ML071350235

NRC Generic Letter 2007-01: Inaccessible or Underground Power Cable Failures That Disable Accident Mitigation Systems or Cause Plant Transients

ML071350235
Person / Time
Site:	San Onofre
Issue date:	05/07/2007
From:	Reilly J T Southern California Edison Co
To:	Document Control Desk, NRC/NRR/ADRO
References
GL-07-001
Download: ML071350235 (4)

Text

N SOUTHERN CALIFORNIA ONJames T. Relly EDISON IVice President An EDISON INTERNATIONAL&

Company May 7, 2007 U.S. Nuclear Regulatory Commission Attn: Document Control Desk 11555 Rockville Pike Rockville, MD 20852

Subject:

San Onofre Nuclear Generating Station, Units 2 and 3 Docket Nos. 50-361 and 50-362 NRC Generic Letter 2007-01: Inaccessible or Underground Power Cable Failures That Disable Accident Mitigation Systems or Cause Plant Transients

Reference:

NRC Generic Letter 2007-01: Inaccessible or Underground Power Cable Failures That Disable Accident Mitigation Systems or Cause Plant Transients, dated February 7, 2007

Dear Sir or Madam:

This is in response to the request in Generic Letter 2007-01 to provide a history of inaccessible or underground power cable failures and to describe inspection, testing, and monitoring programs to detect degradation of inaccessible or underground power cables. The two specific GL 2007-01 requests for information are repeated below with Southern California Edison's responses.

(1) Provide a history of inaccessible or underground power cable failures for all cables that are within the scope of 10 CFR 50.65 (the Maintenance Rule) and for all voltage levels. Indicate the type, manufacturer, date of failure, type of service, voltage class, years of service, and the root causes for the failure.Response: A search of San Onofre Nuclear Generating Station (SONGS) Units 2 and 3 electronic databases did not identify any inaccessible or underground power cable failures at SONGS Units 2 and 3 within the scope of 10 CFR 50.65.(2) Describe inspection, testing and monitoring programs to detect the degradation of inaccessible or underground power cables that support EDGs, offsite power, ESW, service water, component cooling water and other systems that are within the scope of 10 CFR 50.65 (the Maintenance Rule).P.O. Box 128 San Clemente, CA 92674-0128 949-368-1480 Fax 949-368-1490 Document Control Desk-2-May 7, 2007 Response: SONGS maintenance of inaccessible or underground power cables is part of the maintenance of the connected equipment.

Meggering and bridge tests are performed as part of Preventive Maintenance (PM) or Corrective Maintenance (CM) of the Medium Voltage (6.9 and 4.16 KV) Switchgear and 480V AC Load Center and 480V AC Motor Control Center buses and connected equipment.

Successful performance of these tests indicates that the connecting cable which is an integral part is also functional.

The SONGS program for preventing protracted submergence in water of safety related and non-safety related electrical cables includes a flood detection system and the inspection of electrical equipment and components, electrical tunnels, and manholes for submergence.

Flood detection devices installed in many plant locations including inaccessible electrical tunnels, manholes, and Diesel Generator buildings provide alarms in the Control Room. Alarm response procedures require dispatching an operator to the specific location once an alarm is initiated.

For normally inaccessible areas, the Fire Protection Coordinator is contacted and required compensatory measures are taken to allow access (e.g., removal of a manhole cover).Other manholes and cable vaults are inspected annually for water accumulation as part of the Repetitive Maintenance Order program. Any water present is drained from the cable vaults. Occasionally cables have been found partially submerged, but corrective actions that include pumping water out have apparently been effective in keeping SONGS plant cables in a non-submerged condition.

On a shiftly basis, plant operators perform general inspections of accessible areas for observable degraded conditions, including any observable water intrusion into plant equipment and components.

Any degraded condition is either corrected and/or entered into the Corrective Action Program.During severe weather condition warnings, actions are taken to minimize the effect of hurricanes, tornados, flooding, or a tsunami on the safe operation of SONGS.Inspections are initiated per the SONGS severe weather procedure to ensure that missile barrier doors and watertight doors are closed and that hatches, roof, and wall plugs are installed.

Document Control Desk-3-May 7, 2007 Should you have any questions, or require additional information, please contact Ms. Linda Conklin at (949) 368-9443.Sincerely, cc: B. S. Mallett, Regional Administrator, NRC Region IV N. Kalyanam, NRC Project Manager, San Onofre Units 2 and 3 C. C. Osterholtz, NRC Senior Resident Inspector, San Onofre Units 2 and 3 S. Y. Hsu, Department of Health Services, Radiological Health Branch James T. Reilly states that he is Vice President of Engineering and Technical Services, Southern California Edison, is authorized to execute this oath on behalf of Southern California Edison and, to the best of his knowledge and belief, the facts set forth in this letter are true.Respectfully submitted, cre President of Engineering and Technical Services Southern California Edison State of California County of San Diego Subscribed and sworn to (or affirmed) before me this day of flbyJ-rl"T~L personally known to me oe joed t mne on the baSiS Of-SatiSfaetery evidce to be the person who appeared before me.