ML071370358
| ML071370358 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 05/08/2007 |
| From: | Jensen J N Indiana Michigan Power Co |
| To: | Document Control Desk, NRC/NRR/ADRO |
| References | |
| AEP:NRC:7054-02, GL-07-001 | |
| Download: ML071370358 (12) | |
Text
INDIANA MICHIGAN POWERE A unit of American Electric Power Indiana Michigan Power Cook Nuclear Plant One Cook Place Bridgman, MI 49106 AEP.com May 8, 2007 AEP:NRC:7054-02 10 CFR 50.54(f)Docket Nos.: 50-315 50-316 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk 11555 Rockville Pike Rockville, MD 20852 Donald C. Cook Nuclear Plant Units I and 2 90-DAY RESPONSE TO NUCLEAR REGULATORY COMMISSION GENERIC LETTER 2007-01: INACCESSIBLE OR UNDERGROUND POWER CABLE FAILURES THAT DISABLE ACCIDENT MITIGATION SYSTEMS OR CAUSE PLANT TRANSIENTS
Reference:
Nuclear Regulatory Commission Generic Letter 2007-01, "Inaccessible or Underground Power Cable Failures that Disable Accident Mitigation Systems or Cause Plant Transients," dated February 7, 2007.The Nuclear Regulatory Commission issued the referenced generic letter requesting that addressees provide a history of inaccessible or underground power cable failures for all cables that are within the scope of the Maintenance Rule, and a description of the inspection, testing, and monitoring programs to detect the degradation of inaccessible or underground power cables that support systems that are within the scope of the Maintenance Rule.The attachment to this letter provides Indiana Michigan Power Company's response to the generic letter.This letter contains no new commitments.
Should you have any questions, please contact Ms. Susan D. Simpson, Regulatory Affairs Manager, at (269) 466-2428.RGV/rdw
Attachment:
90-Day Response to Nuclear Regulatory Commission Generic Letter 2007-01 4iD-7 U. S. Nuclear Regulatory Commission AEP:NRC:7054-02 Page 2 c: J. L. Caldwell -NRC Region III K. D. Curry -AEP Ft. Wayne, w/o attachment J. T. King -MPSC MDEQ -WHMD/RPMWS NRC Resident Inspector P. S. Tam -NRC Washington, DC U. S. Nuclear Regulatory Commission Page 3 AEP:NRC:7054-02 AFFIRMATION I, Joseph N. Jensen, being duly sworn, state that I am Site Vice President of Indiana Michigan Power Company (I&M), that I am authorized to sign and file this document with the Nuclear Regulatory Commission on behalf of I&M, and that the statements made and the matters set forth herein pertaining to I&M are true and correct to the best of my knowledge, information, and belief.Indiana Michigan Power Company Joei~h N. Jensen Site Vice President SWORN TO AND SUBSCRIBED BEFORE MEDAY OF 0-4. 2007 N -tary)Public My Commission Expires.. --"2 "... .--" '/g .(~
Attachment to AEP:NRC:7054-02 90-DAY RESPONSE TO NUCLEAR REGULATORY COMMISSION GENERIC LETTER 2007-01 Generic Letter (GL) 2007-01, "Inaccessible or Underground Power Cable Failures that Disable Accident Mitigation Systems or Cause Plant Transients," addressed a Nuclear Regulatory Commission (NRC) concern about degradation of electrical power cables located in inaccessible locations.
Because of the concern, the NRC requested that licensees provide information regarding inaccessible cable failures and the programs used to detect inaccessible cable degradation.
The following provides Indiana Michigan Power Company's (I&M's) response to the GL information request.NRC Request 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 offailure, type of service, voltage class, years of service, and the root causes for the failure.I&M Response A failure history search of Donald C. Cook Nuclear Plant's (CNP's) work control, cable management, and corrective action databases was performed.
The following steps were performed to identify inaccessible power cables that are subject to 10 CFR 50.65 (the Maintenance Rule): 1. Identify systems that are subject to 10 CFR 50.65.2. Review electrical physical drawings, conduit and cable schedules, and the cable-management database to identify power cables associated with those systems.3. Review the routing of cables from Step 2 to identify cables that could routinely be exposed to moisture.The preceeding steps resulted in the selection of approximately 680 cables for a failure history review. These cables are routed underground through manhole systems, through conduit embedded in concrete, or in pits beneath motor control centers (MCCs). The cables routed through the MCC pits would not generally meet the definition of inaccessible, but there is a history of these pits containing standing water resulting from blocked drains.A maintenance history search of work control databases, supplemented by key-word searches of corrective action program databases, was conducted for each of the cables to identify if any had ever been replaced due to failure. Where available, corrective action program evaluations were reviewed to determine if a causal evaluation was performed for failed or replaced cables.The scope of cables reported includes both self-revealing failures and preemptive replacements driven by discoveries made during inspection or insulation resistance tests. As indicated in Table 1, Attachment to AEP:NRC:7054-02 Page 2 the majority of the cable replacements identified fall into the preemptive category and specific cause evaluations were not located.The list of cables is provided in Table 1.NRC Request 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).I&M Response The following describes CNP's inspection, testing, and monitoring programs that are used 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).CNP uses on-line partial discharge testing technology to assess the condition of energized medium voltage cables (4 kilovolt (kV) through 35.5 kV for CNP) that are routed through manhole systems or in embedded conduit. At least one test has been conducted on each of the cables within the program population.
The test results have been used to determine the appropriate frequency of retest. For the cable population routed through manholes, periodic maintenance tasks have been created to align with those retest frequencies.
Similar periodic maintenance tasks have not yet been created for the population of cables in embedded conduit, but they will be created based on the initial test results. To date, the testing has not revealed a need to replace any medium voltage cables based on condition assessment.
Manholes containing medium voltage cables are inspected on a periodic basis. The manholes are currently inspected for water on a monthly basis. Any accumulated water is pumped from the manhole as needed.There is currently no formal inspection, testing, or monitoring program for low voltage cables (600 volts and below at CNP) that could be exposed to wet environments.
Megger tests, characterization tests, and visual examinations are frequently performed as part of routine and periodic maintenance tasks; however, a comprehensive inspection/testing/monitoring program for low voltage cables is not presently in place.
Attachment to AEP:NRC:7054-02 Page 3 TABLE 1 LIST OF CABLES Type of Cable Operating Type of Service Failure Years of Apparent Cause and Voltage (End Device) Date Service Manufacturer (volts)(See Referenced Footnote)1 4160 Unit 2 (U2) Middle 2002 24 Mechanical damage. Cable damaged Heater Drain Pump, in terminal box due to excessive 2-PP-22M-MTR bending.2 4160 Unit 1 (Ul) South 2002 24 Replaced as a preventive measure.Heater Drain Pump, Low megger reading during I-PP-22S-MTR preventive maintenance testing.2 4160 Ul North Heater Drain 2002 24 Cyclic fatigue at motor termination.
Pump, 1-PP-22N-MTR 3 600 U1 Control Rod Drive 2003 25 Phase 3 damaged at lug. Cable Motor Generator Set, insulation had a through-insulation I-CRDMG-IS cut under tape.4 600 Ul Filter Supply Pump, 2001 23 Cable preemptively replaced due to 1-PP-70E deteriorated insulation and broken strand in motor terminal box.No loss of function.5 600 U2 Feed Pump Turbine 2000 22 Cable was grounded.Turning Gear Motor, No causal analysis performed.
2-QT-301E Attachment to AEP:NRC:7054-02 Page 4 TABLE 1 LIST OF CABLES Type of Cable Operating Type of Service Failure Years of Apparent Cause and Voltage (End Device) Date Service Manufacturer (volts)(See Referenced Footnote)5 600 UI Condenser A 2005 27 Replaced as a preventive measure.Northeast Inlet Valve, Low megger reading during I-WMO-101 preventive maintenance testing.5 600 U2 Condenser A 2003 25 Replaced as a preventive measure.Northeast Inlet Valve, Low megger readings during testing.2-WMO-101 5 600 U2 Condenser A 2003 25 Replaced as a preventive measure.Northwest Outlet Low megger reading during Valve, preventive maintenance testing.2-WMO-102 5 600 U2 Feed Pump Turbine 2002 24 Replaced as a preventive measure.Condenser Outlet Low megger reading during Valve, preventive maintenance testing.2-WMO-402 5 600 U2 East Feed Pump 1993 15 Replaced as a preventive measure.Middle Turbine Control Low megger readings during Fluid Pump, maintenance testing.2-QT-304-EM Attachment to AEP:NRC:7054-02 Page 5 TABLE 1 LIST OF CABLES Type of Cable Operating Type of Service Failure Years of Apparent Cause and Voltage (End Device) Date Service Manufacturer (volts)(See Referenced Footnote)5 600 U2 Vacuum Priming 2001 23 Cable was grounded.Pump, No causal analysis performed.
I-PP-20-1-MTR 5 600 Ul Condenser B 2005 27 Low resistance readings during Southeast Inlet Valve, normal maintenance testing. Water 1-WMO-203 found in conduit.5 600 U2 Turbine West Lube 2005 27 Ground alarm when pump ran.Oil Tank N Vapor Water was discovered in the motor Extractor, control center pit. One conductor 2-QT-214-WN failed megger test (0 ohm).5 600 U2 Feed Pump Turbine 2005 27 Tested circuit indicated a ground West Control Fluid after a breaker tripped.Pump 3W, No causal analysis performed.
2-QT-304-WW 5 600 U2 Feed Pump Turbine 2002 24 Replaced as a preventive measure.Condenser 2W Outlet Low megger reading during Valve, preventive maintenance testing.2-WMO-404 Attachment to AEP:NRC:7054-02 Page 6 TABLE I LIST OF CABLES Type of Cable Operating Type of Service Failure Years of Apparent Cause and Voltage (End Device) Date Service Manufacturer (volts)(See Referenced Footnote)5 600 U2 Condenser C 2004 26 Low megger reading during Northeast Inlet Valve, preventive maintenance testing.2-WMO-301 Suspect water intrusion into embedded conduit.5 600 U2 Condenser C 2001 23 Tested circuit indicated a ground Northwest Outlet after a breaker tripped.Valve, No causal analysis performed.
2-WMO-302 5 600 U2 Condenser B 2006 28 Replaced as a preventive measure.Northwest Outlet Low megger reading during Valve, preventive maintenance testing.2-WMO-202 5 600 U2 Condenser C 2004 26 Replaced as a preventive measure.Southwest Outlet Low megger reading during Valve, preventive maintenance testing.2-WMO-304 5 600 U2 Condenser B 2004 26 Replaced as a preventive measure.Southwest Outlet Low megger reading during Valve, preventive maintenance testing.2-WMO-204 Attachment to AEP:NRC:7054-02 Page 7 TABLE I LIST OF CABLES Type of Cable Operating Type of Service Failure Years of Apparent Cause and Voltage (End Device) Date Service Manufacturer (volts)(See Referenced Footnote)5 600 Ul West Charging 2004 26 Jacket damage in motor control Pump Discharge to center pit and terminal box. One Reactor Coolant Pump conductor had low megger readings.Seal Water Heat Exchanger Valve, 1-QMO-226 5 600 U2 East Essential 2000 22 Visual inspection found physical Service Water to damage. Low megger readings.Emergency Diesel Generator AB Heat Exchanger Valve, 2-WMO-724 5 600 U2 Essential Service 2005 27 Replaced as a preventive measure.Water to Emergency Low megger reading during Diesel Generator AB preventive maintenance testing.Heat Exchanger Valve, 2-WMO-722 Attachment to AEP:NRC:7054-02 Page 8 TABLE 1 LIST OF CABLES Type of Cable Operating Type of Service Failure Years of Apparent Cause and Voltage (End Device) Date Service Manufacturer (volts)(See Referenced Footnote)6 600 U2 Main Turbine 2006 28 Replaced as a preventive measure.Auxiliary Control Oil Low resistance readings during Pump, normal maintenance testing.2-QT-202-MTR 7 4160 Ul East Essential 1997 24 Mechanical damage due to Service Water Pump, overbend.1-PP-7E-MTR 7 4160 Ul West Essential 1997 19 Replaced as preventive measure.Service Water Pump, Low megger readings during normal 1-PP-7W-MTR maintenance activities.
Cable and manufacturer information was obtained from I&M bills of material, which list several materials and manufacturers.
The bills of material are not specific to individual cables.Footnotes:
Okonite Attachment to AEP:NRC:7054-02 Page 9 TABLE I LIST OF CABLES 2. 5 kV, 3 Twisted Conductor, #4/0, Stranded Aluminum, Shielded, EPR Cable.Manufacturer:
Anaconda or Cypress Wire 3. 600 V, 3 Twisted Conductor, #4/0, Stranded Aluminum, Unshielded Cable. Assumed to be Chlorosulfanated, Neoprene, or EPR.Manufacturer:
Okonite 4. 600 V, 3 Twisted Conductor, #4, Stranded Aluminum, Unshielded Cable. Assumed to be XLPE or EPR.Manufacturer:
Okonite 5. 600 V, 3 Twisted Conductor, #12, Stranded Copper, Unshielded Cable. XLPE or EPR Manufacturer:
The most likely manufacturers were either (in order of likeliness)
Okonite, Cyprus, Essex, or Anaconda.6. 600 V, 3 Twisted Conductor, #2/0, Stranded Aluminum, Unshielded.Cable.
Assumed to be Chlorosulfanated, Neoprene, or EPR.Manufacturer:
Anaconda, South Wire, or Cypress Wire'7. 5 kV, 3 Twisted Conductor, #2, Stranded Aluminum, Shielded, EPR Cable.Manufacturer:
Okonite or Anaconda