ML20125E604
| ML20125E604 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 12/11/1992 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 92-693B, NUDOCS 9212170148 | |
| Download: ML20125E604 (7) | |
Text
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w VIROINIA ELECTHIC AND POWER COMPANY RicliMoxo. VIHOINI A 23201 December 11, 1992 United States Nuclear Regulatory Commission Serial No.
92 603B Attention: Document Control Desk NL&P/CGL RS Washington, D. C. 20555 Docket Nos.- 30-338 50-339 License Nos. NFP-4 Gentlemen:
N FP-7 VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 ADDENDUM TO APPENDIX R REPORT - EXEMPTION REQUEST NO.1 PENETRATIONS IN CHARGING PUMP CUBICLE SO'UTH WALL Inspection Repod No. 50-338, -339/92-18 for North Anna Power Station Units 1 and 2 identified a Level IV Violation relative to non-functional penetration fire barriers on the south wall separating the charging pump cubicles from a common pipe chase. Fire watches were established in the affected areas and, subsequently, the non functional penetrations were sealed, However, for those penetrations that could not be sealed to a rating of three hours, an addendum to the existing Appendix R Exemption Request No.1 is required. The existing Appendix R Exemption Request No.1 was approved by the NRC in a November 6,1986 Safety Evaluation Report (SER).
This letter provides the addendum to the existing Appendix R Exemption Request No.1 (Attachment 1) and the justification for the addendum (Attachment 2).
Pursuant to 10CFR50.12(a), you are requested to review and approve the attached addendum to the existing Appendix R Exemption Request No.1 addressing fire penetration barriers on the south wall of the charging pump cubicles. Subsequent to your approval, this addendum will be included in the next update of the North Anna -
Appendix R report.
If you have questions or require further information, please contact us.
Very truly yours,
[H i
iQ L Qb W. L. Stewart Senior Vice President - Nuclear Attachments:
l 1.
Addendum to Exemption Request No.1 - Appendix R Report - North Anna Power Station 2.
Justification for Addendum - Exemption Request No.1 - North Anna Power I
Station I
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'. S. Nuclear Regulatory Commission U
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ADDENDUM TO EXEMPTION REQUEST # 1 APPENDIX R REPORT NORTH ANNA POWER STATION
-The following changes'are being made to Exemption Request # _ 1, Auxiliary Building - Partial Area Fire Suppression and Detection.
1.
On page 1-7, the first and second paragraph are replaced with the followi.ng three paragraphs:
"three on the east end are for Unit 1, and the remaining _
three are for Unit 2.
The cubicles are constructed of heavy concrete walls on three sides, and the fourth side is a removable wall made of concrete beams.
These walls have an inherent fire rating in excess of 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> (see Exemption Request 7 concerning the removable wall).
The charging pump cubicle walls extend from floor to ceiling on Elevation 244 ft-6 in.
Openings at the floor of the 259 ft-6 in, elevation for each cubicle are diked and include a hatch for personnel entry, ventilation ducts, cable trays, and conduit. The walls extend from floor to ceiling on elevation 244 ft.-6 in.,
and penetrations through the walls are sealed to a rating of 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />.
In the south wall of the charging pump qubicles there are
~
some openings that are not sealed to a3 hour fire rating.
These openings lead to the-corridor and the horizontal pipe chase adjacent to the south wall of the cubicles.
The openings into the corridor consist of~
valve stems _(with valve handles located in the corridor)_-
covered with metal plates.
The pipe penetrations into the pipe chase are covered with metal plates and 1-inch thick panels of Thermo-Lag.
Cubicle 1-1C also has, on the south wall and at the southwest corner of the celling, unsealed blockouts with pipes leading into the-horizontal 'and vertical pipe chases.
Except for the unsealed openings in cubicle 1-lc, the metal plates cover the openings and provide a non-fire rated seal against-the passage of smoke and hot _ gasses."
"The horizontal pipe chase is located south of the charging pump cubicles and extends along the south wall of each pump _ cubicle (See Figure 1.3).
The pipe chase is-open ended at the-pipe penetration areas adjacent ~to the 1
4.
Unit 1 and 2 Containments, and has openings into the adjacent cubicles (scal water filters, heat exchangers,
...etc. ) located on the south side of the' pipe chase.
The vertical pipe chase is. located between cubicles 2-1A and 1-1C and extends vertically to the_ Volume Control Tank (VCT).
This vertical chase has an unsealed -opening into cubicle 1-10 and is open ended at the VCT with no intermediate openings.
The vertical and horizontal pipe chases are not expected to create a fire exposure to the cubicles due to the lack of combustible material in the chases.
A fire in cubicle 1-1C would not be expected to enter the pipe chases due to the negligible amount of combustibles in the chases.
If the fire did enter the chases, it would travel out and away from the adjacent cubicles which have penetrations sealed with metal plates."
"It is not considered
- credible, based on the configuration described
- above, for a
fire in an l
individual charging pump cubicle to expose an-adjacent cubicle or to propagate out of the cubicle.
A fire in cubicle 1-1C would not be expected to _ enter the pipe chases due to the negligible amount of combustibles in l-the chases.
If the fire did enter the chases, it would l
travel out and away from the adjacent cubicles which have penetration _ seals.
The metal plates will provide an adequate seal against the passage of smoke and hot gasses
[
based on the configuration.and lack of combustibles in L
the corridor and pipe chase.
It is not _ considered credible for a. fire in the open ; areas of the 259 ft.-6
-in. elevations to expose a charging-pump (although it may affect the power feeds) or valves within a cubicle since the floor openings have dikes.
It is not credible for a fire to spread from the general areas of the 244 ft-6:in.
elevation into the pipe chase due to the _ negligible
-combustible leading in the area and long travel distance f
from the open ends of the chase to the cubicles."
Figure 1-3 is replaced with the revised Figure 1-3 (attached).
2.
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SM0KE DETECTORS M
MANUAL VALVES FOR CHARGING PUMP FIGURE NO.
l DISCHARGE VIRGlNIA ELECTRIC & POWER COMPANY AUXILIARY BUILDING 1.3 CROSSCONNECT NORTH ANNA POWER STATION ELEVATION 244'-6 UNITS I&2 CAD NO. NA! FIG 72.APR
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e JUSTIFICATION FOR ADDENDUM EXEMPTION REOUEST # 1 NORTH ANNA POWER STATION Exemption Request No.
1 of the Appendix R Report discusses compliance with Appendix R,Section III.G.3, to obtain separation of redundant trains.
In particular, the charging pumps are credited with having 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> rated fire walls, and penetrations in these walls are sealed to a rating of 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />.
This statement is repeated in the NRC's Safety Evaluation Report addressing Exemption Request No.
1.
Contrary to this statement, the cubicle for pump 1-CH-P-1C has unprotected openings into the horizontal and vertical pipe chases.
In addition, the remaining openings from the charging pump cubicles into the horizontal pipe chase are sealed with 1 inch Thermo-Lag over a steel plate (credited as less than a 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> fire rated seal).
There are six charging pumps arranged side by side in individual cubicles on the 244 ft.-6 in, elevation of the Auxiliary Building.
A minimum of one charging pump per unit is needed to bring the units to and maintain shutdown.
In order to provide an alternative shutdown configuration, a cross-connection was added between the discharge headers of the two units' charging pumps.
This-arrangement physically permits one unit's charging pumps to supply makeup flow to the other unit.
The horizontal pipe chase is located south of.the charging pump.
cubicles and-extends along the south-wall of each pump cubicle.-
The pipe chase _ is open ended at the pipe penetration areas-adjacent to the Unit 1 and 2 Containments, and has openings into the cubicles located on the south _ side of the pipe chase. _The vertical pipe chase is_ located between cubicles 2-1A and 1-lc and extends vertically to the Volume Control Tank (VCT).
This vertical chase has an unsealed opening into cubicle 1-lc and-is open ended at the VCT with no intermediate openings.
The pipe. chases are not expected to create a fire exposure to the cubicles due to the lack of combustible material in' the _ chases.
Each_ charging pump-cubicle is provided With one ceiling-mounted and one duct smoke' detector.
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1
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o The charging pump cubicle walls extend from floor to ceiling on Elevation 244'ft-6 in.
Openings at the floor of the 259 ft-6 in.
elevation for each cubicle are diked and include a hatch for personnel entry, ventilation ducts, cable trays, and conduit.
It is not considered credible, based on the configuration described, for a fire in an individual cubicle to expose an adjacent cubicle or to propagate out of the cubicle.
A fire in cubicle 1-1C would not be expected to enter the pipe chases due to the negligible amount of combustibles in the chases.
If a fire did enter the chases, it would travel out and away from the adjacent cubicles which have penetrations sealed.
The loss of pump 1-CH-P-1C would not create an unreviewed safety question since the technical specifications allow operation with one pump inoperable.
It is not credible for a fire to spread from the general arcar of the Auxiliary Building, elevation 259 ft., into the cubicles, since the floor openings have dikes.
It is also not credible for a fire to spread from the general areas of the Auxiliary Building into the cubicles through the pipe chases due to the following:
Negligible combustible loading in the pipe chases.
Negligible combustible loading in the cubicles on the south side of the pipe chase.
Long travel distance from the open ends of the pipe chases.
Metal plate with Thermo-Lag barriers installed on the openings into all cubicles except 1-1C.
Smoke spread into cubicle 1-1C is possible but would not prevent operator actions due to the following:
Operator access is addressed in Evaluation 7,
which states the operator can use SCBA if needed.
Low combustible loading in-the areas of the Auxiliary Building at the ends of the pipe chases.
The orientation of the chases is such that a significant quantity of smoke would not be likely to travel the length of the chases and enter cubicle 1-lc.
In summary, the lack of 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> rated seals for the openings-into the pipe chases does not create an unreviewed safety question since the configurations meet the intent of Appendix R requirements.
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