ML071290578
| ML071290578 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 05/08/2007 |
| From: | Bezilla M FirstEnergy Nuclear Operating Co |
| To: | Document Control Desk, NRC/NRR/ADRO |
| References | |
| GL-07-001, TAC MD4320 | |
| Download: ML071290578 (8) | |
Text
FENOC FirstEnergy Nuclear Operatin ; Company 5501 North State Route 2 Oak Harbor, Ohio 43449 Mark B. Bezilla Vice President - Nuclear 419-321-7676 Fax: 419-321-7582 May 8, 12007 Davis-Besse Nuclear Power Station, Unit 1 Docket No. 50-346 Serial N imber 3333 U. S. NL clear Regulatory Commission Attention: Document Control Desk 11555 FRockville Pike Rockville, MD 20852
Subject:
Response to NRC Generic Letter 2007-01 (TAC No. MD4320)
On February 7, 2007, the NRC issued Generic Letter 2007-01, "Inaccessible or Undergrmund Power Cable Failures That Disable Accident Mitigation Systems or Cause Plant Transients." The NRC issued the letter to: inform licensees that the failure oI certain power cables can affect the functionality of multiple accident mitigaticn systems or cause plant transients; 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 ask licensees to provide information on the monitoring of inaccessible or underground electrical cables. The NRC requested that the information be provided within 90 days of the date of the Generic Letter. provides the FirstEnergy Nuclear Operating Company (FENOC) respons - to address the Generic Letter for the Davis-Besse Nuclear Power Station, Unit 1 (DBNPS). FENOC has concluded that DBNPS is in compliance with the applicable regulatory requirements delineated in the Generic Letter as they apply to inaccessible or underground power cables.
4IQ7
Serial Number 3333 Page 2 of 2 identifies that there are no commitments contained in this response. If there are any questions, or if additional information is required, please contact Mr. Henry L. Hegrat, Supervisor - FENOC Fleet Licensing, at (330) 374-3114.
I declaro; under the penalty of perjury that the foregoing is true and correct.
Executed on May 8, 2007.
Mark B. Bezilla Site Vice President Attachments (2)
- 1.
Fesponse to Generic Letter 2007-01, "Inaccessible or Underground Power Cable Failures That Disable Accident Mitigation Systems or Cause Plant Transients."
- 2.
Commitment List cc:
NRC Project Manager-Davis-Besse Nuclear Power Station NRC Resident Inspector - Davis-Besse Nuclear Power Station NRC Regional Administrator-Region III Utility Radiological Safety Board Serial Number 3333 Page 1 of 5 Response to Generic Letter 2007-01, "Inaccessible or Underground Power Cable Failures That Disable Accident Mitigation Systems or Cause Plant Transients" The NR. issued Generic Letter 2007-01, "Inaccessible or Underground Power Cable Failures That Disable Accident Mitigation Systems or Cause Plant Transients," to inform licensees that the failure of certain power cables can affect the functionality of multiple accident mitigation systems or cause plant transients; inform li:.ensees that in the absence of adequate monitoring of cable insulation, equipment could fail abruptly during service, causing plant transients or disabling acciden: mitigation systems; and ask licensees to provide information on the monitoring of inaccessible or underground electrical cables.
Each Goneric Letter question is listed below, in bold, and is followed by the FENOC response for the Davis-Besse Nuclear Power Station (DBNPS).
- 1.
F rovide 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.
The maintenance history and failure trending programs, including the Corrective Action Program, were reviewed. A search of the Davis-Besse N uclear Records Management System was performed using the following kaywords: cable and failure, cable and fault, cable and replacement, cable and repair, cable and pull to determine past cable failures.
Table 1 contains a list of the inaccessible or underground power cable failures for all cables that are within the scope of 10 CFR 50.65. The Beach Feeder Cable was repaired following the failures in 1997 and 1999.
Following the failure of the Beach Feeder Cable in 2005, the entire cable was replaced. The newly installed Beach Feeder Cable is expected to last longer due to advancements in cable manufacturing that have occurred s nce the cable was originally installed. No failures of 480V cables were identified during the records search.
Serial Number 3333 Page 2 of 5 7able 1 - Failures of 10 CFR 50.65 Inaccessible or Underground F ower Cables Componer t Cable ID Manufacturer Date of Type of Service Years in Root/Apparent Failure Service Voltage Service*
Cause Insula] Shielded Rated tion (YIN)
Voltage Type Beach BPHBEACH Unknown 3/15/05 Energized 13.8kV 28 Age related, Feeder new cable Cable EPR I Y 15kV installed.
E4 Feed APHAAE4A Okonite 4/7/04 Energized 13.8kV 27 Water intrusion into the conduit EPR 15kV due to inadequate
_plant design.
Componert 2PAD113A Okonite 10/2/99 Energized 4160V 22 Water intrusion Cooling into the conduit, Water wicking into the Pump EPR 5kV insulation.
Motor #2I Beach BPHBEACH Unknown 7/1/99 Energized 13.8kV 22 Age related, Feeder damaged Cable EPR Y
15kV portion repaired.
Beach BPHBEACH Unknown 11/15/97 Energized 13.8kV 20 Not evaluated, Feeder damaged Cable EPR 15kV portion repaired.
Turbine APAC208A Okonite 10/19/87 Energized 4160V 10 Indeterminate.
Plant Cooling EPR Y
5kV Water Pump Motor #3 BD Bus Ti, BPXBDO1A Okonite 12/27/84 Energized 13.8kV 7
Inadequate XFMR T FR1ýY 15kV installation of Cable EPR_'__Y15kV stress cones.
EPR - Ethylene Propylene Rubber
- Based on DBNPS Startup in 1977 Table 2 identifies instances in which testing identified that the cable should be replacecl prior to failure. All of the items were identified during the performance of periodic motor testing. With the exception of the cables for the Emergency Instrument Air Compressor Cooling Fan Motors, which are scheduled to be replaced, the cables below have been replaced. All of the replaced cables, for which the need to replace the cable was identified through testing, were replaced prior to failure of the cable or component.
Serial Number 3333 Page 3 of 5 I"able 2 - Degraded 10 CFR 50.65 Inaccessible or Underground Fower Cables Identified Through Testing Prior to Failure Componert Cable ID Manufacturer Date of Type of Service Years in Root /
Testing Service Voltage Service*
Apparent Insul Shielded Rated Cause TypeI (Y/N_
Voltage Emergenc-i BPBF7105B Kerite 10/13/05 De-480V 15 Lower than Instrument BPBF7105C energized expected Air polarization Compressf)r index readings Closed FR3 N
- no cause Cooling Fan determined.
Motors___
EDG Fuel Dil 1PBE1298A Kerite 8/26/03 De-480V 26 Low insulation Tank Pump energized resistance
- Motor, FR3 N
600V caused by MP195-1 water intrusion into the conduit.
Auxiliary 1PE1222A Unknown 7/22/03 De-480V 26 Low insulation Feedwater energized reading and Vent Fan EPR N
600V low Motor #1, polarization MC73-1 index-age related.
Auxiliary BPACO41OA/B Okonite 10/26/02 De-4160 25 Visual Boiler energized inspection -
Forced Dr, ft 5kV Cyclic fatigue.
Fan, MC41 Makeup APACl05A Okonite 10/22/02 Energized 4160 25 Aging - Low Pump Motor insulation
- 1 P
I I
5kV resistance.
Turbine APAC206A Okonite 10/11/01 Energized 4160 24 Indeterminate.
Plant Cooling Water Purr pEPR Y
5kV Motor #1 EPR - Ethylene Propylene Rubber
- Based on DBNPS Startup in 1977 Serial Number 3333 Page 4 of 5
- 2.
Eescribe 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 1D CFR 50.65 (the Maintenance Rule).
FENOC employs the following means of continuous and periodic.
monitoring of these inaccessible cables that are within the scope of 19 CFR 50.65 at DBNPS.
The 480V Distribution System has a high impedance ground fault detection installed on the Nuclear Safety Related buses and on some of the non-safety related buses. FENOC plans to install ground fault protection on other non-safety related buses.
Cperator tour rounds on the 480V ground fault detection systems are performed on each shift. The Operator is required to observe the Ground Indicating Lights at the switchgear equipment and record his observations.
Alarm Response Instructions contain instructions to be followed when a trouble annunciator occurs (which may be due to a ground fault).
Preventive Maintenance (PM) activities have been created to perform rE~sistance/EMAX testing on underground 13.8kV and 4160V cables on n,)n-motor loads on a periodic basis. The current testing frequency for u iderground non-motor load cables is every four years. For 13.8kV and 4160V motor load cables, testing is currently performed at various intervals. Motor testing is performed and measures the Polarization Index (PI)/Dielectric Absorption, performs a rotor influence check, insulation and a step voltage test. PM activities have also been created to replace the 1:3.8kV and 4160V underground cables at an interval of 20 years. A cable replacement program is currently in progress with the most risk significant cables being replaced first.
Periodic testing of the 480V motors from the breaker to the load has been successful in identifying potential cable issues, as documented in the previous table. Individual testing of 480V cables was previously evaluated and determined that testing or replacement of 480V cables and below was not required. Trend analysis of insulation resistance along with comparison to test data from similar cable/motor configurations provides a basis to determine if cable insulation is defective or degrading.
Salected manholes are inspected during PM activities. An open corrective action exists to determine if additional manholes require inspection.
Serial Number 3333 Page 5 of 5 As a result of past cable failures, DBNPS has developed corrective actions and maintenance activities to improve the reliability of susceptible cables, through periodic testing and replacement. Cable replacements are managed as projects to allow optimal coordination of cable ro.placement activities. Cable replacement activities are currently ongoing.
Underground medium voltage non-motor load cables have preventive maintenance activities to periodically test the cables. The remaining underground medium voltage cables are tested as part of periodic motor testing. Motor testing provides a means to determine cable degradation when trended and compared to similar components and configurations.
Serial Number 3333 Page 1 of 1 Commitment List The following list identifies those actions committed to by FirstEnergy Nuclear Operating Company (FENOC) for the Davis-Besse Nuclear Power Station, Unit No. 1. Any other actions discussed in the submittal represent intended or planned actions by FENOC. They are described only as information and are not regulatory commitments. Please notify contact Mr. Henry L. Hegrat, Supervisor-FENOC Fleet Licensing, at (330) 374-3114 of any questions regarding this document or associated regulatory commitments.
Commitment Due Date None N/A