Information Notice 2003-06, Failure of Safety-Related Linestarter Relays at San Onofre Nuclear Generating Station

Failure of Safety-Related Linestarter Relays at San Onofre Nuclear Generating Station

ML031700033
Person / Time
Site:	San Onofre
Issue date:	06/19/2003
From:	Beckner W D NRC/NRR/DRIP/RORP
To:
Hodge, CV, NRR/DRIP/RORP, (415-1861)
References
+sunsimjr=200611, -RFPFR IN-03-006
Download: ML031700033 (5)

June 19, 2003

NRC INFORMATION NOTICE 2003-06:FAILURE OF SAFETY-RELATED LINESTARTERRELAYS AT SAN ONOFRE NUCLEAR GENERATING STATION

Addressees

All holders of operating licenses or construction permits for nuclear power reactors, exceptthose that have permanently ceased operations and have certified that fuel has been permanently removed from the reactor.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to informaddressees of recent failures of safety-related valves due to linestarter relay degradatio The degradation was caused by past use of excessive amounts of trichloroethane-based cleaners during preventive maintenanc It is expected that recipients will review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problem However, suggestions in this information notice are not NRC requirements; therefore, no specific action or written response is required.

Description of Circumstances

San Onofre Nuclear Generating Station utilizes reversing linestarters manufactured by SquareD to operate the motors on safety-related motor-operated valve The linestarter consists of two relays that provide 480 volt power to the motor and contain auxiliary contacts associated with interlock and seal-in function The interlock function provides a means to avoid energizing both open and closed relays at the same tim The seal-in function keeps the relay energized until the valve has completed its strok All reversing linestarters have interlock auxiliary contact San Onofre has 172 Square D linestarters associated with safety-related motor-operated valves, 86 in each unit.On August 30, 2002, a Unit 3 low-pressure safety injection (LPSI) pump mini-recirculation valvefailed to open during surveillance testin Subsequent analysis determined that the plastic housing on an auxiliary contact in the associated linestarter was degrade The licensee determined that the auxiliary contact housing degradation was caused by the past use of excessive amounts of Inhibisol, a cleaning solvent based on trichloroethane (TCE). The cleaning solvent caused the plastic to break dow Over time, small amounts of the plastic came loose and interfered with the electrical contacts, resulting in the valve failur In response to the LPSI pump mini-recirculation valve failure, San Onofre developed a plan toinspect a sample of other safety-related linestarters installed in Units 2 and In October 2002, San Onofre completed the inspection of 19 additional linestarter This sample inspection identified two auxiliary contacts that showed signs of chemical attack (i.e., cloudy plastic contact housing); however, both were found to be functiona Subsequently, the licensee developed a risk-informed plan to inspect all safety-related linestarters and replace all auxiliary contacts showing signs of chemical attac The linestarter inspections were scheduled into online and outage maintenance windows, and will be completed by the end of the Unit 2 outage in 2004.On January 18, 2003, during a Unit 3 refueling outage, the quench tank sample containmentisolation valve failed to open during surveillance testin Examination of the contact revealed that a similar chemical attack had occurred and caused the valve failure.On February 10, 2003, during an inspection of Unit 3 LPSI header stop valve linestarters, anauxiliary contact failed on the 20th cycle of the auxiliary contact tes The linestarter inspectionsincluded a test to cycle each auxiliary contact 20 time This auxiliary contact cycle test was performed to determine the functionality of the auxiliary contacts in the linestarter.On Unit 3, all 86 linestarters have been inspected with two surveillance test failures noted andone maintenance test failur The licensee replaced 42 auxiliary contacts from the linestarters due to evidence of chemical attack on the plastic auxiliary contact housin On Unit 2, 33 linestarters have been inspected as of May 2, 2003, with no failures noted; however, four auxiliary contacts showed signs of chemical attack on the plastic contact case.DiscussionAs a result of the valve stroke failure on August 30, 2002, the licensee initiated a laboratoryanalysis of the suspect auxiliary contact from the linestarte The contact was coated with a plastic residue from the deterioration of the plastic switch bodie The licensee concluded that excessive use of cleaning solvents during previous preventive maintenance activities had caused the failure of the contacts. The licensee believes that all damage to the auxiliary contact housings occurred prior to 1989and is showing up in the recent safety-related valve failure The original linestarter preventive maintenance procedure was issued in April 1984, and required the use of cleaning solvents on linestarters, but had no caution regarding the potential for damage to plastic components within the linestarte Also, the procedure did not require visual inspection of internally mounted auxiliary contact assemblie As a result, Inhibisol was used liberally, which allowed the cleaner to come in contact with plastics that were susceptible to chemical degradatio In April 1989, the licensee recognized that TCE-based cleaners were being used improperly and that controls needed to be implemented to prevent future damage to equipment containing plastic The licensee revised the consumables controls manual to restrict the use of TCE-based cleaners on plastics, and provided guidance on the approved method for use of the cleaner (i.e., spray on cloth, then wipe component). Additionally, the linestarter preventive maintenance procedure was revised to caution that cleaning solvents should be used sparingly to avoid damage to plastic component In response to the recent valve failures, the licensee took action on March 7, 2003, to prohibit the use of all TCE-based cleaners for electrical maintenance application The licensee missed several opportunities from plant and industry experience to recognize theneed for an extent-of-condition revie An extent-of-condition review could have identified any equipment degradation that occurred throughout the plant due to improper use of cleaning solvent One of these prior opportunities was the review of Information Notice 93-76,

"Inadequate Control of Paint and Cleaners for Safety Related Equipment," which the licensee performed in February 199 The review determined that the programs in place were sufficient to avoid problems similar to those discussed in the notic The licensee focused on the TCE-

based cleaner controls in place at the time of the information notice review, but overlooked the fact that safety-related equipment could have been damaged prior to the implementation of the controls in April 198 This oversight was a missed opportunity to correct the equipment deficiency that has been revealed by the recent linestarter failures and the discovery of degraded contacts.The San Onofre linestarter experience emphasizes the need to perform an extent-of-conditionreview to determine equipment impact when an improper maintenance practice is recognized and correcte Further, the root cause analysis revealed that past improper use of corrosive cleaners could result in degraded plant equipment that could remain undetected for a considerable length of time before showing up in equipment failures.This information notice requires no specific action or written respons If you have anyquestions about the information in this notice, please contact one of the technical contacts listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager./RA/William D. Beckner, Program Director Operating Reactor Improvements Program Division of Regulatory Improvement Programs Office of Nuclear Reactor RegulationTechnical Contacts:Gregory G. WarnickVern Hodge623-386-3638301-415-1861 Email:gxw2@nrc.govEmail: cvh@nrc.gov

Attachment:

List of Recently Issued NRC Information Notices The licensee missed several opportunities from plant and industry experience to recognize theneed for an extent-of-condition revie An extent-of-condition review could have identified any equipment degradation that occurred throughout the plant due to improper use of cleaning solvent One of these prior opportunities was the review of Information Notice 93-76,

"Inadequate Control of Paint and Cleaners for Safety Related Equipment," which the licenseeperformed in February 199 The review determined that the programs in place were sufficient to avoid problems similar to those discussed in the notic The licensee focused on the TCE-

based cleaner controls in place at the time of the information notice review, but overlooked the fact that safety-related equipment could have been damaged prior to the implementation of the controls in April 198 This oversight was a missed opportunity to correct the equipment deficiency that has been revealed by the recent linestarter failures and the discovery of degraded contacts.The San Onofre linestarter experience emphasizes the need to perform an extent-of-conditionreview to determine equipment impact when an improper maintenance practice is recognized and correcte Further, the root cause analysis revealed that past improper use of corrosive cleaners could result in degraded plant equipment that could remain undetected for a considerable length of time before showing up in equipment failures.This information notice requires no specific action or written respons If you have anyquestions about the information in this notice, please contact one of the technical contacts listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager./RA/William D. Beckner, Program Director Operating Reactor Improvements Program Division of Regulatory Improvement Programs Office of Nuclear Reactor RegulationTechnical Contacts:Gregory G. WarnickVern Hodge623-386-3638301-415-1861 Email:gxw2@nrc.govEmail: cvh@nrc.gov

Attachment:

List of Recently Issued NRC Information NoticesDISTRIBUTION:ADAMS IN FileADAMS ACCESSION NUMBER:031700033DOCUMENT NAME: G:\RORP\OES\Staff Folders\Hodge\san_line inf.wpdOFFICEOES:RORP:DRIPTech EditorRIVEMCBNAMECVHodgePKleeneGWarnickKParcszewskiDATE06/10/200306/09/200306/12/200306/10/2003OFFICESC:OES:RORP:DRIPPD:RORP:DRIPNAMETReisWDBecknerDATE06/18/200306/19/2003OFFICIAL RECORD COPY

______________________________________________________________________________________OL = Operating License CP = Construction PermitAttachment LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICES_____________________________________________________________________________________InformationDate of Notice N SubjectIssuanceIssued to_____________________________________________________________________________________2003-05Failure to Detect FreespanCracks in PWR Steam Generator Tubes06/05/2003All holders of operating licensesor construction permits for pressurized-water reactors (PWRs).2002-15, Sup 1Potential HydrogenCombustion Events in BWR Piping05/06/2003All holders of operating licensesfor light water reactors, except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reactor.2002-21, Sup 1Axial Outside-diameterCracking Affecting Thermally Treated Alloy 600 Steam Generator Tubing04/01/2003All holders of operating licenseesfor nuclear power reactors, except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reactor vessel.2003-04Summary of Fitness-For-DutyProgram Performance Reports for Calendar Year 200002/06/2003All holders of operating licenseesfor nuclear power reactors, except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reactor vessel.2003-03Part 21 - Inadequately StakedCapscrew Renders Residual Heat Removal Pump Inoperable01/27/2003All holders of operating licensesor construction permits for nuclear power reactors.Note:NRC generic communications may be received in electronic format shortly after they areissued by subscribing to the NRC listserver as follows:To subscribe send an e-mail to <listproc@nrc.gov >, no subject, and the followingcommand in the message portion:subscribe gc-nrr firstname lastname