ML071090014

Response to Generic Letter 2007-01, Inaccessible or Underground Power Cable Failures That Disable Accident Mitigation Systems or Cause Plant Transients, Proposed Alternative Course of Action

ML071090014
Person / Time
Site:	Comanche Peak
Issue date:	05/10/2007
From:	Donohew J NRC/NRR/ADRO/DORL/LPLIV
To:	Blevins M TXU Power
Thadani, M C, NRR/DORL/LP4, 415-1476
References
TAC MD4314, TAC MD4315
Download: ML071090014 (4)

Text

May 10, 2007 Mr. M. R. Blevins Senior Vice President

& Chief Nuclear Officer TXU Power ATTN: Regulatory Affairs P. O. Box 1002 Glen Rose, TX 76043

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION (CPSES), UNITS 1 AND 2 -

RE: GENERIC LETTER 2007-01, INACCESSIBLE OR UNDERGROUND POWER CABLE FAILURES THAT DISABLE ACCIDENT MITIGATION SYSTEMS OR CAUSE PLANT TRANSIENTS, PROPOSED ALTERNATIVE COURSE OF ACTION (TAC NOS. MD4314 AND MD4315)

Dear Mr. Blevins:

On February 7, 2007 the U.S. Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 2007-01, Inaccessible or Underground Power Cable Failures that Disable Accident Mitigation Systems or Cause Plant Transients (Agencywide Documents and Access Management System (ADAMS) Accession No. ML070360665). The purpose of GL 2007-01 is to (1) inform licensees that the failure of certain power cables can affect the functionality of multiple accident mitigation systems or cause plant transients, (2) inform licensees that, in the absence of adequate monitoring of cable insulation, equipment could fail abruptly during service, causing plant transients or disabling accident mitigation systems, and (3) request licensees to provide (a) information on the monitoring of inaccessible or underground electrical cables within 90 days of the date of the GL, or (b) an alternative course of action within 30 days of the date of the GL.

By letter dated March 9, 2007 (CPSES-200700515) (ADAMS Accession No. ML070750360),

TXU Power (the licensee) submitted a 30-day response to the GL for the CPSES, Units 1 and 2. In its letter, the licensee provided an alternative course of action for providing the requested information in accordance with Item (2) of the Required Response, which states Addressees who choose not to provide information requested or cannot meet the requested completion dates are required to submit written responses within 30 days of the date of this generic letter. The responses must address any alternative course of action proposed, including the basis for the acceptability of the proposed alternative course of action.

In its letter, the licensee stated that the twelfth refueling outage for CPSES, Unit 1, started in late February 2007 and is currently scheduled to end in early May 2007 and that all four Unit 1 steam generators and the reactor vessel head are being replaced during this outage. The organizations that would be providing support to prepare and submit the requested information in GL 2007-01 are now focused on the safe implementation of these major outage modifications. As discussed with the NRC staff on February 22, 2007, due to the extensive resources required to support these modifications, the licensee stated that it would provide the

M. R. Blevins requested information in the GL by July 27, 2007, which is 90 days from the end of the outage.

In the letter, the licensee also provided the following additional justification for the proposed extended response date:

• The 6.9 kV and 480 V power system cables are 8 kV and 600 V rated.

The insulation of these cables is adequate for ungrounded systems; however, to reduce the transient over-voltages due to ground faults, the systems are resistance grounded and provided with ground fault protection and detection.

• All power system cables are suitable for installation in wet or dry locations in trays, conduits or underground ducts.

• The 6.9 kV power system cables are generally Ethylene Propylene Rubber (EPR) insulated which is the most resistant insulation to water related failure mechanisms.

• All cables were tested at installation.

• CPSES cable installation was done later than many plants and therefore should be less susceptible to age related cable failures.

The NRC staff reviewed the licensees proposed alternative course of action and the above justification, and concluded that the alternative would be acceptable if the licensee would change its proposed GL response date from July 27, 2007, to June 22, 2007. This was discussed with members of the licensees staff in conference calls on March 20 and 21, 2007, and the licensee agreed to change its response date to June 22, 2007. Based on this, the NRC staff concludes that the licensees alternative course of action for responding to the GL is acceptable for CPSES, Units 1 and 2.

If you have any questions concerning this letter, please contact Mohan C. Thadani at (301) 415-1476.

Sincerely,

/RA/

Jack N. Donohew, Senior Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-445 and 50-446 cc: See next page

M. R. Blevins requested information in the GL by July 27, 2007, which is 90 days from the end of the outage.

In the letter, the licensee also provided the following additional justification for the proposed extended response date:

• The 6.9 kV and 480 V power system cables are 8 kV and 600 V rated.

The insulation of these cables is adequate for ungrounded systems; however, to reduce the transient over-voltages due to ground faults, the systems are resistance grounded and provided with ground fault protection and detection.

• All power system cables are suitable for installation in wet or dry locations in trays, conduits or underground ducts.

• The 6.9 kV power system cables are generally Ethylene Propylene Rubber (EPR) insulated which is the most resistant insulation to water related failure mechanisms.

• All cables were tested at installation.

• CPSES cable installation was done later than many plants and therefore should be less susceptible to age related cable failures.

The NRC staff reviewed the licensees proposed alternative course of action and the above justification, and concluded that the alternative would be acceptable if the licensee would change its proposed GL response date from July 27, 2007, to June 22, 2007. This was discussed with members of the licensees staff in conference calls on March 20 and 21, 2007, and the licensee agreed to change its response date to June 22, 2007. Based on this, the NRC staff concludes that the licensees alternative course of action for responding to the GL is acceptable for CPSES, Units 1 and 2.

If you have any questions concerning this letter, please contact Mohan C. Thadani at (301) 415-1476.

Sincerely,

/RA/

Jack N. Donohew, Senior Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-445 and 50-446 DISTRIBUTION:

PUBLIC LPLIV Reading cc: See next page RidsNrrDorlLpl4 RidsNrrDprPgcb RidsNrrPMMThadani RidsNrrLALFeizollahi RidsAcrsAcnwMailCenter RidsRgn4MailCenter RidsOgcRp RidsNrrDeEeeb Accession No.: ML071090014 OFFICE NRR/LPL4/PM NRR/LPL4/LA PGCB/BC EEEB/BC NRR/LPL4/BC NAME JDonohew LFeizollahi CJackson GWilson THiltz DATE 4/24/07 4/25/07 5/8/07 5/9/07 5/10/07 OFFICIAL RECORD COPY

Comanche Peak Steam Electric Station cc:

Senior Resident Inspector Mr. Richard A. Ratliff, Chief U.S. Nuclear Regulatory Commission Bureau of Radiation Control P.O. Box 2159 Texas Department of Health Glen Rose, TX 76403-2159 1100 West 49th Street Austin, TX 78756-3189 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission Mr. Brian Almon 611 Ryan Plaza Drive, Suite 400 Public Utility Commission Arlington, TX 76011 William B. Travis Building P.O. Box 13326 Mr. Fred W. Madden, Director 1701 North Congress Avenue Regulatory Affairs Austin, TX 78701-3326 TXU Generation Company LP P.O. Box 1002 Ms. Susan M. Jablonski Glen Rose, TX 76043 Office of Permitting, Remediation and Registration George L. Edgar, Esq. Texas Commission on Environmental Morgan Lewis Quality 1111 Pennsylvania Avenue, NW MC-122 Washington, DC 20004 P.O. Box 13087 Austin, TX 78711-3087 County Judge P.O. Box 851 Terry Parks, Chief Inspector Glen Rose, TX 76043 Texas Department of Licensing and Regulation Environmental and Natural Boiler Program Resources Policy Director P.O. Box 12157 Office of the Governor Austin, TX 78711 P.O. Box 12428 Austin, TX 78711-3189 December 2004