[Federal Register Volume 60, Number 141 (Monday, July 24, 1995)]
[Notices]
[Pages 37909-37911]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-18139]
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NUCLEAR REGULATORY COMMISSION
[Docket Nos. 50-266 and 50-301]
Wisconsin Electric Power Co., (Point Beach Nuclear Plant, Units 1
and 2); Exemption
I.
Wisconsin Electric Power Company (WEPCO, the licensee) is the
holder of Facility Operating License Nos. DPR-24 and DPR-27 which
authorize operation of Point Beach Nuclear Plant (PBNP), Unit Nos. 1
and 2. The units are pressurized water reactors (PWR) located in
Manitowoc County, Wisconsin. The licenses provide, among other things,
that the facilities are subject to all rules, regulations, and orders
of the Nuclear Regulatory Commission (the Commission) now or hereafter
in effect.
II
Section III.G.1 of Appendix R to 10 CFR Part 50 requires, in part,
that fire protection features shall be provided for structures,
systems, and components important to safe shutdown and that one train
of systems necessary to achieve and maintain hot shutdown conditions be
free of fire damage.
Section III.G.2 of Appendix R requires that (except as provided for
in Section III.G.3), where cables or equipment (including associated
nonsafety circuits that could prevent operation or cause maloperation
due to hot shorts, open circuits, or shorts to ground) of redundant
trains of systems necessary to achieve and maintain hot shutdown
conditions are located within the same fire area outside of primary
containment, certain specified means be provided to ensure that one of
the redundant trains is free of fire damage.
Pursuant to 10 CFR 50.12(a), the NRC may grant exemptions from the
requirements of the regulations (1) which are authorized by law, will
not present an undue risk to the public health and safety, and are
consistent with the common defense and security; and (2) where special
circumstances are present.
By letter dated August 5, 1994, as supplemented by letters dated
September 9, 1994, October 31, 1994, and February 28, 1995, the
licensee requested an exemption from Section III.G.2.b of Appendix R to
10 CFR Part 50, to the extent that it requires the separation of
redundant trains of safe shutdown cables and equipment by a horizontal
distance of more than 20 feet, with no intervening combustibles, in the
auxiliary feedwater pump fire area. Intervening combustibles in the
form of cable fill in three cable trays, added as part of the diesel
generator addition project, are located within the separation space
between redundant trains of cables and equipment required to achieve
and maintain safe shutdown after a fire. In addition, the horizontal
separation provided between redundant auxiliary feedwater pumps is only
14 feet.
The staff previously granted an exemption for intervening
combustibles in this fire area in a Safety Evaluation dated July 3,
1985. This evaluation stated that the minimum separation between
redundant trains was 26 feet with a maximum separation of 60 feet.
However, this space contains cable trays installed horizontal and
parallel to the trays containing redundant cables. Based on the wide
separation of the redundant trains, the configuration and limited
amount of intervening combustibles, and the installed automatic Halon
suppression system, the staff concluded that it is unlikely that an
exposure fire or electrically initiated fire of the sufficient
magnitude to prevent safe shutdown could develop prior to actuation of
the Halon system and the arrival of the fire brigade. The three new
cable trays (GW01-03, GN 01-03, and GC01-02), installed as part of the
diesel generator addition project, are routed perpendicular to the
redundant trains and provide a continuous path of combustibles between
the redundant trains of equipment and cabling. This new configuration
is outside the scope of the exemption granted to the licensee on July
3, 1985.
[[Page 37910]]
The auxiliary feedwater pump fire area contains the following safe
shutdown equipment and cables: Two steam-driven and two motor-driven
auxiliary feedwater pumps; local control panels for the motor-driven
feedwater and service water pumps; power and control cables for the
charging pumps; instrumentation equipment and cables; residual heat
removal and component cooling water pump cables; and emergency AC power
and DC control cables.
One auxiliary feedwater pump and one service water pump are
required to remain operable to achieve hot shutdown following a fire.
The conduits containing power cables for one train of charging pumps
for each unit in this area are enclosed in a fire barrier having a
rating of one hour, in accordance with the requirements of Section
III.G.2.c of Appendix R to 10 CFR Part 50. Instrumentation cables in
trays and some conduits are separated by a minimum horizontal distance
of 20 feet. This separation distance is not free of intervening
combustibles. Instrumentation cables routed in conduit that are not
separated by a horizontal distance of 20 feet have been enclosed in a
fire barrier assembly having a rating of 1 hour, in accordance with the
requirements of Section III.G.2.c of Appendix R to 10 CFR Part 50. The
licensee has provided repair procedures and materials so that systems
in this area necessary to achieve and maintain cold shutdown can be
repaired within 72 hours, in accordance with the requirements of
Section III.G.1.b of Appendix R to 10 CFR Part 50.
The cables installed in the new trays meet the flame spread
requirements specified in IEEE 383. To minimize the potential for fire
propagation involving the new cable trays, the licensee has installed
sheet metal tray covers on the top and bottom of each tray, installed a
single layer of ceramic fiber blanket on top of the cables in each
tray, and installed fire breaks at each end of each tray. In Generic
Letter 86-10, ``Implementation of Fire Protection Requirements,'' the
staff stated that cables routed in trays that are either fully open or
fully closed should be considered as intervening combustibles. However,
cables in trays having a solid sheet metal bottom, sides and top, if
protected by automatic detection and suppression systems, have been
found acceptable under the exemption process. The auxiliary feedwater
pump fire area is provided with an automatic fire detection and alarm
system that was designed in accordance with National Fire Protection
Association (NFPA) 72D, ``Standard for the Installation, Maintenance,
and Use of Proprietary Protective Signalling Systems,'' and NFPA 72E,
``Standard on Automatic Fire Detectors.'' The Halon system installed in
the area was designed in accordance with NFPA 12A, ``Halon 1301 Fire
Extinguishing Systems.''
To evaluate the fire hazard associated with this modification and
the adequacy of the protection provided, the licensee contracted with
Hartford Steam Boiler-Professional Loss Control to perform a fire
protection engineering analysis. This analysis was submitted by
licensee letter dated February 28, 1995. The analysis concluded that
the new cable trays would not serve as an intervening combustible and,
therefore, would not provide a path for fire propagation between
redundant safe shutdown trains.
Redundant equipment and cabling in the auxiliary feedwater pump
fire area are separated by a horizontal distance ranging from a minimum
of 14 feet, for the adjacent motor-driven auxiliary feedwater pumps, to
31 feet for the local control panels. The separation between the steam-
driven auxiliary feedwater pumps is 29 feet. Each auxiliary feedwater
pump is separated from the other pumps by concrete missile barrier
walls that extend from the floor of the room to the ceiling.
Combustibles located in this area consist of cable insulation on
the approximately 184,000 feet of cable exposed in trays, approximately
two gallons of lube oil located in the auxiliary feedwater pumps, and
any transient combustibles that may be used or stored. Transient
combustibles and hot work activities in this area are administratively
controlled by plant procedures.
Fire detection and suppression systems designed, installed and
maintained in accordance with the requirements prescribed in the NFPA
codes have been demonstrated to be effective in the early notification
and suppression of fires at nuclear power facilities. Actuation of the
automatic Halon fire extinguishing system, coupled with the rapid
response of the plant fire brigade to the notification provided by the
fire detection system installed in this area, gives reasonable
assurance that fires in the auxiliary feedwater pump fire area will be
promptly detected, controlled, and extinguished and, therefore, do not
present a significant hazard to plant safety.
Fire test conducted by the NRC, other government agencies, and the
nuclear industry to evaluate the effectiveness of enclosing cable trays
with sheet metal covers, or installing ceramic fiber blankets over
cables in trays, have demonstrated that these methods, used
independently or in combination, are effective in reducing the
potential for ignition of, and flame spread along, cables installed in
trays. The tests sponsored by the NRC were published in NUREG/CR-0381,
SAND 78-1456, ``A Preliminary Report on Fire Protection Research
Program Fire Barriers and Fire Retardant Coating Tests.'' Flame spread
tests of the ceramic fiber blanket used in the auxiliary feedwater pump
room (Carborundum Durablanket-S), in accordance with Underwriters
Laboratories Test Standard 723, ``Test for Surface Burning
Characteristics of Building Materials,'' demonstrate that this material
has a flame spread rating of 0 and a smoke developed rating of 0. The
use of IEEE 383 cables, the ceramic fiber blanket, and sheet metal
cable tray covers provide reasonable assurance that a fire will not
spread along the cables form one train of redundant safe shutdown
equipment to the other.
The plant configuration, administrative controls, and the fire
protection provided for the auxiliary feedwater pump fire area provide
reasonable assurance that at least one train of equipment and cabling
required to achieve and maintain safe shutdown will remain operable
following a fire in this area. This determination is based upon: (1)
The code compliant automatic detection and suppression systems provided
in the area; (2) the manual fire suppression capability provided in
this area; (3) the sheet metal cable tray covers installed on the top
and bottom of cable trays GN01-03, GW01-03 and GG01-04; (4) the ceramic
fiber blanket installed on top of the cables in the new trays; (5) the
use of IEEE 383 qualified cable in the new trays; (6) the spatial
separation provided between redundant trains of equipment required for
safe shutdown after a fire; and (7) the lack of sufficient combustibles
in the vicinity of the new trays to present an exposure fire hazard.
On the basis of this evaluation, the Commission concludes that the
three cable trays installed as part of the diesel generator addition
project do not present an undue risk to the public health and safety.
Therefore, the licensee's request for an exemption from the technical
requirements of Section III.G.2.b of Appendix R to 10 CFR Part 50, for
the auxiliary feedwater pump fire area is acceptable.
III
The Commission has determined, pursuant to 10 CFR Part 50.12, that
this
[[Page 37911]]
exemption as described in Section II above is authorized by law, will
not present an undue risk to the public health and safety, and is
consistent with the common defense and security. Furthermore, the
Commission has determined that special circumstances as provided in 10
CFR 50.12(a)(2)(ii) are present in that application of the regulation
in the particular circumstances is not necessary to achieve the
underlying purpose of the rule. The underlying purpose of Section
III.G.1 of Appendix R is to ensure that one train of systems needed for
hot shutdown be free of fire damage. Application of this section (to
the extent that it requires the separation of redundant trains of safe
shutdown cables and equipment by a horizontal distance of more than 20
feet, with no intervening combustibles, in the auxiliary feedwater pump
fire area) is not necessary to achieve the underlying purpose of the
rule because the licensee's proposal still provides reasonable
assurance that one safe shutdown train will be free of fire damage.
IV
Accordingly, the Commission hereby grants an exemption from the
requirements of Section III.G.2.b of Appendix R to 10 CFR Part 50 to
allow the intervening combustibles in the form of cable fill in three
cable trays to remain installed in the auxiliary feedwater pump fire
area. These trays were added as part of the diesel generator addition
project, and are located within the separation space between redundant
trains of cables and equipment required to achieve and maintain safe
shutdown after a fire.
Pursuant to 10 CFR 51.32, the Commission has determined that the
granting of this exemption will have no significant impact on the
quality of the human environment (60 FR 35755).
This exemption is effective upon issuance.
Dated at Rockville, Maryland this 18th day of July 1995.
For the Nuclear Regulatory Commission.
Jack W. Roe,
Director, Division of Reactor Projects III/IV, Office of Nuclear
Reactor Regulation.
[FR Doc. 95-18139 Filed 7-21-95; 8:45 am]
BILLING CODE 7590-01-M
