05000327/LER-1997-007-01, :on 970404,DG Started When Drill Bit Being Used to Drill Into Electrical Panel in Main Control Room,Cut Into Cable.Caused by Drill Bit Penetrating Energized Wire Bundle Causing Short.Work Stopped on All Electrical Mods for S
| ML20147J433 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 05/01/1997 |
| From: | Gilley S TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML20147J419 | List:
|
| References | |
| LER-97-007-01, LER-97-7-1, NUDOCS 9705070157 | |
| Download: ML20147J433 (8) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2) |
| 3271997007R01 - NRC Website | |
text
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 (4-95)
EXPIRES O4/30/98 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY INFORMATION COLLECTION REQUEST: 50.0 LICENSEE EVENT REPORT-(LER)
H,lRSiTHE CEN ING FROC E S AFED W TO N7USTRY
"^
(See reverse for required number of fHE" F
AT AND RE GEMEN T
digits / characters for each block) 6 F33), U.S. NUCLEAR REGULATORY COMMISSION.
F C4.!TV NAME 11)
DOCIIET NUMBER (2)
PAGE (3) j SsquOyah Nuclear Plant (SON) Unit 1 05000327 1OF8 TiVLE 143 l Diesel generator starts that reSulted frOm cutting a cable while drilling a panel and during repairs to the damaged Cable.
4 EVENT DATE (5)
LER NUMBER (6)
REPORT DATE (7)
OTHER FACluTIES INVOLVED (B)
SEQU NT AL R
MONTH DAY YEAR YEAR MONTH DAY YEAR NU R
FACILITY NAME DOCKET NUMBER 04 04 97 97 007 00 5
01 97 g
NA 05000 N
THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR B: (Check one or more) (11)
OPERATING MODE (9) 20.2201(b) 20.2203(aH2)(v) 50.73(a)(2HQ 5'.).73(a)(2)(viin POWER 20.2203(ann 20.2203(aH3Ha 5033(aH2Hin 5033(aH2Hx) 000 LEVEL (10) 20.2203(aH2H6 20.2203(a)(3Hi0 50.73(a)(2)(iii) 73.71 20.2203(a)(2)(in 20.2203(aH4)
X 50.73(aH2Hiv)
OTHER 20.2203(aH2Hm) 50.36(c)(1) 50.73(a)(2Hv)
Spgci{y gAbstr t elow 20.2203(a)(2)(iv) 50.36(cH2) 50.73(a)(2)(vid LICENSEE CONTAC1 FOR THIS LER (12)
NAME TELEPHONE NUMBLR (include Area Codel Steve Gilley, Licensing Engineer (423) 843-7427 i
COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)
R RTA E R
RTAB E
CAUSE
SYSTEM COMPONENT MANUFACTURER gpg;:
CAUSE
SYSTEM COMPONENT MANUFACTURER W%
i
$%3 SUPPLEMENTAL REPORT EXPECTED (14)
EXPECTED MONTH DAY YEAR YES SUBMISSION l
X NO (if yes, comple's EXPECTED SUBMISSION DATE).
DATE(15)
ABSTRACT (Limit to 1400 spaces. Le., approximately 15 single-spaced typewritten lines) (16)
On April 4,1997, at approximately 0130 hours0.0015 days <br />0.0361 hours <br />2.149471e-4 weeks <br />4.9465e-5 months <br />, Eastern Standard Time EST), with Unit 1 in a refueling outage with the core offloaded and Unit 2 in power operation at a Safety Feature (ESP) actuation occurred. Diesel generators (DGs) I A-A,2A-A, and 2B-B) started when a drill bit being used to drill into an electrical panel in the mam control room, cut into the ca9e bundle connecting the I A-A 6900-V Shutdown Board (ipment clearance and did not start. A s SDBD) normal feeder handswitch to its associated electrical circuits. The 1B-B DG was tagged with an equ occurred at approximately 1036 hours0.012 days <br />0.288 hours <br />0.00171 weeks <br />3.94198e-4 months <br />, EST, dunng repair of the damaged cable bundle, when persormel cut i
multiple wires simultaneously. The alternate feeder breaker for the I A-A 6900-V SDBD tripped, which deenergized the board. The load shedding circuitry stripped all loads and three DGs (I A-A,2A-A, and 28-B; started and the I A-A DG energized the board (DG IB-B was already running as the result of a test in progress). The root cause of the first event was inadequate work practice brought on by overconfidence and lack of adherence to job performance standards. The root cause of the second event was improper control over sensitive plant activity due to lack of adherence to job performance standards. Following the first event, work was stopped for all electricil modifications for one shift, and stand down meetings were held site-wide to discuss the event. The work arder was revised to ensure the engineer would perform an evaluation of the conditions prior to drilling. Following the second event, work activities on the cable repair were suspended and an assessment of electrical maintenance employee performance was performed. Disciplinary actions have been taken with the appropriate individuals.
9705070157 970501 PDR ADOCK 05000327 S
PDR q
.LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOL 7Mr LER NUMBER (6)
PAGE (3)
YEAR H SEQUENTIAL NUMBER H REVISION NUMBER SQN Unit 1 05000327 97..
007 og 2 of 8 TEXT (if more space is required, use additional copies of NRC Form 366A) 07)
I.
PLANT CONDITIONS
Unit I was in a refueling outage with the core offloaded. Unit 2 was in power operaLan at approximately 100 percent.
II.
DESCRIPTION OF EVENT
A.
Event:
On April 4,1997, at approximately 0130 hours0.0015 days <br />0.0361 hours <br />2.149471e-4 weeks <br />4.9465e-5 months <br />, Eastern Standard Time (EST),
with Unit 1 in a refueling outage with the core offloaded an inadvertent Engineered Safety Feature (ESF) actuation occurred. A hole was being drilled in a control room panel to install a cover over a hole where a switch had been removed. When the drill penetrated the panel, the forward progress of the drill caused the drill bit to come into contact with a control power cable bundle inside the panel. The bundle consisted of eleven wires, four of these were damaged. The control power cable bundle served to connect the I A-A 6900-V Shutdown Board (SDBD) normal feeder breaker handswitch to its associated electrical circuits. The penetration by the drill bit resulted in the instantaneous opening of the normal feeder breaker [EIIS Code BKR] for the I A-A 6900V SDBD. Automatic load shedding circuitry stripped the loads from the I A-A 6900-V SDBD, the three available diesel generators (DGs)
(l A-A,2A-A, and 2B-B) started and the I A-A DG energized the board. The IB-B DG was tagged with an equipment clearance and did not start.
The second ESF actuation occurred at approximately 1036 hours0.012 days <br />0.288 hours <br />0.00171 weeks <br />3.94198e-4 months <br /> EST during activities associated with the repair of the damaged cable bundle. Personnel had cut the wires in the bundle individually without incident and then proceeded to cut the wires simultaneously to facilitate installation of a new connector on the end of the b adie. This would allow the damaged area which was near the end of the cable bundle to be eliminated. When the wires were cut, the alternate feeder breaker [ Ells Code BKR] for the I A-A 6900-V SDBD tripped, which deenergized the board again. Automatic load shedding circuitry stripped the loads from the I A-A 6900-V SDBD, three DGs (1 A-A, 2A-A, and 2B-B) started and the I A-A DG energized the board (DG 1B-B was already running as the result of a test in progress).
NRC FORM 36TA {4-95)
1 a
.LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION I
FACILITY NAME (1)
DOCKET LER NUMBER (6)
PAGE (3) q YEAR l SEQUENTlAL NUMBER l REVISION NUMBER SON Unit 1 05000327 97 __
007 og 3 of 8
{
EXT tif more space is required, use additional copies of NRC Form 366A) (17)
B.
Inoperable Structures. Components, or Systems that Contributed to the Event:
None.
]
C.
Dates and Approximate Times of Maior Occurrences:
April 3,1997 Two switches were removed from the 1-M-1 panel in the main control room and work to install covers over the holes was initiated. Operations personnel informed the craftsmen that the adjacent 3
switches were SDBD handswitches. After unsuccessfully attempting to obtain a shortened drill bit or drill stop collar, the individuals determined on their own without
)
consulting supervision to proceed with the activity because they felt they could accomplish the work without the special tools.
April 4,1997 During the drilling operation, the drill bit protruded into
~0129 EST the cable bundle and damaged the cable and the drill bit acted as a short circuit to energize the trip coil causing the normal feeder breaker for the I A-A 6900-V SDBD to trip. DGs l A-A,2A-A, and 28-B started and 1 A-A DG energized the I A-A 6900-V SDBD (DG 1B-B was tagged with an equipment clearance and did not start).
Two courses of action were initiated to restore the I A-A 6900-V SDBD to either of its offsite power sources by restoring either the normal or alternate feeder breaker.
One course of action was to verify operability of the alternate feeder breaker, parallel the SDBD to its alternate power source, then unload and shut down the I A-A DG.
3 The second course of action was to repair the damaged control power cable bundle and return l A-A SDDD to its normal power source.
i j
.LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET LER NLMBER (6)
PAGE (3)
YEAR l SEQUENTIAL NUMBER l REVISION NUMBER j
SQN Unit 1 05000327 97 __
oog oo 4 of 8 TEXT Of more sp&ce is required, use additional copies of NRC Form 366A4 (17)
April 4,1997 After it was determined that the I A-A 6900-V SDBD
- - 0655 EST could be placed on the alternate feeder, the necessary procedure changes were complete, and the alternate feeder breaker to the I A-A 6900-V SDBD was closed.
April 4,1997 The I A A DG was shut down.
~0715 EST April 4,1997 The work order for the repak of the damaged cable was
~0715 EST planned believing that the alternate feeder breaker to the I A-A 6900-V SDBD would remain open throughout the repair and post maintenance test and included a signoff to i
verify the breaker was open prior to performing the work.
The work order required the I A-A 6900-V SDBD alternate feeder breaker to be verified in the open position. The verification was performed, but was performed on the incorrect breaker, i
April 4,1997 Operations requested a step-by-step brief on the work
~0725 EST which was about to take place to repair the damaged cable. Operations asked if voltage checks have been i
performed on the cable bundle and were told that they have been checked and are deenergized. (Later it was discovered that only one of two terminal blocks were checked.) The terminal block which was not checked had i
two wires in the cable bundle that were energized from a control power circuit.
1 April 4,1997 All the wires in the bundle are trimmed simultaneously, j
1036 EST resulting in the tripping of the I A-A 6900-V SDBD alternate feeder breaker. The I A-A 6900-V SDBD deenergizes and 1 A-A,2A-A, and 2B-B DGs start and 1 A-A DG energizes the I A-A 6900-V SDBD. The IB-B DG was already running as part of an unrelated maintenance activity.
. ~.
i LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET LER NUMBER (6)
PAGE (3)
YEAR l SEQUENTIAL NUMBER H REutSION NUMBER SQN Unit 1 05000327 37 __
007 oo 5 of 8 j
TEXT tif more space is reqwred, use additional copies of NRC Form 366A) (17) i April 4,1997 Unit 2 entered LCO 3.8.1.1.c due to loss of offsite power
{
1036 EST source to l A-A 6900-V SDBD and one DG inoperable.
April 4,1997 DG IB-B stopped.
i 1126 EST i
4 April 4,1997 DG 2A-A and 2B-B stopped.
I135 EST i
April 4,1997 Unit 2 exited LCO 3.8.1.1.c The normal feeder breaker 2131 EST to the I A-A 6900-V SDBl; has been closed. The I A-A i
DG is connected in parallel with the offsite power to the 1 A-A 6900-V SDBD.
April 4,1997 The Diesel l A feeder breaker to the I A-A 6900-V SDBD l
2202 EST was opened and the 1 A DG was being shut down.
D.
Other Systems or Secondarv Functions Affected:
J l
None.
E.
Method of Discovery
The DG starts were annunciated in the MCR.
I F.
Oncrator Actions:
MCR operators responded as prescribed by emergency procedures. In both i
instances, operators diagnosed the condition as an inadvertent ESF and secured the work activity, in the both events the 2A-A and 2B-B DGs started as a result of the ESF and were subsequently shut down by the operators. In the j
first event operators stopped the I A-A DG after closing the alternate feeder breaker (the IB-B was tagged and did not start). In the second event, the IB-B DG which was already running as part of an unrelated test was stopped.
l Following repairs to the cable the normal feeder breaker to the I A-A 6900-V j
SDBD was closed and the I A-A DG was shut down.
2 h'RC FORM 366A (4 95) i
- - ~. ~
i
\\
4, LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET LER NUMBER (6)
PAGE (3)
YEAR l SEQUENTIAL NUMBER l REVISION NUMBER SON Unit 1 05000327 97 __
007 oo 6 of 8 i
TEXT Uf rnore space is requued, use addinonai copies of NRC Form 366At (17)
G.
Safety System Responses:
i The plant responded as expected to both loss-of-power conditions. In the first event, the three available DGs started (the IB-B DG was tagged out for maintenance) and the I A-A DG energized the I A-A 6900-V SDBD as designed. In the second event, three DGs started (the IB-B DG was already 4
running as part of a maintenance activity) and the I A-A DG energized the j
1 A-A 6900-V SDBD as designed.
Ill.
CAUSE OF TIIE EVENT 4
A.
Immediate Cause:
The immediate cause of the first condition was that the drill bit penetrated the j
energized wire bundle causing a short that energized the trip coil for the normal feeder breaker to the I A-A 6900-V SDBD.
a i
The immediate cause of the second condition was that when the wires in the 1
bundle were cut simultaneously causing the alternate feeder breaker to the 1 A-A 6900V SDBD to trip.
i B.
Root Cause:
The root cause of the first event was inadequate workpractice in that the hole was drilled without positive protection controls in place for the cable.
I The root cause of the second event was inadequate workpractices and adherence to site policies and procedures by multiple individuals during performance of sensitive activities.
C.
Contributine Factors In the second event, the alternate breaker and its control circuits should have been tagged out of service under a hold order when the circuits for the normal feeder breaker were tagged.
WRC FORM 306A (4-95)
.LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET LER NU!MBER (6)
PAGE (3)
YEAR l SEQUENTIAL NUMBER g REVISION NUMBER SQN Unit 1 Os000327 97..
007 oo 7 of 8 TEXT Of rnore space es required, use additional copies of NRC Form 366A) 07)
IV.
ANALYSIS OF TIIE EVENT The operability of the 6900-V SDBDs and their associated distribution system ensures that the necessary power is supplied to the equipment requiring AC power during a loss of offsite power and/or accident condition. In the events described by this LER, a loss of power condition occurred on the I A-A 6900-V SDBD, generating a signal that started the available DGs as designed. The plant response to the events were consistent with responses described in the final safety analysis report and accordingly, the events did not adversely affect the health and safety of plant personnel or the general public.
V.
CORRECTIVE ACTIONS
A.
Immediate Corrective Actions
Following the first event, work was stopped for all electrical modifications for one shift, stand down meetings were held site-wide discussing the situation and the measures that needed to be taken. The work order was revised to add a holdpoint to ensure the engineer performed an evaluation of the conditions prior to drilling. The workplans in progress were reviewed and pre-job briefings were given to modifications personnel again.
Following the second event, work activities on the cable repair were suspended. An assessment of electrical maintenance shop employee performance was performed and resulted in the removal of individuals from plant duties. A plan was also developed to provide for additional evaluation and training.
This event has been communicated through onshift briefings and a follow-up training letter to licensed operators.
MCR operators responded to both events by promptly diagnosing the condition and taking steps to restore one of the offsite power sources to the SDBD.
Disciplinary actions have been taken with the appropriate individuals.
..LICENSEE EVENT REPORT (LER)'
i TEXT CONTINUATION FACILITY NAME (1)
DOCKET LER NUMBER (6)
PAGE (3)
YEAR g SEQUENTLAL NUMBER l REVISION NUMBER SON Unit 1 05000327 97 __
007 oo 8 of 8 TEXT Of more space is required, use edditional copies of NRC form 366A) (17) ~
1 B.
Corrective Actions to Prevent Recurrence:
Management has instituted a site-wide initiative emphasizing the requirements for pre-job briefings and procedural adherence. No additional corrective actions are necessary to prevent recurrence. These events occurred as a result of human performance problems and the appropriate disciplinary actions have been taken.
VI.
ADDITIONAls INFORMATION A.
Failed Components:
None.
B.
Previous IIRs on Similar Events:
A review of previous reportable events identified one LER (50-327/87-060) where an engineered safety system actuation occurred when, during the performance of a special maintenance instruction, an electrician's knife blade came into contact with two bare energized studs while cutting the plastic tie wraps from some cables. As a result, the normal feeder breaker for the IB-B shutdown board tripped and all operable DGs started. The corrective actions included covering the bare studs to prevent inadvertent shorting during the remaining performances of the special maintenance instruction. The corrective actions would not have prevented the events described in this LER.
C.
Additional Information
An enhancement is planned to the emergent work process to require a risk assessment by a senior reactor operator prior to conduct of work.
VII.
COMMITMENTS
None.