Information Notice 2012-11, Age Related Capacitor Degradation
| ML120330272 | |
| Person / Time | |
|---|---|
| Site: | Hatch, Surry  |
| Issue date: | 07/23/2012 |
| Revision: | 0 |
| From: | Dudes L A, McGinty T J Division of Construction Inspection and Operational Programs, Division of Policy and Rulemaking |
| To: | |
| Alexion, T W, NRR/DPR, 415-1326 | |
| Shared Package | |
| 4 | List: |
| References | |
| FOIA/PA-2013-0030, FOIA/PA-2013-0139 IN-12-011 | |
| Download: ML120330272 (5) | |
ML120330272 July 23, 2012 NRC INFORMATION NOTICE 2012-11: AGE-RELATED CAPACITOR DEGRADATION
ADDRESSEES
All holders of an operating license or construction permit for a nuclear power reactor under Title 10 of the Code of Federal Regulations (10 CFR) Part 50, "Domestic Licensing of Production and Utilization Facilities," except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reactor vesse All holders of or applicants for an early site permit, standard design certification, standard design approval, manufacturing license, or combined license issued under 10 CFR Part 52,
"Licenses, Certifications, and Approvals for Nuclear Power Plants."
PURPOSE
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform addressees of recent problems involving age-related degradation of capacitor The NRC expects that recipients will review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problem Suggestions contained in this IN are not NRC requirements; therefore, no specific action or written response is require
DESCRIPTION OF CIRCUMSTANCES
Surry Power Station Unit 1 On June 8, 2010, an automatic reactor trip occurred from full power because of an inadvertent electrical contact made during maintenance activitie The plant conditions encountered and system responses as a result of the trip were generally as expected, except as noted belo Approximately 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> following the event, failure of a resistor/capacitor (RC) suppressor in a nuclear instrument (NI) cabinet resulted in a small control room fire, which was extinguished by the use of manual carbon dioxide fire extinguisher Approximately 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> later, another RC suppressor failed in a second NI cabinet, causing a control power fuse to blow and the source range NIs to become deenergize The source-range NIs were restored in about 5 minute (No power failures or blown fuses resulted from the RC suppressor failures in the first NI cabinet.) The most probable cause of the RC suppressor failures was age-related hardening and cracking of the RC suppressor's epoxy insulation, which allowed degradation of the RC suppressor capacito These RC suppressors were original plant equipment and had not been replace The capacitor degradation allowed the RC suppressor circuit to draw excessive current and overhea The excessive heat caused the epoxy in the RC suppressor to ignit The older (date codes from 1969 to 1971) suppressors contained epoxy which is not flame retardan Subsequent to this event, the licensee opted to install newer RC suppressors which use a flame retardant epox Additional information is available in NRC Special Inspection Report 05000280/2010006, dated September 10, 2010, and can be found on the NRC's public website in the Agencywide Documents Access and Management System (ADAMS) under Accession No. ML10256033 Edwin I. Hatch Unit 2 Between March 2005 and February 2009, three loss-of-offsite-power/loss-of-coolant-accident (LOSP/LOCA) loading timers associated with redundant plant service water pumps for the two Unit 2 and swing emergency diesel generators experienced failure After the failure in February 2009, the licensee established a root cause team which determined the failures were caused by age-related degradation of electrolytic capacitor Specifically, the power supplies for the LOSP/LOCA circuitry were exhibiting excessive voltage ripple on their output The root cause team attributed this to degradation of electrolytic capacitors in the power supply circuits, which tend to exhibit increased noise toward the end of lif These capacitors had been installed for 20 years, which was beyond their vendor- recommended service life of 10 year Additional information is available in NRC Inspection Report 05000366/2009005, dated February 12, 2010, and can be found on the NRC's public Web site in ADAMS under Accession No. ML10043049 Additional Examples of Age-Related Degradation of Capacitors and Other Components Additional examples of problems involving age-related degradation of capacitors can be found on the NRC's public Web site in ADAMS under Accession No. ML12033A04 NRC IN 2012-06, "Ineffective Use of Vendor Technical Recommendations" provides additional insight on components that are left in service beyond the vendor-recommended service lif IN 2012-06 can be found on the NRC's public Web site in ADAMS under Accession No. ML11230070
DISCUSSION
Criterion XVI, Corrective Action, of Appendix B, "Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants" to 10 CFR Part 50 requires licensees to assure that conditions adverse to quality are promptly identified and corrected and corrective actions are taken to preclude repetitio Regulatory Guide 1.33, "Quality Assurance Program Requirements (Operation)" (ADAMS Accession No. ML003739995), Section 9.b, states "preventive maintenance schedules should be developed to specify lubrication schedules, inspections of equipment, replacement of such items as filters and strainers, and inspection or replacement of parts that have a specific lifetime such as wear rings." RC suppressors contain a capacitor and a resistor connected in serie Both components are normally completely encased in a molded epoxy package with an electrical lead from one end of the resistor and one end of the capacitor extending ou In a non-degraded condition, the epoxy electrically insulates the RC suppressor's capacitor, resistor, and their conductive surfaces in an encapsulated environment devoid of oxygen, moisture, and other air contaminant Aging adversely affects the capacitors in RC suppressors by causing the epoxy insulation to harden and crack over tim This degrades the capacitor, allowing a high flow of current and excessive heatin The excessive heat can then ignite the epoxy in the RC suppresso Although newer RC suppressors use a fire retardant epoxy, capacitor overheating can still cause failur Capacitors also may exhibit tendencies to leak, drift, or make electronic noise, as a result of varying environmental conditions (e.g., shifts in temperature, humidity levels, or both). Extreme temperature conditions can be problematic for capacitors that contain aluminum electrolyte At lower temperatures, capacitance falls off rapidl At higher temperatures, the electrolyte may be lost through evaporation, thereby accelerating leakag This may result in premature circuit damage or malfunctio Capacitors are energy storage devices that are widely used in electronic and electrical power circuit Operating experience has shown that capacitors have finite lifetime Placing these capacitors in a periodic preventative maintenance program that accounts for both time in storage and time in service can address the adverse effects of aging capacitors in equipment circuitry and prevent equipment failure
CONTACT
This IN requires no specific action or written respons Please direct any questions about this matter to the technical contacts listed below or to the appropriate Office of Nuclear Reactor Regulation project manage /RA by SBahadur for/ /RA by JLuehman for/ Timothy J. McGinty, Director Laura A. Dudes, Director Division of Policy and Rulemaking Division of Construction Inspection Office of Nuclear Reactor Regulation and Operational Programs Office of New Reactors
Technical Contacts: Rossnyev Alvarado, NRR Robert Bernardo, NRR 301-415-6808 301-415-2621 E-mail: Rossnyev.Alvarado@nrc.gov E-mail: Robert.Bernardo@nrc.gov Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under NRC Librar
CONTACT
This IN requires no specific action or written respons Please direct any questions about this matter to the technical contacts listed below or to the appropriate Office of Nuclear Reactor Regulation project manage /RA by SBahadur for/ /RA by JLuehman for/
Timothy J. McGinty, Director Laura A. Dudes, Director Division of Policy and Rulemaking Division of Construction Inspection Office of Nuclear Reactor Regulation and Operational Programs Office of New Reactors
Technical Contacts: Rossnyev Alvarado, NRR Robert Bernardo, NRR 301-415-6808 301-415-2621 E-mail: Rossnyev.Alvarado@nrc.gov E-mail: Robert.Bernardo@nrc.gov Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under NRC Librar ADAMS Accession No: ML120330272 *via e-mail TAC No. ME7139 OFFICE NRR/DIRS/IOEB NRR/DE/EICB Tech Editor BC:NRR/DIRS/IOEB NAME RBernardo RAlvarado JDougherty* HChernoff (EThomas Acting) DATE 4/6/2012 4/17/2012 2/14/2012 6/21/2012 OFFICE BC:NRR/DE/EICB BC:NRR/DLR/RASB BC:NRO/DE/ICE D:NRR/DE NAME JThorp MMarshall* TJackson* PHiland (MCheok for) DATE 4/17/2012 6/26/2012 6/20/2012 6/25/2012 OFFICE NRR/DPR/PGCB NRR/DPR/PGCB BC:NRR/DPR/PGCBD:NRO/DCIP NAME CHawes TAlexion DPelton LDudes (JLuehman for) DATE 7/05/2012 7/06/2012 7/17/2012 7/20/2012 OFFICE D:NRR/DPR NAME TMcGinty (SBahadur for) DATE 7/23/2012 OFFICIAL RECORD COPY