ML20149D267
| ML20149D267 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 07/11/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20149D255 | List: |
| References | |
| NUDOCS 9707170067 | |
| Download: ML20149D267 (11) | |
Text
\\.
l p zed p
- a UNITED STATES o.
s j
NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20066-4001
% * * * *
- p$
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION LICENSEE REQUEST FOR EXEMPTION FROM l
SECTION III.G.2.c 0F APPENDIX R TO 10 CFR PART 50 i
THREE MILE ISLAND NUCLEAR GENERATING STATION. UNIT 1 DOCKET NO. 50-289 1.
INTRODUCTION Appendix R, " Fire Protection Pror -
telear Power Facilities Operating Prior to January 1, 1979," to Title n
,no Code of Federal Reaulations (10 CFR) Part 50, establishes fire protection features required to satisfy General Design Criterion 3, " Fire protection," of Appendix A to 10 CFR Part 50, with respect to certain generic issues for nuclear power plants licensed to operate prior to January 1, 1979.
By letters dated l
August 16 and August 28, 1996, and supplement dated January 3, 1997, GPU Nuclear, the licensee for Three Mile Island Nuclear Generating Station, Unit 1 (TMI-1), requested an exemption from the technical requirements of Section III.G.2.c of Appendix R to 10 CFR Part 50 which specifies the separation of i
l certain redundant safe shutdown circuits with 1-hour fire-rated barriers and l
automatic suppression and detection syttems.
2.
EXEMPTION REQUESTED The licensee requested 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 suppression systems in fire areas where redundant circuits required for safe shutdown are separated by fire barriers having a i
1-hour rating and have fire detectors installed.
3.
DISCUSSION The licensee has completed a review of installed Thermo-Lag fire barriers in THI-1. The licensee is qualifying the installed Thermo-Lag barriers that are the subject of this exemption request as 1-hour rated fire barriers and is requesting an exemption from the requirements of 10 CFR Part 50, Appendix R, Section III.G 2.c, for an automatic suppression system in certain fire areas where circuits of redundant safe shutdown equipment in the same fire area are enclosed in a 1-hour fire barrier.
The licensee's request encompasses nine fire areas where Thermo-Lag is installed on electrical raceways and was originally installed to provide ENCLOSURE 9707170067 970711 PDR ADOCK 05000209 P
( 3-hour' separation between redundant circuits located in the same fire area in accordance with Section III.G.2.a of Appendix R.
In a letter of August 16, 1996, the licensee committed to augment the existing detection systems in these fire areas / zones such that each of the nine fire areas is protected by an area-wide automatic detection system.
l The licensee has requested the exemption for the following fire areas / zones, all of which are contained in the control building structure in the plant:
CB-FA-2b, CB-FA-2c, CB-FA-2d, CB-FA-2e, CB-FA-2f, CB-FA-29, CB-FA-3a, CB-FA-3b, and FH-FZ-5.
l The licensee has administrative controls in place over transient combustibles l
and work in the plant in accordance with 10 CFR 50, Appendix R, Section III.K, Sections 1-8, as documented in an NRC Safety Evaluation dated June 4, 1984.
These controls require total insitu plus allowable transient fire load in a fire area / zone (or cumulative load) to be half of that which would challenge the lowest rated barrier in the zone.
These limits are documented in licensee l
procedures that are referenced in and implement the licensee's Fire Protection Program under license condition 2.c(4).
Due to the re-rating of fire barriers in the areas discussed from 3-hour to 1-hour barriers, the allowable transient limits will have to be lowered for these areas to femain in compliance with Appendix R,Section III.K, commitments.
The licensee will lower these limits for these fire areas to remain in compliance, and will invoke temporary compensatory measures should the transient fire loads exceed the allowable l
limits, as described in their letter dated August 16, 1996.
The licensee completed an evaluation of all the Thermo-Lag fire bhrriers which are subject to this exemption request in Topical Report #094, "TMI 1 Evaluation of Thermo-Lag Fire Barriers," dated July 10, 1996, provided in a letter dated August 28, 1996.
'The licensee found that they 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. A l
summary of each of the nine fire areas is presented below.
3.1 Fire Area CB-FA-2b l
This area is located on elevation 322' of the coatrol building and measures approximately 48 feet x 20 feet x 15 feet high. The principle combustibles in the area are electrical equipment (switchgear) and exposed cable insulation.
Most of the cable insulation in the area meets the Institute of Electrical and Electronics Engineers (IEEE) 383 standard for flammability.
The fire hazard in this area is low to moderate.
Fire protection features for this area include a heating, ventilation, and air conditioning (HVAC) duct smoke detection system which actuates an alarm in the control room.
This is to be augmented with an area-wide early warning fire detection system. A fire hose station is available in an adjacent fire zone, and is capable of bringing a hose stream to bear on any location within this fire area.
In addition, portable CO and dry chemical extinguishers are 2
available in the adjacent stair tower.
It is estimated by the licensee that 1
l
' the full fire brigade complement could bring manual suppression to bear on a fire in this fire area in 15 minutes.
The specific safe shutdown circuits and equipment protected by the existing Thermo-Lag fire barriers in this fire area are associated with the following functions:
1
.Make-up and Supporting Functions Reactor Coolant System (RCS) Pressure Steam Generator Pressure and Level e
Source Range Monitoring j
e Electrical Power System e
l These circuits require fire barrier protection in order to ensure a safe shutdown path is available if a fire damages the redundant unprotected l
circuits and equipment in this fire area. Cables for the above functions are protected in four different barrier " envelopes" including a number of different Thermo-Lag protected configurations, including conduits, condulets and. cable trays as well as penetration interfaces.
Several of the envelopes pass over heavily loaded cable trays and switchgear, which could act as a possible ignition source. A fire in the cable trays could expose the protected envelopes.
3.2 Fire Area CB-FA-2c i
This area is located on elevation 322' of the control building and measures approximately 48 feet x 22 feet x 15 feet high.
The principle combustible in the area is exposed cable insulation. Most of the cable insulation in the l
area meets the IEEE 383 standard for flammability. The fire loading for this j
area is considered to be low.
l Fire protection features for this area include an HVAC duct smoke detection t
system which actuates an alarm in the control room.
This is to be augmented with an area-wide early warning fire detection system. A fire hose station is available in an adjacent fire zone, and is capable of bringing a hose stream to bear on any location within this fire area.
In addition, portable CO and 2
dry chemical extinguishers are availtble in the adjacent stair tower.
It is estimated by the licensee that the full fire brigade complement could bring manual suppression to bear on a fire in this fire area in 15 minutes.
The specific safe shutdown circuits and equipment protected by the existing Thermo-Lag fire barriers in this fire area are associated with the'following functions:
3 team Generator Pressure and Level e
Electrical Power System e
These circuits require fire barrier protection in order to ensure a safe shutdown path is available if a fire damages the other unprotected circuits i
and equipment in this fire area.
Cables for the above functions are p/wmed in three different barrier envelopes which contain a number of different j
Thermo-Lag protected configurations, including conduits, condulets, and boxes i
i i
- as well as penetration interfaces. Two of the envelopes in this fire brea are not located near in-situ combustibles or ignition sources. The third is located above a heater controller (electrical panel) with no intervening combustibles.
3.3 Fire Area CB-FA-2d This area is located on elevation 322' of the control building and measures approximately 23 feet x 30 feet x 15 feet high.
The principle combustible in the area is exposed cable insulation. Most of the cable insulation in the area meets the IEEE 383 standard for flammability. The fire loading for this area is low to moderate.
Fire protection features for this area include an HVAC duct smoke detection system which actuates an alarm in the control room.
This is to be augmented with an area-wide early warning fire detection system. A fire hose station is available in an adjacent fire zone, and is capable of bringing a hose stream to bear on any location within this fire area.
In addition, portable CO and dry chemical extinguishers are available in the adjactnt stair tower. Ilis estimated by the licensee that the full fire brigac!e complement could bring manual suppression to bear on a fire in this fire area in 15 minutes.
The specific safe shutdown circuits and equipment protected by the existing Thermo-Lag fire barriers in this fire area are associated with the following functions:
Reactor Coolant Pump Thermal Barrier Cooling Electrical Power System These circuits require fire barrier protection in order to ensure a safe shutdown path is available if a fire damages the other unprotected circuits and equipment in this fire area.
Cables for the above functions are protected in three different barrier envelopes which contain a number of different Thermo-Lag protected configurations, including conduits, condulets, and penetration interfaces. All of the envelopes pass over heavily loaded cable trays, while two of them are also over 120V/250V de distribution panels, which could serve as an ignition source.
3.4 Fire Area CB-FA-2e This area is located on elevation 322' of the control building and measures approximately 23 feet x 30 feet x 15 feet high.
The principle combustible in the area is exposed cable insulation. Most of the cable insulation in the area meets the IEEE 383 standard for flammability. The fire loading in this area is considered low to moderate.
Fire protection features for this area include an HVAC duct smoke detection system which actuates an alarm in the control room.
This is to be augmented with an area-wide early warning fire detection system. A fire hose station is available in an adjacent fire zone, and is capable of bringing a hose stream to bear on any location within this fire area.
In addition, portable CO and 2
=
g 5-dry chemical extinguishers are available in the adjacent stair tower.
It is estimated by the licensee that the full fire brigade complement could bring manual suppression to bear on a fire in this fire area in 15 minutes.
The specific safe shutdown circuits and equipment protected by the existing Thermo-Lag fire barriers in this fire area are associated with the non-nuclear instrumentation / integrated control system (NNI/ICS) cabinet. This circuit requires fire barrier protection in order to insure power to train "A" instrumentation outside this fire area. Cables for the above functions are protected in an envelope with four Thermo-Lag protected configurations, including two conduits, a condulet, and a penetration interface.
This envelope passes over two side-by-side heavily loaded cable trays.
3.5 Fire Area CB-FA-2f This area is located on elevation 322' of the control building and. measures approximately 24 feet x 30 feet x 15 feet high.
The principle combustibles in the area are battery cases and exposed cable insulation. Most of the cable insulation in the area meets the IEEE 383 standard for flammability.
The fire loading for this area is considered low.
Fire protection features for this area include an HVAC duct smoke detection system'which actuates an alarm in the control room.
This is to be augmented with an area-wide early warning fire detection system. A fire hose station is available in an adjacent fire zone, and is capable of bringing a hose stream to bear on any location within this fire area.
In addition, portable C0 and dry chemical extinguishers are available in the adjacent stair tower. Ikis j
estimated by the licensee that the full fire brigade complement could bring manual suppression to bear on a fire in this fire area in 15 minutes.
The specific safe shutdown circuits and equipment protected by the existing Thermo-Lag fire barriers in this fire area are associated with the following functions:
l Make-up and Supporting Functions
=
Reactor Coolant Pump Thermal Barrier Cooling Electrical Power System These circuits require fire barrier protection in order to ensure a ' safe shutdown path is available if a fire damages the other unprotected circuits
{
and equipment in this fire area. Cables for the above functions are protected in a barrier envelope which contains a box and a cable tray protected by 1
Thermo-Lag. This envelope passes about 5 feet above a heavily loaded open
{
cable tray.
i 3.6 Fire Area CB-FA-2a This area is located on elevation 322' of the control building and measures approximately 24 feet x 30 feet x 15 feet high.
The principle combustibles in the area are battery cases and exposed cable insulation. Most of the cable insulation in the area meets the IEEE 383 standard for flammability.
The fire loading in this area is considered low.
I
- Fire protection features for this area include an HVAC duct smoke detection system which actuates an alarm in the control room. This is to be augmented s
with an area-wide early warning fire detection system. A fire hose station is available in an adjacent fire zone, and is capable of bringing a hose stream to bear on any location within this fire area.
In addition, portable C0 and dry chemical extinguishers are available in the adjacent stair tower.
Ikis estimated by the licensee that the full fire brigade complement could bring manual suppression to bear on a fire in this fire area in 15 minutes.
The specific safe shutdown circuits and equipment protected by the existing Thermo-Lag fire barriers in this fire area are associated with the NNI/ICS cabinet. This circuit requires fire barrier protection in order to ensure power to instrumentation outside this fire area. Cables for the above functions are protected in an envelope which contains a box and a cable tray protected by Thermo-Lag. The envelope is not located near any in-situ combustibles.
3.7 Fire Area CB-FA-3a This area is located on elevation 338'-6" of the control building and measures approximately 49 feet x 17 feet x 16 feet high. The principle combustibles in the area are electrical equipment (switchgear) and exposed cable insulation.
]
Most of the cable insulation in the area meets the IEEE 383 standard for flammability.
The fire loading for this area is considered moderate.
Fire protection features for this area include an HVAC duct smoke detection system which actuates an alarm in the control room.
This is to be augmented with an area-wide early warning fire detection system. A fire hose station is available in an adjacent fire zone, and is capable of bringing a hose stream to bear on any location within this fire area.
In addition, portable C0 and dry chemical extinguishers are available in the adjacent stair tower. Ilis estimated by the licensee that the full fire brigade complement could bring manual suppression to bear on a fire in this fire area in 15 minutes.
The specific safe shutdown circuits and equipment protected by the existing Thermo-Lag fire barriers in this fire area are associated with the following functions:
Supporting Functions for Make-up Reactor Coolant Pump (RCP) Thermal Barrier Cooling Electrical Power System These circuits require fire barrier protection in order to ensure a safe shutdown path is available if a fire damages the other unprotected circuits and equipment in this fire area.
Cables for the above functions are protected in two different envelopes of different Thermo-Lag protected configurations, including conduits, condulets, and boxes as well as penetration interfaces.
One envelope is located 2 to 3 feet above a heater controller.
The other passes 5 feet over a heavily loaded open cable tray and 6 feet over the ID 4160V Switchgear.
It is located inside a fireproofed I-beam where it is routed over the switchgear.
7 -.
. _ _ - ~.
s 3.8 Fire Area CB-FA-3b This area is located on elevation 338'-6" of the control building and measures a) proximately 49 feet x li feet x 16 feet high. The principle combustibles in tie area are electrical equipment (switchgear) and exposed cable insulation.
Most of the cable insulation in the area meets the IEEE 383 standard for flamability. The fire loading for this area is considered moderate.
Fire protection features for this area include an HVAC duct smoke detection systam which actuates an alarm in the control room.
This is to be augmented with an area-wide early warning fire detection system. A fire hose station is available in an adjacent fire zone, and is capable of bringing a hose stream to bear on any location within this fire area.
In addition, portable CO and 2
dry chemical extinguishers are available in the adjacent stair tower.
It is estimated by the licensee that the full fire brigade complement could bring manual suppression to bear on a fire in this fire area in 15 minutes.
The specific safe shutdown circuits and equipment protected by the existing Thermo-Lag fire barriers in this fire area are associated with the following functions:
Make-up RCS Pressure Electrical Power System These circuits require. fire barrier protection in order to ensure a safe shutdown path-is available if a fire damages the other unprotected circuits and equipment in this fire area.
Cables for the above functions are protected in four different barrier envelopes which contain a number of different i
Thermo-Lag protected configurations, including conduits, condulets, and boxes as well as penetration interfaces.
Three of the envelopes described above i
pass either over or under a heavily loaded open cable tray.
The fourth
. envelope is not located near any in-situ combustibles.
3.9 Fire Zone FH-FZ-5 This fire area is located in the Control Building, with dimensions 120 feet x 21 feet x 80 feet high.
The zone covers four einvations 322'-0", 338'-6",
355'-0", and 380'-0".
Each elevation floor except 322'-0" consists of steel grating.
The principle combustibles in the area are electrical equipment (switchgear) and exposed cable insulation.
Most of the cable insulation in the area meets the IEEE 383 standard for flammability. The fire loading in the area is high.
The principle contributor to the high fire loading begins on elevation 338'-6" with an office complex area.
Concentrations of Class A combustibles, which are the principle contributor to the fire loading in this area, are located on elevations 35S'-0" and 338'-6" of this fire zone. The ceiling of the 322'-0" elevation is reinforced concrete except for an opening via grating to elevation 338'-6" about 30 feet from the Thermo-Lag envelope.
There are intervening combustibles between the fire barrier envelope and the open
.N 7
- i grating, but exposure to the envelope will most likely come from combustibles located in the vicinity of the envelope, not from the office complex on the floors above.
Fire protection features-in this area include area-wide detection in the Instrument and Controls I&C) shop on the 355'-0" level. The licensee has i
committed to install area (-wide detection on the 322'-0" elev J
{
area.
Each elevation'is provided with two hose stations with the exception of the 380'-0" elevation where only one r.ation is available.
Portable fire i
extinguishers are available on all levels.
It is estimated by the licensee that the full fire brigade complement could bring manual suppression to bear 4
on a fire in this fire area in 15 minutes.
i The specific safe shutdown circuits and equipment protected by the existing
+
Thermo-Lag fire barriers in this fire area are associated with the following i
i functions:
j Make-up Reactor Coolant Pump Thermal Barrier Cooling i
These circuits require fire barrier protection in order to ensure a safe j
shutdown path is available if a fire damages the other unprotected circuits and equipment in this fire area.
Cables for the above functions are protected in a fire barrier envelope which contains a number of different Thermo-Lag i
protected configurations, including conduits, condulets, and penetration i
interfaces. This envelope, which is located on the 322'-0" location, is in i
close proximity with a cable tray that carries redundant cabling and passes j
over switchgear.
i 4.
EVALUATION l
These fire areas do not currently meet the technical requirements of Section III.G.2.c of Appendix R because an automatic fixed fire suppression system is not provided in any of the fire areas.Section III.G of appendix R could be satisfied by either protecting each envelope with a 3-hour fire-rated barrier, or by installing automatic fixed fire suppression in addition to the fire detectors in each fire area, along with verifying that all barriers had a 1-hour fire rating..
In its submittal, the licensee states that installation of an automatic suppression system is not desirable because of possible electrical equipment damage from a water suppression system and personnel hazard concerns from a carbon dioxide suppression system. Halon gas.cannot be used due to environmental concerns. Modification of the existing fire barriers to achieve a
a 3-hour rating would present a substantial cost hardship.
4.1 Fire Areas CB-FA-2b. CB-FA-2c. CB-FA-2d. CB-FA-2e. CB-FA-2f. CB-FA-2a.
j CB-FA-3a. and CB-FA-3b i
For a postulated fire in 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 loss of redundant trains of j
several different safe shutdown circuits, including reactor make-up and h
l
4 9
4 supporting functions, RCS pressure control, steam generator pressure and level f
functions, source range monitoring, electrical power system function, NNI/ICS cabinets, and RCP thermal barrier cooling functions, could occur.
These i
circuits must be maintained functional and free from fire damage to assure safe shutdown of the plant.
Fires in the fire areas discussed above are postulated to be slowly developin cable fires, with possible ignition sources including electrical switchgear, g i
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 i
of the envelopes are in close proximity to heavily loaded cable trays, which a
could contribute to a postulated fire. The fire loadings for the fire areas j
mentioned above range from low to moderate.
j The licensee has committed to install area-wide early warning fire detection in all of the fire areas described above.
The system to be installed is
{
designed to detect invisible molecules gene.ated during the precombustion i
stages of an incipient fire and provides active and continuous sampling of the air.
The system operates independently of air movement and is much more sensitive than conventional ionization detection.
The licensee also committed i
to upgrade the Thermo-Lag barriers in the fire arers mentioned above to at t
least a 1-hour fire rating.
t If a fire was to occur in a given fire area, detection from the proposed area-1-
wide detection system would most likely be rapid.
The existing HVAC smoke detection system would isolate room ventilation upon detecting smoke in the 4
Indication of fire would be received in the control room, and if area.
necessary, the fire brigade would be dispatched soon thereafter.
Fire brigade response to any of the fire areas upon receipt of an alarm has been conservatively estimated at 15 minutes. Manual firefighting equipment (hand-i 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 the above areas in 15 minutes or less.
A i
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 exposure threat to the Thermo-Lag protected circuits in these areas 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, administrative controls limiting the transient combustibles in the areas mentioned, and a rapid fire brigade j
response meets tne defense-in-depth principle. Therefore, there is reasonable assurance that a fire in any of the fire areas discussed above will not 4
]
adversely offect the ability to achieve and maintain safe shutdown.
The underlying purpose of Appendix R,Section III.G.2.c, is to establish fire 2
i protection features such that the ability to perform safe shutdown functions l
in the event of a fire will be maintained.
Based on the above, the staff concludes that the underlying purpose of the rule is satisfied. Therefore, this request for exemption from the requirements of Appendix R,Section III.G.2.c, meets the special circumstances delineated in 10 CFR 50.12(a)(2)(ii). The application of the regulation in
1 a
10 -
this circumstance is not necessary to achieve the underlying purpose of the rule since the above discussion demonstrates that with respect to the fire areas / zones where the installed Thermo-Lag barriers have at least a 1-hour fire endurance rating and there is manual suppression available and fast response area-wide detection, and administrative controls limiting transient combustibles, there is an adequate level of safety in terms of maintaining the ability to perform safe shutdown functions in the event of a fire, and, therefore, the underlying purpose of the rule is met.
4.2 Fire Zone FH-FZ-5 The staff does not believe that reasonable assurance has been provided that l
fire area FH-FZ-5 is protected to the same degree as the fire areas evaluated i
in Section 4.1, above. The Thermo-Lag protected envelope in fire zone FH-FZ-5 j
passes directly over switchgear and is in close proximity to cable trays which present a combustible hazard. Tne combustible loading in this area is higher i
than all the others, and area-wide detection is not available on all the
{
elevations of this fire area.
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 area, made up of protected j
conduit. The staff does not believe that there would be undue hardship j
involved in upgrading this envelope to a 3-hour fire rating.
l 5.
CONCLUSION 5.1 Fire Areas CB-FA-2b. CB-FA-2c. CB-FA-2d. CB-FA-2e. CB-FA-2f. CB-FA-2a.
4 1
CB-FA-3a. and CB-FA-3b On the basis of the NRC staff evaluation above, and contingent on the installation of area-wide detection and the upgrading of fire barriers to ensure that all barriers have a 1-hour fire rating (as the licensee committed to in its submittal of August 16,1996), and the implementation of the administrative controls discussed herein, the staff concludes that an i
exemption from the technical requirements of Section III.G.2.c of Appendix R to the extent that it requires the installation of automatic suppression systems, should be granted for fire areas CB-FA-2b, CB-FA-2c, CB-FA-2d, CB-FA-l 2e, CB-FA-2f, CB-FA-2, CB-FA-3a, and CB-FA-3b.
9 i
5.2 Fire Zone FH-FZ-5 4
i Based on the above evaluation, the staff concluded that the licensee's request i
for an exemption from the technical requirements of Section III.G.2.c of Appendix R should be denied for fire area FH-FZ-5.
i Principle contributors:
C.S. Bajwa and E.A. Connell Date: July 11, 1997 i
1 a
- -.