IR 05000400/1989027
| ML18005B124 | |
| Person / Time | |
|---|---|
| Site: | Harris  |
| Issue date: | 10/27/1989 |
| From: | Conlon T, Harris J, Miller W, Ruff A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML18005B123 | List: |
| References | |
| 50-400-89-27, NUDOCS 8911010067 | |
| Download: ML18005B124 (12) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION
REGION II
101 MARIETTASTREET, N.W.
ATLANTA,GEORGIA 30323
++*++
Report No.:
50-400/89-27 Licensee:
Carolina Power and Light Company P. 0.
Box 1551 Raleigh, NC 27602 Docket No.:
50-400 License No.:
NPF-63 Facility Name:
Harris 1, Inspection Conducted:
October 10-12, 1989 Inspectors A.
Ru
,
earn Leader J.
rris er go pp gf Date Signed ate 1gne ate sgne Approved b
.
Thomas
.
on on, Chief Plant Systems Section Engineering Branch Division of Reactor Safety Date Signed SUMMARY Scope:
This special announced inspection was conducted to 'investigate a fire that occurred at the Shearon Harris Nuclear Plant.
The fire 'was due to an electrical fault and a subsequent fire that occurred at 2306 p.m.
on October 9, 1989.
Results:
In the areas inspected, violations or deviations were not identified.
Overall the fire fighting operations limited the fire damage to the points of origin and prevented the fire spread to adjacent equipment.
This can be attrib'uted to a
sound brigade training program,and the professionalism demonstrated by the fire brigade members.
However, the decision to respond to the, fire without self contained breathing apparatus, although not a factor in this fire is not considered a
good practice.
Corrective action should be taken to prevent future occurrence on this item.
8~11010067
-
REPORT DETAILS 1.
Persons Contacted Licensee Employees H. Avinger, Senior Electrical Engineer
- G. Collins, Manager Operations
- G. Forehand, Manager, guality Assurance/guality Control
- C. Gibson, Director, Projects and Procedures
- J. Hammond, Manager, Onsite Nuclear Safety K. Hefner, Senior Electrical Engineer
- C. Hinnant, Plant General Manager
- A. Howe, Senior Specialist Regulatory Compliance
- J. Morris, Senior Electrical Engineer R. Rabuld, Senior Electrical Engineer
- R; Richey, Manager, Harris Nuclear Project
- J. Sipp, Manager, E and RC
- M. Stokes, Senior Specialist Fire Protection
- M. Wallace, Senior Specialist Regulatory Compliance
- E. Willex, Manager Outages and Modifications
'L.
Woods, Engineering Supervisor Technical Support
- R. Zula, Project Engineer Technical Support Other licensee employees contacted during this inspection craftsmen, engineers, operators, mechanics, security force technicians, and administrative personnel.
included members, NRC Resident Inspectors
- J. Tedrow, Senior Resident Inspector
- M. Shannon, Resident Inspector
- Attended exit interview 2.
Followup on Regional Request (92705)
a.
.On October 9, 1989, the plant was operating at 100 percent reactor power.
At approximately 11:06 p.m., four loud bangs or explosions were heard followed by receipt of multiple annunciator alarms in the control room.
Both the turbine and reactor tripped automatically.
The trips were apparently caused by an electrical fault in the generator to the main station transformer distribution system.
This fault caused excessive heat in the bus which ignited combustible components in the duct termination box at the transformer
"8" and the grounding of the neutral transformer on the 286 elevation of the turbine building.
The heat also ruptured the hydrogen seal of the generator.
When the seal ruptured the hydrogen, normally maintained
v at approximately 60 psi, was discharged out the ruptured seal to the south end of'he generator on the 314 elevation, and to the area directly beneath the generator at the 286 elevation.
This hydrogen gas provided additional fuel which was immediately ignited by the heat from the electrical fault.
Therefore, within seconds, there were at least three separate fires involving the main transformer B, area around the neutral transformer and exciter end of the generator.
The fire brigade responded to the fire at 11:ll p.m.
Offsite assistance was also requested and was provided by the Holly Springs and Fuquay-Varina Fire Department.
b.
Sequence of Events, October 9, 1989 and October 10, 1989.
A roximate Time October
1989 Events 2303 PM 2306 PM 2309 PM 2311 PM 2314 PM Four loud bangs or explosion noises heard.
Turbine trip from generator lockout relay.
Reactor'trip from turbine trip.
Auxiliary operator reported fire in "B" phase generator transformer.
Fire brigade was dispatched South end of turbine building was evacuated.
Fire brigade was assembled in staging area on the Northwest corner of 261 elevation of turbine building.
Auxiliary operators reported:
arcing and sparks coming from 236 elevations of south end.of turbine building.
Fire Technical Aid (Fire brigade member)
arrived at B transformer.
Manually tripped transformer deluge fire protection valve from manual actuation station in South end 261 elevation of turbine building.
Both fire pumps started on pressure drop from activated deluge system.
Fire brigade members arrived at transformer in full turnout gear except for.self contained breathing apparatu A roximate Time October
1989 cont d Events 2315 PN 2318 PN 2319 PN 2320 PM Two fire brigade members were dispatched to the 286 elevation of the turbine building to obtain foam fire fighting equipment and noted flame approximately eight feet long and four inches in diameter coming from the ceiling area.
Auxiliary operator advised control room of potential hydrogen gas fire in the ceiling of 286 elevation at southeast corner of turbine building.
Fire brigade members pulled three one and half inch fire hoses from standpipe hose station in south end of 286 foot elevation of turbine building.
Auxiliary operator isolated hydrogen to generator by closing valve at the hydrogen skid.
The fire brigade team leader responded to the 286 elevation south portion of turbine building to direct the fire fighting operations.
The shift supervisor requested assistance from offsite via 911 emergency telephone system.
One fire brigade member checked the 314 elevation of the turbine building for fire spread and found a four foot wide by four foot long fire coming from the South end of the generator.
A one and half inch fire hose was pulled from the standpipe hose stations located on the west side of the 314 elevation of the turbine building.
Wade County Emergency Center dispatched a fire alarm to Holly Springs and Fuguay-Varnia Fire Department A roximate Time cto er
Tcont d Events 2324 PM 2332 PM 2336 PM The generator fire was extinguished.
However, hose streams continued to discharge into the fire damaged generator for cooling and to prevent reignition.
Emergency Alert classification was declared.
Holy Springs Fire Department arrived at the fire scene with one pumper and nine fire fighters including the fire chief, and assisted the fire brigade at the 286 and 314 elevations of the turbine building.
One additional one and a half inch hose was pulled from a standpipe hose station, on the 314 elevation, water was directed to the fire area.
2341 PM 2400 PM October 10, 1989 0004 AM The Fuguay
- Varnia Fire Department arrived at-the fire scene with one pumper, one utility truck and nine fire fighters including the fire chief.
They assisted the fire brigade members at each fire location.
State and counties were notified of
"Alarm Emergency Classifications."
v Fi.re on 286 elevations of Turbine building was under control but still burning from hydrogen being released into fire area from the damaged hydrogen oil system.
Emergency medical unit from Apex arrived on the fire scene.
0011 AM 0022 AM NRC notified of alert classification.
NRC resident inspector arrived on sit A roximate Time Octo er,
cont d
Events 0030 AM Fire fighting personnel were directed to move away from the 286 elevation fire areas as the hydrogen pressure decreased in generator.
There was concerns that fire might enter the generator and explode.
The hose nozzles were tied down and left unattended and were being discharged into the fire.. The deluge valve to the transformer fire protection system was closed.
0040 AM 0059 AN 0102 AM Operators started to purge the generator with C02.
Fire fighters were permitted to enter the fire area and continue fire fighting operations.
Technical Support Center was activated.
Fire on 314,elevation of the turbine building at generator was verified to be extinguished and all fire hoses were secured.
0103 AN 0105 AM 0115 AM 0135 AN 0145 AN 0242 AN Generator CO, pressures was at 2 psi.
Transformer
"B" still had small fire in duct termination box on top of generator.
Fire brigade was prepared to discharge foam/water hose streams to extinguish the remaining fire.
However, at 0115 AM foam was discharged into all three transformers oil collection pits by the fire fighters as a fire prevention measure.
Fire fighter discharged one dry.
chemical extinguisher into termination box on top of transformers.
This extinguished the remaining fire..
All fires were extinguished.
Walkdown inspection initiated.
Alert Terminate c ~
Sequence of Events.
The turbine building fire was extinguished at 12:45 a.m.
on October
by water supplied from the turbine building fire protection hose stations.
The fire was prevented from spreading to the transformer by manually activating the water spray fire protection system provided for the transformer.
The fire in the duct termination box on top of the transformer was extinguished by means of a portable dry chemical extinguisher at 1:45 a.m.
on October 10.
d.
The NRC inspectors reviewed the fire fighting operations performed and found these actions to be satisfactory.
The decisions to request offsite assistance in the early stages of the fire was considered prudent since the normal five man plant fire brigade is only designed to combat a single fire and not to fight multiple fires which are burning at the same time.
The prompt actions by the Fire Protection Technical Aid to manually activate the transformer deluge system reduced, manual fire fighting requirements and provided
, appropriate protection for preventing the spread of this fire to the transformer.
Overall, the fire fighting operators limited the fire damage to the points of origin and prevented the fire spread to adjacent plant equipment.
This can be attributed to a sound fire brigade training program and the professionalism demonstrated by the fire brigade members.
However, the decisions to respond to the fire without self contained breathing apparatus, although not a factor in'his fire is not considered a good practice, and 'corrective action should be taken to prevent further occurrence on this item.
Following the fire the plant was maintained in hot shutdown, mode 3, and the licensee elected to enter the refueling outage which was originally scheduled to start on October 21, 1989.
e.
The NRC inspectors interviewed the fire chiefs from the responding offsite fire departments.
The fire chiefs expressed their appreciation for the cooperation provided by the plant staff during the emergency events and the training provided to the fire fighters.
The security access provided to fire department responding to this event was well organized and permitted rapid egress into the protected area by responding to the fire fighting personnel.
Observations in the Electrical Area for Event of 10-9-89.
In accordance with CP8L's IBMDPROC08 - Relay Coordination-OS4, SHNPP's protective relay systems of the main generator, the main transformer and the unit auxiliary transformers, through the operation of generator lock out relays (86-G1A and 86-G1B) comprise a
unified generator-power transformers protective relay system.
The components of the system are, (1) Generator-main transformer protective relay system, including the relay protection of the isolated phase bus connection between the components, ana (2) Unit auxiliary transformers 1A and 1B protective relay system At SHHPP all electrical faults, with few exception within the boundaries of the. above system, result in an immediate trip.
The trips are actuated with the operation of either one of the generator lock out relays 86-G1A or 86-GIB.
These trips refer to the practice of closing the turbine valves, opening of the high voltage generator breakers and removing excitation to the main generator.
The Sequence of Events (SOE)
Recorder indicated that an electrical fault sensed by the Generator-Main Transformer protective relay system (87/GMTl)
was the initiating event for the October 9th occurrence.
The October 9th significant SOE through the reactor trip are shown below:
Time 23:05:34.391 23:05:34.464 23:05:34.545 87/GMTl Transformer Differential Relay picks up and sends a
signal to
lockout relay--73 milliseconds later, The first of three low DEH hydraulic pressure switch trips indicating the
lockout relay has picked up and the turbine is tripping.
81 milliseconds later, Reactor trip breaker opens.
A licensee representative also stated that oscillograph traces show that the main transformer breakers opened within 4 cycles (66.6 milliseconds)
of fault detection which also co'nfirms that the
lockout relay, had picked up.
It appears that all safety systems functioned satisfactorily and as designed.
The licensee, his vendors, and consultants are in the process of doing further investigation, components are being opened and megger testing of the main generator was to commence late on October 12, 1989.
The Iso-Phase vendor representatives were scheduled to be on site October 14, 1989.
The damage reported elsewhere in this report was visually observed and the root cause(s)
for this event cannot be determined until a
"more detailed investigation is performed.
The licensee's detailed investigation and the opening of components to determine the root cause(s)
is still in process.
The Licensee stated that a detailed report would be prepared and that a L'icensee Event Report (LER) would be issued in 30 days.
As stated previously it appears that all safety systems functioned satisfactorily and as designe.
Exit Interview The inspection scope and results were summarized on October 12, 1989, with those persons indicated in paragraph 1.
The inspectors described the areas inspected and discussed in detail the inspection results listed above.
5.
Acronyms and Initialisms SHNPP -
Shearon Harris Nuclear Power Plant SOE
-
Sequence. of Events LER
-
Licensee Event Report CP&L
-
Carolina Power and Light Company