[Federal Register Volume 62, Number 139 (Monday, July 21, 1997)]
[Notices]
[Pages 39032-39034]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-19063]
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NUCLEAR REGULATORY COMMISSION
[Docket No. 50-289]
GPU Nuclear Corporation; Three Mile Island Nuclear Generating
Station, Unit 1; Exemption
I
GPU Nuclear Corporation (GPU or the licensee) is the holder of
Facility Operating License No. DPR-50 for the Three Mile Island Nuclear
Generating Station, Unit 1 (TMI-1 or the facility). The facility
consists of one pressurized water reactor located at the licensee's
site in Dauphin County, Pennsylvania. The license provides, among other
things, that it is subject to all rules, regulations and orders of the
Nuclear Regulatory Commission (the Commission or NRC) now and hereafter
in effect.
II
Section III.G.2 to Appendix R of 10 CFR part 50 specifies the fire
protection requirements for redundant trains of systems necessary to
achieve and maintain safe shutdown conditions
[[Page 39033]]
when the redundant trains are located within the same fire area.
Subsection III.G.2.c requires that automatic fire suppression systems
shall be installed in fire areas where redundant circuits required for
safe shutdown are separated by fire barriers having a 1-hour rating and
have fire detectors installed. By letter dated August 16, 1996,
supplemented by letters dated August 28, 1996, and January 3, 1997, the
licensee requested an exemption from the requirements of Section
III.G.2.c of Appendix R, to the extent that it requires the
installation of automatic fire suppression systems. The exemption was
requested for fire areas CB-FA-2b, CB-FA-2c, CB-FA-2d, CB-FA-2e, CB-FA-
2f, CB-FA-2g, CB-FA-3a, and CB-FA-3b, and fire zone FH-FZ-5 at TMI-1.
The licensee is seeking this exemption in accordance with the
provisions of 10 CFR 50.12.
The licensee's request encompasses eight fire areas and one fire
zone where Thermo-Lag fire barrier systems were installed on electrical
raceways to protect circuits required for safe shutdown. The Thermo-Lag
barriers were originally installed to provide 3-hour separation between
redundant circuits located in the same fire area. As part of the
licensee's review of installed Thermo-Lag fire barriers at TMI-1, the
licensee identified locations that do not support a 3-hour rating.
The licensee requested the exemption after determining that
installation of fire suppression systems in the affected areas was not
a viable alternative for meeting the regulatory requirements of Section
III.G.2.c. The licensee stated that installation of an automatic
suppression system is not desirable because of the potential for
electrical equipment damage from a water suppression system and because
of personnel hazard concerns from a carbon dioxide suppression system.
Halon gas suppression systems cannot be used because of environmental
considerations. The licensee determined that modification of the
existing Thermo-Lag fire barrier envelopes within the affected fire
areas to achieve a 3-hour rating, and thereby eliminating the
regulatory requirement for fire suppression systems, represented a
substantial hardship without a significant increase in the level of
protection provided.
In lieu of installing automatic fire suppression systems, the
licensee proposed installing area-wide automatic fire detection systems
in each of the affected areas and establishing a minimum 1-hour fire
rating for the existing Thermo-Lag fire barriers.
III
The NRC staff has completed its safety evaluation of the licensee's
request for exemption from certain requirements of Section III.G.2.c of
Appendix R. The staff's review included an evaluation of the fire
hazards, the fire protection features and the safe shutdown circuits
present in each of the affected fire areas.
The licensee has administrative controls in place for transient
combustibles and work in the plant in accordance with Section III.K of
Appendix R as documented in an NRC Safety Evaluation dated June 4,
1984. These controls require, in part, that total in-situ plus
allowable transient fire loads (or cumulative load) in a given fire
area/zone be half of that which would challenge the lowest rated fire
barrier in the zone. These limits are documented in licensee procedures
that are referenced in and implemented by the licensee's Fire
Protection Program.
The licensee completed an evaluation of the Thermo-Lag fire
barriers which are the subject in this exemption request in Topical
Report #904, ``TMI 1 Evaluation of Thermo-Lag Fire Barriers,'' dated
July 10, 1996, and provided in a letter dated August 28, 1996. The
licensee found that the subject Thermo-Lag barriers either currently
have a fire rating of 1-hour or more (in accordance with an American
Society for Testing and Materials (ASTM) E-119 fire exposure test) or
the licensee has committed to upgrade the existing barriers to achieve
a 1-hour rating.
For a postulated fire in areas CB-FA-2b, CB-FA-2c, CB-FA-2d, CB-FA-
2e, B-FA-2f, CB-FA-2g, CB-FA-3a, and CB-FA-3b, the loss of redundant
trains of several different safe shutdown circuits, including reactor
make-up and supporting functions, RCS pressure control, steam generator
pressure and level functions, source range monitoring, electrical power
system function, non-nuclear instrumentation/integrated control system
(NNI/ICS) cabinets, and reactor coolant pump (RCP) thermal barrier
cooling functions, could occur. These circuits must be maintained
functional and free from fire damage to assure shutdown of the plant.
Fires in these eight fire areas are postulated to be slowly
developing cable fires, with possible ignition sources, including
electrical switchgear, fan motors, or heater controllers. Exposure of
the protected envelopes to fire could be expected in some of the fire
areas, should a fire occur. Some of the envelopes are in close
proximity to heavily loaded cable trays, which could contribute to a
postulated fire. The fire loadings for these fire areas range from low
to moderate.
The licensee has committed to augmenting the existing detection
systems in the eight fire areas listed above with area-wide early
warning fire detection systems. The systems to be installed are
designed to detect invisible molecules generated during the
precombustion phases of an incipient fire and to provide active and
continuous sampling of the air. The systems operate independently of
air movement and are much more sensitive than conventional ionization
detection.
If a fire were to occur in a given fire area, detection by the
proposed area-wide detection system would most likely be rapid. The
existing heating, ventilation, and air conditioning (HVAC) smoke
detection systems would isolate--5-room ventilation upon detecting
smoke in the area. Indication of fire would be received in the control
room, and if necessary, the fire brigade would be dispatched. The fire
brigade response time to any of the fire areas upon receipt of an alarm
has been conservatively estimated at 15 minutes. Manual firefighting
equipment (hand-held fire extinguishers and hose stations) is available
in, or adjacent to, all of the fire areas. Manual suppression could be
brought to bear on a fire within any of these fire areas within 15
minutes.
For fire areas CB-FA-2b, CB-FA-2c, CB-FA-2d, CB-FA-2e, CB-FA-2f,
CB-FA-2g, CB-FA-3a, and CB-FA-3b, the exposure threat of the Thermo-Lag
protected circuits is low due to the proximity of the Thermo-Lag
envelopes to intervening combustibles. Therefore, a 1-hour barrier
coupled with an area-wide early warning fire detection system and a
rapid fire brigade response meets the defense-in-depth principle. There
is reasonable assurance that a fire in any of these fire areas will not
adversely affect the ability to achieve and maintain safe shutdown.
The staff does not believe the same assurance has been provided for
fire zone FH-FZ-5. The Thermo-Lag protected envelope in fire zone FH-
FZ-5 passes directly over switchgear and is in close proximity to cable
trays which present a combustible hazard. The combustible loading in
this zone is higher than the other eight fire areas, and the area-wide
detection is not available on all elevations of this fire zone. Given
these factors, there is no reasonable assurance that a fire would not
damage cables in the protected envelope. There is only one Thermo-Lag
envelope in this zone, made up of protected conduit. The staff does not
believe an undue hardship exists with
[[Page 39034]]
respect to upgrading this envelope to a 3-hour fire rating.
On the basis of the NRC staff evaluations discussed above, and
contingent on the installation of area-wide fire detection systems,
upgrading the existing Thermo-Lag fire barriers to ensure a minimum 1-
hour fire rating, and continued implementation of the administrative
controls previously discussed, the staff has concluded that an
exemption from the technical requirements of Section III.G.2.c of
Appendix R, to the extent that it requires the installation of
automatic fire suppression systems, should be granted for fire areas
CB-FA-2b, CB-FA-2c, CB-FA-2d, CB-FA-2e, CB-FA-2f, CB-FA-2g, CB-FA-3a,
and CB-FA-3b. The staff has concluded that the licensee's exemption
request for fire zone FH-FZ-5 should be denied.
IV
The Commission has determined that, pursuant to 10 CFR 50.12, the
exemption requested by the licensee in the letter dated August 16,
1996, supplemented by letters dated August 28, 1996, and January 3,
1997, for fire areas CB-FA-2b, CB-FA-2c, CB-FA-2d, CB-FA-2e, CB-FA-2f,
CB-FA-2g, CB-FA-3a, and CB-FA-3b, is authorized by law, will not
present an undue risk to public health and safety, and is consistent
with the common defense and security. The Commission has further
determined that special circumstances are present in that application
of the regulation is not necessary to achieve the underlying purpose of
the rule, which is to establish fire protection features such that the
ability to perform safe shutdown functions in the event of a fire is
maintained.
Therefore, contingent on the installation of an area-wide fire
detection system in the affected fire areas and upgrading the existing
Thermo-Lag fire barriers within the affected fire areas to ensure a
minimum 1-hour fire rating, and continued implementation of the
administrative controls discussed above, the Commission hereby grants
GPU Nuclear Corporation an exemption from the technical requirements of
Section III.G.2.c of Appendix R, to the extent that it requires the
installation of automatic fire suppression systems, for fire areas CB-
FA-2b, CB-FA-2c, CB-FA-2d, CB-FA-2e, CB-FA-2f, CB-FA-2g, CB-FA-3a, and
CB-FA-3b, at TMI-1. The request for exemption for fire zone FH-FZ-5,
included by the licensee in the same submittal, is denied.
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 (62 FR 37082).
This exemption is effective upon issuance.
Dated at Rockville, Maryland, this 11th day of July 1997.
For the Nuclear Regulatory Commission.
Samuel J. Collins,
Director, Office of Nuclear Reactor Regulation.
[FR Doc. 97-19063 Filed 7-18-97; 8:45 am]
BILLING CODE 7590-01-P
