Information Notice 1998-36, Inadequate or Poorly Controlled, Non-Safety-Related Maintenance Activities Unnecessarily Challenged Safety Systems

Inadequate or Poorly Controlled, Non-Safety-Related Maintenance Activities Unnecessarily Challenged Safety Systems

ML031040558
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	09/18/1998
Revision:	0
From:	Roe J W Office of Nuclear Reactor Regulation
To:
References
IN-98-036, NUDOCS 9809210079
Download: ML031040558 (7)

~0- f9Acre September 18, 1998NRC INFORMATION NOTICE 98-36: INADEQUATE OR POORLY CONTROLLED, NON-SAFETY-RELATED MAINTENANCE ACTIVITIESUNNECESSARILY CHALLENGED SAFETY SYSTEMSAddresseeAll holders of operating licenses for nuclear power reactors.purposeThe U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to alertaddressees to several recent events in which inadequate or poorly controlled, non-safety-related maintenance activities resulted in unnecessary challenges to safety systems. It isexpected that recipients will review the information for applicability to their facilities and consideraction, as appropriate to avoid similar problems. However, suggestions contained in thisinformation notice are not NRC requirements; therefore, no specific action or written responseis required.

Description of Circumstances

BRAIDWOOD UNIT 2On January 18, 1996, with Braidwood Unit 2 operating at full power, .offsite power was lost.Inadequately secured roofing repair materials located on the roof of the adjacent servicebuilding were blown off the roof during a rain storm, causing a phase-to-ground arc on one oftwo station auxiliary transformers (SATs). As designed, the second SAT tripped when the firstSAT failed. Both emergency diesel generators (EDGs) automatically started and all safe-shutdown loads automatically sequenced on to the engineered safety feature (ESF) buses. Allautomatic bus transfers occurred as designed, maintaining power to non-ESF buses from theunit auxiliary transformers (UATs). The reactor remained stable at full power throughout theevent. To restore offsite power to Unit 2, the licensee cross-tied both Unit 2 ESF buses to therespective ESF buses of Unit 1, which also remained at full power throughout the event.Inspection of the faulted SAT revealed damage to (1) the Phase B and C bushings and (2) agas detector relay on top of the transformer where heavy arcing occurred. The licenseedetermined that the Initiating event was a Phase C arc-to-ground, followed by a Phase B tovNOrT g NO -98T- goz 98 0e 8<9809 td n f IN 98-36September 18, 1998 Phase C arc. A 345-kilovolt switchyard breaker, Which connected the SAT to the switchyardring bus, was also damaged. Approximately one square foot of the Phase B bushing wasblown out.BYRON UNIT IOn May 23, 1996, with the Unit 1 reactor shut down In excess of a month for a refueling outage,offsite power was lost when one of the two Unit I SATs Isolated because of a Phase A toPhase B current differential relay operation. The second SAT tripped as designed when thefirst SAT failed. Both EDGs automatically started and all safe-shutdown loads automaticallysequenced on to the ESF buses. Because the reactor was shut down, power to non-ESFbuses was lost and two service water pumps and a station air compressor common to bothByron units tripped. Without the service water pumps, Unit 2, which was operating at fullpower, had no cooling water to many loads, including the main generator auxiliaries, station aircompressors, condensate pumps, and condensate booster pumps. Subsequently, Unit 2 wasmanually tripped.The licensee determined that the SAT that initially tripped underwent a phase-to-ground fault ona Phase B insulator. The failed insulator was located outdoors, about halfway between the SATand the auxiliary building. After Initiating, the arc continued down the bus bar, Increasing inwidth until It involved the other two phases. Air and water present in the bus bar duct washeated by the arc and resulted in pressurization of the duct.Chronic water leakage through inadequately caulked Insulator mounting holes and through animproperly compressed gasket caused degradation of the insulator metal inserts and Insulatormaterial between these inserts. Eventually, the bus flashed to ground through the degradedinsulator and initiated the transient.PERRYOn June 5, 1997, Perry was operating at full power when an automatic reactor scram occurredfollowing a three-phase fault in one of two high-voltage secondary winding terminationcompartments of the UAT. The fault resulted in the actuation of the auxiliary transformer phasedifferential relay, a main generator lockout, a main turbine trip, and fast closure of the turbinecontrol valves.At the time of the transient, safety-related electrical loads were being supplied by the in-servicestartup transformer. The non-safety-related electrical loads supplied by the transformerautomatically transferred to the startup transformer except for the bus that was faulted.Operators stabilized the plant without major complication.The licensee determined that the fault had developed as a result of an accumulation of moistureand dust that had entered the termination compartment housing where a 2-Inch-long piece ofgasket material was missing from the compartment housing-to-transformer sealing surface.The missing piece of gasket material may have been lost during work performed when K>1IN 98-36September 18, 1998 replacing the auxiliary transformer following failure of the transformer on May 30, 1996. Thecause of that failure was attributed to Inadequate original design or poor assembly practices orboth.POINT BEACH UNIT IDuring a severe storm on January 8, 1998, a ground In the low-voltage-side bus duct causedthe failure of the Unit I SAT. This failure and a failure of the 13.8-kilovolt automatic bus transferto the Unit 2 SAT resulted in the loss of normal power to the Unit I safeguards buses. TheEDGs subsequently started and restored power to the buses. Unit I remained at 98 percentpower throughout the transient. Unit 2 was in cold shutdown.The licensee attributed the failure of the transformer to the buildup of condensation internal tothe buses and long-term insulation degradation In the bus duct on the low-voltage side of thetransformer. Before the transformer failed, the circuit breaker for a heater designed to keep thebus duct dry would not remain closed. Consequently, in August 1996, the licensee left thecircuit breaker open and wrote a work order for its repair. However, work schedulers did notrecognize that the bus duct heater was inoperable with the circuit breaker open, and the workorder was erroneously classified as "minor maintenance" and given low priority. At the time thetransformer failed, the work order was in the "backlog' of maintenance Items. In addition to theinoperable heater, the:licensee determined that the lack of a routine inspection program for thebus ducts may have contributed to the event. Inspection of the bus ducts after the transformerfailed revealed insulation breakdown that would likely have been Identified through a periodicInspection program.DiscussionThese events illustrate the potentially significant consequences of inadequate or poorlyperformed maintenance activities on non-safety-related plant components. Unnecessarychallenges to plant safety systems or control room operators or both could result frominadequate control or inattention to detail during non-safety-related maintenance activities. Thepotential impact on safety systems of such activities as the re-roofing of nuclear power plantsupport buildings, the Installation of gaskets, or the caulking of outdoor components, couldeasily be overlooked. In addition, several of the events discussed here highlight the need forlicensees to have better control over the maintenance activities of contractor and non-stationutility employees, and the need for thorough periodic walkdowns or preventive maintenance onauxiliary transformers and the associated outdoor bus duct IN 98-36September 18, 1998 This information notice requires no specific action or written response. However, recipients arereminded that they are required to consider Industry-wide operating experience (including NRCINs) where practical, when setting goals and performing periodic evaluations under Section50.65, "Requirements for Monitoring the Effectiveness of Maintenance at Nuclear PowerPlants," of Part 50 of Title 10 of the Code of Federal Regulations. If you have any questionsabout the information In this notice, please contact one of the technical contacts listed below orthe appropriate Office of Nuclear Reactor Regulation (NRR) project manager.eJack , Acting DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical contacts: Mike Kunowski, Region IlIl John Neisler, Region IlIl630-829-9816 630429-9718E-mail: mak3@nrc.gov E-mail: jhn@nrc.gov

Attachment:

List of Recently Issued NRC Information Notices A,(ttachment 1IN 98-36September 18, 1998 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformationNotice No.Date ofIssuanceSubject98-35Threat Assessments andConsideration of HeightenedPhysical Protection Measures914/98Issued toAll U.S. NRC fuel cycle facilitiespower and non-power reactorlicensees (Safeguard issues, notfor public disclosure.)98-3498-3398-3298-31NRC Configuration ControlErrorsNRC Regulations ProhibitAgreements that restrict orDiscourage an Employee fromParticipating In Protected ActivitiesProblems Associated with Post-Fire Safe-Shutdown CircuitAnalyses8/28/9881281988126198All holders of Operating licensesfor nuclear power reactors, exceptfor those who have ceasedoperations and have certified thatfuel has been permanentlyremoved from the reactor vesselAll holders of a U.S. NuclearRegulatory Commission (NRC)license.All holders of operating licensesfor nuclear power reactors, exceptthose who have permanentlyceased operations and havecertified that fuel has beenpermanently removed form thereactorAll holders of operating licencesfor nuclear power reactors, exceptthose licensees that havepermanently ceased operationsand have certified that fuel hasbeen permanently removed fromthe reactor vessel.Fire Protection System Design 8/26/98Deficiencies and Common-ModeFlooding of Emergency Core CoolingSystem Rooms at Washington NuclearProject Unit 2OL = Operating LicenseCP = Construction Permit

-IN 98-36September 18, 1998 This information notice requires no specific action or written response. However, recipients arereminded that they are required to consider industry-wide operating experience (including NRCINs) where practical, when setting goals and performing periodic evaluations under Section50.65, "Requirements for Monitoring the Effectiveness of Maintenance at Nuclear PowerPlants," of Part 50 of Title 10 of the Code of Federal Regulations. If you have any questionsabout the information in this notice, please contact one of the technical contacts listed below orthe appropriate Office of Nuclear Reactor Regulation (NRR) project manager.Jack W. Roe, Acting DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical contacts: Mike Kunowski, Region IlIl630-829-9816E-mail: mak3@nrc.govJohn Neisler, Region IlIl630-829-9718E-mail: jhn@nrc.gov

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List of Recently Issued NRC Information Notices*See previous concurrence C,,tt & e.**E-mail concurrence c<f()DOCUMENT NAME: G:\NICK\REGION.INTo receive a copy of this document, indicate in the box C=Copy wlo attachment/enclosure E=Copy with attachmentlenclosure N = No copyOFFICE PECB I Tech Ed I Reg III Reg [ il I PECB I C:PECB l_ji D MNAME NFields* RSanders* MKunowski** JNeisler** RDennig* JStolz* JRoDATE 09/03/98 08/26/98 09/03/98 Ii09/03/98 09/14/98 J 09/14/98 \/98OFFICIAL RECORD COPY IN 98-xxSeptember xx, 1998 This information notice requires no specific action or written response. However, recipie arereminded that they are required to consider industry-wide operating experience (includ g NRCINs) where practical, when setting goals and performing periodic evaluations under ection50.65, "Requirements for Monitoring the Effectiveness of Maintenance at Nuclea owerPlants," of Part 50 of Title 10 of the Code of Federal Regulations. If you have ny questionsabout the information in this notice, please contact one of the technical con cts listed below orthe appropriate Office of Nuclear Reactor Regulation (NRR) project man er.Jack W. Roe, Acting irectorDivision of Reactor rogram ManagementOffice of Nuclea eactor RegulationTechnical contacts: Mike Kunowski, Region IlIl Joh eisler, Region IlIl630-829-9816 63 -829-9718E-mail: mak3@nrc.gov -mail: jhn@nrc.gov

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List of Recently Issued NRC Info tion NoticesDOCUMENT NAME: G:\NICK\REGION.INTo receive a copy of this document, Indicate in the box C=Copy wlo attachmentenclosure E=Copy with attachmentlenclosure N = No copyOFFICE PECB. I _ Tech Ed I _ Reg I _I lI Reg 11 l 1/E "ECB (A)D:DRPM lNAME NFiells' { RSanders MKu owsk Jeisler ennig l l JRoel DATE /3/98 1SW98 17/3/98 15/3198 lH/ 48 q/l98 l I /98OFFICIAL RECORD COPY I