CST Made a 4-hour report to the NRC in accordance with 10CFR50.72.(b).2.ii D. Other S stems or Seconda Functions Affected:

None.

E. Method of Discove This condition was discovered when the unit 2 control room received a half scram on the 28 RPS bus and associated ESF actuations.

F. 0 erators Actions:

The 28 RPS bus was restored and the systems were returned to normal.

G. Safet S stem Res onse:

All safety systems operated as expected in response to this event.

III. CAUSE OF THE EVENT A. Immediate Cause:

The immediate cause of this event was loss of the 28 RPS bus when the 28 RPS bus NORMAL/ALTERNATEswitch was placed to the NORMAL position.

B. Root Cause:

The root cause of this event was the failure of the SST UO [utility, licensed] preparing the clearance to exercise proper attention to detail to ensure the tagged position for the 28 RPS NORMAL/ALTERNATE switch was listed as ALTERNATE on the clearance component position sheet.

C. Contributin Factors:

The SSS (utility, nonlicensed] reviewing the clearance failed to identify that the 28 RPS MG set was being tagged and that the NORMAL/ALTERNATEswitch position should be listed as ALTERNATE.

IV. ANALYSIS OF THE EVENT This half-scram event occurred on Unit 2 and involved the Unit 2 RPS bus "B." Effects on Unit's 1 and 3 were limited to the start of SGT, CREV initiation, and the isolation and tri in of the res ective unit's Refuel Zone NRC FORM 366 I4-95I

1i NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION I4 95I LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME 1 OOCKET LER NUMBER 6 PAGE 3 YEAR SEQUENTIAL REVISION NUMBER 4OF4 Browns Ferry Nuclear (BFN),Plant Unit 2 05000260 199 - 001 - 00 8

TEXT (If more spaceis required, use addirional copies of NRC Form 366A/ I17)

Ventilation. The systems affected during this event are designed to shut down the reactor, contain and process, any radioactive releases, and to fulfilltheir safety functions upon loss of initiation logic power. A full scram was not initiated because RPS,bus 2A remained energized during the event. The systems responded correctly to the loss of power to the 28 RPS bus and, therefore, plant safety was not adversely affected. All initiations and isolations/actuations were consistent with, and to be expected with the loss of the 28 RPS bus.

All systems were subsequently restored and this event did not affect the health and safety of plant personnel or the public.

V. CORRECTIVE ACTIONS A. Immediate Corrective Actions:

The 28 RPS bus was restored to its transformer source and Unit 1, 2, and 3 systems affected by the loss of the bus were returned to normal.

B. Corrective Actions to Prevent Recurrence:

Appropriate personnel corrective actions have been taken with the SST UO who prepared the clearance and with the SSS for his failure to properly verify that the switch position was correct. For a six-week period, a second SST UO will be required to review any clearance written by the SST UO involved in this event, prior to his presenting the clearance to the SSS for review.'I.

ADDITIONALINFORMATION A. Failed Com onents:

None.

B. Previous Similar Events:

LER 296/95004 was similar because ESF actuations occurred from a loss of power to RPS bus 3A when a 480 volt shutdown board was transferred to a de-energized alternate supply. This event was caused by personnel error in that the licensed operator did not transfer the board in accordance with procedural requirements.

ln the'event described in this LER,'the 28 RPS bus had already been transferred to its alternate supply and the NORMAL/ALTERNATEcontrol switch placed in the ALTERNATE position. The AUOs were tagging equipment as specified on the clearance component position sheet. However, the position of the 28 RPS bus NORMAL/ALTERNATEcontrol switch was incorrectly listed as NORMALon the clearance sheet. When the AUOs transferred the switch to the specified NORMAL position, a loss of power to the RPS bus occurred. This event was not the result of a failure to follow procedure, and the corrective actions taken for LER 296/95004 would not have precluded this event.

Vll. COMMITMENTS None.

'VAdoes not consider these corrective actions regulatory commitments. TVA's Corrective Action Program. will track corn letion of these actions.

NRC FORM 366 I4-65I

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