ML20005F207

LER 89-040-00:on 891205 & 06,automatic Actuations of Emergency Diesel Generator Occurred as Result of Loss of Power to 480-volt ESF Bus.Caused by Personnel Error During Bus Transfer.Mgt Briefings conducted.W/900104 Ltr

ML20005F207
Person / Time
Site:	Arkansas Nuclear
Issue date:	01/04/1990
From:	Ewing E, Taylor L ARKANSAS POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
1CAN019004, 1CAN19004, LER-89-040, LER-89-40, NUDOCS 9001160051
Download: ML20005F207 (5)

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f Artcnsas P wer & Light Company p.j ' Je .; , Arkansa', Nuclear One

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January 4,1990 ,

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U.S. Nuclear Regulatory Commission Document Control Desk

/ Mai1L$tation PI-137

= Wast-ington, D.C. 20555 SUBJECI': Arkansas Nuclear.One - Unit 1 Docket No. 50-313 i

s. License No. DPR-51 Licensee Event Report No. 50-313/89-040-00 Gentlemen:

In accordar.ce with 10CFR50.73(a)(2)(iv), attached is the subject report concerning two Emergency. Diesel Generator actuations which occurred due to loss oi' power to a 480 volt Engineered Safeguards bus caused by personnel

. error.

Very truly yours,

/ ,

E. C. Ewing General-Manager, Technical Support and Assessment ECE/RHS/sgw attachment cc: Regional Administrator Region IV i U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlington, TX 76011 l

INPO Records Center 1500 Circle 75 Parkway

l. Atlanta, GA 30339-3064 L

9001160051 993104 PDR ADOCK 05000313 PDC

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.. An Ente <gy Company

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, , Ptem 1062.01 A NRC Form 366s U.S. Nuclear Regulatory Commission +

(D-83) Approved DMB No. 3150-0104 Empires: 8/31/85 LICEN$EE EVENT REP 0RT (L E R) -

FACILITY NAME (1) Arkansas Nuclear One Unit One IDOCKET NUMBER (2) IPAGE (3) 10151010101 31 11 31110Flol4 TITLE (4) Two Emergency Dieset Generator Actuations Due to Loss of Power to a 480V Engineered safeguards Bus caused By Personnel Error EVENT DATE (5) I LER NUMBER (6) i REPORT DATE (7) l OTHER FACILtTIES INVOLVED (8) l l l l 15equentiell IRevisioni i l i l Monthi Day lYear lYear i I Number I i humber IMonthi Day lYear i Facility Names IDocket Number (s) l l l l l l .1 l l l l 10151010101 I l ,

Il 21 01 $l Bf 91 81 91--I O l'41 0 l--I O I O I of II 01 41 91 01 10151010101 1 1 OPERATING l lTHis REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR B:

MDDE (9) i Ni (Check one or more of the fo110winn) (11)

POWERI l._I 20.402(b) 1 _t 20.405(c) l_El 50.73(a)(2)(iv) 1 _t 73.71(b)

LEVEll l__l 20.405(a)(1)(1) I,_,1 50.36(c)(1) l__l 50.73(a)(2)(v) l__l 73.71(c)

(10) 1010101 1 20.405(a)(1)(11) I,_,1 50.36(c)(2) 1._l 50.73(a)(2)(v11) l__l Other (Specify in l__l 20.405(a)(1)(iii) l__l 50.73(a)(2)(1) 1 _l 50.73(a)(2)(v111)(A)l Abstract below and

, l__l 20.405(a)(1)(tv) l__l 50.73(a)(2)(11) 1._I 50.73(a)(2)(viii)(B)l in Text, NRC Form t

l I I 20.405(a)(1)(v) I I 50.73:o)(2)(111) I i 10.73(a)(2)(x) I' 366A)

LICENSEE CONTACT FOR THl$ L !R (12) home i Teleohone Number lArea i Larry A. Taylor, Nuclear Safety and Licensing Specialist ICode i 1510111916141-13111010 CONPLETE ONE LINE FOR EACH CDNPONENT FAILURE DESCRIBED IN THIS REPORT (13)

. l l l lReportabiel l l l l lReportablel r Causelsysteel Conoonent IManufacturerl to NPRDS I ICausel5ysteel Component IManufacturerl to NPRDS I i 1- l- 1 l l l l l l l l l 1 I l I i l i l  ! I I I I I I l I i i i I I I l 1 i i l l 1 i l 1 1 ,

l l l i I ~ l i I1 I I l I l l I I I i l l i I I l 1 SUPPLEMENT REPORT EXPECTED (14) l EXPECTED l Monthi Day lYear

~ _ l SUBMISSION l i l l l Yes (If ves, complete Expected Subsission Date) Ik l No l DATE (15) l I I i 1 1 ABSTRACT (Lielt to 1400 spaces,1.e. , approximately fif teen single-space typewritten lines) (16)

On December 5, 1989 at 0645 and December 6, 1989 at 2205, while the plant was shutdown in a maintenance i outage, automatic actuations of an Emergency Diesel Generator (EDG) occurred as a result of loss of '

power to a 480 volt (v) Engineered Safeguards (ES) bus. Prior to both events, the 85 and B6 480v E5 busses were crossconnected to facilitate maintenance activities. The December 5 event occurred as a result of a personnel error which occurred while operators were attempting to "splitout" the 85 and B6 busses and return the ES power distributtor< system lineup to normal. The error resulted in a loss of l Power to bus 86 which caused the offsite feeder breaker for 4.16 kilovolt bus A4 to open and initiated a start of the 'B' EDG which tied on to the A4 bus. The December 6 event was also the result of a l personnel error which caused a loss of power to 480v Es bus 85. This condition caused the offsite feeder breaker for A3 to trip and the ' A' EDG to start. The momentary loss of power to A3 caused the operating Decay Heat Removal (DHR) pump to trip. DHR flow was lost for approximately 9 einutes and resulted in a Reactor Coolant System temperature increase of 17 degrees. Management briefings were l conducted for the operating crews prior to restart from the outage covering the lessons learned froe

these events. On-shift guidance with respect to management expectations regarding watchstanding professionalise and formality and attention to detail is also being provided.

l

. s Form 1062.01B NRC Form 366A U.S. Nuclear Regulatory Commission (9-83) : Approved DMB No. 3150-01D4 Expires: B/31/B5 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITY NAME (1) l DOCKET NUMBER (2) l LER NUMBER (6) l PAGE (3) l l l 15equentiall (Revision l Arkansas Nuclear One, Unit One l l Yearl i Number 1 i Number l 10151010101 31 11 31 81 91--l 0141 01--I 0 1 0 101210Fl014 TEK1 (If more space is required, use additional NRC Form 366A's) (17)

A. Plant Status At the time of these events, Arkansas Nuclear One, Unit 1 (ANO-1) was in the cold shutdown condition.

Midcycle outage IMB9 was in progress.

B. Event Description Dn December 5,1989 at approximately 0645 hours0.00747 days <br />0.179 hours <br />0.00107 weeks <br />2.454225e-4 months <br />, while licensed plant operators were in the process of restoring the Engineered Safeguards (ES) electrical distribution system lineup to normal, a momentary loss of power to 4160V ES bus A4 and 480V ES bus B6 occcrred. The 'B' Emergency Diesel Generator (EDG) automatically started and raenergized bus A4.

The electrical distribution lineup prior to this event was as follows (see Figure 1): 4.16KV switchgear A3 was being powered from switchgear A1 (supplied by offsite power) and 4.16KV switchgear A4 was being supplied by A2. 480Y ES bus B5 was being supplied by A3 via circuit breakers A-301 and B-512, 480V ES bus 86 was crossconnected to 85 through circuit breakers B-513 and B-613. The feeder breakers from A4 to B6 (A 401, B-612) were open. The 'A' EDG was being run for surveillance testing and was tied to A3 and operating in parallel with the offsite power system. Decay Heat Removal (DHR) pump P-34A was in - '

service.

Three operators were involved in the bus transfer. It should be noted at this time that the normal feeder breakers to B5 and 86 (B-512 B-612) and the B5/86 crosstie breakers (B-513, B-613) are each electrically interlocked to trip when the otiier three are closed. The sequence of events leading up to the diesel start was as follows:

e Operator #1 closed the 4.16KV feeder breaker from A4 to 86 (A-401).

e Operator #2 held the handswitch for B-512 in the close position to prevent it from tripping due to the interlock discussed above. .

e Dperator #1 held the handswitches for B-513 and B-613 in the close position to prevent the inadvertent l loss of power to B6.

l

• Operator #3 closed the 480V feeder breaker from A-4 to B-6 (B-612) and held the switch in the close position.

I e Operator #1 then released the handswitches for B-513 and B-613.

When the switch for B-613 was released, breaker B-613 tripped, the 'B' EDG started automatically, the A2 to A4 feeder breaker (A-409) tripped, as designed, and the EDG tied to A4. At this time, the operators observed that the feeder breaker from A4 to B6 (A-401) was open with the handswitch in the I

normal after close position, indicating that the breaker had tripped. This resulted in completely doenergizing the B6 bus and initiating the EDG start due to an undervo?tage condition on 86. Since l

the operators did not know why A 401 had tripped, tt ey reestablished power to B6 from 85 by reclosing breaker B-613 and opening B-612. At 0700, the A2 supply to A4 was restored and the 'B' EDG was secured.

At 0745, the electrical distribution lineup was returned to a normal alignment (85 and 86 split).

A second inadvertent loss of power to a 480V E$ bus and subsequent EDG start occurred on December 6, l 1989 at approximately 2205.

l The electrical distribution lineup prior to this event was as follows. 480V E5 busses 85 and 86 were crossconnected through their respective crosstie breakers (B-513, B-613). 86 was being powered from 4.16KV bus A4 through faeder breakers A-401 and B-612. The A3 to B5 feeder breakers (A-301 and B-512) were open, racked down and tagged out to allow inspection of 4.16KV/480Y transformer X5. DHR pump P-34A was in service.

After completion of the transformer inspection, a plant auxiliary operator was instructed to go to the A3 switchgear room and remove the hold cards from breaker A-301 and B-512 and rack in the breakers in preparation for closing the breakers. Af ter racking in the breakers, the operator was in the process of charging the springs for breaker B-512 when it inadvertently closed and immediately reopened. At this time the B6 crosstie breaker (B-613) opened, since it is interlocked with B-512, B-513 and B-612

4: .

Form 1062.018

- Nic Fom 366A U.S. Nuclear Regulatory Commission (9-83) Approved Ope No. 3,150-0104 Empires 8/31/85 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION

- FACILITY N M (1) l DOCKET NUISER (2) l LER NupeER (6) l PAGE (3) l l l 15equentiell l Revision!

Arkansas Nuclear One, Unit Dne l l Yearl l Number l l Number l 101510f0f01 31 Il 31 el 91--I of 41 01--I 01 Ol01310Flol4 TEXT (if more space is required, use soditional NRC Fom 366A's) (17) to open when the other three are closed. The tripping of breaker B-613 caused a loss of power to bus 95 which initiated an autostart of the 'A' EDG due to undervoltage on 85. The Al to A3 feeder breaker tripped, as designed, and the EDG output breaker closed, reenergizing bus A3. The momentary loss of power to 4.16KY bus A-3 caused the breaker for DHR psamp P-34A to trip, resulting in a loss of DMR flow. The operators immediately reenergized bus 95 from A3 by closing breakers A-301 and B-512. '

At approximately 2210, bus A3 was paralleled to Al and the EDG was secured. At 2214. DHR pump P-34A was restarted and DHR flow was mestablished. DHR cooling flow had been interrupted for approximately 9 minutes. During this time Reactor Coolant System (RCS) [AB) temperature increased from 103 degrees to 120 aegrees.

C. Safety Significance The EDGs response to the loss of power to the E5 bus during both events was as designed. All interlocks and breakers functioned as required. During the first event, the operating DHR pump (P-34A) was being powered from A3 and the momentary loss of power to A4 did not cause a loss of DHR flow. However, during the second event, DHR flow was lost for approximately nine minutes Msulting in an increase in pCS temperature of approximately seventeen degrees. Although the DHR pump was available for restart famediately after tripping, decay heat loads were such that it was not necessary to restart the pump until the electrical distribution lineup was nomalized. Considering that DHR cooling was reestablished expeditiously and that the EDGs responded properly during these events, their safety significance is considered minimal.

D. Root Cause In an effort to determine the causes of the two events discussed in this report, an evaluation of the design of the 480V E5 bus tie and feeder breakers was conducted. This evaluation verified that there were no design deficiencies which could have caused or contributed to the events. Additionally, functional testing of the involved breakers was perfomed which verified that all the breakers operated as designed.

L The exact cause of why breaker A-401 was either open or tripped during the first event or why breaker B-512 inadvertently closed during the second event could not be detemined. However, since the breaker design was verified to be correct and the breakers were proven t5 be operable, the most likely cause of these events is considered to be personnel error during the bus transfer evolutions.

i E. Basis for Reportability These events are reportable in accordance with 10CFR50.73(a)(2)(iv), as automatic actuations of an Engineered Safety Feature.

F. Corrective Actions A senior management evaluation of these events determined that increased emphasis needed to be placed

on watchstanding professionalism and formality. Management briefings were conducted for operating crews prior to restart from outage 1M89 covering the results of this evaluation.

Additionally, senior management and supervisory personnel are providing on-shift guidance to shif t personnel. This guidance includes management expectations regarding watchstanding professionalism

, and formality, attention to detail, procedure compliance and safety.

I A review of operating procedures will be conducted to evaluate the need to require sign-off steps when crossconnecting or restoring E5 electrical busses to nomal configuration while shutdown, and to determine if additional procedural enhancements are necessary. This review is expected to be completed by March 31, 1990.

During the next Requal Cycle, training will be provided on 480V breaker operations and on 85 - 86 breaker interlocks. This training is expected to be completed by March 31, 1990.

G. Additional Information There have been no previous EDG actuations caused by personnel error reported.

Energy Industry Identification System (EIIS) codes are indicated in the text as [XX).

r' 1, . . . .

l Fore 1062.018

' i Nilt Fors 366A- U.S. Nuclear Regulatory Commission I: (9 83) Approved Ole No. 3150-0104 -

Empires: 8/31/85 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITY NAME (1) l DOCKET NUDGER (2) l LER NupeER (6) l PAGE (3)~

l l l lSequentiall l Revision!

' Arkansas Nuclear One, Unit One l l Yearl l Number l l Number l 10151010101 31 11 31 81 91--I 01 41 OI--I 01 0101410F1014 l TEXT (If more space is required, use additional NRC Fors 366A's) (17)

E FIGURE 1 SIMPLIFIED SCHEMATIC OF ES ELECTRICAL DISTRIBUTION SYSTEM t

EDG ' A. FROM 4160V , FROM 41s0V EDG 'B' SWOR 'A1' sWOR 'A2' A300 A408 I

4.1sMV sWOR 'A3'(Es) Y usMv sWaa A< <Es>

L yg A A g s

'A301 A305 A309 A409 A405 A401 V y V l VMw ,.. A ,,,, <===* t >=i =>

c ETIIII III' '1T1 Ik B812 Sei2 T esov Es Sus 'Bs' esov as Sus se' A

3813 B413 i/

1 --_ _ _ _ - _ _ _____ - _- _ _ _ _ - _ _ _ - _ - _ - _ .

_ - . . - .