ML070740056
| ML070740056 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 03/08/2007 |
| From: | Bowman C South Texas |
| To: | Document Control Desk, NRC/NRR/ADRO |
| References | |
| G25, GL-07-001, NOC-AE-07002126 | |
| Download: ML070740056 (4) | |
Text
Nuclear Operating Company
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South Tcwas Project Ekctric Generafng Station PO. Box 289 Wadsworth, Texas 77483 March 8, 2007 NOC-AE-07002126 File No.: G25 10 CFR 50.54(f)
U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 South Texas Project Units 1 and 2 Docket No. STN 50-498, STN 50-499 Response to Request for Information on Generic Letter 2007-01, "Inaccessible or Underground Power Cable Failures that Disable Accident Mitigation Systems or Cause Plant Transients" This letter is in response to the Nuclear Regulatory Commission's (NRC) request for information pursuant to Generic Letter 2007-01.
Specifically, Generic Letter 2007-01 requests that licensees provide the following information by May 8, 2007:
- 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.
- 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).
OR Submit a written response within 30 days that addresses any alternative course of action proposed, including the basis for the acceptability of the proposed alternative course of action.
The STP Nuclear Operating Company (STPNOC) believes that the requested completion date of 90 days from the date of the generic letter imposes an undue burden on STPNOC resources.
The Unit 2 refueling outage is scheduled during the 90 day window allowed to respond to the generic letter. Prior to the outage many of the STPNOC engineering resources are involved in outage support activities. To allow sufficient time to prepare a quality response, STPNOC will respond to the Generic Letter by July 26, 2007, as discussed in a teleconference with the NRC staff on February 22, 2007.
The following information provides the technical justification for this extension.
- 1. Initial search of the Corrective Action Program database did not find any cable failures within the scope of the Generic Letter.
ST1 32124269
NOC-AE-07002126 Page 2 of 3
- 2. The 480vac, 120vac, 125vdc and 250vdc systems are all ungrounded and monitored with continuous ground fault detectors.
- 3. Medium voltage cables are all Ethylene Propylene Rubber (EPR) insulated which is the most resistant to water related failure mechanisms.
- 4. Cables were tested at installation.
- 5. STP cable installation was done later than many plants and incorporated improvements in pulling procedures and compounds resulting in lower pull stresses.
- 6. STP has been proactive in replacing cables in particular the ECW 480vac motor control center power feeders where insulation resistance reading were trending low. The cables are being replaced prior to the low insulation resistance readings being an operability concern.
- 7. STP has a program that inspects for and removes water from the underground cable vaults and manholes. The preventions in place include sump pumps, inspection ports at sealed manhole covers, repairing manhole seals, and procedural controls over work in manholes.
- 8. STP periodically tests a representative sample of 480vac, 4,160vac and 13,800vac cables as part of the Preventive Maintenance program.
The list of commitments is provided as an attachment to this letter.
If there are any questions, please contact either Mr. Scott Head at (361) 972-7136 or me at (361) 972-7454.
I declare under penalty of perjury that the foregoing is true and correct.
Executed on Zoo-/
Charles T. Bowman Date General Manager, Oversight tck/
Attachment:
List of Commitments
NOC-AE-07002126 Page 3 of 3 cc:
(paper copy)
(electronic copy)
Regional Administrator, Region IV U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011-8064 Richard A. Ratliff Bureau of Radiation Control Texas Department of State Health Services 1100 West 49th Street Austin, TX 78756-3189 Senior Resident Inspector U. S. Nuclear Regulatory Commission P. O. Box 289, Mail Code: MN116 Wadsworth, TX 77483 C. M. Canady City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704 A. H. Gutterman, Esquire Morgan, Lewis & Bockius LLP Mohan C. Thadani U. S. Nuclear Regulatory Commission Steve Winn Christine Jacobs Eddy Daniels Marty Ryan NRG South Texas LP Ed Alarcon J. J. Nesrsta R. K. Temple Kevin Polio City Public Service Jon C. Wood Cox Smith Matthews C. Kirksey City of Austin
Attachment NOC-AE-07002126 Page 1 of 1 LIST OF COMMITMENTS The following table identifies the actions necessary to fulfill the commitment made in this letter to submit the information requested by GL 2007-01. Statements in this submittal with the exception of the one in the table below are provided for information purposes and are not considered commitments. Please direct questions regarding these commitments to Scott Head at (361) 972-7136.
Commitment Expected CR Action No completion time Submit the requested information by July 26, 2007 CR 07-2088-2 July 26, 2007