B17531, Informs NRC of Corrective Actions Chosen to Address Various Thermo-Lag Issues at Millstone Unit 2

Informs NRC of Corrective Actions Chosen to Address Various Thermo-Lag Issues at Millstone Unit 2

ML20195G874
Person / Time
Site:	Millstone
Issue date:	11/13/1998
From:	Bowling M NORTHEAST NUCLEAR ENERGY CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
B17531, GL-92-08, GL-92-8, TAC-M85571, NUDOCS 9811230160
Download: ML20195G874 (6)

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.N & M R Pe Ferry Rd. (Route 156), Waterford, CT 06385 Nudear Energy Millstone Nuclear Power Station .

Northeast Nuclear Energy Company P.O. Box 128 Waterford, CT 06385-0128 (860) 447 1791 l l

Fax (860) 444-4277 The Northeast Utilities System NOV i 31998 Docket No. 50-336 J B17531 ,

I Re: Generic Letter 92-08 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555

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1 Millstone Nuclear Power Station, Unit No. 2 Thermo-Laa Fire Barrier issue (TAC M85571)

The purpose of this letter is for Northeast Nuclear Energy Company (NNECO) to inform l the NRC Staff of corrective actions chosen to address various Thermo-Lag issues at l Millstone Unit No. 2.- Except as noted, this letter does not include ampacity related  !

. issues which are being addressed separately (TAC MA3392).

in a meeting held between members.of NNECO and the NRC Staff, on April 24,1997,-

(summarized in a meeting summary dated May 12,1997,0)) NNECO informed the Staff that various corrective actions were being considered to address Thermo-Lag related issues. The corrective actions being considered at the time included the following:

justify or upgrade existing installations,. reroute cables, add suppression, credit operator action, request exemptions and/or use alternate shutdown approaches.

The final corrective actions to resolve the Thermo-Lag issues at Millstone 2 are described in Attachment 1. These corrective actions are in various stages of design and implementation. Should the corrective actions described in this letter be revised, NNECO will inform the NRC Staff, as appropriate. NNECO reiterates its commitment to resolve all Thermo-Lag Fire Barrier issues prior to the restart of Millstone Unit No. 2

- (Mode 4) from the current outage. (Reference letter dated July 8,1997.*)

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[ There are no regulatory commitments contained within this letter.

") . U.S. Nuclear Regulatory Commission, " Meeting Summary Regarding the April 24, 1997, Meeting Held to Discuss Thermo-Lag Fire Barrier issues - Millstone Nuclear Power Station, Unit No. 2," dated

' May 12,1997.

" ~. M. L. Bowling letter to U.S. Nuclear Regulatory Commission, " Millstone Nuclear Power Station, Unit No. 2 - Revised Schedule Thermo Lag Fire Barrier issue (Generic Letter 92-08)," dated July 8,1997.

9811230160 981113 F PDR P ADOCK05000336h PDR u

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U.S. Nucletr Regulatory Commission B17531\Page 2 If you have any questions, please contact Mr. Ravi Joshi at (860) 440-2080.

4 NORTHEAST NUCLEAR ENERGY COMPANY l

Nbh Martin L. Bowling, Jr. j Recovery Officer - Technical Services Attachments (1) cc: H. J. Miller, Region I Administrator D. G. Mcdonald, Jr., NRC Senior Project Manager, Millstone Unit No. 2 D. P. Beaulieu, Senior Resident inspector, Millstone Unit No. 2 E. V. Imbro, Director, Millstone ICAVP inspections S. Dembek, NRC Project Manager, Millstone Unit No.1

Docket No. 50-336 B17531 Attachment 1 Millstone Nuclear Power Station, Unit No. 2 Corrective Actions Thermo-Lag Fire Barrier Issue (TAC M85571)

November 1998

m 1 U.S. Nucl::ar Regulatory Commission B17531\ Attachment 1\Page 1 Millstone Unit No. 2 l Corrective Actions l Thermo-Lao Fire Barrier Issue (TAC M85571)

Charaina Pump Room (Appendix R Fire Area R-4)

Thermo-Lag 330-1 protecting Charging Pump cables in the Charging Pump Room has l been removed. The Facility Z2 cables associated with Charging Pumps 'B' and 'C' are ,

being rerouted within the individual pump cubicles, through the floor of the Charging '

Pump Room and into the "A" ESF Room, below. A request for exemption from the requirements of 10CFR50 Appendix R for the Charging Pump Room has been submitted (reference letter dated July 31, 1998.* That exemption request provides technical justification that the physical separation between the redundant Charging Pumps and cables within this room provides an equivalent level of protection to that required by Section lil.G.2 of Appendix R.

Removal of the Thermo-Lag in this room resolves ampacity concerns with cables previously protected by Thermo-Lag. Reroute of the Facility Z2 Charging Pump cables, together with existing separation between the Charging Pumps, as described in the exemptien request, ensure that at least one Charging Pump remains available to support safe shutdown following a fire in the Charging Pump Room.

Turbine Buildina (Appendix R Fire Area R-3)

The Thermo-Lag 330-1 on the Millstone Unit 1 to Millstone Unit 2 electrical backfeed cables in the Turbine Building has been removed. This resolves ampacity concerns with these cables.

Service Water Pump cables run through the Turbine Building and could be damaged by a fire in this area. A hard pipe connection between the Fire Water System and the Service Water lines to the Emergency Diesel Generator coolers has been installed in the Auxiliary Building. This connection allows Fire Water to cool an Emergency Diesel Generator without reliance on Service Water. With the aid of this modification, electrical power can be reestablished to support safe shutdown following a Turbine Building fire without reliance on Unit 1 to Unit 2 electrical backfeed.

The Thermo-Lag 330-1 on the Turbine Driven Auxiliary Feedwater Pump cables in the Turbine Building has been removed. The cables have been rerouted from the Turbine ,

Building to run directly from the Auxiliary Building West Penetrations Area to the l Turbine Driven Auxiliary Feedwater Pump Room. This modification ensures the l availability of the Turbine Driven Auxiliary Feedwater Pump to support safe shutdown I following a fire in the Turbine Building.

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l W M. L. Bowling letter to U.S. Nuclear Regulatory Commission, " Millstone Nuclear Power Station, Unit No. 2 - 10CFR50, Appendix R - Request for Exemptions," dated July 31,1998.

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7 U.S. Nucler Regulatory Commission B17531 %ttichm:nt 1\ Pag 3 2  !

Auxiliary Buildina Cable Vault (Appendix R Fire Area R-1)

The Auxiliary Building Cable Vault is equipped with area wide fire detection and automatic suppression systems. Thermo-Lag 330-1 was used to protect the following cables:

o Power Feeder Cables to Facility Z2 480V MC' 961 o Power Feeder Cables to Facility Z2 Battery Charger o DC1 120 VAC and 125 VDC Power Cables for Fire Shutdown Panel C09 and C10 o Facility Z2 Power and Control Cables for Charging Pumps 'B' and 'C' o Power and Control Cables for Charging Header Isolation Valve 2-CH-429 The power cables for Charging Pumps 'B' and 'C' will be rerouted out of the Auxiliary Building Cable Vault such that they will no longer enter Appendix R Fire Area R-1.

Instead, they will run directly from MCC B61 to the West Penetrations Area. The Facility Z2 control cables for Charging Pumps 'B' and 'C' will remain routed through the Auxiliary Building Cable Vault, and protected by Thermo-Lag 330-1.

The Thermo-Lag installations in this area are being upgraded to a one-hour rating per the NEl application guide to meet the requirements of Section Ill.G.2.c of 10CFR50 Appendix R. Calculations are being performed to confirm that cables protected by Thermo-Lag in this area will operate within their ampacity limits (being addressed by TAC MA3392).

Turbine Buildina Z1 East 4160V Cable Vault (Appendix R Fire Area R-14)

The Turbine Building East Cable Vault is equipped with area wide fire detection and automatic suppression systems. Thermo-Lag 330-1 is used to protect Appendix R related Z2 instrument and control cables routed through this area.

The Thermo-Lag installations in this area are being upgraded to a one-hour rating per the NEl application guide to meet the requirements of Section Ill.G.2.c of 10CFR50 Appendix R. Calculations are being performed to confirm that cables protected by Thermo-Lag in this area will operate. within their ampacity limits (being addressed by TAC MA3392).

Facility Z1 Lower 4160V Switchaear Room (Appendix R Fire Area R-14)

Thermo-Lag 330-1 was used to protect Appendix R related Z2 instrument and control cables in the Lower 4160V Switchgear Room.

l * - - U.S. Nucirr Reguttory Commission B17531 %ttachment 1\P;ga 3 l

Therm,o-Lag. installations in this area are being upgraded to a three-hour rating by i installing a layer of Thermo-Lag 770-1 material over existing Thermo-Lag 330-1. The  !

three-hour fire rating meets the requirements of Section Ill.G.2.a of 10CFR50 Appendix R. The three-hour rating is based on fire endurance testing conducted by Florida Power & Light Company for this type of configuration. This test has been evaluated for use at Millstone Unit No. 2 and accepted. Calculations are being performed to confirm that cables protected by Thermo-Lag in this area will operate l within their ampacity limits (being addressed by TAC MA3392).

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