Information Notice 1995-10, Potential for Loss of Automatic Engineered Safety Features Actuation

Potential for Loss of Automatic Engineered Safety Features Actuation

ML031060352
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:	02/03/1995
Revision:	0
From:	Grimes B K Office of Nuclear Reactor Regulation
To:
References
IN-95-010, NUDOCS 9502030313
Download: ML031060352 (8)

UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555February 3, 1995NRC INFORMATION NOTICE 95-10: POTENTIAL FOR LOSS OF AUTOMATIC ENGINEEREDSAFETY FEATURES ACTUATION

Addressees

All holders of operating licenses or construction permits for nuclear powerreactors.PurDoseThe U.S. Nuclear Regulatory Commission (NRC) is issuing this informationnotice to alert addressees to the potential for loss of the automaticactuation function of engineered safety features (ESF) as a result ofelectrical faults in some non-class 1E input signals. It is expected thatrecipients will review the information for applicability to their facilitiesand consider actions, as appropriate, to avoid similar problems. However,suggestions contained in this information notice are not NRC requirements;therefore, no specific action or written response is required.

Description of Circumstances

On February 2, 1995, the licensee for the Diablo Canyon facility reported tothe NRC a condition that could result in the failure of one train of theirsolid state protection system (SSPS) during a main steamline break in theturbine building (10 CFR 50.72 report number 28318). The licensee postulateda break of a main steamline at the turbine stop valve in the turbine building.If the steamline breaks completely, it is free to rotate approximately 10degrees. The 10-degree rotation of the steamline could result in the steamjet from the faulted steamline striking an electrical Junction box. TheJunction box contains terminations for non-safety input signals to the SSPS,turbine stop valve position indication (four circuits, two circuits for eachtrain).The force of the steam jet impinging on the Junction box is postulated todestroy the box and result in electrical faults in the affected non-safetyinputs to the SSPS. The high current resulting from the electrical faultswould cause 15-ampere fuses to open, interrupting 120-V ac power supply to thefaulted circuits. Since dc power supplies for SSPS logic and ESF trainactuation relays are supplied by the same 15-ampere fuses, opening of thefuses would also interrupt power to the SSPS logic channels and possibly oneESF train actuation relay bank. This would render one SSPS train inoperable.If a single failure of the other SSPS train is considered, as is required inPD/2 Z4.I-1otc 9e-0lo 7~o2I 39502030313Pi( oil ' 1 V<-- IN 95-10February 3, 1995 the high energy line break analysis methodology, both trains of the SSPS wouldbe rendered inoperable and no ESF actuations would be automatically availableto mitigate the consequences of the steamline break. The reactor tripcircuitry would be de-energized resulting in a reactor trip. Manual actioncould be initiated to operate individual pieces of equipment.NRC inspectors determined that other non-class IE circuits that provide inputto the SSPS were not properly isolated. These circuits include turbine autostop oil (three circuits), seismic trip (constructed to class lE standard),12-kV undervoltage, 12-kV underfrequency, and reactor coolant pump breakerposition indication. An electrical fault in any of these circuits could causeloss of power to SSPS logic circuit in the same way described above.Although a single main steamline break would likely render only one SSPS traininoperable, either train could be rendered inoperable depending upon thelocation of the steamline break. The licensee declared the ESF portion of thesolid state protection system inoperable and entered Technical Specification3.3.2 for inoperable ESF instrumentation and then Technical Specification3.0.3 limiting condition for operation to start shutdown of both units within1 hour.On February 1, 1995, the licensee for the Salem facility notified the NRC thatit had been determined that the design of the SSPS at its facility was similarto that at the Diablo Canyon facility (10 CFR 50.72 report number 28321). TheSalem licensee concluded that a main steamline break could have the sameeffect on non-class 1E circuits as that postulated at the Diablo Canyonfacility. In addition, the licensee concluded that a seismic event couldchallenge both trains of SSPS since both junction boxes associated with bothtrains of SSPS are located in the turbine building (the Diablo Canyon licenseeis continuing to evaluate seismic and other vulnerabilities of these non-classIE circuits). The circuits that are potentially affected at Salem includeturbine stop valve position indication, auto-stop oil pressure switches, andreactor coolant pump breaker position indication. The circuit faultsinitiated by the steamline break or seismic event could result in loss ofpower to SSPS logic circuitry similar to that postulated by the Diablo Canyonlicensee. The resulting impact would be either a partial or total loss of theautomatic actuation function of the SSPS. The reactor trip circuitry would bede-energized, resulting in a reactor trip. Manual action would be required tomitigate the consequences of a main steamline break event. The licenseedeclared the SSPS inoperable and began a shutdown of Unit I as required byTechnical Specifications. (Unit 2 was already shut down.)DiscussionThe licensees are undertaking similar corrective actions. The electricalsupply to the SSPS dc power supplies will be taken from a point electricallyupstream of the 15-ampere fuse referred to above. This modification willensure that opening of the fuse, because of faults in the non-class IEcircuits, does not cause a loss of power to the class IE dc power supplies.Figure 1 is a one-line diagram illustrating the as-found condition of a singlechannel of the SSPS at Diablo Canyon. Two out of four channels are

< J IN 95-10February 3, 1995 potentially affected in SSPS Train A and two out of four channels arepotentially affected in SSPS Train B.The Diablo Canyon licensee plan for repairs includes drafting a formalmodification procedure, curtailing work near the vulnerable junction boxes,deferring train-related maintenance and surveillance during the modificatidnperiod, maintaining constant power level, testing the procedure on a mock-up,de-energizing one channel at a time while modifying that channel (the reactortrip bypass breaker will be closed during the modification), trainingoperators on safety considerations during the repairs, and postmodificationtesting. The licensee estimated that the increase in core damage frequencyduring the repair period would be less than 2E-7. (The Salem licensee repairplan was not available when this information notice was prepared.)This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, DirectorDivision of Project SupportOffice of Nuclear Reactor RegulationTechnical contacts: E. Nick Fields, NRR(301) 415-1173Cliff Doutt, NRR(301) 415-2847

Attachments:

1. Figure 12. List of Recently Issued NRC Information NoticesChar I-Figure 1 SOUD STATE PROTEClION SYSTEM, TRAIN A, CHANNEL 1, SIMPLIFIED SCHEMATIC.BEFORE DESIGN CHANGE.ciiURItoCBREAKER20AIDAOUTPUT, POWERSUPPLYNOTUSED\n I Xt -Ty t ' ' ? "V T I-u15ABA BALOGMC LPO POWESUPPLY SuPPlY48V 1WOA SATURBwoEAUTO STOPOIL PRESS 1I SEISMICTRIPTURDWEISTEAM STOPVALVECLOSEDISEISCTRIPasm 112KVBUS DUNDER-FREOUNCY 1I IIIRCPIIBKROPEN IH 'IPRESSURE IBISThBLEI12KVBIS DTUDER-VOLTAGE I(ISEIsmCI TRIPrY-I12KVBUSEUNDER-_ FRREUE1N 1(IK1(09K1¶K136-cK15IK1IK15K11$K137 >K123.III_____ -t tIq ty WmX * %09%0u" w KPtachment 2IN 95-10February 3, 1995 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to95-0995-0895-0795-06Use of InappropriateGuidelines and Criteriafor Nuclear Piping andPipe Support Evaluationand DesignInaccurate Data Obtainedwith Clamp-On UltrasonicFlow Measurement InstrumentsRadiopharmaceutical VialBreakage during PreparationPotential Blockage ofSafety-Related Strainersby Material Brought InsideContainment01/31/9501/30/9501/27/9501/25/95All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All USNRC medical licenseesauthorized to use byproductmaterial for diagnosticprocedures.All holders of OLs or CPsfor nuclear power reactors.95-0595-04Undervoltage ProtectionRelay Settings Out ofTolerance Due to TestEquipment HarmonicsExcessive Cooldown andDepressurization of theReactor Coolant SystemFollowing a Loss ofOffsite Power01/20/9501/19/95All holdersPermits forreactors.All holdersfor nuclearof Constructionnuclear powerof OLs or CPspower reactors.95-03Loss of Reactor CoolantInventory and PotentialLoss of Emergency Mitiga-tion Functions While ina Shutdown Condition01/18/95All holders of Ols or CPsfor nuclear power reactors.OL = Operating LicenseCP -Construction Permit IN 95-10February 3, 1995 potentially affected in SSPS Train A and two out of four channels arepotentially affected in SSPS Train B.The Diablo Canyon licensee plan for repairs includes drafting a formalmodification procedure, curtailing work near the vulnerable Junction boxes,deferring train-related maintenance and surveillance during the modificationperiod, maintaining constant power level, testing the procedure on a mock-up,de-energizing one channel at a time while modifying that channel (the reactortrip bypass breaker will be closed during the modification), trainingoperators on safety considerations during the repairs, and postmodificationtesting. The licensee estimated that the increase in core damage frequencyduring the repair period would be less than 2E-7. (The Salem licensee repairplan was not available when this information notice was prepared.)This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, DirectorDivision of Project SupportOffice of Nuclear Reactor RegulationTechnical contacts:E. Nick Fields, NRR(301) 415-1173Cliff Doutt, NRR(301) 415-2847

Attachments:

1. Figure 12. List of RecentlyIssued NRC Information NoticesDOCUMENT NAME: 95-10.IN*See revious concurrenceOFC OECB:DOPS SC/OECB:DOPS PUB:ADM C/OECB:DOPSNAME NFields* EGoodwin* Tech Ed* AChaffee*DATE 02/03/95 02/03/95 02/03/95 02/03/95OFC HICB:DRCH C/HICB:DRCH D/DRCHNAME CDoutt4' JWermiel o BBoger+ ___________DATE 02/03/95 02/03/95 02/03/95 02/ 3!/95OFFICIAL RECORD COPY IN 95-XXFebruary xx, 1995 potentially affected in SSPS Train A and two out of four channels arepotentially affected in SSPS Train B.The Diablo Canyon licensee plan for repairs includes drafting a formalmodification procedure, curtailing work near the vulnerable junction boxes,deferring train-related maintenance and surveillance during the modificationperiod, maintaining constant power level, testing the procedure on a mock-up,de-energizing one channel at a time while modifying that channel (the reactortrip bypass breaker will be closed during the modification), trainingoperators on safety considerations during the repairs, and postmodificationtesting. The licensee estimated that the increase in core damage frequencyduring the repair period would be less than 2E-7. (The Salem licensee repairplan was not available when this information notice was prepared.)This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, DirectorDivision of Project SupportOffice of Nuclear Reactor RegulationTechnical contacts: Nick Fields, NRR(301) 415-1173Cliff Doutt, NRR(301) 415-2847

Attachment:

1. Figure 12. Figure 23. List of Recently Issued NRC Information NoticesDOCUMENT NAME: G:\OECB\DIABLO1.INSee previous concurrenceOFC OECB:DOPS SC/OECB:DOPS PUB:ADM C/OECB:DOPSNAME NFields* EGoodwin* Tech Ed* AChaffee*DATE / /95 / /95 02/03/95 / /95OFC HICB:DRCH D DDRQH D/DRCH D/DOPSNAME CDoutt BBoger BGrimesDATE 93 5 / 3 /95 / /95 IN 95-XXFebruary xx, 1995 potentially cted in SSPS Train A and two out of four channels arepotentially af ed in SSPS Train B. Figure 2 illustrates the proposeddesign change, i ing replacing the 15-ampere fuse with an 8-ampere fuse toensure proper coor ion of circuit protective devices. (The Salem designchange employs a diff t 'ujse size)The Diablo Canyon license lans for repairs include drafting a formalmodification procedure, cur ing work near the vulnerable panels, deferringtrain-related maintenance and s -veillance during the modification period,maintaining constant power level, esting the procedure on a mock-up, de-energizing one channel at a time wh e modifying that channel (the reactortrip bypass breaker will be closed du ng the modification), training ofoperators on safety considerations durn the repairs, and post-modificationtesting. The licensee estimated that the ncrease in core damage frequencyduring the period of repair would be less t n 2E-7. (The Salem licensee'srepair plans were not available when this inf mation notice was prepared).This information notice requires no specific act or written response. Ifyou have any questions about the information in thi notice, please contactone of the technical contacts listed below or the app iate Office ofNuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, DirectorDivision of Project SupportOffice of Nuclear Reactor RegulationTechnical contacts: Nick Fields, NRR(301) 415-1173Cliff Doutt, NRR(301) 415-2847

Attachments:

1. Figure 12. Figure 23. List of Recently Issued NRC Information NoticesDOCUMENT NAME: G:\OECB\DIABL01.IN*See previous concurrenceOFC lOECB:DOPS lSC/OECB:DO$ l PUB:ADM l C/OECB:DOPS lNAME NFields EGoodwin D Tech Ed* AC& &eDATE 2 /f 1 9 /95 i3 902/03/95 /3 /95OFC HICB:DRCH C/HICB:DRCH D/DRCH D/DOPSNAME CDoutt JWermiel BBoger BGrimesDATEl //95 / /95 / 95 /_ /95OFFICIAL RECORD COPY