ML20028C691
| ML20028C691 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 01/04/1983 |
| From: | Clark R Office of Nuclear Reactor Regulation |
| To: | Musolf D NORTHERN STATES POWER CO. |
| Shared Package | |
| ML20027D404 | List: |
| References | |
| TAC-49949, TAC-49950, NUDOCS 8301130224 | |
| Download: ML20028C691 (24) | |
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DISTRIBUTION:
g Socliet File NRC PDR L PDR NSIC ORB #3 Rdg Docket flos. 50-202 DEisenhut and 50-300 JHeltemes OELD ELJordan kh" f<r. D. f4. f'usolf fluclear Support Services Department RFerguson f!orthern States Power Company RAClark 414 flicollet Mall - 8th Floor hC t
flinneapolis, f.tinnesota 55401 an
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SUBJECT:
DRAFT SER Ofl APPEf' DIX R EXEfaPTI0ff REQUEST WehahecompletedourrehiewofyourAppendixRexemptionrequestsubmitted by letters dated June 30 and October 22, 1992 for the Prairie Island fluclear Generating Plant Unit f!os. I and 2. is our. draft SER related to your exemption requests and Enclosure 2 is the evaluation on your analytical methods perforned by our consultant, Brookhaven National Laboratory.
Uc request that you review these enclosures for accuracy of technical content and inform us within three weeks of any corrections you consider necessary. With respect to followup action regarding exemption denials, there are three options:
(1) appeal denials to fiRR managemnt; (2). propose another alternative that requires an exemption; or (3) make nodifications to neet the specific requirenents of Appendix R.
Please inform us within three uceks regarding which action you plan to take.
If.an appeal neeting.is requested, it should be limited
- o the technical review of the information on the record and should be held within six weeks.
If,fordeniedexemptions,you,choosetoproposeanalternatihewhichalso
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requires an exemption,.it should be filed under the provisions of Sec-tion 50.12 of 10 CFR Part 50.
If you choose to propose such an alternative I
we request that you do so within 60 dzys.
1 If, for denied exer.jptions, you propose to nake modifications which meet the specific requirements, of Section III.G of Appendix R, no additional submittal is necessary, unless the modifications are to provide alterna-l tive sbutdown capability.
In these cases, you will be given 6 months i
to provide the description of the modifications for alternative shutdown capability.
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t Mr. D. M. Musolf If you have any questions regarding this lottar or the enclosures, please contact your Project Pfanager.
Sincerely, G:p.la.\\ Sf;y nd UY R.f. art A. C!crK Robert A. (lark, Chief Operating Aeactors Branch #3 Div111on of Licensing
Enclosures:
As stated cc w/ enclosures:
See next page omce>
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oan p OFFICIAL RECORD COPY usam mi awm snc ronu ais oow ancu om
Northern States Power Company cc:
Gerald Charnoff, Esquire Shaw, Pittman, Potts and Trowbridge 1800 M Street, N.W.
Washington, D. C.
20036 Mr. Louis J. Breimburst Mr. R. L. Tanner Executive Director County Auditor Minnesota Pollution Control Agency Red Wing, Minnesota 55066 1935 W. County Road B2 Roseville, Minnesota 55113 U. S. Environmental Protection Agency Federal. Activities Branch Region V Office ATTN:
Regional Radiation Representative 230 South Dearborn Street Chicago, Illinois 60604 Mr. E. L. Watzl, Plant Manager Prairie Island Nuclear Generating Plant Northern States Power Company Route 2 Welch, Minnesota 55089 Jocelyn F. Olson, Esquire Special Assistant Attorney General 3
Minnesota Pollution Control Agency 1935 W. County Road 82 Roseville, Minneosta 55113 U.S. Nuclear Regulatory Commission Resident Inspectors Office Route #2, Box 500A Welch, Minnesota 55089 Regional Administrator Nuclear Regulatory Commission, Region III Office of Executive Director for Operations 799 Roosevelt Road Glen Ellyn, Illinois 60137 6
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9 Exemption Request Prairie Island Nuclear Generat,ing Plant Units 1 and 2
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Docket No. 50-282/50-306 1.0 Introduction By letter date,d June 30, 1982 the licensee requested exemptions from Section III.G of Appendix R within 9 plant fire areas.
By letter dated October 22, 1982, the licensee provided' additional information.
Section III.G.2 requires that one train of cables and equipment necessary to achieve and maintain safe shutdown be maintained free of fire damage by one of the following means:
Separation of cables and equipment and associated non-safety a.
circuits of redundant trains by a fire barrier having a 3-hour rating.
Structural steel forming a part of or supporting such fire barriers shall be protected to provide fire resistance equivalent to that required of the barrier; b.
Separation of cables and equipment and associated non-safety circuits of redundant trains by a horizontal distance of mere than.20 feet with no intervening combustibles or fire hazards.
In addition, fire detectors and an automatic fire suppression system shall be installed in the fire area; or l
l c.
Enclosure of cables and equipment and associated non-safety circuits of one redundant train in a fire barrier having a l
1-hour rating.
In addition, fire detectors and an automatic fire suppression system shall be installed in the fire area.
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If these conditions are not met,Section III.G.3 requires alternative shutdown capability independent of the fire area of concern.
It also requires a fixed suppression system in the fire area of concern if it contains a large concentration of cables or other combustibles.
These alternative requirements are not deemed to be equivalent for all configurations, however, they provide equivalent protection for those configurations in which they are accepted.
Because it is not possible to predict the specific conditions under which fires may occur and propagate, the design basis protective features are specified in the rule rather than the design basis fire.
Plant specific features may require protection different than the measures specified in Section III.G.
In such a case, the licensee must demonstrate, by means of a detailed fire hazards analysis, that existing protection or existing protection in conjunction with proposed modifications will provide a level of safety. equivalent
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to the technical requirements of Section III.G of Appendix R.
In summary,Section III.G is related to fire protection features for ensuring that systems and associated circuits used to achieve and main-tain safe shutdown are free of fire damage.
Fire protection configura-tions must either meet the specific requirements of Section III.G or alternative fire protection configurations must be justified by a fire hazard analysis.
Our general criteria for accepting alternative fire protection con-figurations are the following:
The alternative assures that one train of equipment necessary to achieve hot shutdown from either the control room or emergency control stations is free of fire damage.
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The alternative assures that fire damage to at least one train of equipment necessary to achieve cold shutdown is limited such that it can be repaired within a reasonable time (minor repairs with components stored on-site).
Modifications required to meet Section III.G would not enhance fire protection safety above that provided by either existing or proposed alternatives.
Modifications required to meet Section III.G would be detrimental to overall facility safety.
2.0 Analytical Method The licensee employed an analytical method to demonstrate the inherent protection afforded to existing safe shutdown systems.
The intent of this method was to provide common parameters by which individual fire sr areas could be judged, to demonstrate that verbatim compliance with Section III.G of Appendix R would not enhance the fire protection for safe shutdown.
The method can be summarized as follows:
The redundart cables and components of concern are identified; Their geometry and configuration within the fire area are described.
The type of cable insulation and failure criteria are specified.
The minimum quantity of flammable liquid needed to produce suffi-cient heat fiux and heat energy to damage the cables is calculated, considering several heat transfer modes, i.e. radiation, plume impingement, and stratification.
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4 The analysis determines the heat flux into the room needed to cause electrical failure of redundant cables.
This heat flux is converted to a quantity of flammable liquid, usually acetone, of approximately 10 to 20 gallons, in a circular pool configuration.
We and our contractor Brookhaven National Laboratory have reviewed the analytical method.
Attached as enclosure 2 is a copy of their report. We have determined that the results of the methodology, as applied, do not demonstrate the equivalence of the protection provided for safe shutdown to the specific alternatives set forth in Section III.G of Appendix R.
For example:
The method does not consider the heat released to the room by secondary fires involving in-situ combustibles. The method uses an electrical failure criteria with the thermal energy release to the room by a single exposure fire. When the cables of concern are at the conditions of electrical failure, other cables within the enclosure are burning and also releasing energy to the room.
The method does not consider the increased heat release rate of a given fire when it occurs against a wall or in a corner; the method only considers the heat release of a fire as it occurs in an open area.
The method does not consider the effects of excess pyrolyzate l
resulting from the degradation of plastics burning in the stratified layer.
The method does not consider all of the alternatives set forth in Section III.G. i.e., 3-hour fire barrier,1-hour fire barrier with suppression system, twenty-feet separation free of combus-t-
tibles with automatic suppression and alternate or dedicated
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shutdown capability independent of the area.
The method only considers separation without automatic suppression and uses. a stratification model which does not include the effects of separ-ation.
The licensee has not used the results of this analysis to compare the protection provided with that specified in Section III.G.
The licensee has only stated that the accumulation of the calculated quantity of flammable liquids in the required configuration is an unrealistic condition, and vill be prevented by administrative controls. We do not deem this to be a valid argument because there is no positive means of preventing the accumulation of transient materials in individual plant areas.
As documented in Inspection and Enforcement Branch Reports, recent' inspections at plants such as Davis Besse (50-346/82-03, April 1, 1982), Duane Arnold (50-331/81-25, January 11, 1982), D. C. Cook (50-315/82-11, December 31, 1981), and Nine Mile Point (50-220/82-09), have se demonstrated that substantial quantities of hazardous substances such as 55 gallon drums of waste oil'are located in even highly restricted and controlled entry areas.
We have not relied upon the results of the licensee's analysis in our evaluation. We have evaluated each exemption request using our
. standard method of review:
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a) Review the information submitted and that existing in the docket file to determine the configuration of the redundant components, b) Evaluate the existing fire protection, proposed modifications, and'other compensating features or mitigating factors to determine the overall level of fire protection in the area of concern, and i
c) Determine if the overall level of safety is equivalent to that i
provided by Section III.G of Appendix R.
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6 3.0 Fire Area 31:
"A" Train Hot Shutdown Panel; Instrument Air Room and Auxiliary Feedwater Pump Room and Fire Area 32: "B" Train Hot Shutdown Panel: Instrument Air Room and Auxiliary Feedwater Pump Room f
3.1 Exemption Requested The licensee requests exemptions from Section III.G.2 to the extent that it requires 20 feet of separation without. intervening combustibles between redundant trains.
3.2 Discussion Fire Area 31 and 32 are located in the north cent'ral ground floor section of the Auxiliary Building at elevation 695 ft.
The area is completely enclosed by 3-hour rated fire walls with 3-hour-rated fire seals provided for combustible pathway penetrations.
Fire e-Area 31 is separated from Fire Area 32 by a 3-hour-rated fusible linked sliding door which closes to isolate Fire Area 31 from Fire Area 32 in the event of a fire.
The fire protection in the area consists of automatic sprinklers, smoke detectors, standpipe hose stations and portable fire extinguishers.
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l Fire Area 31 contains Motor Cnntrol Centers MCC-2A1 and 2A2, #12 j
(motor-driven Unit 1) and #22 (turbine-driven Unit 2) Auxiliary i
Feedwater Pumps, #123 Instrument, Air Compressor with associated equipment, and "A" Train Hot Shutdown Panel for Units 1 and 2.
One of the two motor control centers (either 2A1 or 2A2) is necessary for safe shutdown as are the auxiliary feedwater pumps.
It should be noted, however, that opposite train pumps are l'ocated in Fire Area 32-thereby ensuring separation by 3-hour fire rated barriers.
Of the three instrument air compressors, one is located in Fire Area 31, I
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7 representing Division A.
The other two compressors (Division B) are located in Fire Area 32, again providing separation by 3-hour. fire rated barriers.
Fire Area 32 is located in the central ground floor section of the safeguards corridor in the Auxiliary Building at the 695 ft.
elevation.
The fire area is completely enclosed by 3-hour-rated walls with 3-hour-rated fire seals provided for combustible pathway penetrations.
The fire protection in the area consists of auto-matic sprinklers, smoke detectors, standpipe hose stations and portable fire extinguishers.
Fire Area 32 contains Motor Control Centers MCC-1A1 and MCC-1A2, #11 (turbine driven, Unit 1) and #21 (motor driven, Unit 2) Auxiliary Feedwater Pumps,.1121 and #122 Instrument Air Compressors with associated equipment, and "B" train Hot Shutdown Panel for Units 1 and 2.
e The safe shutdown evaluation identified the coexistence of redundant power and control cables required for safe shutdown with less than twenty feet horizontal separation.
The redundant cables are installed in open horizontal cable trays between 16 and 18 feet above the floor, and within 3 feet of the ceiling.
The redundant cables crossover one another and are separated by approximately one foot at the cross:over.
The licensee proposes to install thermal barriers on the top and bottom of the Division B cable trays and wrap all Division B conduits in one-hour fire rated barriers.
By letter dated October 22, 1982, the licensee also proposes to modify the existing automatic sprinkler systems presently installed at the ceiling level, to also provide total area sp'rinkler coverage below the cable trays and piping in the areas.
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The combustibles in Fire Area 31 are lubricating oil and cable insulation.
The combustibles comprise a fuel load of 4,742 BTU /sq.
ft., which if totally consumed, would correspond to a fire severity of 4 minutes on the ASTM E-119 standard time temperature curve.
The combustibles in Fire Area 32 are lubricating oil and cable insulation. The combustibles comprise a fuel load of 7,843 BTV/sq.
ft., which if totally consumed, would correspond to a fire severity of 6 minutes on the ASTM E-119 standard time temperature curve.
3.3 Evaluation These areas do not comply with Section III.G because they do not have twenty feet of separation free of intervenin'g combustibles or one hour fire rated barriers.
There is no alternative shutdown capability independent of this area.
The features in this area which are offered as compensation for the lack of 20 feet separation or one hour barriers are the thermal shield installed on both the top and bottom of the Division B cable trays.
The thermal shields can not be considered equivalent to a one-hour fire rated barrier, as they may only inhibit fire l
damage for several minutes.
However because of the low in-situ combustible fuel loads, we find for anticipated transient combustible exposure fires the thermal shields will protect the Division B cable trays from direct flame impingement or a descending hot layer for a reasonable period of time until the automatic sprinklers installed at the ceiling level and below the cable trays are activated to mitigate the effects of the fire.
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9 The low in-situ fuel load in conjunction with the proposed thermal shields provide reasonable assurance that the automatic detection and sprinkler systems will be ac.tivated before the redundant.
cables are damaged.
3.4 Conclusion Based on our evaluation, we conclude that with the proposed modifi-cations, the level of safety provided in the Train A and Train B Hot Shutdown Panel, Instrument air and Auxiliary Feedwater Pump Rooms (Fire Areas 31 and 32) will be equivalent to the technical requirements of Section III.G of Appendix R and therefore, the licensee's requests should be granted.
4.0 Fire Area 58: Auxiliary Building Ground Floor Level Unit 1 Fire Area 73: Auxiliary Building Ground Floor Unit 2 Fire Area 74: Auxiliary Building Mezzanine Level Unit 2 q;
4.1 Exemption Requested The licensee requests exemptions from Section III.G.2 to the extent that it requires 20 feet of separation without intervening combustibles between redundant trains and the installation of an automatic fire suppression system.
4.2' Discussion Fire Area 58 Fire Arba 58 is located on the ground floor immediately northwest of the containment building for Unit 1, at the 695 ft. elevation. The fire area is enclosed by 3-hour rated walls on all but the west side, with 3-hour-rated fire seals provided for combustible pathway
10 penetrations.
The west side of Fire Area 58 is separated from the nearest area of concern in Fire Area 73, by approximately 100 ft of horizontal separation.
The height of the ceiling in the area is 19 ft.
The fire protection in the area consists of smoke detectors, standpipe hose stations and portable fire extinguishers.
Fire Area 58 contains motor control centers MCC-1K1, 1K2, and 1KA2;
- 11 and #21 Component Cooling Water Pumps; #11 and #12 Residual Heat Removal Pumps, located in separate pits; and #12 Charging Pump and
- 12 Safety Injection Pump, each located in separate compartments in separate pits.
Either MCC-1K1 or MCC-1K2 must be available for safe shutdown.
MCC-1KA2 is fed from MCC-1K2 while the redundant motor control center to MCC-1KA2 is located in another fire area.
The component cooling water pumps each have the redundant division pump
(#12 and #22) also located in another fire area.
Also, the residual heat removal pump and the Chemical Volume Control System pumps (Charging Pump Division A and Safety Injection Pump Division B) are e
physically located in separate rooms.
The safe shutdown evaluation identified the co-existence of power and control cables required for redundant safe shutdown with less than twenty feet horizontal separation. The redundant cables are installed in open horizontal cable trays between 11 and 18 feet above the floor.
Each division is i,eparated'by 8 feet and installed within 3 feet of the ceiling.
The combustible in the area is cable insulation, comprising a fuel load of 9,990 BTV/sq. ft., which if totally consumed, would correspond to a fire severity of approximately 7.5, minutes on the ASTM E-119 standard time temperature.
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11 The licensee proposes to install thermal shields on the bottom of the Division B cable trays.
By letter dated October 22, 1982,,the licensee has also proposed to provide thermal shields on the top of some Division B cable trays where practical.
Fire Area 73 Fire Area 73 is identical to Fire Area 58, but is located in Unit 2.
The safe shutdown evaluation identified the co-existence of redundant power and control cables required for safe shutdown with less than twenty feet horizontal separation.
The redundant cables are installed in open horizontal and. vertical cable trays installed between 13 and 16 feet above the floor.
Each division is separate by approximately 5 feet horizontally and installed within 3 feet of the ceiling.
e The combustible in the area is cable insulation.
The cable insulation comprises a fuel load.of 7,810 BTU /sq. ft. which if i
totally consumed, would correspond to a fire severity of approxi-mately 6 minutes on the ASTM E-119 standard time temperature curve.
The licensee proposes to install thermal shields on the bottom of the Divisfon B cable trays.
By letter dated October 22, 1982, the licensee has also proposed to provide thermal shields on the top of some Division B cable trays where practical.
Fire Area 74
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l Fire Ar'ea 74 is located on the mezzanine level immediately north of, and adjacent to, the Containment Building for Unit 2, directly above Fire Area 73 at an elev.ation of 715 ft. The room is enclosed by 3-hour-rated fire walls on all but the east side with 3-hour rated l
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12 fire seals provided for combustible pathway penetrations.
The east side of Fire Area 74 is separated from the nearest area of concern in Fire Area 59 by approximately 100 ft.
The height of the ceiling in the area is 19 ft.
Fire protection in the area consist of smoke detectors, standpipe hose stations and portable fire extinguishers.
Fire Area 74 contains cable and conduit needed for safe shutdown.
The safe shutdown evaluation identified the coexistence of redundant cables required for safe shutdown with less than twenty feet horizontal separation.
The redundant cables are installed in horizontal cable trays between 12 and 19 feet above the floor.
Each division is separated by approximately 8 feet and installed within 3 feet of the ceiling.
The combustible in the area is cable insulation comprising a fuel load of 14,700 BTU /sq. ft. which if totally consumed, would correspond to a fire severity of approximately 11 minutes on the ASTM E-119 m
standard time temperature curve.
By letter dated October 22, 1982, the licensee proposes to install fire stops in non-safety trays to prevent the possibility of propagating fires from one division to another.
l The licensee justifies these alternatives on the basis of (1) All cables and qualified to IEEE Std-383(2) the in-situ combustible loadings are light, (3) smoke detection is provided and (4) an analytical model was employed to show that the magnitude of an exposure fire needed to damage redundant components is significantly higher than reasonable expected.
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13 4.3 Evaluation These areas do not comply with Section III.G because they do not have automatic fire suppression systems and twenty feet of separation free of intervening combustibles or one hour fire rated barriers.
There is no alternative shutdown capability independent of these areas.
There are generally two mechanisms by which fire damage is propagated; either an exposure fire in close proximity to the redundant equipment or an exposure fire at any point in the room of sufficient magnitude to form a stratified layer of hot gases at the ceiling level, which descends to the floor level at a rate correlated to the room volume, the burning time and fuel quantity.
In the case of a fire which produces a stratified layer of hot gases at the ceiling level, the most severe damage will occur to cables and equipment located within several feet of the ceiling. The redundant cables in each fire area are installed within three feet of the ceiling.
This configuratio.n does not provide
. t, reasonable protection from a hot gas layer.
A local exposure fire could also cause damage to the redundant cables if they are exposed to a heat flux of sufficient intensity.
The features in the fire areas which are offered as compensation for the lack of Section III.G required protective features are the proposed thermal shields and that all cables are qualified to IEEE-383.
l Neither of these can be considered equivalent to a one-hour fire rated l
barrier, as they may only inhibit fire damage for several minutes.
The fire areas do not present any other features that would compensate for the lack of protective features specified by Section III.G.
Because'of the close proximity of redundant safe shutdown cables that are not protected by an automatic suppression system, an exposure fire in any of the fire area,s could damage both trains prior to the response of the fire brigade. There will be a time lag between the e-
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14 ignition of the fire, detector response, and the arrival of the fire brigade.
The existing protection does not provide reasonable assurance that redundant cables of both trains will not be damaged in this time interval.
The existing protection in each of these fire areas does not provide a level of fire protection equivalent to Section III.G.
Modifications such as the installation of an automatic sprinkler system and one-hour fire rated barriers would provide the requisite levels of safety.
4.4 Conclusion Based on our evaluation, the level of existing protection for Fire Area 58 Auxiliary Building Ground Floor Level Unit 1, Fire Area 73 Auxiliary Building Ground Floor Unit 2 and Fire Area 74 Auxiliary Building Mezzanine Level Unit 2 does not provide a level of fire protection equivalent to the technical requirements of.Section III.G of Appendix R.
Therefore, the exemptions should be denied.
5.0 Fire Area 37: Unit 1 Normal Switchgear Room Fire Area 60: Auxiliary Building Operating Level, Unit 1 Fire Area 75: Auxiliary Building Operating Level, Unit 2 5.1 Exemption Requested The licensee requests exemptions from Section III.G.2 to the extent it requires the installation of an automatic fire suppression system.
5.2 Discussions Fire Area 37 Fire Area 37 is located on the ground level of the turbine building at an elevation of 695 ft.
The area is enclosed by 3-hour rated fire walls on all sides with 3-hour rated fire seals provided for
15 combustible pathway penetrations.
The height of the ceiling in the area is 19 ft.
Fire protection in the area consist of smoke.
detectors, standpipe hose stations and portable fire extinguishers.
This fire area contains emergency diesel generator power cables of redundant divisions from which one train is necessary for safe shutdown.
Both division cables are routed in conduit through the area. The existing horizontal separation between the redundant emergency diesel generator power supplies is greater than twenty feet.
The combustible in the area is cable insulation comprising a fuel
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load of 12,400 BTV/sq. ft., which if totally consumed, would correspond to a fire severity of approximately 10' minutes on the ASTM E-119 standard time temperature curve.
Fire Area 60 w
Fire Area 60 is located on the operating level of the Auxiliary Building immediately north and west of the Unit 1 containment building at an elevation of 735 ft.
The area is enclosed by 3-hour-rated fire walls on all sides, with 3-hour-rated fire.
seals provided for combustible pathway penetrations. The height of the ceiling in the area is 19 ft.
Fire protection in the area' consist of smoke detectors, standpipe hose stations and portable fire extinguishers.
This fire area contains Motor Control Centers MCC-1LA1 and MCC-1LA2, one of which is required for safe shutdown.
Loss of MCC-1LA1 and MCC-1LA2 due to fire will result in the loss of the following critical functions required for safe shutdown:
1.
Unit I redundant steam supply to the turbine driven auxiliary i
feedwate pump.
2.
Redundant RHR suction valves.
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16 The motor central centers and associated cable entering and leaving the motor control centers are horizontally separated by 22 feet.
The fuel load in t.he area is negligible.
Fire Area 75 Fire Area 75 is located on the operating level of the Auxiliary Building immediately north and east of the unit 1 containment building at an elevation of 735 ft. The area is enclosed by 3-hour-rated fire walls on all sides with 3-hour-rated fire seals provided for combustible pathway penetrations.
The height of the ceiling in the area is 19 ft.
Fire protection in the area consist of smoke detectors, standpipe hose stations and portable fire extinguisilers.
Fire Area 75 contains two saftguard Motor Control Centers, MCC-2LA1 and MCC-2LA2, one of which is required for safe shutdown.
Loss of MCC-2LA1 and MCC-2LA2 due to a fire will result in the loss of the a
following critical functions required for safe shutdown.
1.
Unit 2 redundant steam supply to the turbine driven auxiliary feedwater pump.
2.
Redundant RHR suction valves.
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The motor central centers and associated cable entering and leaving the motor control centers are horizontally separated by 22 feet.
The fuel load in the area is negligible.
The licensee justifies these alternatives on the basis of (1) All cables are qualified to IEEE-383 (2) the in-situ combustible loadings are light, and (3) smoke detection is provided in each area.
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l 17 5.3 Evaluation e
These areas do not comply with Section III.G because they do not have an automatic fire suppression system.
There is no alternative shutdown capability independent of these areas.
Because there are negligible in-situ combustibles in these areas, any posulated fire would involve transient combustible materials.
A fire in these areas would be of limited severity and duration.
The installed early warning detection system would be able to promptly detect incipient fire conditions, and the separation between redundant trains in each area will maintain the integrity of the cables and equipment until the fire brigade is able to respond and to extinguish the fire.
The fire brigade should be capable of reaching each of these areas within a few minutes after an alarm is received in the control room.
It is our opinion that this combination of protective features provide reasonable assurance y
that one train of equipment necessary for safe shutdown will be maintained free of fire damage.
5.4 Conclusion Based on our evaluation, the level of existing protection for Fire Areas 37 Unit 1 Normal Switchgear Room, Fire Area 60 Auxiliary Building Operating Level, Unit 1 and Fire Area 75 Auxiliary Building Operating Level, Unit 1 provides a level of fire protection equivalent to the technical requirements of Section III.G of Appendix R.
Therefore, the exemptions should be granted.
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18 6.0 Fire Area 59: Auxiliary Building Mezzanine Level Unit 1 6.1 Exemption Requested The licensee requests an exemption from Section III.G.2 of Appendix R to the extent that it requires one-hour fire rated barriers or 20 feet of horizontal separation free of intervening combustibles to separate redundant divisions and a total area automatic fire suppression system.
6.2 Division Fire Area 59 is located on the mezzanine level in the immediate northwest corner of Unit I containment, directly above Fire Area 58 at an elevation of 715 ft.
The fire area is enclosed by 3-hour-rated fire walls on all but the west side, with 3'-hour-rated fire seals provided for combustible pathway penetrations. The west side of Fire Area 59 is separated from the nearest area of concern in Fire Area 74 by approximately 100 ft. of horizontal separation.
s-The height of the ceiling in the area is 19 ft.
Fire protection in the area consists of smoke detectors, standpipe hose stations and portable fire extinguishers, and a wet pipe sprinkler system which provides spot area coverage only around trays.
This fire area contains two Motor Control Centers, MCC-1L1 and MCC-1L2, and redundant division cables for safe shutdown equip-ment.
One of the motor central centers is required for safe shut-down.
The redundant cables are installed in open horizontal trays between 13 and 19 feet above the floor.
The cables are separated by approximately 4 feet 6 inches and installed within 3 feet of the ceiling.
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The combustible in the area is cable insulation comprising a fuel load of 25,000 BTU /sq. ft., which if totally consumed, would.
correspond to a fire severity of 19 minutes on the ASTM E-119 standard time temperature curve.
The licensee proposes to install fire stops in non-safety cable trays to prevent the possibility of propagating fires between redundant divisions.
The licensee justifies this alternative on the basis of (1) All cables are qualified to IEEE-383, (2) partical area sprinkler protection has been provided, (3) the in-situ combustible loading is light, (4) s;noke detection is provided and (5) an analytical model was employed to show that the magnitude of 'an exposure fire needed to damage redundant components is significantly higher than reasonably expected.
o 6.3 Evaluation This area does not comply with Section III.G.2 because it does not have a total area automatic suppression system'and twenty feet of separation free of intervening combustibles or one hour fire-rated barriers. There is no alternative shutdown capability independent of this ar'ea.
The features in this area which are offered as compensation for the lack of Section III.G protective features are the proposed fire stops and that all cables are qualified to IEEE-383 Std.
Neither of these can be considered equivalent to a one-hour fire rated barrier, as they ma5' only inhibit fire damage for several minutes.
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20 The lack of separation between redundant cable trays represents a e_
significant threat to safe shutdown capability. A fire involving combustible materials located in the proximity of the redundant shutdown systems may cause failure of those systems prior to fire suppression action by the fire brigade or the fixed fire suppression system.
The automatic sprinkler systems will mitigate the fire hazard but may not provide fast total coverage of cabling and/or the floor area. Without the required separation distance, or the install-ation of a one-hour fire rated barrier, as required by Section III.G.2, we do not have reasonable assurance that damage to redundant trains would not occur pending activation of the suppression system.
The existing protection in this fire area does not provide a level
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of fire protection equivalent to Section III.G.
Modifications such as the installation of one-hour fire rated barriers would provide the requisite level of safety.
6.4 Conclusion i
Based on our evaluation, the level of existing protection for Fire Area 59 Auxiliary Building Mezzanin.e Level Unit 1 does not provide i
a level of fire protection equivalent to the technical requirements of Section III.G of Appendix R.
Therefore, the exemption should be denied.
l Summary Based on our evaluation, we conclude that the licensee's proposals for the following four areas do not represent an acceptable level of (c
safety to that which would be achieved with compliance with the requirements of Section III.G of Appendix R to 10 CFR 50:
+-e
,y eee-
- eae
- ._ee e-4e. e.i a m -,
m
- m.
8
21 1.
Auxiliary Building Ground Floor Level Unit 1 (Fire Area 58) 2.
Auxiliary Building Mezzanine Level, Unit 1 (Fire Area 59),
3.
Auxiliary Building Ground Floor Level Unit 2 (Fire Area 73) 4.
Auxiliary Building Mezzanine Level Unit 2 (Fire Area 74)
Therefore, the licensee's request for exemptions for these areas should be denied.
In five areas of the plant, we agree with the licensee that modifi-cations required to meet Section III.G would not enhance fire safety above that provided by existing and proposed alternatives.
There-fore, the licensee's request for exemptions for the following areas should be granted:
1.
Train A Hot Shutdown Panel, Instrument Air and Auxiliary Feed-water Pump Room (Fire Area 31).
v 2.
Train B Hot Shutdown Panel, Instrument Air and Auxiliary Feed-water Pump Room (Fire Area 32) 3.
Normal Switchgear Room Unit 1 (Fire Area 37) 4.
Auxiliary Building Operating Level Unit 1 (Fire Area 60) l 5.
Auxiliary Building Operating Level Unit 1 (Fire Area 75) l l
l l
l
.