ML18036B356

LER 93-008-00:on 930616,turbine Stop Valve Limit Switch Malfunctioned & Failed to Deenergize Associated RPS Relays Due to Personnel Error.Work Order Initiated to Repair Limit Switch to Allow Reperformance of SI.W/930715 Ltr

ML18036B356
Person / Time
Site:	Browns Ferry
Issue date:	07/15/1993
From:	Jay Wallace, Zerigue O TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-008-01, LER-93-8-1, NUDOCS 9307220316
Download: ML18036B356 (18)

Text

ACCEI.ERATQD DOCUMENT DISTRIBUTION SYSTEM REGULA~I INFORMATION DISTRIBUTIOQ3YSTEM (RIDE)

ACCESSION NBR:9307220316 DOC.DATE: 93/07/15 NOTARIZED: NO DOCKET ¹ FACIL:50-260 Browns Ferry Nuclear Power Station, Unit 2, Tennessee 05000260 AUTH. NAME AUTHOR AFFILIATION WALLACE,J.E. Tennessee Valley Authority ZERIGUE,O.J. Tennessee Valley Authority RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 93-008-00:on 930616,turbine stop valve limit switch malfunctioned' failed to deenergized its associated RPS relays due to personnel error. Initiated work order to repair DISTRIBUTION CODE: IE22T COPIES RECEIVED'LTR l limit switch to allow reperformance of SI.W/930715 ltr.

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

NOTES:

ENCL 2 SIZE: 8 RECIPIENT COPIES RECIPIENT COPIES ID'CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-4 1 1 PD2-4-PD 1 1 ROSS,T. 1 1 INTERNAL: ACNW 2 2 ,ACRS 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DE/EELB 1 1 NRR/DE/EMEB 1 1 NRR/DORS/OEAB 1 1 NRR/DRCH/HHFB 1 1 NRR/DRCH/HICB 1 1 NRR/DRCH/HOLB 1 1 NRR/DRIL/RPEB 1 1 NRR/DRSS/PRPB 2 2 NRR DSSA/SPLB 1 1 NRR/DSSA/SRXB 1 1 @G E 02 1 1 RES/DSIR/EIB 1 1 RGN2 FILE 01 1 1 EXTERNAL: EG&G BRYCEFJ.H'RC 2 2 L ST LOBBY WARD 1 1 PDR 1 1 NSIC MURPHYFG.A 1 1 NSIC POORE,W. 1 1 NUDOCS FULL TXT 1 1 NOTE TO ALL"RIDS" RECIPIENTS:

DESK.

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL ROOM Pi-37 {EXT. 504-2065) TO ELIMINATE YOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 32 ENCL 32

Ii II Tennessee Vattey AutnorrtyPost Office Box 2000. Decatur, Alabama 35609.20CO O. J, "Ike" Zeringue Vice PresiCent. Browns Ferry Nuclear Plant JUL 15 t9m U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555

Dear Sir:

TVA' BROWNS FERRY NUCLEAR PLANT (BFN) UNITS 1, 2, AND 3 DOCKET NOS. 50-259~

260, AND 296 FACILITY OPERATING LICENSE DPR-33, 52, AND 68 LICENSEE EVENT REPORT 50-260/93008 The enclosed report provides details, concerning an event that resulted in a condition prohibited by technical specifications (TS). This event was a result of personnel error in that an individual did not determine that a failed component affected a second trip system that was required by TS.

This report is submitted in accordance with 10 CFR 50.73(a)(2)(i)(B).

Sincerely,

~'Z<<>4(~

0 J. Zeringue Enclosure cc: See page 2 oooo>>

93072203i6 9307is PDR ADOCK 05000260 8 PDR

II U.S'. Huclear Regulatory Commission JUL i5 1993 cc (Bnclosure):

IHPO Records Center Suite 1500 1100 Circle 75 Parkway Atlanta, Georgia 30339 Paul Krippner American Nuclear Insurers Town Center, Suite 300S 29 South Main Street West Hartford, Connecticut 06107 HRC Resident Inspector Browns Ferry Nuclear Plant Route 12, P;0. Box 637 Athens, Alabama 35609-2000 Regional Administrator U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, Suite 2900.

Atlanta, Georgia 30323 Thierry M. Ross U.S. Huclear Regulatory Commission One White Flint, Horth 11555 Rockville Pike Rockville, Maryland 20852

NRC (6-09)

Form 366 FACILITY NAHE (1) i NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

Approved OHB No. 3150-0104 Expires 4/30/92 IDOCKET NUMBER (2) I~P ~~

r w F r N 1 r n BFN TITLE (4) LCO For A Turbine Stop Valve Was Exceeded Due To Personnel .Error Resulting In A Condition Prohibited T

V NT DAY P T I 1

'I I I SE()UENTIAL I I REVISIONI' I I FACILITY NAMES iDOCKET NUMBER(S)

NTH 0 Y A N H T D I I I I I I I I

1 I I I 071 593I OPERATING I ITHIS REPORT IS SUBMITTED PURSUANT TO THE RE()UIREHENTS OF 10 CFR 5:

MODE h k n rmr f 1 w' F20.402(b) I I20 405(c) ) (50.73(a)(2)(iv) (73.71(b)

POWER I I [20.405(a)( l)(i) I I50 36(c)( 1) ) (50.73(a)(2)(v) l73 71(c)

LEVEL 'I (20.405(a)( l)(ii) I I50 36(c)(2) '( )50.73(a)(2)(vii) )OTHER (Specify in 1 ]20.405(a)( l)(iii) IWI50 73(a)(2)(i)(B)( (50.73(a)(2)(viii)(A) Abstract below and in (20.405(a)( l)(iv) I I50 ~ 73(a)(2)(ii) ) (50.73(a)(2)(viii)(B) Text, NRC Form 366A)

.4 1 v I N NT T NAME I AREA CODE I Ww 1 mli n i r H T N I P NNT FAI P R I I I IREPORTABLEI I I I I IREPORTABLEI Y T H HP N T HAN F T NPRD R T P D I I I I I I I I I I I I I I I I I PP HN P TD 14 I I SUBMISSION I I I Y f 0 0 T ABSTRACT (Limit to 1400 spaces, i.e., approximately fifteen single-space typewritten lines) (16)

On June 16, 1993, at 0637 hours0.00737 days <br />0.177 hours <br />0.00105 weeks <br />2.423785e-4 months <br />, during the performance of a functional test for the Nl turbine stop ~al~e closure for the reactor protection system (RPS) trip, an anticipated half scram signal was not received when the valve was closed to approximately 90 percent of full open. Operations personnel removed the fuse to the Bl trip relays. However, Operations personnel did not remove the fuse to the Al trip relay within one hour as required by technical specification. Theprohibited event is reportable in accordance with 10 OFR 50.73(a)(2)(i)(B) as a condition by, TS.

The root cause for this event was determined to be personnel error for failing to remove fuses for Al and Bl RPS relays within the time requirement specified in TS.

Namely, Operations personnel did not realize that the limit switch also affected the Al trip circuit.

A work request to repair the turbine stop valve's limit switch was initiated by a unit operator. Operations personnel removed a fuse to simulate the condition that the valve was closed. Upon further review, Operations personnel concluded that the broken component, also affected the Al RPS trip system and removed the Al trip system relay fuse- Operations personnel will be required to read this event to ensure a heightened awareness to this unique plant condition. The turbine stop valve and main steam isolation valve divisional surveillance instructions will be revised to include checks of the relays not being tested in the other RPS, division.

NRC Form 366(6-89)

0 II Il

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

TEXT CONTINUATION FACILITY NAME (1) IDOCKET NUMBER (2)

I I I ISEQUENTIAL f /REVISIONI I I I I Browns Ferry Unit 2 I A I I I I TEXT (If more space is required, use additional NRC Form 366A's) ( 17)

I. PLANT CONDITIONS Unit 2 was at approximately 70 percent power (2290 MWT) after a refueling outage. Units 1 and 3 were shutdown and defueled.

II. DESCRIPTION OF EVENT A. ~t:

On June 16, 1993, at 0637 hours0.00737 days <br />0.177 hours <br />0.00105 weeks <br />2.423785e-4 months <br /> during the functional test, the 81 turbine stop valve [V] of the reactor protection system (RPS) [JC] was closed to approximately 90 percent of full open. This closure should have initiated a turbine stop valve closure half scram with annunciation in the Control Room; however, the anticipated half scram signal was not received. A unit operator [utility, licensed] noted the test discrepancy and initiated a work request. It was found that the Nl turbine stop valve limit switch malfunctioned and failed to deenergize its associated RPS relays. At 0710 hours0.00822 days <br />0.197 hours <br />0.00117 weeks <br />2.70155e-4 months <br />, Operations personnel [utility, licensed] determined that an limiting condition for operations (LCOi) for Technical Specification 3.1.A was entered which requires a minimum number of instrument channels that must be operable for MODE OF OPERATIONS when fuel is in the vessel.

Operations personnel removed the fuse [FU] to the Bl trip relays [RLY]

which in the opinion of Shift Operations Supervisor [utility, licensed],

satisfied the TS LCO. However, it was not recognized that removal of the fuse to the Al trip relay was also required to satisfy the TS LCO.

At approximately 0740 hours0.00856 days <br />0.206 hours <br />0.00122 weeks <br />2.8157e-4 months <br />, an NRC Inspector asked an Assistant Shift Operations Supervisor (ASOS) [utility, licensed] to confirm what corrective actions were taken in regards to the Nl turbine stop valve limit switch problem. While explaining the corrective actions taken at 0710 hours0.00822 days <br />0.197 hours <br />0.00117 weeks <br />2.70155e-4 months <br />, the ASOS identified that the limit switch [SW] also affected the Al RPS relay and that additional corrective actions were required. At 0832 hours0.00963 days <br />0.231 hours <br />0.00138 weeks <br />3.16576e-4 months <br />, the fuse for the Al relay was removed. Thus, the LCO for TS 3.1.A was exceeded for approximately one hour.

This event is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by TS.

NRC Form 366(6-89)

II 0 NRC Form 366A U.. NUCLEAR REGULATORY COMMISSION Approved OMB No. 3150-0104 (6-89) Expires 4/30/92 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) IOOCKET NUMBER (2)

I I I ISEQUENTIAL I IREVISIONI I I I I Browns Ferry Uni t 2 I I I I I F

TEXT (If more space is 'required, use additional NRC Form 366A's) (17) t t t t t t The limit switch for lever the return tl turbine stop valve was disassembled. A piece spring was found lodged in 'the switch that of the switch prevented internal movement of the switch. In addition,. the limit switch was calibrated on May 19, 1993, and was functionally tested on May 24, 1993, without any problems.

C. t June 16, 1993 at 0637 CDT During a functional test, an anticipated half scram was not received.

June 16, 1993 at 0710 CDT Operations personnel determined that an LCO was entered and removed a fuse to deenergize the RPS Bl relays.

June 16, 1993 at 0832 CDT Operations personnel removed another fuse for RPS Al relay.

The LCO was exited.

June 17, 1993 at 0620 CDT The repair of the limit switch was completed and the functional test was performed successfully.

D. the None.

E. Mt While confirming to an NRC Inspector what corrective actions were taken for the failure of the fkl'urbine stop valve limit switch. The Unit 2 ASOS identified that the 81 turbine stop valve limit switch also had an input to the Division I RPS relays and that additional corrective actions were required.

NRC Form 366(6-89)

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

TEXT CONTINUATION FACILITY NAHE (1) IDOCKET NUHBER (2)

I I I I SEQUENTIAL I I REVISIONI I I I I Browns Ferry Unit 2 -.I I I I I TEXT (If more space is required, use additional NRC Form 366A's) (17) t t When Operations personnel were notified by a unit operator that the limit switch would not open, Operations personnel removed the fuse for the Bl RPS relays. When the ASOS discovered that the Al RPS relay was also affected, the Al RPS relay fuse was removed.

G. t t None.

III. CAUSE OF THE EVENT The immediate cause for the event was the failure to remove both the fuse for the Nl RPS relays and the fuse for the Al relay within the one-hour time requirement specified in TS.

B. ~R~t The root cause for this event was determined to be personnel error for failing to deenergize the entire trip system within the one-hour time requirement. Operations personnel did not realize that the broken limit switch affected Bl and Al RPS relays.

C. t t n t A contributing factor was that operators did not generally understand that the 81 turbine stop valve limit switch provided an input to both RPS channels. At the time of the event, only RPS Division II was being tested and believing that this division. was the only division affected, Operations personnel failed to adequately research the affects of this limit switch failure on RPS Division I. It should be noted that main this unique configuration exists for the turbine stop valves and the steam isolation valves (MSIV).

NRC Form 366(6-89)

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

TEXT CONTINUATION FACILITY NAHE (1) (DOCKET NUHBER (2)

I I I ISEQUENTIAL 'I IREVISIONI I I I I Browns Ferry Unit 2 I Y A I I I I TEXT (If more space is required, use additional NRC Form 366A's) (17)

IV. ANALYSIS OF THE EVENT Each of the four turbine stop valves is equipped with position switches which provide a valve closed signal to the RPS logic. Closure of any combination of three stop valves will cause a full scram in all cases. Therefore, the lodging of the piece of the switch lever return spring which prevented the movement of the position switches would not have affected the closure of tl turbine stop valve. At full power operations and with the generator tied to the grid, the only logic input that will close the turbine stop valves is a turbine trip. If a turbine trip were to occur, the demand for all valves to go closed would be signaled and the four turbine stop valve would close. In addition, the turbine control valves would close and also initiate an RPS scram on all channels. This scram in effect would over ride the absence of the turbine stop valve channel Bl input. Therefore, a full scram would occur and not adversely affect the health and safety of the public.

V. CORRECTIVE ACTIONS e t tv t When Operations personnel were notified by a unit'perator that the limit switch would not open, Operations personnel removed the fuse for the Bl RPS'elays. When the ASOS discovered that the Al RPS relay was also affected, the Al RPS relay fuse was removed. The unit operator initiated a work order to repair the limit switch to allow the reperformance of the SI.

tv t t t Operators will be required to read this event to ensure a heightened awareness to this unique plant condition. 'Operations incorporated a description of this event into the night orders. The Operations individual who misevaluated the consequences of the broken component was counseled. The turbine stop valve and main steam isolation valve divisional SIs will be revised to include checks of the relays not being tested in the other RPS division.

These corrective actions should preclude recurrence.

NRC Form 366(6-89)

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

TEXT CONTINUATION FACILITY NANE (1) /DOCKET NUNBER (2)

I I I I SEQUENTIAL I I REVI S ION I I I I I Browns Ferry Unit 2 I I I I I TEXT (If more space is required,, use additional NRC Form 366A's) (17)

VI. ADDITIONAL INFORMTION A.

NAAMCO Model D2400Z Snap Lock Limit Switch.

TVA reviewed previous LER reports to determine if similar past events have occurred and if so, why corrective actions had been unsuccessful in preventing this event.

Previous LERs have been issued as a result of exceeding LCO time limit.

However, corrective actions taken in these previous events could not have prevented the June 16, 1993 event.

II. COMMITMENTS Operators will be required to read this event to ensure a heightened awareness to this unique plant condition. This review will be completed by September 14, 1993.

The turbine stop valve and main steam isolation valve divisional SIs will be revised to include checks of the relays not being tested in the other RPS division. This revision will be completed by August 31, 1993.

Energy Industry Identification System (EIIS) system and component codes are identified in the text with brackets (e.g., [XX]).

NRC Form 366(6-89)

~I Qi C