Information Notice 1994-79, Microbiologically Influenced Corrosion of Emergency Diesel Generator Service Water Piping

Microbiologically Influenced Corrosion of Emergency Diesel Generator Service Water Piping

ML031060426
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:	11/23/1994
From:	Grimes B K Office of Nuclear Reactor Regulation
To:
References
IN-94-079, NUDOCS 9411170039
Download: ML031060426 (9)

IUNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555November 23, 1994NRC INFORMATION NOTICE 94-79:MICROBIOLOGICALLY INFLUENCED CORROSION OFEMERGENCY DIESEL GENERATOR SERVICE WATER PIPING

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 degradation resulting from microbiologicallyinfluenced corrosion in carbon steel piping systems that supply service waterto emergency diesel generators. It is expected that recipients will reviewthe information for applicability to their facilities and consider actions, asappropriate, to avoid similar problems. However, suggestions contained inthis information notice are not NRC requirements; therefore, no specificaction or written response is required.

Description of Circumstances

Haddam Neck PlantOn February 12, 1994, a through-wall leak developed in the service watersystem supply piping to the "A" emergency diesel generator. The leak occurredin a weld in an area of low flow, where the licensee was doing light surfacegrinding to prepare for ultrasonic test (UT) inspection. Previously, in March1993, the licensee had found a similar leak associated with the "B" emergencydiesel generator. After removing the leaking section and examining the pipe,the licensee determined that the leak was caused by poor initial weld qualityand microbiologically influenced corrosion. Lack of penetration of some weldscreated a crevice condition. Radiographic tests (RT) of additional emergencydiesel generator service water system piping revealed three additional weldsthat could form similar leaks. It was during preparation of one of thesewelds for UT examination that the through-wall leak associated with the "A"emergency diesel generator was found.The licensee had previously performed a structural integrity determination in1993 by radiography. Though based on a uniform wall loss instead of a sharp,disruption, the licensee had at that time concluded that the worst-casedegraded cross-section of the as-found pipe welds, located in the unisolableportions of the emergency diesel generator supply piping, met the GenericLetter 90-05 acceptance criteria for structural integrity and that thedegraded piping would have sufficient mechanical and structural integrity toremain operable. &_ r" .in '^*94170C9411170039towzl +2ji)K I TE NO-riceH#-14-u1T4 lII /-

IN 94-79November 23, 1994 Beaver Valley Power Station. Unit IOn May 6, 1994, the licensee found a through-wall leak (an 8 mm [5/16 inch]diameter hole) on the "Al train reactor plant river water system header to theemergency diesel generators. The leak developed on the below-grade portion ofthe 15-cm [6-inch] diameter A106 Grade B carbon steel piping. The licenseeexcavated the "A" and 'B" train headers, ultrasonically examined them usingthe "autoscan" area mapping technique, and found localized pitting to lessthan minimum required wall thickness in three additional locations along the"A" train piping. The pits were not clustered or closely spaced, but werelocated along the pipe length between the five and seven o'clock positions.For reference, the nominal pipe wall thickness is 6.4 mm [0.25 inch] andminimum code wall thickness is 1.5 mm [0.06 inch].The licensee evaluated the pitting in accordance with the American Society ofMechanical Engineers (ASME) Code of record. The basis for the localizedthinning evaluation was conducted in accordance with industry guidance, EPRINP-59IISP, "Acceptance Criteria for Structural Evaluation of Erosion-CorrosionThinning in Carbon Steel Piping." This evaluation was reviewed by personnelin NRR and deemed as an acceptable conservative means of demonstrating ASMECode conformance. The licensee determined microbiologically influencedcorrosion to be the cause of the pitting and through-wall leak. The licenseeremoved a 0.61 m [24 inch] long section of piping to culture and characterizethe microbial activity and perform additional ultrasonic testing.The general inside surface of the piping was moderately corroded, withlocalized pits and tubercles. Cultures from the pits contained sulfur-reducing bacteria and the anaerobic bacteria Clostridium. The tubercleformation was the result of the growth of the iron-oxidizing bacteriaGallionella. Ultrasonic examinations of a heat-affected zone indicated thatthe weld examined was not subject to preferential microbiologically influencedcorrosion attack.DiscussionStagnant or intermittent-flow conditions, as in the case of emergency dieselservice water supply headers, are conducive to the growth of microorganismsthat can accelerate corrosion rates. Service water supply lines to emergencydiesel generators are stagnant because motor-operated isolation valves arenormally maintained shut (except during monthly surveillance testing).Crevices such as those in piping welds that lack penetration can enhancemicrobiologically influenced corrosion attack by giving a place for depositsand, therefore, for the bacteria to collect. Microbial films form whenaerobic species, such as iron-oxidizing bacteria, create anaerobic conditionsunderneath them for microorganisms, such as sulfate-reducing bacteria, toaccumulate at the metal surface. Sulfate-reducing bacteria attack the metalsurface, produce corrosive chemicals, and cause deep pitting.

K>J IN 94-79November 23, 1994 Microbiologically influenced corrosion on carbon steel will increase generalcorrosion, through-wall pitting, and the formation of tubercles. Tuberclesconsist of corrosion products, microbes, and debris. Tubercle growth couldrestrict cooling water flow to equipment.Stainless steel piping is not immune to microbiologically influenced corrosionbecause microbes can attack at the weld heat affected zone (HAZ) in stainlesssteels when this zone becomes sensitized. Microbiologically influencedcorrosion can also damage metals lined with polymeric materials, typically atcoating imperfections.Once microbial films are established on metal surfaces, they are extremelydifficult to eliminate because of the resiliency of the individualmicroorganisms. Biocides are applied by some licensees in areas wherecontinuous flow conditions cannot be maintained. However, biocide treatmentsare not always effective against established microorganism colonies becausethe biocide cannot penetrate through the tubercles or aerobic biofilms.Treatment against established colonies involves a combination of mechanical orchemical pipe cleaning, continued water treatment and regular maintenance.Continuous flow conditions have been found to prevent the attachment andgrowth of microbial films.It may be necessary to replace materials if microbiologically influencedcorrosion severely damages them or where mitigation measures cannot bring thesystem condition under control. Possible alternatives include replacingcarbon steel with stainless steel or replacing stainless steel with moreresistant materials, such as 6-percent molybdenum stainless steels, nickelbase alloys, titanium, or nonmetallic materials.The licensee did not regularly treat the Beaver Valley River water supplylines to the diesel with biocide or corrosion inhibitors. The chlorinationinjection point for the main river water headers is downstream of the branchlines to the emergency diesel generators. It also appears that the existingprogram at Haddam Neck of hypochlorite injection was not successful inmitigating the microbiologically influenced corrosion problems in stagnantdead-end lines at such locations as the emergency diesel generator supply.

IN 94-79November 23, 1994 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.Vv BaDD ision f Project SupportOffice of Nuclear Reactor RegulationTechnical contacts: Michael Modes, RI James A. Davis, NRR(215) 337-5198 (301) 504-2713Peter P. Sena, RI Vern Hodge, NRR(412) 643-2000 (301) 504-1861Attachment:List of Recently ssued NRC Information Noticeshi It6 J'4 K>AttachmentIN 94-79November 23, 1994 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to94-7894-7794-7693-60,Supp. 194-7594-7494-7394-7294-71Electrical ComponentFailure due to Degrada-tion of Polyvinyl ChlorideWire InsulationMalfunction in Main Gen-erator Voltage RegulatorCausing Overvoltage atSafety-Related ElectricalEquipmentRecent Failures of Charging/Safety Injection Pump ShaftsReporting Fuel Cycleand Materials Events tothe NRC Operations CenterMinimum Temperaturefor CriticalityFacility ManagementResponsibilities forPurchased or ContractedServices for RadiationTherapy ProgramsClarification of Critical-ity Reporting CriteriaIncreased Control RodDrop Time from CrudBuildupDegradation of ScramSolenoid Pilot ValvePressure and ExhaustDiaphragms11/21/9411/17/9410/26/9410/20/9410/14/9410/13/9410/12/9410/05/9410/04/94All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor pressurized waterreactors.All 10 CFR Part 70fuel cycle licensees.All holders of OLs or CPspressurized-water reactors(PWRs).All U.S. Nuclear RegulatoryCommission MedicalLicensees.All fuel fabricationfacilities.All holders of OLs or CPsfor pressurized waterreactors.All holders of OLs or CPsfor boiling water reactors(BWRs).OL -Operating LicenseCP = Construction Permit

-1/4<> A~-' IN 94-79November 23, 1994 The licensee did not regularly treat the Beaver Valley River water supplylines to the diesel with biocide or corrosion inhibitors. The chlorinationinjection point for the main river water headers is downstream of the branchlines to the emergency diesel generators. It also appears that the existingprogram at Haddam Neck of hypochlorite injection was not successful inmitigating the microbiologically influenced corrosion problems in stagnantdead-end lines at such locations as the emergency diesel generator supply.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.Original signed by B.D. Liaw forBrian K. Grimes, DirectorDivision of Project SupportOffice of Nuclear Reactor RegulationTechnical contacts:Michael Modes,(215) 337-5198RIJames A. Davis, NRR(301) 504-2713Peter P. Sena, RI(412) 643-2000Vern Hodge, NRR(301) 504-1861Attachment:List of Recently Issued NRC Information Notices*err DDrFlVT) rnCUriRFNrENOFFICE *OGCB/DORS *TECH ED *REGION I *REGION INAME CVHodge JDMain MCModes PPSenaDATE J 09/08/94 09/09/94 09/01/94 10/03/94__ _ _ _ _ _ _ _ _ -EI I __ If_*Ann-nfEDrIOTAN TI

• FMrR/nF*S:EMCB/DE*C: EMCB/DE, I vv.1,EI *vI __ , --ARBlough JADavis RAHermann JRStrosnider10/03/94 09/20/94 09/20/94-~~~ II f*n. nr*nCrRR /nnP5I *C AFCBIDOPSI D:DdPWi/Orv.LvL _. -BWSheron RLDennig AEChaffee G& I _J110/06/94 10/20/94 10/25/94 1 1 ff_/_ 4 LjDOCUMENT NAME: 94-79.IN

IN 94-XXOctober xx, 1994 inhibitors. The chlorination injection point for the main riverwater headers is downstream of the branch lines to the emergencydiesel generators. It also appears that the existing program atHaddam Neck of hypochlorite injection was not successful inmitigating the microbiologically influenced corrosion problems instagnant dead-end lines to such locations as the emergency dieselgenerator supply.This information notice requires no specific action or writtenresponse. If you have any questions about the information inthis notice, please contact one of the technical contacts listedbelow or the appropriate Office of Nuclear Reactor Regulation(NRR) project manager.Brian K. Grimes, DirectorDivision of Operating ReactorSupportOffice of Nuclear ReactorRegulationTechnical contacts: Michael Modes, Region I(215) 337-5198Peter P. Sena, Region I(412) 643-2000James A.Davis, NRR(301) 504-2713Attachment: List of Recently Issued NRC Information Notices*SEE PREVIOUS CONCURRENCEOFFICE *OGCB/DORS *TECH ED *REGION I *REGION INAME CVHodge JDMain MCModes PPSenaDATE 09/08/94 j09/09/94 09/01/94 10/03/94._ -11*Ann:DRA/RFCION I I *EMCB/DE I *S:EMCB/DE I *C:EMCB/DEARBlough JADavis RAHermann JRStrosnider10/03/94 09/20/94 09/20/94 09 94--I -I ~' -7 i*n FOEC 6I1QS I C:994A2'OPS I IWS/NRRBWSheron RLW A af e B j jes10/06/94 10/9 1,/94 10/ /94 _________DOCUMENT NAME: NECK-MIC. INY

-IN 94-XXSeptember xx, 1994 stagnant dead-end lines to such locations as the emergency dieselgenerator supply.This information notice requires no specific action or writtenresponse. If you have any questions about the information inthis notice, please contact one of the technical contacts listedbelow or the appropriate Office of Nuclear Reactor Regulation(NRR) project manager.Brian K. Grimes, DirectorDivision of Operating ReactorSupportOffice of Nuclear ReactorRegulationTechnical contacts:Michael Modes, Region I(215) 337-5198Peter P. Sena, Region I(412) 643-2000James A. Davis, NRR(301) 504-2713Attachment: List of Recently Issued NRC Information Notices.-- "tf A R'lena-*QVV DPRVUSTnT1 CONCURRENCE--.:L: -a V -__s_ ___ -r- -m --OFFICE *OGCB/DORS *TECH ED *REGION I REGION I ANAME CVHodge I JDMain MCModes PPSenaDATE j09/08/94 09/09/94 09/01/94 ff /o3/94_ I ., ._IIannlnPq/RFnTON T*EMCB/DE*S: EMCB/DEC;EMCB/DE fir-_ I___ __a _ v_ --ARBlough JADavis RAHermann LdRStrosnider-___ /9 09/20/94 09/20/94 09/X6/941~.1DkbzAC:OGCB/DORSD:DORS/NRRBW on ELDoolittle BKGrimes__/__ /94 09/ /94 09/ /94DOCUMgNT NAME: NECK-MIC.1firA-- 016 IIN 94-XXSeptember xx, 1994 This information notice requires no specific action or writtenresponse. If you have any questions about the information inthis notice, please contact one of the technical contacts listedbelow or the appropriate Office of Nuclear Reactor Regulation(NRR) project manager.Brian K. Grimes, DirectorDivision of Operating ReactorSupportOffice of Nuclear ReactorRegulationTechnical contacts:Michael Modes, Region I(215) 337-5198Peter P. Sena, Region I(412) 643-2000James A. Davis, NRR(301) 504-2713Attachment: List of Recently Issued NRC Information Notices*SEE PREVIOUS CONCURRENCE --- eIml e .Ac>Iveiw 6 2OFFICE OGCB/DORS TECH ED A REGION I REGION INAME CVHodge k ^JDMain MCModes PPSenaDATE 1 O9/08/94 09/09/94 09/01/94 09/ /94ADD:DRS/REGION IEMCB/DES:EMCB/DFC:EMCB/DEARBlough JADa RAHermann JRStrosnider09/ /94 09/0O/94 09/7v/94 09/ /94D: DEAC:OGCB/DORSD:DORS/NRRBWSheron ELDoolittle BKGrimes09/ /94 09/ /94 09/ /94DOCU;MENT NAME: NECK-MIC.INF