ML20128L536
| ML20128L536 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 02/16/1993 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 93-027, 93-27, NUDOCS 9302190283 | |
| Download: ML20128L536 (11) | |
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VIROINIA ELECTRIC AND Powen COMPANY RICIIMOND. VIRGINIA 23201 February 16, 1993 United States Nuclear Regulatory Commission Serial No.93-027 Attention: Document Control Desk NL&P/CGL R1 Washington, D. C. 20555 Docket Nos.
50-338 339 License Nos. NFP-4 Gentlemen:
NFP-7 VIRGINIA ELECTRIC AND POWER COMPAt[Y NORTH ANNA POWER STATION UNIT _S 1 AND 2 REVISION TO APPENDIX R REPORT - EXEMPTION REQUEST NO. 25 CHILLER ROOM DOOR FIRE RATING Exemption Request No. 25 to the North Anna Appendix R Report is being revised to delete the requirement for a 3-hour fire rating of the chiller room doors. Maintaining a 3-hour fire rating for the chiller room doors and associated penetration seals is unnecessary and overly restrictive, as discussed herein. This letter provides the revis;on to the existing Appendix. tixemption Request No. 25 (Attachment 1) and the r
justification for the revision (Attachment 2). The existing Appendix R Exemption Request No. 25 was approved by the NRC in a Novernber 6,1986 Safety Evaluation Report (SER).
Pursuant to 10CFR50.12(a), you are requested to review and approve the attached revision to the existing Appendix R Exemption Request No. 25 addressing the fire rating of the chiller room doors. Subsequent to your approval, this revision will be included in the next update u: the North Anna Appendix R Report.
If you have questions or require further information, please contact us.
Very truly yours, 4
A W. L. Stewart Senior Vice President - Nuclear Attachments:
1.
Revision to Exemption Request No. 25 - Appen* R Report - North Anna Power Station 2.
Justification for Revision - Exemption Request No. 25 - North Anna Power Station =
.1G0011 50021 0283 930216 PDR ADOCK 05000338 P
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U. S. Nuclear Regulatory Commission Region 11 101 Marietta Street, N. W.
Suite 2900 Atlanta, Georgia 30323 Mr. M. S. Lesser NRC Senior Resident inspector North Anna Power Station s
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- 25. CHILLER ROOMS - LACK OF THREE-HOUR FIRE BARRIER 4
EXEMPTION RE0 VEST j
Per the provisions of 10 CFR 50.12, Virginia Electric and Power Company requests exemption from the specific 4
requirements of Appendix R,Section III.G.2(a) requiring a three-hour fire barrier between the Unit 1 and Unit 2 Chiller Rooms. This request applies to North Anna Units 1 and 2, 4
l DESCRIPTION OF EXEMPTION The Chiller Rooms provide chilled water to the air ccnditioning systems for the Control Room and the Emergency Switchgear Rooms. The air conditioning is required to keep both of the above areas tenable for operator actions.
Each unit has a separate Chiller Room, but both are part of the Turbine Building fire area (Fire Area 8) due to unrated ventilation openings into the-Turbine Building basement.
This exemption will show that separation equivalent to that required by Appendix R,Section III.G.2(a) exists betwee,) the two Chiller Rooms.
1 AREA DESCRIPTION i
Both t~e Unit 1 and the Unit 2 Chiller Rooms are located in the 254 ft.-elevation n
(basement) of the Service Building. The Chiller Rooms are both bounded to the south by the respective unit's Emergency Switchgear Room-(E3GR) air conditioner room. The l
wall between these areas is three-hour-rated reinforced concrete.
A three-hour-labeled door and frame are in this wall as well as a 12 in. Schedule 40 pipe for ESGR emergency pressurization (see Exemption Request 14). The Unit 2 Chiller Room also has an air conditioner duct (with a three-nour wrap) running through this south wali as well as the east wall abutting the Instrumentation Rack Room. 'The north wall of both Chiller Rooms is abutting the Turbine Building basement, Elevation 254 ft. This wall is a minimum of 12 in, concrete. The doors between these areas I
are metal, and the frames are channel steel in concrete similar to'those described J
ER25 25-1 Revised 11/92
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in Exemption 16.
There are also two ventilation openings in this wall for each Chiller Room.
j The east and west walls of the Chiller Rooms for Units 1 and 2, respectively, are I
minimum 12 in concrete against grade. The opposite walls (west and east for each l
room) are a minimum 12 in concrete against the Instrumentation Rack Room of the ESGR.
l The Unit 1 Chiller Room has a floor area of approximately 1260 ft8 and the Unit 2 l
Chiller Room has an area approximately 1025 ft2, J
The Chiller Rooms contain the chillers for the air conditioners and the air bottles for Control Room pressurization.
The basement of the Turbine Building (part of the same fire area as the Chiller Rooms) contains pumps, the condensers, lube oil components, cables, pipes, etc.
There is a block wall dividing the Unit I side of the Turbine Building from the Unit 2 side. This wall goes from the floor of the 254 ft, elevation to the bottom of the 303 ft. elevation (the operating floer).
FIRE PROTECTION SYSTEMS Both Chiller Rooms are equipped with - smoke detectors which annunciate via the Robertshaw fire alarm system to the continuously-manned Control Room.
The Turbine Building has an area-wide sprinkler system on the 254 ft, elevation as well as on the 279 ft. elevation. Automatic deluge ' systems protect the major lube oil components located on the 254 ft. elevation.
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Fire extinguishers are located throughout both areas and hose stations are located in the Turbine Building adjacent to the Chiller Rooms.
ER25 2 Revised 11/92-
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SAFE SHU1DOWN SYSTEMS The Chiller Rooms contain chillers which are required for air.. conditioning in;the t
-Control Room and the ESGR. Air conditioning is necessary in' these areas to assure l
tenability for operator actions. One Chiller Room operable will provide sufficient 4
cooling to keep. the Control Room tenable. for over 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
4 FIRE HA7ARDS ANALYSIS j.
k-The fire hazards analysis to 'show adequate separation between -the Units'l and 2 e
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Chiller Rooms can be divided into two sections:
first, an analysis of the.
j separation of each Chiller Room from the~ Turbine Building basement and, secondly, l
an analysis of.the separation of the Chiller Rooms from one another via the Turbine-Building Basement.
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The Chiller. Rooms are separated from the Turbine Building basement-by. a minimum
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12 in. concrete wall..This wall provides an excess of three-hour fire separation, j
except for unrated openings in the wall..The door between the Chiller Rooms and the j.
Turbine Building is metal.
The frame-.is not labeled but is heavy gauge channel j
steel in the concrete wall. A detailed description of similar-frames is given in l
Exemption Request 16. These frames are equal or superior to standard labeled door-frames.
f There are two ventilation openings--approximately 4 ft. x 4 'ft. in each Turbiree Bui'iding/ Chiller Room wall. These openings constitute unsealed penetrations between the two areas.
These openings are approxiinately 10 ft. abovc the floor with one
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about 8.ft, on each side of'the door.
Each opening is: protected with a missile barrier consisting of three - rows of interlocking = 1/4 in, steel- "I"-beams.
This barrier will act' as both a heat sink and -a flame arrestor;! therefore, it will mirimize the amount of heat: passing into the room.
There is a 3--ft. flood barrier on the Chiller Room side -of the door that will-prevent oil flow into the room beyond this barrier. There is a 3'-3" flood barrier on the Air Conditioning Room side of the south wall 'of the Chiller Rooms,: in order ER25 25-3
' Revised 11/92.
to divert flood waters toward the Turbine Building away from the Emergency Switchgear Rooms.
Therefore, it is very unlikely a fire could spread from the Turbine Building to either Chiller Room based on the wall thickness, metal door, ventilation missile barrier construction and the flood barrier.
The second phase of this analysis is to determine the possibility of fire spread from one Chiller Room to the other Chiller Room from a fire in the Turbine Building basement.
The primary hazards in the Turbine Building are the various lube oil components such as the oil purifier unit, hydrogen / seal oil unit, and the oil reservoir.
The components are protected with automatic deluge systems and curbs and/or trenches. These measures will prevent or severely limit a lube oil fire from progressing beyond the lube oil component. An automatic wet-pipe sprinkler system is installed on this elevation (254 ft.) and on the mezzanine level (Elevation 279 ft.) above. This system wil' help control fires in the general area.
There is a block wall between the Units 1 and 2 side of the Turbine Building. This wall divides the basement and mezzanine levels.
The operating floor (Elevation 303 ft.) is continuous for both units.
This wall will prevent spill fires from involving both sides of the Turbine Building.
The Chiller Rooms are physically separated by approximately 240 ft. on center.
It has been shown above that fire spread from the Turbine Building into the Chiller Rooms is unlikely and that simultaneous exposure to both the units' Chiller Rooms is high unlikely.
CONCLUSIONS Virginia Electric and Power Company has concluded that the current configuration of the Units 1 and 2 Chiller Rooms provides equivalent separation of the redundant chiller units to that required by Appendix R,Section III.G.2(a).
The technical bases that justify this exemption can be summarized as follows:
ER25 25-4 Revised 11/92
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The wall between the Chiller Rooms and the Turbine Building j
basement is of minimum 12 inch thick reinforced concrete construction.
2.
The ventilation openings between the - Chiller Rooms and the Turbine Building are 10 ft. ausve the floor and are protected by three rows of interlocking 1/4 in, thick "I"-beains.
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3.
A 3 ft. flood barrier is located just inside the Chiller Rooms to prevent oil flow into the room from the Turbine Building.
4.
The Turbine Building elevation ev.
sing the Chiller Rooms is equipped with automatic sprinkler; S.
The lube oil components in the Turbine Building are equipped with j
automatic deluge system and curbs and/or trenches to control oil flow.
6.
There is a fire wall between Units I and 2, on the 254 ft. and 5
279 ft, elevations of the Turbine Building.
7.
The Chiller Rooms are physically separated by approximately 240 ft, on center.
Attached are photographs for the. exemption being requested which show either.the general area and/or specific equipment in the area of concern (Photograph ~ Nos.
8408106, 8408109 and 8408110).
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ER25 25-5 Revised 11/92
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PLAN ELEV. 254'-0" NOTE: REDRAWN IN ENTIRETY i
REVISED 11-92 i
FIGURE NO~
VIRGINIA ELECTRIC & POWER COMPANY CHILLER ROOMS 25-1 NORTH ANNA POWER 3TATION ELEVATION 254'-0 i -
UNITS I&2
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I JUSTIFICATION FOR REVISION OF EXEMPTION REQUEST # 25 NORTH ANNA POWER STATION Exemption Request No. 25 of the Appendix R Report discusses compliance with Appendix R,Section III.G.2.a, to obtain separation of redundant trains.
In particular, the Unit 1 and 2 Chiller Rooms do not comply with Section III.G.2.a because unrated ventilation openings exist in the north wall of each Chiller Room adjacent to the turbine building basement.
The exemption request states that with the exception of these ventilation openings, the walls between the Chiller Rooms and the Turbine Building are 3-hour rated.
Each Unit's Chiller Room north wall has a double door arrangement, with a transom panel located in the frame above the doors.
The doors in this wall are also 3-hour rated, installed in channel steel frames similar to those described in Exemption 16.
These statements are repeated in the NRC's Safety Evaluation Report (SER) addressing Exemption Request No. 25.
Contrary to these statements, in order to facilitate certain plant design modifications, it is our intention to modify the Chiller Room doors in such a way that the UL 3-hour fire rating would be voided.
Maintaining a 3-hour fire rating for the Chiller Room doors and associated penetration seals is unnecessary and overly restrictive since there are unrated ventilation openings in the walls where the doors are located.
Appendix R requirements involve separation between the Unit 1 and Unit 2 Chiller Rooms.
One Chiller Room operable will provide sufficient cooling to keep the Control Room tenable for over 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, as required by Appendix R.
There are many factors about the configuration which provide separation between the two Chiller Rooms, and will prevent a single fire in the Turbine Building from disabling more than one Chiller Room.
As stated in the NRC's SER (page 25):
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o-t Until the fire is extinguished by the fire brigade or automatic suppression systems, the spatial separation and intervening masonry wall in the Turbine Building, the general area fire suppression system in the Turbine Building, the fire detection system in the chiller rooms, and the lack of intervening combustibles will provide sufficient protection to provide reasonable assurance that a chiller room would remain free of fire damage.
The above paragraph identifies that there are sufficient factors (independent of the Chiller Room / Turbine Building wall) to provide separation of the Appendix R safe shutdown systems.
Lack of a 3-hour rating on the fire doors and penetration seals is justified based on the same factors which justify the unrated ventilation openings in the Chiller Room wall:
o The Chiller Rooms are physically separated by approximately 240 ft..on center.
O There is a masonry fire wall between Units 1 and 2 on the Turbine Building basement and mezzanine levels.
O The Turbine Building basement _and mezzanine levels are provided with a general area automatic sprinkler system.
O The Chiller Rooms are provided with a fire detection system.
O There is a 3 ft, flood barrier just inside the Chiller-Rooms to prevent oil flow into the rooms from the Turbine Building.
The Chiller Room wall separates the hazards of the Turbine Building from the hazards in the Cniller Room.
This wall is required to provide seismic, missile, and radiation protection for j
the Control Room cooling system components (UFSAR 9.4.1).
The construction of the wall is designed to provide this separation, and a sliding missile shield door is provided for-this door opening.
(Note: The exemption is being updated to delete the statement that the missile door is normally kept closed while the units are at power, since this statement has no bearing on the 2
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exemptian.)
This wall is not specifically required to provide fire i
separation,' although the construction of the wall will provide some i
degree of fire separation between the hazards in the adjacent areas.
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