ML20079E954
| ML20079E954 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 01/09/1984 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | NORTHERN STATES POWER CO. |
| Shared Package | |
| ML20079E957 | List: |
| References | |
| TAC-53558, TAC-53559, NUDOCS 8401180011 | |
| Download: ML20079E954 (7) | |
Text
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UNITED STATES OF AMERICA I
NUCLEAR REGULATORY COMMISSION In the Matter of
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Docket Nos. 50-282 NORTHERN STATES POWER
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and 50-306 COMPANY
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(Prairie Island Nuclear Generating Plant Unit Nos. I and 2)
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EXEMPTION I.
The Northern States Power Company (the licensee) is the holder of Facility Operating License Nos. OPR-42 and DPR-60 which authorize operation of the Prairie Island Nuclear Generating Plant, Unit Nos.1 and 2.
These licenses provide, among other things, that they are subject to all rules, regulations and Orders of the Commission now or hereafter in effect.
The facility comprises two pressurized water reactors at the licensee's site located in Goodhue County, Minnesota.
II.
On November 19, 1980, the Commission published a revised Section 10 CFR 50.48 and a new Appendix R to 10 CFR 50 regarding fire protection features of nuclear power plants (45 FR 76602). The revised Section 50.48 and Appendix R became effective on February 17, 1981.
Section III of Appendi> R contains fif teen subsections, lettered A through 0, each of which specifies require-monts for a particular aspect of the fire protection features at a nuclear power plant.
One of these fifteen subsections, III.G., is the subject of this exemption request. Specifically, Subsection III.G.2 requires that one I
train of cables and equipment necessary to achieve and maintain safe-shutdown be maintained free of fire damage by one of the following means:
8401180011 840109 PDR ADOCK 05000202 F
. a.
Separation of cables and equipment and associated non-ssfety circuits of redundant trains by a fire barrier having a 3-hour rating.
Struc-tural 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-safaty circuits or redundant trains by a horizontal distance of more 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 c.
Enclosure of cables and equipment and associated non-safety circuits of one redundant train in a fire barrier having a 1-hour rating.
In addition, fire detectors and an automatic fire suppression system shall be installed in the fire area.
III.
By letters dated February 17 and March 11, 1983 and supplemented by letters dated May 16 and September 2,1983, the licensee requested an exemption from installing a fixed suppression system in fire areas described below as re-quired by Subsection III.G.2 of Appendix R.
The Auxiliary Building ground floor level is one fire area which is designated as two fire zones-58 and 73.
The Auxiliary Building mezzanine level is the second fire area which is
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designated as two fire zones-59 and 74. The two fire areas are enclosed by three-hour rated walls with three-hour rated seals provided for combus-tible pathway penetrations. The two fire zones within the fire areas are separated from the nearest area of concern by approximately 100 feet.
The
! acceptability of the exemption request for the four fire zones within these two fire areas is addressed below.
More details are contained in the NRC staffs' related Safety Evaluation (SE) dated January 9,1984, which is included herein by reference.
IV.
Auxiliary Building Grnynd Floor Level Unit 1 (Fire Zone 58)
Auxiliary Building Ground Floor Level Unit 2 (Fire Zone 73)
The licensee requested an exemption from Subsection Ill.G.2. to the extent that these fire zones lack an automatic fire suppression system.
The combustible in fire zone 58 is cable insulation containing a fuel load of 10,354 BtV/ft2 which, if totally consumed, would result in a fire severity of approximately 8 minutes on the ASTM E-119 standard time-tempera-ture curve. The combustible ir. fire zone 73 is cable insulation containing a fuel load of 8,000 BtV/ft2 which, if totally consumed, would result in a fire severity of approximatly 6 minutes on the ASTM E-119 standard time-tem-perature curve.
Fire protection in these zones consists of smoke. detectors, standpipe hose sta'. ions and portable fire extinguishers. All redundant hot shutdown equipment is separated by greater than 20 feet free of intervening combustibles.
The redundant power, control and instrument cables are in-stalled in open horizontal cable trays between 11 and 18 feet above the floor. The divisions are separated by approximately 8 feet horizontally and are installed 3 feet below the ceiling.
The licensee has coninitted to enclose all Division B safe shutdown cable in a one-hour fire rated barrier and to similarly enclose Division A safe
shutdown cable trays in the vicinities of the motor control centers and coordinates identified in the NRC's Safety Evaluation for each zone.
The fuel load in these zones, including anticipated transients combustibles, is low. Hazardous quantities of transient combustibles would not be expected in these fire zones for several reasons.
First, the zones are not adjacent to or near any major plant traffic route.
Second, maintenance and operations in these zones do not involve the use of combustible materials. Third, acces-sibility to these zones is restricted to personnel performing essential duties in the zones because of potential radiation hazards.
On this basis, we agree with the licensee that any fires in these zones resulting from transient combustibles would be of low severity and short duration.
Due to the presence of the smoke detectiun system and the availability of adequate manual fire fighting equipment, the fire brigade would be ex-pected to extinguish a postulated fire before significant damage occurred.
During the time a fire is being detected and extinguished as a result of fire brigade intervention, the one-hour fire-rated barriers enclosing safe shutdown cable trays and spatial separation between safe shutdown equipment provide reasonable assurance that one shutdown division will remain _ free of fire damage.
Based on our evaluation, we conclude that, with the existing fire pro-tection combined with the licensee's commitment to provide an additional level of fire protection for fire zones 58 and 73, fire protection features are equivalent to the requirements specified in Subsection III.G.2 of Appendix R and therefore the licensee's requested exemption is granted for these fire zones.
Auxiliary Building Mezzanine Level Unit 1 (Fire Zone 59)
Auxiliary Building Mezzanine Level Unit 2 (Fire Zone 74)
The licensee requested an exemption from Subsection III.G.2 to the extent that these fire zones lack an automatic fire suppression system.
The combustible in fire zone 59 is cable insulation containing a fuel load of 20,000 BtV/ft2, which, if totally consumed, would result in a fire severity of approximately 15 minutes on the ASTM E-119 standard time-tempera-ture curve.
Similarly the combustible in fire zone 74 is cable insulation containing a fuel load of 18,111 Btu /ft2 which, if totally consumed, would result in a fire severity of approximately 14 minutes on the ASTM E-119 standard time-temperature curve.
The fire protection in these zones consists of smoke detectors, standpipe hose stations and portabic fire extinguishers.
These fire zones contain motor control centers and redundant division cables for safe shutdown equipment. The motor control centers are separated by approximately 28 feet free from intervening combustibles. The redundant cables are installed in open horizontal trays between 13 and 19 feet above the floor.
Each division is separated by approximately 8 feet and installed within 3 feet of the ceiling. To further increase the level of fire pro-tection in these zones, the licensee committed to enclose all redundant Division B safe shutdown cables in a one-hour fire rated barrier.
The fuel load in these zones, including anticipated transients combustibles, is low. Hazardous quantities of transient combustibles would not be expected in these fire zones for several reasons.
First, the zones are not adjacent to or near any major plant traffic route.
Second, maintenance and operations in l
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. 9 these zones do not involve the use of combustible materials. Third, acces-sibility to these zones is restricted to personnel performing essential duties in the zones because of potential radiation hazards.
On this basis, we agree with the licensee that any fires in these zones resulting from transient combustibles would be of limited severity and duration.
Because smoke detectors are installed in the fire zones and because of the availability of adequate manual fire fighting equipment, the fire brigade would be expected to extinguish a postulated fire before significant damage occurred. During the time a fire is being detected and extinguished as a result of fire brigade intervention, the one-hour fire rated barriers enclosing safe shutdown cable trays and spatial separation between safe shutdown equip-nent will provide reasonable assurance that one safe shutdown division will remain free of fire damage.
Based on our evaluation, we conclude that, with the existing fire pro-tection combined with the licensee's commitment to provide an additional level of fire protection for zones 59 and 74, the fire protection features are equivalent to the requirements specified in Subsection III.G.2 of Apper. dix R and therefore the licensee's requested exemption is granted for these fire zones.
These exemptions are contingent upon the licensee's maintenance of admini-strative control of transient conbustibles which are equivalent to those specified in Sections III.K.1 through III.K.8 of Appendix R of 10 CFR 50 and any characterization of transient combustibles or design features which are specifically discussed in the NRC staff's Safety Evaluation.
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l V.
Accordingly, the Commission has determined that, pursuant to 10 CFR 50.12, an exemption is authorized by law and will not endanger life or property or common defense and security and is otherwise in the public interest and hereby grants an exemption from the requirements of Subsection III.G.2. of Appendix R to 10 CFR 50 to the extent discussed in Section IV above.
The NRC staff has determined that the granting of this Exemption will not result in any significant environmental impact and that pursuant to 10 CFR 51.5(d)(4) an environmental impact statement or negative declaration and environmental impact appraisal need not be prepared in connection with this action.
OR THE NUCLEAR REGULAT00v COMMISSION
.f b-WD rre 1(p3 isenhor,uC m Director Division o Licensing Office of Nuclear Reactor Regulation Dated at Bethesda, Maryland this 9th day of January,1984.
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