ML20079E967
| ML20079E967 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 01/09/1984 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20079E957 | List: |
| References | |
| TAC-53558, TAC-53559, NUDOCS 8401180015 | |
| Download: ML20079E967 (6) | |
Text
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UNITED STATES
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~t NUCLEAR REGULATORY COMMISSION L
p WASHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO EXEMPTIONS FROM 10 CFR 50, APPENDIX R NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNITS 1 AND 2 DOCKET NOS. 50-282 AND 50-306 1.0 Introduction By letters dated February 17 and March 11, 1983 the licensee requested exemp-tions from Section III.G of Appendix R.
By letters dated May 16 and September 2, 1983, 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:
a.
Separation of cables and equipment and associated non-safety 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-safety circuits of 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 addi-tion, fire detectors and an automatic fire suppression system shall be installed in the fire area.
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 con-centration of cables or other combustibles.
These alternative requirements are not deemed to be equivalent for all con-figurations, however, they provide equivalent protection fnr those configura-tions in which they are accepted.
l 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 8401180015 840109 PDR ADOCK 05000282 F
e.
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 pro-tection in conjunction with proposed modifications will provide a level of safety equivalent 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 maintain safe shut-down are free of fire damage.
Fire protection configurations 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 configurations 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.
The alternative assures that fire damage to at least one train of equip-ment 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 reautred to meet Section III.G would be detrimental to overall facility safety.
2.0 Auxiliary Building Elevation 695 ft. (Fire Zones 58 and 73) 2.1, Exemption Requested i
The licensee requests an exemption from Section III.G.2 to the extent it requires the installation of an automatic fire suppression system.
2.2 Discussion Elevation 695 ft. of the Auxiliary Building :s one fire area which is designated as two fire zones, 58 and 73.
The fire area is enclosed by three-hour-rated walls, with three-hour-rated fire seals provided for combustible pathway penetrations. 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.
I a.
Fire Zone 58 i
The combustible in the area is cable insulation, comprising a tuel load of 10,354 BTU /sq. tt., which if totally consumed, would correspond to a fire l
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. severity of approximately 8 minutes on the ASTM E-119 standard time tempera-ture curve. The zone contains Division A and Division B equipment and cables, i.e., motor control centers MCC-1K1, IK2, and 1KA2; Component Cooling Water Pumps #11, #12, #21 and #22; Residual Heat Removal Pumps #11 and #12, located in separate pits; Charging Pumps #11, #12 and #13 and Safety Injection Pump
- 1?.
All redundant hot shutdown equipment is separated by greater than 20 ft.
free of intervening combustibles. The charging pumps and safety injection pumps are located in separate compartments.
Redundant cold shutdown equipment located in this area includes Residual Heat Removal (RHR) pumps #11 and #12.
The pumps are installed in 30 foot deep concrete pits. The pits are separated by 3 foot thick reinforced concrete walls.
Curbs and drains have been provided to prevent the spill of a flammable liquid into the pits. The redundant power, control and instrumentation cables are installed in open horizontal cable trays between 11 and 18 feet above the floor. The divisions are separated by 8 feet and are installed within 3 feet of the ceiling.
The licer.see has committed to enclose all Division B safe shutdown cables in a one-hour fire rated barrier and to similarly enclose Division A safe shut-down cable trays in the vicinity of MCC 1K2 (Division B) bounded by coordinates 6.1/G, 6.1/H, 7.3/G and 7.3/H in a one-hour fire rated barrier.
b.
Fire Zone 73 The combustible in the zone is cable insulation. The cable insulation com-prises a fuel load of 8,000 BTU /sq. ft. which, if totally consumed, would correspond to a fire severity of approximately 6 minutes on the ASTM E-119 standard time temperature curve. The redundant pawer, control and instru-mentation cables are installed in open horizontal cable trays between 13 and 16 feet above the floor. The divisions are separate by appoximately 5 feet horizontally and installed within 3 feet of the ceiling.
The licensee has committed to enclose all Division B cables in a one-hour fire rated barrier and to similarly enclose Division A safe shutdown cable trays in the vicinity of Division B MCC 2K-2 bounded by coordinates 10.7/G, 10.7/H and 11.7/G and 11.7/H.
2.3 Evaluation The fire protection in this area does not comply with the technical require-ments of Section III.C.2 of Appendix R because an automatic fire suppression system is not installed in the area.
The fuel load in these zones, including anticipated transients, is low.
Hazardous quantities of transient combustibles would not he expected in these fire zones for several reasons.
First, the zones are not adjacent to or near any major plant traffic route.
Second, maintensnce 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 lf.nited severity and duration.
Due to the presence of the smoke dei.ection system and 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 spacial separation between safe shutdown equipment will provide reasonable assurance that one shutdown division will remain free of fire damaae.
2.4 Conclusion Based on our evaluation, the existing fire protection combined with the licensee's commitments provides a level of fire protection in the Auxiliary Building Elevation 695 ft. (Fire Zones 58 and 73) equivalent to the technical requirements of Section III.G.2, therefore, the exemption should be granted.
3.0 Auxiliary Building Elevation 715 ft. (Fire Zones 59 and 74) 3.1 Exemption Requested The licensee requests an exemption from Section III.G.2 to the extent it requires the installation of an automatic fire suppression system.
3.2 Discussion Elevation 715 ft. of the Auxiliary Building is one fire area which is designated as two fire zones, 59 and 74.
The fire area is enclosed by three-hour-rated fire walls with three-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 consists of smoke detectors, standpipe hose stations and portable fire extinguishers.
a.
Fire Zone 59 The combustible in the zone is cable insulation comprising a fuel load of 20,000 BTU /sq. ft. which, if totally consumed, would correspond to a fire severity of 15 minutes on the ASTM E-119 standard time temperature curve.
This fire area contains two Motor Control Centers, MCC-1L1 and MCC-1L2, and redundant division cables for safe shutdown equipment. One of the motor control centers is required for cold safe shutdown. The motor control centers are separated by 28 feet free of intervening combustibles.
The redundant cables are installed in cpen 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.
. The licensee has committed to enclose ail redundant Division B safe shutdown cables in a one-hour fire rated barrier.
h.
Fire Zone 74 The combustible in the zone is cable insulation comprising a fuel load of 18,111 BTil/sq. f t. which, if totally consumed, would correspond to a fire severity of approximately 14 minutes on the ASTM E-119 standard time tempera-ture curve.
This fire zone contains two Motor Centers, MCC-2L1 and MCC-2L2 and redundant cables required for safe shutdown. One of the motor control centers is required for cold shutdown. The redundant motor control centers are separated by 28 feet free of intervening combustibles. The redundant cables are installed in horizontal cable trays between 12 and 19 feet above the floor. Each divi-sion is separated by approximately 8 feet and installed within 3 feet of the ceiling.
The licensee committed to enclose all Division B safe shutdown cables in a one-hour fire rated barrier.
3.3 Evaluation The fire protection in this area does not comply with the technical require-ments of Section III.G.2 of Appendix R because an automatic fire suppression system is not installed in the area.
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, accessibility 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 brigad,e 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 interventien, the one-hour fire rated barriers enclosing safe shutdown cable trays and spacial separation between safe shutdown equipment will pro-vide reasonable assurance that one safe shutdown division will remain free of fire damage.
3.4 Conclusion Based on our evaluation, the existing fire protection combined with the licensee's commitments provides a level of fire protection in the Auxiliary Building Elevation 715 ft. (Fire Zones 59 and 74) equivalent to the technical requirements of Section III.G.2, therefore tne exemption should be granted.
4.0 Sumary Based on our evaluation, the following exemptions should be granted:
1.
Auxiliary Building Elevation 695 ft. (Fire Zones 58 and 73) 2.
Auxiliary Building Elevation 715 ft. (Fire Zones 59 and 74).
Date:
January 9, 1984 Principal Contributor:
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J. Stang I
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