ML20149D252
| ML20149D252 | |
| Person / Time | |
|---|---|
| Site: | Indian Point, Crane  |
| Issue date: | 07/11/1997 |
| From: | Collins S NRC (Affiliation Not Assigned) |
| To: | GENERAL PUBLIC UTILITIES CORP. |
| Shared Package | |
| ML20149D255 | List: |
| References | |
| NUDOCS 9707170060 | |
| Download: ML20149D252 (7) | |
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7590-01-P UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION j
In the matter of
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GPU NUCLEAR CORPORATION
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Docket No. 50-289
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Three Mile Island Nuclear
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Generating Station, Unit 1
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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 (THI-l 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 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, 1
supplemented by letters dated August 28, 1996, and January 3, 1997, the 9707170060 970711 PDR ADOCK 05000289 P
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l 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 l
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.
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. 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 I 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-1 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-Il9 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, CB-FA-2f, CB-FA-29, 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
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~ l 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-2, CB-FA-3a, and CB-FA-3b, the exposure threat of the Thermo-Lag protected 9
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 respect to upgrading this envelope to a 3-hour fire rating.
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On the basis of the NRC staff evaluations discussed above, and contingent on the installation of area-wide fire detection systems, upgrading i
the existing Thermo-Lag fire barriers to ensure a minimum 1-hour fire rating, I
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-29, 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 t' at special circumstances are present in that application of the. regulation is not necessary to achieve the underlying purpose cf the rule, which is to establish fire protection features such that the ability to pedorm safe shutdown functions in the event of a fire is maintained.
l Therefore, contingent on the installation of an area-wide fire detection l
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 l
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above, the Commission hereby grants GPU Nuclear Corporation an exemption from a
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 H
fire areas CB-FA-2b, CB-FA-2c,'CB-FA-2d, CB-FA-2e, CB-FA-2f, CB-FA-29, 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.
p Pursuant to 10 CFR 51.32, the Commission has determined that the 4
granting of this exemption will have no significant impact on the quality of
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I the human environment (62 FR 37082).
This exemption is effective upon issuance.
FOR THE NUCLEAR REGULATORY COMMISSION Original signed by:
Samuel J. Collins, Director Office of Nuclear Reactor Regulation Dated at Rockville, Maryland, this lith day of July 1997.
DOCUMENT NAME: G:\\BUCKLEY\\EXEMP.GPU
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$641+tfs DATE 06/20/97 06/23/97 07/08/97
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