ML20072F953
| ML20072F953 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 08/18/1994 |
| From: | Bowling M VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 94-444, NUDOCS 9408240140 | |
| Download: ML20072F953 (7) | |
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VIIMUNIA Eu:crHIC AND POWI5H Com'ANY ltsenuann,Vsuasssa ununs August 18, 1994 i
United States Nuclear Regulatory Commission Serial No.94-444 Attention: Document Control Desk DE&S/LTW-CGL R1 Washington, D. C. 20555 Docket Nos.
50-338 50-339 License Nos.
NPF-4 NPF-7 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 BESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING ADDENDUM TO APPENDIX R EXEMPTION REQUEST NO.1-PENETRATIONS IN CHARGING PUMP CUBICLES' SOUTH WALL By a July 14,1994 letter, the NRC requested additional information regarding an addendum to the previously approved North Anna Appendix R Exemption Request No.1. The addendum, which was transmitted on December 11,1992 (by letter Serial No. 92-693B), addressed penetrations in the south wall of the charging pump cubicles.
The response to the request for additional information is provided in the attachment.
Please contact us if you require further information.
Very truly yours,
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u M. L. Bowling, Manager Nuclear Licensing & Programs Attachment-Response to NRC Request for Additional Information Regarding Addendum to Appendix R Exemption Request No.1 - Penetrations in Charging Pump Cubicles' South Wall - North Anna Power Station Units 1 and 2 9
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U. S.' Nuclear Regulatory Commission Region ll 101 Marietta Street, N. W.
Suite 2900 Atlanta, Georgia 30323 Mr. R. D. McWhorter NRC Senior Resident inspector North Anna Power Station
ATTACHMENT RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING ADDENDUM TO APPENDIX R EXEMPTION REQUEST NO.1 -
PENETRATIONS IN CHARGING PUMP CUBICLES' SOUTH WALL NORTH ANNA POWER STATION UNITS 1 & 2 NRC Question:
1.
Revision 3 of Exemption 1 in the submittal of March 21,1986, was related to the specific requirements of 10 CFR 50 Appendix R, Section Ill.G.2(b), which states
" 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 combustible or fire hazards. In addition, fire detectors and an automatic fire suppression system shall be installed in the fire area;" The lack of 3-hour rated fire barriers, which is the subject of the December 11,1992 request, is not within the scope of Section Ill.G.2(b). The correct reference is Section Ill.G.2(a), which addresses separation by 3-hour fire barriers. The exemption should be revised to reflect the proper section of the regulation from which relief is being requested. If desired, a revised Exemption 7 could be submitted by the licensee. Exemption 7, approved in the November 6,1986, Safety Evaluation, addresses the lack of 3-hour fire rated separation for the charging pump cubicles.
flesoonse:
Revision 3 of Exemption Request No.1 in the submittal of March 21,1986, requested exemption from the specific requirements of 10 CFR 50 Appendix R, Section Ill.G.3 (alternative shutdown). While the specific changes contained in the addendum to Exemption No.1 (requested on December 11,1992) deal with openings in 3-hour fire barriers, the main purpose of submitting these changes was to clarify the description given on page 1-7 of Exemption Request No.1 regarding the barriers. This is necessary to show the potential interaction between the charging pump cubicles and the alternative shutdown fire zones.
The focus of Exemption Request No.1 is to show that the safe shutdown components of one unit are adequately separated from the safe shutdown components of the opposite unit in accordance with Section Ill.G.3 (alternative shutdown), except that fire detection and fire suppression is not provided throughout the fire area. As shown in Exemption Request No.1, page 1-5, the entire Auxiliary Building is divided into two
" fire zones" (zone 11-1 and zone 11-2). The components in one zone provide alternative shutdown capability for the components in the other zone. The two zones are shown to be physically and electrically independent of each other. The techniques used to show physical independence of the two zones include having 20 foot separation between components and having 3-hour rated concrete walls separating the charging pump cubicles.
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Since.the charging pump cubicles are defined as separate " fire areas", openings in the charging pump cubicle boundaries have been evaluated in accordance with Generic Letter 86-10, Enclosure 1, Interpretation 4. The evaluation concluded that the barriers are sufficient to withstand the hazards associated w;ih the area.
The description of the openings in these barriers was clarified in the addendum because the original barrier description did not accurately define the separation between the charging pump cubicles and the two " fire zones"in the Auxiliary Building.
Therefore, Exemption Request No.1, along with the addendum, requested exemption from the specific requirements of 10CFR50 Appendix R, Section Ill.G.3, rather than Section Ill.G.2(a) or Section Ill.G.2(b).
NRC Ouestion:
2.
With regard to the penetrations that could not be sealed to a rating of three hours, explain why the penetrations could not be adequately sealed and specify the number, size and location of the penetrations addressed by the exemption request. Also provide the equivalent fire rating of the subject penetration seals (if any). Verify that the walls, including all penetrations, separating each charging pump from the adjacent charging pump (s) are qualified as 3-hour fire barrier assemblies.
Resoonse:
The following penetrations are not sealed to a rating of three hours:
a)
In cubicle 1-1C, there is a pipe chase located in the southwest corner of the room near the ceiling (refer to Figure 1.3 of the addendum). This pipe chase is open into the cubicle and open on each end (i.e., at the radioactive pipe chase, elevation 254'-6", and at the volume control tank cubicle, elevation 274'-0"). The ends of the pipe chase are approximately 1'6" x 3'6' and 1'6" x 4'6", respectively.
The pipe chase is not sealed due to the congestion of the pipes and due to the associated radiation levels.
b)
In each of the six cubicles there is a blockout opening into the pipe chase. Each blockout is approximately 2'0" x 3'6". The blockouts are each sealed by a metal plate and a 1" thick panel of Thermo-Lag. The metal plates provide a non fire rated seal against the passage of smoke and hot gases. The Thermo-Lag provides approximately a one hour fire rating, although no credit is taken for this fire rating in the addendum.
c)
In each of the six cubicles there are two openings into the corridor for valve reach rods. Each opening is approximately 2" diameter to allow for movement of the approximately 1/2" rod. The openings are covered with metal plates on the corridor side of the barrier. The metal plates provide a non-fire rated seal against the passage of smoke and hot gases. A design change is currently in progress to Page 2 of 5
remove one of these reach rods from each cubicle and replace it with a flood barrier. The 2" holes will be completely sealed by a metal plug on each side of the barrier with a threaded rod running through the barrier to hold the plugs in place.
All other penetrations from the charging pump cubicles into the corridor are sealed with a three-hour rated fire seal.
The walls separating each charging pump from the adjacent charging pump (s) consist of an 18" thick reinforced concrete wall, except for one section of the barrier between pumps 1-CH-P-1C and 2-CH-P-1 A. This section was recently upgraded by a design change to a 3-hour rated fire barrier configuration consisting of 5/8" thick sheets of Type X gypsum board. All penetrations in these interior walls between cubicles are sealed with a 3-hour rated silicone foam penetration seal and were recently inspected.
NRC Ouestion:
3.
With regard to Fire Area 11, provide an explanation of the transient combustible materials that are handled, stored, transported or used in this area and an evaluation of the exposure hazard to the charging pump cubicles represented by the transient combustibles. Verify that the Thermo-Lag installed in this area has been considered as an in situ combustible in the Fire Hazard Analysis.
Response
Transient combustibles that are handled, stored, transported or used in this area consist of grease, lube oil, miscellaneous Class A combustibles, and charcoal material for filter replacement. The station has procedures in place to control the use of these materials. Since these transient combustibles are limited in their use (typically to what is required for use during a single shift), fire from these transients would contribute very little to a fire involving the in situ combustibles, as discussed in the exemption.
The small quantity of Thermo-Lag material installed in each cubicle (i.e., a panel about 2'0"x3'6") is not considered as an in situ combustible in the Fire Hazard Analysis since it is negligible relative to the other Class A and Class B combustibles included in fire area 11.
Even if the Thermo-Lag was considered an in situ combustible, the conclusions of our Fire Hazards Analysis would not be impacted.
NRC Question:
4.
With regard to the open areas of elevation 259-feet 6-inches, describe the impact on safe shutdown capability if the power feeds to the charging pumps are damaged by a fire in this area. Also, provide a basis for the statement that "It is not considered credible for a fire in the open area of the 259 ft-6 in elevation to expose a charging pump or valves within a cubicle since the floor openings have dikes."
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Respons~ei The routing of the charging pump power feeds on elevation 259'-6" is described on pages 1-7,1-8, and shown on Figure 1-2 of Exemption No.1. Since the Unit 1 power feeds are in a separate fire zone from the Unit 2 power feeds, if a fire in this area damages one set of power feeds, the charging pump cross-connect (located in charging pump cubicles 1-1C and 2-1 A) can be manually opened and charging flow can be supplied from the opposite unit.
There are a few openings through the floor of elevation 259'-6"into the charging pump cubicles below. These openings include a personnel entry hatch and a ventilation duct for each cubicle, two openings for cable penetrations into cubicle 1-1 A, and one opening for tubing into cubicle 2-1 A. Each opening has a 4" high dike around it to prevent liquid from entering the cubicles in the event of a spill on elevation 259'-6". If a fire occurs in the noen area of the 259'-6" elevation, it will not expose a charging pump or valves within a u.bicle due to the following factors:
a)
Building configuration (large open spaces and sections of grating in floors) is such that heat will rise up to the upper elevations of the Auxiliary Building, b)
Flammable liquid spill will not be able to flow into the cubicles due to the dikes, and c)
Openings into the cubicles are below the base of the fire.
NRC Ouestion:
5.
With regard to elevations 244-feet 6-inches and 259-feet 6-inches, verify that the charging pump cubicles are agl provided with automatic sprinkler protection. The of the November 6,1986, Safety Evaluation states on page 4, "A sprinkler system is installed over the CCW and charging pumps and their power feeds in the 259-foot,6-inch and 244-foot,6-inch elevations." Please resolve the discrepancy.
Resoonse:
The automatic sprinkler system in the Auxiliary Building does not extend into the charging pump cubicles, so the charging pumps themselves are not protected. The I
wording in the November 6,1986, NRC Safety Evaluation is inaccurate.
The wording in Revision 3 of Exemption Request No.1, as submitted on March 21, 1986, clearly states that the sprinkler system protects the CCW pumps and the power feeds for both the charging pumps and CCW pumps. This is stated in the third paragraph of page 1-3, in the third paragraph of pcge 1-10, in conclusion item 7 on page 1-13, and is shown on figures 1-2 and 1-3.
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1 As stated 'o'n page 1-10 of Revision 3 of Exemption Request No.1, the basis for the accepiability of a partial sprinkler system for the CCW pumps and for the power feeds for both the charging and CCW pumps is as follows:
"This' basis is that the overall combustible loading is low enough that a fire originating outside the sprinkler protected area will not propagate to a i
magnitude that could overwhelm the partial sprinkler system. In addition, the goal is to prevent a fire from disabling both units' charging and CCW systems."
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