ML20029D815

LER 94-005-00:on 940403,inadvertent Fwis Occurred.Caused by Personnel Failure to Follow Work Document Instructions. Corrective Action:Individuals Were Counseled on Requirements to Follow Work Document Instruction steps.W/940503 Ltr

ML20029D815
Person / Time
Site:	Sequoyah
Issue date:	05/03/1994
From:	Bajraszewski J, Powers K TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-94-005, LER-94-5, NUDOCS 9405100139
Download: ML20029D815 (9)

Text

I

. r ,

s k

Tennessee vanev Autnanty, Post once 90,2000, sovity-omy. Tennessee 37379-2000 Ken Powers Vco Prescent. Sm.oyt Nxkrar Plant May 3, 1994 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Gentlemen:

TENNESSEE VALLEY AUTHORITY - SEQUOYAH NUCLEAR PLANT UNIT 1 - DOCKET NO. 50-327 - FACILITY OPERATING LICENSE DPR LICENSEE EVENT REPORT (LER) 50-327/94005 The enclosed LER provides details concerning inadvertent feedwater isolations that occurred during the preparation for unit start-up. These events are being reported in accordance with 10 CFR 50.73(a)(2)(iv) as automatic engineered safety feature actuations.

Sincerel ,

]

Ken Powers Enclosure i cc: See page 2 l

l i

i IC00'? 4 i S

9405100139 940503 g PDR ADOCK 05000327 PDR u S 4

U.S. Nuclear Regulatory Commission Page 2 May 3, 1994 cc (Enclosure):

INFO Records Center Institute of Nuclear Power Operations 700 Galleria Parkway Atlanta, Georgia 30339-5957 Mr. D. E. LaBarge, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 NRC Resident Inspector Sequoyah Nuclear Plant l 2600 Igou Ferry Road Soddy-Daisy, Tennessee 37379-3624 Regional Administrator i U.S. Nuclear Regulatory Commission l Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323-2711

NRC form 366 U.S. NUCLEAR REGULATORY COMMISSION Approved OMB No. 3150-0104 (5-92) Expires 5/31/95 LICENSEE EVENT REPORT (LER)

FACILI1Y NAME (1) lDOCKETNUMBER(2) l f.AGL13L

_Segqgy3h_Naglgar PlanilSQt{L_Unli 1 IQl5j0lalRj3JLlLlll0LLOL1 TITLE (4)

_1nadvertent fer.dwa.ter Isolations (FWIs) DRrlDS Er.tPAIAllon for Unit Start-ug

_EvfftT_ DAY (5) 1 LER HU!iBER (6) LR_f PQRT DATE (7) l OTHER FACILITIES INVQ1XLQ_13) l l l l l$EQUENTIALl l REVISION l l l l FACILITY NAMES lDOCKETNUMBER(S)

MQNlti[ DAY l YEA 8_jyJA.R_kj__NytiQER l [JVfLDELitmwLOALirIA8_I 10151010L1 II I l 1 LI l_I I l l I 1 014101319141914l l0l015l l 0 1 0 1 01 51 01 31 91 41 __10]1LQ10lallI OPERATING l lTHISREPORTISSUBMITTEDPURSUANTTOTHEREQUIREMENTSOf10CFR%:

MODE l l_[Chesk_Que_Qr_ mart _Qf thel 0llRwin9Mlli (9) l 31 l20.402(b) l_l20.405(c) lMl50.73(a)(2)(iv) l_l73.71(b)

POWER l L_l20.405(a)(1)(1) l_l50.36(c)(1) Ll50.73(a)(2)(v) l_l73.71(c)

LEVEL l l_l20.405(a)(1)(ii) l_l50.36(c)(2) l_]S0.73(a)(2)(vil) l_l0THER(Specifyin

__[10) 10 10 10_L_ l20.405( a)(1 )( l i i ) l_l50.73(a)(2)(i) l_l50.73(a)(2)(viii)(A) l Abstract below and in l_l20.405(a)(1)(iv) l_l50.73(a)(2)(li) l_l50.73(a)(2)(viii)(B) l Text, NRC form 366A)

L_lzoaasta)(1)(v) I istL22Laitziliii) I 15L231anzux) I LICENSEE CONTACT FOR THIS LER (12)

NAME l TELEPHONE _NVliHER lAREACODEl Alairanewski . Compliante_Lirensing LLLLLLLa_LLLLI - LLl_LL4J1 COMPLETE ON.LLlL4E FOR EACH COMPQNEtiLf.A11URLDESfRLSED_LN THIS REPORT (13) l l l l REPORTABLE l l l l l l REPORTABLE l C AUS E} $ Y S T E M I COMPQNENL} MANUF AC T URER L10_1EPRQS_L [CAustl31sIEt1LCOMPONENT lMANVfAClyRE8j_IQ_NERpll I I I I I I I I I I I X LAl A l BilLRLkWLlllLLI Y I I I 1 i i I L_L_1 I I I I I I l 1 l 1 l l 1 I l 11 I I I I l_j i I I I _1 11 I I 1_11 1 J l I l

_ SUP_P1E!1LNI ALREEDR13XELCIED _114 ) l LXPECTED lLiQN_TE LRALLY{AL

__ L__ l SUBMISSION l l l l YES (If ves. (pmplete EXPECTEDJURM1331(LN_DAIE) l X l N0 j DATE (15) L_L_LL_1 I ABSTRACT (Limit to 1400 spaces, i.e.. approximately fifteen single-space typewritten lines) (16)

On April 3, 1994, at 1024 and 1840 Eastern daylight time (EDT) and on April 9, 1994, at 0239 EDT with Unit 1 in hot standby (Mode 3), inadvertent FWIs occurred. The first event occurred during troubleshooting activities with the reactor trip breaker (RTB) auxiliary contacts as a result of personnel's failure to follow the work instruction.

The involved individuals were counseled on the requirements to follow work document instruction steps. The second event occurred upon closure of the RTBs in the preparation for rod-drop testing. The subsequent testing and inspection of the breaker did not confirm the root cause of the spurious WI. Test instrumentation data indicated that the signal may have been created by voltage spikes during movement of the auxiliary switch rotary contacts as the breaker traveled to the closed position. The third event occurred during observation of the RTB after one of the two RTBs failed to close. While explaining an observed difference between two breaker-locking levers, an individual inadvertently moved the locking lever on the closed breaker. This resulted in the breaker traveling to the open position and the initiation of an FWI. The cause of the event was personnel error. The appropriate disciplinary action was taken with the involved individual. Both RTBs were replaced. The replacement breakers were inspected, tested, and placed in service.

NRC Form 366(6-89)

I NRC Form 366A U.S. NUCLEsR REGULATORY COMMISSION Approved OMB No. 3150-0104 (5-92) Expires 5/31/95 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) lDOCKETNUMBER(2) l LER N1LMQER (6) l l PA$E (3) l l l l SEQUENTIAL l l REVISION l l l l l Sequoyah Nuclear Plant (SQN), Unit 1 l [YH Bj _j_j M ER l _lJiMEL1 l l l l

[QJ3]Q.l0LQ13 12 17 19_LLl--I O l 0 1 5 l-!_D I Ol_0]_Zj0Fl017 TEXT (If more space is required, use additional NRC Form 366A's) (17)

I. PLANT CONDITIONS Unit I was in hot standby, Mode 3, for the three events.

II. DESCRIPTION OF L.ENT A. Etents Event No. 1 On April 3, 1994, at 1024 Eastern daylight time (EDT), an inadvertent feedwater isolation (WI) occurred. The event occurred during the performance of troubleshooting activities associated with the reactor trip breaker (RTB) (EIIS Code AA) auxiliary contacts. During testing of the contacts for voltage and resistance, the mechanics connected the test equipment to the wrong set of contacts, resulting in the initiation of an FWI signal. The engineered safety feature actuation was discussed between the control room operators and the mechanics, and the control room operators determined that the actuation was addressed by work document precautionary notes. Because the potential for an WI actuation was identified in the work document, it was determined that the event was not required to be called in to NRC (event notification under 10 CFR 50.72). After the troubleshooting of the RTB subsequent to Event No. 2, reportability was reevaluated and it was determined that the FWI inadvertently actuated by the mechanics was reportable. The confusion associated with event reportability stemmed from the belief that the precautionary note contained in the procedure implied that the WI actuation was part of a preplanned sequence of events.

Event No. 2 i On April 3, 1994, at 1840 EDT, an inadvertent WI occurred. The event occurred upon closure of the RTBs (EIIS Code AA) in preparation for rod (EIIS Code i AA)-drop testing. As the RTBs traveled closed, a spurious FWI signal was generated by one of the two RTBs.

Event No. 3 On April 9, 1994, at 0239 EDT, an inadvertent FWI occurred. The event occurred during observation of the RTBs (EIIS Code AA) after one of the two RTBs failed to close. Before the event, the control room operator attempted to close the RTBs in the preparation for rod-drop testing. When the operato'r initiated RTB closure, one of the two RTBs failed to close. Operations personnel proceeded to the breaker compartment area to examine the breakers. While explaining an observed difference between the two breaker-locking levers, an individual inadvertently moved the locking lever on the closed breaker. This resulted in the breaker traveling to the open position and the initiation of an FWI.

NRC form 366(6-89)

NRC form 366A U.S. NUCLEAR REGULATORY COMMISSION Approved OMB No. 3150-0104 (5-92) Expires 5/31/95 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) lDOCKETNUMDER(2) l_ (E!LHUMQER_{bL j._ l PAGE_(3) l l l l SEQUENTIAL l l REVISION l l l l l Sequoyah Nuclear Plant (SQN), Unit 1 l (YEAR _Ll_UWDEL_LLnuMetti l l l l

[E1510.lEl0}3_lLll._[9_ld j-l_Q_[_Q_l 5 l l Q_LO_[ 01 31QEl 01 7 TEXT (If more space is required, use additional NRC Form 366A's) (17)

B. InQpe rable_ lit ruc turCS_,_CompQnen t a ,_DI_SyS tema_rnat_ cont ribu t e d_t o_the_even t Event No. 1 During routine testing of RTB "A" contacts, it was identified that a high resistance existed on the breaker's auxiliary contact that is an input to the P-4 logic of the solid-state protection system. The breaker was removed from its compartment for troubleshooting to determine the cause of the high resistance. The breaker contacts were cleaned, tested, and found to be acceptable.

Event No. 2 By the use of alarm data, it was determined that a spurious FWI signal was initiated by RTB "A" as it traveled to the closed position. Subsequent to the l event, troubleshooting was performed to determine the cause for the spurious j FWI. The breaker was repeatedly cycled with test instrumentation connected to i critical locations of the breaker and the control circuit. No anomalies were identiffed. The "A" breaker was replaced.

Event No. 3 After troubleshooting and replacement of the "A" RTB for Event No. 2 and testing of the replacement breaker, the main control room operator initiated breaker closure with the main control room handswitch. RTB "B" did not close.

It could not be determined why RTB "B" failed to close. The inspection of the "B" breaker did not identify any failed components. The "B" breaker was replaced.

C. Datea_and_Approxima.te Times oL11ajor Occurrencea April 2, 1994 RTB "A" failed breaker-contact testing on an auxiliary at 0120 EDT contact. The breaker was removed from the compartment for troubleshooting.

April 3, 1994 During troubleshooting, mechanics were in the process of at 1024 EDT taking breaker contact voltage and resistance readings.

An FWI was inadvertently initiated by the mechanics.

April 3, 1994 RTB "A" was reinstalled in its compartment and was at 1750 EDT returned to service.

April 3, 1994 The RTBs were closed. Breaker closure initiated a at 1840 EDT spurious FWI.

NRC Form 366(6-89)

NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION Approved OMB No. 3150-0104 (5-92) Enpires 5/31/95 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) lDOCKETNUMBER(2)j LER NUMBLR (6) l l PAGE_13) l l l l SEQUENTIAL l l REVISION l l l l l Sequoyah Nuclear Plant (SQN), Unit 1 l jlfARju l NUl1QER l l NILMEIR_1 l l l l 101510121213121719_I4I--I010IsI--I01 0 LaL410tL2LL TEXT (If more space is required, use additional NRC Form 366A's) (17)

April 9, 1994 The control room operator attempted to close the RTBs.

at 0227 EDT RTB "B" did not close. An assistant shift operations supervisor (AS0c' M an assistant unit operator were sent to the RTB a m to look for obvious reasons for the failure of Breaker ~a" to close.

April 9, 1994 The ASOS inadvertently moved the locking lever at 0239 EDT on RTB "A" while explaining an observed difference between RTB "A" and "B" locking levers. RTB "A" tripped open. The opening of the breaker initiated an FWI as designed.

l D. Other Systems or Secondary Functians Affectnd l

None.  ;

E. tielhoLoLDisfov_ery l l

In each event, various annunciators alarmed on the main control room panels. l The control room operators determined that an FWI occurred. l l

F. Opfrat.oI_Acliona l In each event, no operator actions were required in response to the INIs.

Operations personnel reestablished long-cycle feedwater operation after the FWI signal was cleared.

G. Saf3_tv System RespanSS No safety system responses were required for the events. The equipment receiving the FWI signal responded as designed.

III. CAUSE OF EVENT A. Immadialf_CAuan Event No. 1 >

l l The immediate cause of the FWI signal was that test equipment was connected to i the wrong set of contacts.

l Event No. 2 The immediate cause of the INI was a spurious signal during the closure of the RTBs.

NRC Form 366(6-89) l

NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION Approved OMB No. 3150-0104 (5-92) Expires 5/31/95 '

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) lDOCKETNUMBER(2) I LER NUMMR_(ftl_1 l PAGE (3) l l l l SEQUENTIAL l l REVISION l l l l l Sequoyah Nuclear Plant (SQN), Unit 1 l lYEARl l NUMBER l . L.t1 UMBER l l l.l l 101510101013 12 l 7 19 14 l-l 0 1 0 l 5 l-l 0 1 0 1 01 510r1 01 7-TEXT (If more space is required, use additional NRC form 366A's) (17) ,

Event No. 3 The immediate cause of the FWI signal was the inadvertent opening of the "A" RTB.

B. Raol_Cause Event No. 1 The cause for the inadvertent FWI was personnel's failure to follow work document instructions for equipment troubleshooting. The mechanics developed the troubleshooting work. instruction and incorrectly believed that steps could be changed during implementation of the troubleshooting instruction. While performing multiple checks of the auxiliary contacts for voltage and .

resistance, an individual incorrectly connected the-test equipment to take )

l measurements from the secondary contacts in the back of the breaker cubicle instead of using the terminal strip as required by the work document. The wrong contacts were connected, resulting in the FWI actuation.

Event No. 2 The cause of the spurious signal was not confirmed. Subsequent to the event, troubleshooting was performed to determine the event's root cause. The spurious signal could not be re-created. The review of test data indicated that the FWI signal may have been initiated by voltage spikes during the movement of the breaker's auxiliary switch rotary contacts as the breaker traveled to the closed position. Discussions with the equipment supplier determined that voltage spikes are not unexpected and are.a result of minute surface irregularities of the contacts. The voltage spikes observed during equipment troubleshooting exceeded the voltage and time thresholds of the solid state protection system for logic change. By engineering judgement, it was determined that the movement of the rotary switch could have initiated the event.

Event No. 3 The cause of the equipment failure resulting in RTB "B" failing to close could not be determined. Equipment examination subsequent to the failure did not identify any hardware damage or failed components. The possible causes for the failure of the breaker to close are the failure of the inertia latch to return to its rest position or the sticking of the 52x relay contact linkage in the drop-out position.

The root cause of the tripping of the "A" RTB was personnel error. The involved individual did not perform self-checking while explaining an observed difference between the RTBs. The individual inadvertently moved a sensitive component (breaker-locking lever) within the breaker compartment.

NRC form 366(6-89)

NRC iorm 366A U.S. NUCLEAR REGULATORY COMMISSION Approved OMB No. 3150-0104 (5-92) Expires 5/31/95 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) lDOCKETNUMBER(2) I L.IR_M)MBER (61 I {__P_AJE ( 3 )

l l l l SEQUENTIAL l l REVISION l l l l l Sequoyah Nuclear Plant (SQN), Unit 1 l lYEAR l l NUMBER l l NUMBER l l l l l 1915101010!3 12 17 19 14 l - 1 0 1 0 I s 1 - 1 0 1 0 1 01 610f1J1LL TEXT (If more space is required, use additional NRC Form 366A's) (17)

C. ContIlhnting_Fac tore None.

IV. ANALYSIS OF EVENT When the unit is in power operation, an WI signal limits the amount of mass in the steam generator in the event of a main steam line break. This limits the energy of a blowdown and prevents the overcooling of the primary system. In the events described in this LER, the WI had no ef fect because the main feedwater isolation valves were closed before the WI signals were initiated. Additionally, the safety functions of the RTBs and WI logic were verified to perform as designed. At no time was there a threat to the health and safety of plant personnel or the general public.

V. CORRECTIVE ACTION A. Immediate Corrective Action No immediate corrective actions were required for the events. Operators promptly diagnosed the plant condition and took actions to restore the affected plant equipment.

B. CoIIsctive Action to Prevent Rfic.urInnce Event No. 1 The involved individuals were counseled on the requirements to follow work l document instruction steps, i Event No. 2 l

The "A" RTB was replaced. The replacement breaker was inspected, tested, i verified to operate properly, and placed in service.

The procedures that close the RTBs will be revised to require the WI reset button to be held in during the closure of the breakers.

1 Event No. 3 l The "B" RTB was replaced. The replacement breaker was inspected, tested, ,

verified to operate properly, and placed in service. The breaker that failed to close was returned to the manufacturer for inspection / evaluation. The inspection results will be reviewed for the need to develop corrective actions.

The appropriate disciplinary action was taken with the involved individual.

NRC form 366(6-89)

+ .

NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION Approved OMB No. 3150-0104 (5-92) Expires 5/31/95 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) l00CKETNUMBER(2) l LERNUtgm_(jL_l } PAGL(3) l l l l SEQUENTIAL l l REVISION l l l l l Sequoyah Nuclear Plant (SQN), Unit 1 l .llLAR_j__l_fiVMER 1 l NVWfjL1 l l l l Inisjalol0lL1L1LitlL1--LLLLI 5 l-l Ll_0_Lol_11ariaLL TEXT (If more space is required, use additional NRC form 366A's) (17)

VI. ADDITIONAL INFORMATION A. FallasLComponenis Reactor trip breaker, Westinghouse Electric Corporation Breaker Model No. DB-50.

B. PIRYious_Elmilar_ Events Event Nos. 1 and 2 A review of 17 previous FWI event LERs did not identify any similar events where the FWI was initiated as a result of the closure of the RTBs. One event (LER 327/89035) occurred during RTB testing as a result of an inadequate i procedure. The corrective action from that event would not have prevented the event described in this LER.

Event No. 3 A review of previous events identified 11 events (LERs 327/84055, 85023, 86025, 86041, 87060, 89013, 90002, 91011, 93003, 328/92011 and 94003) where the risk I I

associated with the activity being performed was not properly evaluated. Each of the events involved activities associated with sensitive equipment. The corrective actions taken for 10 of the events were specific to the individual event and would not have prevented the event described in this LER. The corrective actions taken for LER 327/93003 were of a generic nature to address the activities associated with sensitive equipment. The procedures that were ,

established and the training that was provided as a result of that event should I have prevented the event described in this LER. l VII. COMMITMENT The procedures that close the reactor trip breakers will be revised by August 22, 1994, to require the FWI reset button to be held in during the closure of the breakers.

NRC form 366(6-89)