NL-05-0960, Response to Request for Additional Information Related to Requests for Exemption/Amendment from Fire Protection Requirements
| ML051640200 | |
| Person / Time | |
|---|---|
| Site: | Farley  (NPF-002, NPF-008) |
| Issue date: | 06/09/2005 |
| From: | Stinson L Southern Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-05-0960 | |
| Download: ML051640200 (6) | |
Text
L M. Stinson (Mike)
Vice President Southern Nuclear Operating Company, Inc.
40 Inverness Center Parkway Post Office Box 1295 Birmingham, Alabama 35201 Tel 205.992.5181 Fax 205.992.0341 SOUTHERNAM COMPANY Energy to Serve YourWorld' NL-05-0960 June 9, 2005 Docket Nos:
50-348 50-364 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Joseph M. Farley Nuclear Plant - Units I and 2 Response to Request for Additional Information related to Requests for Exemption/Amendment from Fire Protection Requirements at Farley Nuclear Plant Ladies and Gentlemen:
On January 19, 2005, Southern Nuclear Operating Company (SNC) requested an exemption for Unit I from 10 CFR Appendix R Section III.G.2 and an amendment for Unit 2 to use fire rated electrical cable which has been demonstrated to provide an equivalent level of protection as would be provided by a one-hour rated electrical cable raceway fire barrier enclosure as described by 10 CFR 50, Appendix R,Section III.G.2 for protection of safe shutdown control circuits located in fire areas 1-013, 1-042, 2-013, and 2-042.
Per a facsimile from the NRC to SNC dated May 17, 2005 and a subsequent conference call on June 1, 2005, the NRC initiated a request for additional information (RAI). The attached enclosure provides the NRC RAI questions and the SNC responses to those RAI questions.
As stated in the January 19, 2005 letters, SNC requests NRC approval of the Unit I exemption and the Unit 2 amendment by January 21, 2006.
(Affirmation and signature provided on the following page.)
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U. S. Nuclear Regulatory Commission NL-05-0960 Page 2 Mr. L. M. Stinson states he is a Vice President of Southern Nuclear Operating Company, is authorized to execute this oath on behalf of Southern Nuclear Operating Company and to the best of his knowledge and belief, the facts set forth in this letter are true.
This letter contains no NRC commitments. If you have any questions, please advise.
Respectfully submitted, SOUTHERN NUCLEAR OPERATING COMPANY L. M. Stinson
.. Sworn to and subscribed before me this 9 day of d r t.
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NOTrANYMESTAWOT ANAMA ATLAS MY COMMISSTON EXPIRES: June 10, 2X
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Enclosure:
SNC Response to NRC Request for Additional Information cc:
Southern Nuclear Operating Company Mr. J. T. Gasser, Executive Vice President Mr. J. R. Johnson, General Manager - Plant Farley RTYPE: CFA04.054; LC# 14280 U. S. Nuclear Regulatorv Commission Dr. W. D. Travers, Regional Administrator Mr. R. E. Martin, NRR Project Manager - Farley Mr. C. A. Patterson, Senior Resident Inspector - Farley
Joseph Al. Farley Nuclear Plant Units 1 and 2 Response to Request for Additional Information related to Requests for Exemption/Amendment from Fire Protection Requirements at Farley Nuclear Plant Enclosure SNC Response to NRC Request for Additional Information
Response to RAI NI-05-0960 Enclosure Page 1 of 3 NRC Question 1:
Page 10 of the licensee's "Appendix R, One-Hour Rated Fire Resistive Control Cable Test" report states:
TIME OBSERVATION 0:00 Furnace ignited at 10:52 AM.
5:00 Furnace interior pressure adjusted to +0.01 WC at a point 3/4' ' below slab, resulting in a neutral pressure plane position approximately 12" below the underside of the slab.
20:00 Megger testing began.
30:00 Furnace operating normally. No visual observations within the furnace.
45:00 Furnace operating normally. Still no obvious changes inside.
60:00 Megger testing still not complete for the first round. The client requested that the furnace be kept on, but that the temperature be held steady and continuously at the El 19 sixty-minute temperature (1700 degrees F).
61:00 First round of meggering completed.
Generic Letter 86-10, Supplement 1, Attachment to Enclosure 1,Section IV "Cable Insulation Tests" states: "To provide reasonable assurance that the cables would have functioned during and after the fire exposures, Megger tests need to be performed before the fire test, at multiple time intervals during the fire exposure (i.e. every 20 minutes during the 1-hour fire test) for instrumentation cables only, and immediately after the fire endurance test to assess the cable installation resistance levels. This testing will assure that the cables will maintain the insulation resistance levels necessary for proper operation of instruments."
The test appears to deviate from the GL 86-10, S.1 criteria (there is a 40 minute time interval between Megger testing). This deviation is not explicitly identified nor evaluated for acceptability by the licensee's submittal.
Identify any deviations from GL86-10, S.1 test criteria and provide an evaluation for why the deviation(s) is acceptable.
SNC Response:
The Mineral Insulated (MI) cables at Farley Nuclear Plant (FNP) were tested for use in low voltage control circuits.Section IV CABLE INSULATION TESTS contained in the Attachment to Enclosure I of GL 86-10, Supplement 1, contains criteria for conducting Megger tests. The 3rd paragraph of section IV indicates that the 20-minute interval during the one-hour fire test is for instrumentation cables only. The 4h paragraph of this section states, "The Megger tests (pre-fire, during the fire (if performed), and immediately after the fire test conditions) should be done conductor-to-conductor for multi-conductor and conductor-to-ground for all cables." 500 VDC Megger testing to obtain conductor-to-conductor and conductor-to-ground insulation resistance values were performed pre-fire, during the fire test, and after the hose stream test. To insure that conductor-to-conductor and conductor-to-ground insulation resistance (IR) readings were obtained for all conductor combinations at the peak ASTM one-hour test temperature, the fire test was extended for an additional 38 minutes and 12
Response to RAI NL-05-0960 Enclosure Page 2 of 3 seconds with the furnace temperature held as close as possible to 1700 degrees F until all IR values were recorded. Obtaining insulation resistance values during the fire test by the test method applied provided conservative test results that meet the fire Megger testing requirements of GL 86-10, Supplement 1, for the Farley specific one-hour rated control cable application.
A formula is also provided in Section IV for determining the minimum acceptable insulation resistance. This formula was not used to determine the minimum acceptable IR test value. See our response to Question 2 below for an explanation of the method used to determine the plant and circuit specific minimum acceptable test IR value.
We found no other deviations from the applicable GL 86-10, Supplement I test criteria.
NRC Question 2:
Page 7 of the licensee's "Appendix R, One Hour Fire Resistive, Control Cable Fire Test" report Section 3 entitled "Acceptance Criteria" states:
"A minimum conductor to conductor or conductor to cable sheath (shield) insulation resistance (IR) value of 5.7 megohms per foot is considered to be the test acceptance criteria.
The cable IR values obtained during the fire test exposure and after application of the hose stream will be used to demonstrate the functional capability of FNP specific Appendix R control circuit applications."
(a.) Explain how the value of 5.7 M]/ft. was derived. Provide any applicable assumptions with relevant bases.
(b.) Clarify why the minimum insulation resistance value of 5.7 M]K/ft. is an acceptable value for the use of the cables at Farley Nuclear Plant.
SNC Response (a) & (b):
Based on the review of previous MI cable fire test results, a minimum IR value was selected that was reasonably expected to be achievable during the Farley specific one-hour fire test.
This minimum insulation resistance value was then used to evaluate the Farley specific control circuitry (that will use the MI cable) for functional impacts associated with increased conductor-to-conductor or conductor-to-ground leakage currents. A review of the elementary diagrams was performed and determined that the only potential failure mechanism due to increased leakage current from the energized conductors to the ground that would flow through the control circuit protective devices would be tripping of the protective devices. The results of the plant circuit specific analysis concluded that the control circuit protective devices will not trip during a fire event with an IR value of 5.7 M]'ft.
The minimum IR value recorded during fire test was 0.8 Mfl, and with 24.167 feet of cable inside the furnace, that equated to 19.3 Mf/ft (reference Pages 14 and 15 of the test report).
This is far in excess of the Farley specific minimum acceptance value of 5.7 Mf/ft.
Response to RAI NL-05-0960 Enclosure Page 3 of 3 I r NRC Question 3:
Discuss how the fire rated cable is protected against mechanical damage from non-fire rated equipment that may fail and fall in the event of a fire in the area.
SNC Response:
The fire areas where the MI cables are routed are protected with area wide automatic fire suppression and detection systems, and the MI cable is fire rated for one hour as required by Appendix R Section III.G.2.c.
Routing for each MI cable was established by plant walk-down to protect against potential physical hazards. The one-hour fire rated MI cables are also safety related and will be installed to meet the FNP routing requirements for Class IE cable protection from physical hazards. The cables are only routed in safety related Class 1 structures, and all safety related and non-safety equipment and components in these structures are seismically supported.