Information Notice No. 88-96: Electrical Shock Fatalities at Nuclear Power Plants
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
December 14, 1988
Information Notice No. 88-96: ELECTRICAL SHOCK FATALITIES AT NUCLEAR
POWER PLANTS
Addressees:
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose:
This information notice is being provided to alert addressees to events
involving fatalities from electrical shock that have occurred at nuclear
reactor facilities. In addition to causing tragic personnel loss, some of
these events have had significant nuclear safety implications because of the
loss or potential loss of safety-related equipment. It is expected that
recipients will review the information for applicability to their facilities
and consider actions, as appropriate, to avoid similar problems. However,
suggestions contained in this information notice do not constitute NRC
requirements; therefore, no specific action or written response is required.
Description of Circumstances:
At Wolf Creek on September 13, 1988, an electrician, who was attempting to add
new wires to a 3/4-inch conduit containing 480-volt energized circuits, was
electrocuted. The electrician had difficulty inserting a nonconducting snake
through the conduit fire seals. Some of the energized wires in the conduit
were damaged during either a previous modification or attempts to remove the
fire seals. The electrician disconnected the conduit from a junction box in
order to remove the fire seals. At this point, the ungrounded conduit
apparently came in contact with the damaged energized wires, becoming
energized itself. The electrician, who was standing on some piping holding
the conduit, provided the missing ground and was electrocuted.
An electrocution occurred under similar circumstances at Quad Cities Unit 1,
on July 16, 1971. An electrician was pulling a new conductor into position in
the high pressure coolant injection (HPCI) room, and for some reason the cable
became energized, causing the death of the electrician.
At Wolf Creek, on October 14, 1987, an electrical technician, who was cleaning
the potential transformer cubicles on the 'B' train emergency safety features
switchgear, came in contact with a 4160-volt energized line and was electro-
cuted. Miscommunication regarding the equipment that was to be deenergized,
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failure to follow work procedures requiring voltage checks on supposedly
deenergized equipment, and the defeating of safety features built into the
potential transformer drawers all contributed to the cause of this tragedy.
Wolf Creek has two redundant 4160-volt safety features busses (NB01 and NB02,
shown in Figure 1), each fed from separate transformers. Each of these trans-
formers also feeds an alternate crossover line to the other bus to permit
powering this opposite bus in case the normal power source for the bus fails.
In order to permit the "B" train switchgear to be cleaned, inspected and
tested, a shift supervisor prepared a clearance to deenergize the switchgear.
In doing this, he left the normal transformer (XNB02) for the "B" train
switchgear energized. He reasoned that this transformer should be left ener-
gized to provide redundant power to the "A" train via the alternate line, and
he believed that he had the concurrence of the Electrical Department for this
configuration. The electrical supervisor with whom he discussed this matter,
however, believed that the shift supervisor was referring to the fact that the
alternate line to the "B" side from the "A" side transformer (XNB01) was to be
left energized, as this line could not be deenergized without shutting down
the "A" bus also. Thus the incoming lines from both transformers to the "B"
train switchgear remained energized, but the electricians believed that the
line from the "B" side transformer had been deactivated.
This misunderstanding would have been discovered if the workmen had followed
the maintenance procedure for this work, which required that all of the sta-
tionary disconnects in each cubicle be checked using high voltage gloves and a
voltage tester to ensure that no voltage was present. In this case, the
day-shift electricians who were doing this part of the procedure only checked
a few of the disconnects.
The night shift was working by the time the electricians got to the cleaning
of the potential transformer drawers. These drawers are arranged such that
when they are pulled out the exposed part of the drawer is deenergized,
regardless of the electrical status of the rest of the switchgear. However,
the electrical technician, who was doing the cleaning, and his supervising
electrician decided to pull the tops off the potential transformer cubicles in
order to facilitate the work.
While the electrical technician was working on the potential transformer on
the switchgear (NB0209) for the line from the normal "B" train transformer, he
came in contact with an energized potential transformer stub and was
electrocuted. The breaker (PA0201) in the line feeding the "B" side
transformer apparently tripped immediately after the energized stub was
contacted. However, the victim was in contact with the cabinet (NB0212) for
the energized line from the "A" side transformer. His sleeve, ignited by
arcing current, was on fire. This apparently led other electricians in the
area who responded to the emergency to believe that the victim was still in
contact with energized equipment. Using belts and hoses, the electricians
tried unsuccessfully to remove the victim. At this point, the Halon fire
protection system in the switchgear room was initiated by the fire, forcing
the electricians out of the room temporarily.
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The electricians in the switchgear area relayed incorrect information to the
control room that a man was hung up on the breaker (NB0212) for the still-
energized alternate line from the "A" side transformer. In their haste to
free the victim, the operators opened the breaker (NB0112) downstream from the
point at which the alternate line to the "B" bus (NB02) leaves the line from
the 'A' side transformer (XNB01). Consequently, this action deenergized the
"A" bus (NB01), but not the alternate line to the B" bus. This action caused
the "A" side diesel generator (NE01) to start, repowering the "A" bus.
However, when the control room personnel were informed that the alternate line
to the "B" side was still energized, they disconnected all power sources,
including the running diesel for both busses by opening breakers 13-48 and
NB0111. As a result, all of the emergency safety systems, including the
operating residual heat removal system, were deactivated.
After the victim had been removed, the operators tried to repower the "A" bus
(NB01) by closing the breaker (NB0111) to the still running diesel but discov-
ered that the diesel generator controls had to be reset in the diesel
generator room first. The "A" bus was then repowered from its normal
transformer (XNB01). The residual heat removal system was out of service for
17 minutes during this event. However, the core was only partially loaded
with fuel at the time, and the reactor coolant temperature rise was
negligible. The Wolf Creek staff have since provided a modification to the
diesel controls to permit them to be reset from the control room after the
diesel power has been interrupted from the control room.
This Wolf Creek event also has a similar precedent. An electrical worker was
electrocuted at the San Onofre Nuclear Power Plant on November 22, 1980 when
he came in contact with a 4-kv line while he was cleaning breaker cubicles.
Discussion:
Working on or around live circuits is common practice at nuclear power plants.
As these events show, this practice can not only be very hazardous to person-
nel, but because of the need to take extraordinary actions during emergency
situations, it can have a serious impact on reactor safety as well. Licensees
are encouraged to review their maintenance practices to ensure that the
following considerations are applied to electrical maintenance activities:
1. Equipment clearance procedures assure that work on live circuits is
undertaken only when absolutely necessary and that when this is the case,
proper consideration is given to the potential for electrical shock and
the loss of safety-related equipment.
2. Procedures for pulling new cables or wires past energized wires include
provisions to prevent damage to the existing wires, prohibitions against
the ungrounding of conduits and junction boxes containing live wires, and
provisions to isolate the electrical workers from the energized wires.
3. Clearance procedures assure that when work on or around energized equip-
ment is necessary, the operators and everyone involved with the actual
work clearly understand exactly which equipment is out of service and
which equipment is to be left energized.
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4. Maintenance supervision ensures that everyone working on electrical
equipment is aware of the importance of following safety procedures, such
as those that require checking for voltage on contacts that are expected
to be deenergized. This safety procedure is particularly important when
more than one crew is involved in the work.
5. Maintenance safety procedures include warnings against defeating protec-
tive features designed to deenergize equipment when it is serviced.
No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact one of the techni-
cal contacts listed below or the Regional Administrator of the appropriate
regional office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: R. Vickrey, RIV
(817) 860-8239
Donald C. Kirkpatrick, NRR
(301) 492-1152
Attachments:
1. Figure 1, Electrical One-Line Diagram
2. List of Recently Issued NRC Information Notices
. Attachment 2
IN 88-96
December 14, 1988
Page 1 of 1
LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
_____________________________________________________________________________
Information Date of
Notice No._____Subject_______________________Issuance_______Issued to________
88-95 Inadequate Procurement 12/8/88 All holders of OLs
Requirements Imposed by or CPs for nuclear
Licensees on Vendors power reactors.
88-94 Potentially Undersized 12/2/88 All holders of OLs
Valve Actuators or CPs for nuclear
power reactors.
88-93 Teletherapy Events 12/2/88 All NRC medical
licensees.
88-92 Potential for Spent Fuel 11/22/88 All holders of OLs
Pool Draindown or CPs for nuclear
power reactors.
88-91 Improper Administration 11/22/88 All holders of OLs
and Control of or CPs for nuclear
Psychological Tests power reactors and
all fuel cycle
facility licensees
who possess, use,
import, export, or
transport formula
quantities of
strategic special
nuclear material.
88-90 Unauthorized Removal of 11/22/88 All NRC licensees
Industrial Nuclear Gauges authorized to
possess, use,
manufacture, or
distribute
industrial nuclear
gauges.
88-89 Degradation of Kapton 11/21/88 All holders of OLs
Electrical Insulation or CPs for nuclear
power reactors.
88-88 Degradation of Westinghouse 11/16/88 All holders of OLs
ARD Relays or CPs for nuclear
power reactors.
_____________________________________________________________________________
OL = Operating License
CP = Construction Permit
Page Last Reviewed/Updated Tuesday, March 09, 2021