Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
October 31, 1990
Information Notice No. 90-69: ADEQUACY OF EMERGENCY AND ESSENTIAL
LIGHTING
Addressees:
All holders of operating licenses or construction permits for nuclear
power reactors.
Purpose:
This information notice is intended to alert addressees to a possible
problem concerning the adequacy of emergency and essential lighting at
commercial power reactor facilities. 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:
On March 3, 1989, Unit 3 at the Palo Verde Nuclear Generating Station
experienced a reactor/turbine trip, main steam isolation, containment
isolation, and safety injection as a result of a grid-induced load
rejection event. This event included three significant system failures:
(1) half of the steam bypass control system malfunctioned; (2) the
atmospheric dump valves (ADVs) failed to operate from the control room
and the remote shutdown panel; and (3) the emergency lighting in the main
steam support structure (MSSS) failed, hampering the operators in their
attempt to cope with the ADV failures. Being unable to maintain pressure
control on the secondary side by operating the ADVs from the control room
or the remote shutdown panel, plant personnel attempted to establish
local (manual) control of the ADVs in the MSSS. When operators first
entered the MSSS, they found no direct lighting. Normal lighting was
lost due to the loss of power to the non-Class 1E electrical busses in
the plant. The emergency lighting was not properly positioned in the
north MSSS room (containing the ADVs for the No. 1 steam generator) to
provide adequate lighting for the operators to perform their required
activities and was not functioning at all in the south MSSS room
(containing ADVs for the No. 2 steam generator). Because of a burned-out
light bulb, plant personnel could not restore essential lighting (from
Class 1E power sources) in the south MSSS room.
9010250054
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During the NRC inspection (50-530/89-13) conducted by an augmented
inspection team (AIT) sent to examine the event at Palo Verde, the staff
found deficiencies in the licensee's maintenance and testing of emergency
and essential lighting. The team discovered that plant personnel had
waived the quarterly preventive maintenance (PM) tasks on the MSSS
emergency and essential lights for five consecutive quarters. By
grouping the lights in the MSSS with the lights in the containment
building, which were inaccessible during power operations, the PM tasks
were waived for the MSSS lights during each of these periods along with
the containment lights. NRC inspections further revealed that the
licensee, prior to the performance of the 8-hour lighting unit discharge
test, performed preventive maintenance (i.e., battery replacement,
addition of electrolyte, cleaning of battery terminals, and battery
charging) on the lighting unit battery. This preventive maintenance
practice resulted in not verifying the performance of the 8-hour emergency
lighting units in the "as found" condition. The inspections also revealed
that the licensee had failed to implement the relevant portions of its
quality assurance program for emergency lighting. Because of these
failures, the emergency lighting was not properly tested, and
deficiencies were not properly corrected.
After the event, plant personnel reconstructed the design bases of the
lighting system and conducted walkdown inspections of the emergency and
essential lighting in the plant. In some instances, the licensee found
the lighting to be inadequate to perform the required tasks because the
original design did not require emergency lights or because the emergency
lights provided inadequate illumination. In addition, the licensee
identified many areas that required the installation of or modification
to lighting to meet the licensee's design bases and the requirements in
10 CFR Part 50 Appendix R.
Background:
At Palo Verde, the essential lighting system is an integral part of the
normal lighting system that provides illumination if the normal lighting
system fails. The essential lighting system is rated non-Class 1E but is
powered from Class 1E sources. The system provides lighting in the
control room, in the shutdown panel area, in the main walkways and
stairs, in the Class 1E switchgear rooms, in areas having Class 1E
equipment, and in areas used for the safe shutdown of the reactor. Upon
loss of the normal lighting system, the essential lighting system
provides adequate illumination for the safe shutdown of the reactor. The
system receives power from two redundant and independent Class 1E ac
busses. Each redundant Class 1E ac bus supplies power to 50 percent of
the essential lighting in the vital areas. The diesel generators provide
backup power.
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The emergency lighting system receives dc power from two redundant Class
1E batteries through inverters and provides illumination for the control
room, the auxiliary electrical equipment rooms, the stairways, and the
points leading to plant exits. The system is normally deenergized and is
automatically energized upon loss of ac power to the normal system. The
emergency lighting system is also composed of 8-hour and 1 1/2-hour
(individually battery-powered) emergency lighting units. The 8-hour
emergency lighting units are designed to meet the technical requirements
of 10 CFR 50 Appendix R, Section III.J which requires that emergency
lighting units with at least an 8-hour battery power supply be provided
in all areas needed for operation of safe shutdown equipment and in
access and egress routes thereto. The 1 1/2-hour emergency lighting
units are installed to meet the requirements of the Life Safety Code.
These lighting units are generally installed in plant locations to
accommodate the safe evacuation of personnel in the event of a fire in
such areas.
Discussion:
During the Palo Verde event, the inadequate lighting conditions
significantly complicated the licensee's efforts to cope with the initial
failure of the ADVs, which delayed the commencement of the controlled
removal of decay heat as called for by the emergency operating
procedures.
It is important to note that adequate PM and routine testing programs for
essential and emergency lighting systems are helpful in ensuring adequate
illumination for the operation of safe shutdown equipment. Emergency
lighting is a key fire protection feature associated with supporting
post-fire safe shutdown operations. The exercise of good engineering
design practices that conform to industry standards ensures the ability
of the lighting system to provide adequate station lighting in all vital
areas during all types of accident or transient conditions. The
implementation of an effective PM and testing program which demonstrates
lighting system operability is important. Emergency lighting PM programs
recommended by manufacturers generally include routine monitoring of the
battery condition for each lighting unit, periodic load testing to verify
that the lighting unit and its associated charger are functioning
properly, and a periodic "as found" 8-hour lighting unit discharge test.
In addition, the Palo Verde event identified that the inadvertent
repositioning of the emergency lighting fixtures can cause inadequate
illumination and that routine verification of emergency lighting fixture
orientation can ensure that emergency lighting is effective.
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This information notice requires no specific action or written response.
If you have any questions about the information in this notice, please
contact one of the technical contacts listed below or the appropriate NRR
project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: N. K. Trehan, NRR
(301) 492-0777
S. R. Peterson, NRR
(301) 492-3062
Attachment: List of Recently Issued NRC Information Notices
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