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

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| issue date = 11/23/1994
| issue date = 11/23/1994
| title = Microbiologically Influenced Corrosion of Emergency Diesel Generator Service Water Piping
| title = Microbiologically Influenced Corrosion of Emergency Diesel Generator Service Water Piping
| author name = Grimes B K
| author name = Grimes B
| author affiliation = NRC/NRR
| author affiliation = NRC/NRR
| addressee name =  
| addressee name =  
Line 14: Line 14:
| page count = 9
| page count = 9
}}
}}
{{#Wiki_filter: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
{{#Wiki_filter:I
 
===UNITED STATES===
NUCLEAR REGULATORY COMMISSION
 
===OFFICE OF NUCLEAR REACTOR REGULATION===
WASHINGTON, D.C. 20555
 
===November 23, 1994===
NRC INFORMATION NOTICE 94-79:
 
===MICROBIOLOGICALLY INFLUENCED CORROSION OF===
EMERGENCY DIESEL GENERATOR SERVICE WATER PIPING


==Addressees==
==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.
All holders of operating licenses or construction permits for nuclear power
 
reactors.
 
PurDose
 
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
 
notice to alert addressees to degradation resulting from microbiologically
 
influenced corrosion in carbon steel piping systems that supply service water
 
to emergency diesel generators.
 
===It is expected that recipients will review===
the information for applicability to their facilities and 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==
==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.
===Haddam Neck Plant===
On February 12, 1994, a through-wall leak developed in the service water
 
system supply piping to the "A" emergency diesel generator. The leak occurred
 
in a weld in an area of low flow, where the licensee was doing light surface
 
grinding to prepare for ultrasonic test (UT) inspection.
 
===Previously, in March===
1993, the licensee had found a similar leak associated with the "B" emergency
 
diesel generator. After removing the leaking section and examining the pipe, the licensee determined that the leak was caused by poor initial weld quality
 
and microbiologically influenced corrosion. Lack of penetration of some welds
 
created a crevice condition.
 
Radiographic tests (RT) of additional emergency
 
diesel generator service water system piping revealed three additional welds
 
that could form similar leaks.
 
===It was during preparation of one of these===
welds 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 in
 
1993 by radiography. Though based on a uniform wall loss instead of a sharp
 
,disruption, the licensee had at that time concluded that the worst-case
 
degraded cross-section of the as-found pipe welds, located in the unisolable
 
portions of the emergency diesel generator supply piping, met the Generic
 
Letter 90-05 acceptance criteria for structural integrity and that the
 
degraded piping would have sufficient mechanical and structural integrity to
 
remain operable.
 
&_
r"
.
 
in '^*
94170C
 
9411170039 towzl +2ji
 
)K I TE NO-rice
 
H#-14-u1 T4 lII /-
-"5
 
IN 94-79 November 23, 1994 Beaver Valley Power Station. Unit I
 
On 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 the
 
emergency diesel generators. The leak developed on the below-grade portion of
 
the 15-cm [6-inch] diameter A106 Grade B carbon steel piping.
 
===The licensee===
excavated the "A" and 'B" train headers, ultrasonically examined them using
 
the "autoscan" area mapping technique, and found localized pitting to less
 
than minimum required wall thickness in three additional locations along the
 
"A" train piping.
 
The pits were not clustered or closely spaced, but were
 
located 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] and
 
minimum code wall thickness is 1.5 mm [0.06 inch].
 
The licensee evaluated the pitting in accordance with the American Society of
 
Mechanical Engineers (ASME) Code of record.
 
===The basis for the localized===
thinning evaluation was conducted in accordance with industry guidance, EPRI
 
NP-59IISP, "Acceptance Criteria for Structural Evaluation of Erosion-Corrosion
 
Thinning in Carbon Steel Piping." This evaluation was reviewed by personnel
 
in NRR and deemed as an acceptable conservative means of demonstrating ASME
 
Code conformance. The licensee determined microbiologically influenced
 
corrosion to be the cause of the pitting and through-wall leak. The licensee
 
removed a 0.61 m [24 inch] long section of piping to culture and characterize
 
the microbial activity and perform additional ultrasonic testing.
 
The general inside surface of the piping was moderately corroded, with
 
localized pits and tubercles. Cultures from the pits contained sulfur- reducing bacteria and the anaerobic bacteria Clostridium. The tubercle
 
formation was the result of the growth of the iron-oxidizing bacteria
 
Gallionella. Ultrasonic examinations of a heat-affected zone indicated that
 
the weld examined was not subject to preferential microbiologically influenced
 
corrosion attack.
 
Discussion
 
Stagnant or intermittent-flow conditions, as in the case of emergency diesel
 
service water supply headers, are conducive to the growth of microorganisms
 
that can accelerate corrosion rates. Service water supply lines to emergency
 
diesel generators are stagnant because motor-operated isolation valves are
 
normally maintained shut (except during monthly surveillance testing).
 
Crevices such as those in piping welds that lack penetration can enhance
 
microbiologically influenced corrosion attack by giving a place for deposits
 
and, therefore, for the bacteria to collect. Microbial films form when
 
aerobic species, such as iron-oxidizing bacteria, create anaerobic conditions
 
underneath them for microorganisms, such as sulfate-reducing bacteria, to
 
accumulate at the metal surface.
 
Sulfate-reducing bacteria attack the metal
 
surface, produce corrosive chemicals, and cause deep pitting.
 
K>J
 
IN 94-79 November 23, 1994 Microbiologically influenced corrosion on carbon steel will increase general
 
corrosion, through-wall pitting, and the formation of tubercles. Tubercles
 
consist of corrosion products, microbes, and debris. Tubercle growth could
 
restrict cooling water flow to equipment.
 
Stainless steel piping is not immune to microbiologically influenced corrosion
 
because microbes can attack at the weld heat affected zone (HAZ) in stainless
 
steels when this zone becomes sensitized. Microbiologically influenced
 
corrosion can also damage metals lined with polymeric materials, typically at
 
coating imperfections.
 
Once microbial films are established on metal surfaces, they are extremely
 
difficult to eliminate because of the resiliency of the individual
 
microorganisms. Biocides are applied by some licensees in areas where
 
continuous flow conditions cannot be maintained. However, biocide treatments
 
are not always effective against established microorganism colonies because
 
the biocide cannot penetrate through the tubercles or aerobic biofilms.
 
Treatment against established colonies involves a combination of mechanical or
 
chemical pipe cleaning, continued water treatment and regular maintenance.
 
Continuous flow conditions have been found to prevent the attachment and
 
growth of microbial films.
 
It may be necessary to replace materials if microbiologically influenced
 
corrosion severely damages them or where mitigation measures cannot bring the
 
system condition under control.
 
===Possible alternatives include replacing===
carbon steel with stainless steel or replacing stainless steel with more
 
resistant materials, such as 6-percent molybdenum stainless steels, nickel
 
base alloys, titanium, or nonmetallic materials.
 
The licensee did not regularly treat the Beaver Valley River water supply
 
lines to the diesel with biocide or corrosion inhibitors. The chlorination
 
injection point for the main river water headers is downstream of the branch
 
lines to the emergency diesel generators. It also appears that the existing
 
program at Haddam Neck of hypochlorite injection was not successful in
 
mitigating the microbiologically influenced corrosion problems in stagnant
 
dead-end lines at such locations as the emergency diesel generator supply.
 
IN 94-79 November 23, 1994 This information notice requires no specific action or written response. If
 
you have any questions 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.
 
Vv BaD
 
===D ision f Project Support===
Office of Nuclear Reactor Regulation
 
Technical contacts: Michael Modes, RI
 
===James A. Davis, NRR===
(215) 337-5198
(301) 504-2713 Peter P. Sena, RI
 
===Vern Hodge, NRR===
(412) 643-2000
(301) 504-1861 Attachment:
 
===List of Recently ssued NRC Information Notices===
hi
 
It6 J'4


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
K>
Attachment


-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
IN 94-79


* 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
===November 23, 1994 LIST OF RECENTLY ISSUED===
NRC INFORMATION NOTICES


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
Information


-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
Date of


}}
Notice No.
 
Subject
 
Issuance
 
Issued to
 
94-78
94-77
94-76
93-60,
Supp. 1
94-75
94-74
94-73
94-72
94-71
 
===Electrical Component===
Failure due to Degrada- tion of Polyvinyl Chloride
 
===Wire Insulation===
Malfunction in Main Gen- erator Voltage Regulator
 
===Causing Overvoltage at===
Safety-Related Electrical
 
Equipment
 
Recent Failures of Charging/
 
===Safety Injection Pump Shafts===
Reporting Fuel Cycle
 
and Materials Events to
 
the NRC Operations Center
 
===Minimum Temperature===
for Criticality
 
===Facility Management===
Responsibilities for
 
===Purchased or Contracted===
Services for Radiation
 
===Therapy Programs===
Clarification of Critical- ity Reporting Criteria
 
===Increased Control Rod===
Drop Time from Crud
 
Buildup
 
===Degradation of Scram===
Solenoid Pilot Valve
 
===Pressure and Exhaust===
Diaphragms
 
11/21/94
11/17/94
10/26/94
10/20/94
10/14/94
10/13/94
10/12/94
10/05/94
10/04/94
 
===All holders of OLs or CPs===
for nuclear power reactors.
 
===All holders of OLs or CPs===
for nuclear power reactors.
 
===All holders of OLs or CPs===
for pressurized water
 
reactors.
 
===All 10 CFR Part 70===
fuel cycle licensees.
 
===All holders of OLs or CPs===
pressurized-water reactors
 
(PWRs).
 
===All U.S. Nuclear Regulatory===
Commission Medical
 
Licensees.
 
===All fuel fabrication===
facilities.
 
===All holders of OLs or CPs===
for pressurized water
 
reactors.
 
===All holders of OLs or CPs===
for boiling water reactors
 
(BWRs).
 
OL - Operating License
 
CP = Construction Permit
 
-
1/4<>
A~-'
IN 94-79 November 23, 1994 The licensee did not regularly treat the Beaver Valley River water supply
 
lines to the diesel with biocide or corrosion inhibitors. The chlorination
 
injection point for the main river water headers is downstream of the branch
 
lines to the emergency diesel generators.
 
===It also appears that the existing===
program at Haddam Neck of hypochlorite injection was not successful in
 
mitigating the microbiologically influenced corrosion problems in stagnant
 
dead-end lines at such locations as the emergency diesel generator supply.
 
This information notice requires no specific action or written response.
 
If
 
you have any questions 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.
 
===Original signed by B.D. Liaw for===
Brian K. Grimes, Director
 
===Division of Project Support===
Office of Nuclear Reactor Regulation
 
Technical contacts:
Michael Modes,
(215) 337-5198 RI
 
===James A. Davis, NRR===
(301) 504-2713
 
===Peter P. Sena, RI===
(412) 643-2000
 
===Vern Hodge, NRR===
(301) 504-1861 Attachment:
 
===List of Recently Issued NRC Information Notices===
*err DDrFlVT)
rnCUriRFNrEN
 
OFFICE
 
*OGCB/DORS
 
*TECH ED
 
*REGION I
 
*REGION I
 
NAME
 
CVHodge
 
JDMain
 
MCModes
 
PPSena
 
DATE
 
J
 
09/08/94
09/09/94
09/01/94
10/03/94
__
_
_
_
_
_
_
_
_ -EI
 
I
 
__
If_
*Ann-nfEDrIOTAN T
 
I
 
* FMrR/nF
 
*S:EMCB/DE
 
*C: EMCB/DE
 
,
I
 
vv.1,EI
 
*vI
 
__
,
- -
ARBlough
 
JADavis
 
RAHermann
 
===JRStrosnider===
10/03/94
09/20/94
09/20/94
-~~~
II
 
f
 
*n. nr
 
*nCrRR /nnP5 I *C AFCBIDOPS
 
I D:DdPWi/Or
 
v.LvL
 
_.
 
-
BWSheron
 
RLDennig
 
AEChaffee
 
G&
I _J1
10/06/94
10/20/94
10/25/94
1 1 ff_/_ 4 Lj
 
DOCUMENT NAME:
94-79.IN
 
IN 94-XX
 
October xx, 1994 inhibitors.
 
===The chlorination injection point for the main river===
water headers is downstream of the branch lines to the emergency
 
diesel generators.
 
===It also appears that the existing program at===
Haddam Neck of hypochlorite injection was not successful in
 
mitigating the microbiologically influenced corrosion problems in
 
stagnant dead-end lines to such locations as the emergency diesel
 
generator supply.
 
This information notice requires no specific action or written
 
response.
 
===If you have any questions 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.
 
===Brian K. Grimes, Director===
Division of Operating Reactor
 
Support
 
===Office of Nuclear Reactor===
Regulation
 
Technical contacts:
 
===Michael Modes, Region I===
(215) 337-5198
 
===Peter P. Sena, Region I===
(412) 643-2000
 
===James A.Davis, NRR===
(301) 504-2713 Attachment:
 
===List of Recently Issued NRC Information Notices===
*SEE PREVIOUS CONCURRENCE
 
OFFICE
 
*OGCB/DORS
 
*TECH ED
 
*REGION I
 
*REGION I
 
NAME
 
CVHodge
 
JDMain
 
MCModes
 
PPSena
 
DATE
 
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/DE
 
ARBlough
 
JADavis
 
RAHermann
 
===JRStrosnider===
10/03/94
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-
IN 94-XX
 
September xx, 1994 stagnant dead-end lines to such locations as the emergency diesel
 
generator supply.
 
This information notice requires no specific action or written
 
response.
 
===If you have any questions 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.
 
===Brian K. Grimes, Director===
Division of Operating Reactor
 
Support
 
===Office of Nuclear Reactor===
Regulation
 
Technical contacts:
 
===Michael Modes, Region I===
(215) 337-5198
 
===Peter P. Sena, Region I===
(412) 643-2000
 
===James A. Davis, NRR===
(301) 504-2713 Attachment:
 
===List of Recently Issued NRC Information Notices===
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IN 94-XX
 
September xx, 1994 This information notice requires no specific action or written
 
response.
 
===If you have any questions 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.
 
===Brian K. Grimes, Director===
Division of Operating Reactor
 
Support
 
===Office of Nuclear Reactor===
Regulation
 
Technical contacts:
 
===Michael Modes, Region I===
(215) 337-5198
 
===Peter P. Sena, Region I===
(412) 643-2000
 
===James A. Davis, NRR===
(301) 504-2713 Attachment:
 
===List of Recently Issued NRC Information Notices===
*SEE PREVIOUS CONCURRENCE
 
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09/
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09/
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NECK-MIC.INF}}


{{Information notice-Nav}}
{{Information notice-Nav}}

Latest revision as of 10:49, 16 January 2025

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, 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, Crane  
Issue date: 11/23/1994
From: Grimes B
Office of Nuclear Reactor Regulation
To:
References
IN-94-079, NUDOCS 9411170039
Download: ML031060426 (9)
v • d • e


I

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555

November 23, 1994

NRC INFORMATION NOTICE 94-79:

MICROBIOLOGICALLY INFLUENCED CORROSION OF

EMERGENCY DIESEL GENERATOR SERVICE WATER PIPING

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

PurDose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information

notice to alert addressees to degradation resulting from microbiologically

influenced corrosion in carbon steel piping systems that supply service water

to emergency diesel generators.

It is expected that recipients will review

the information for applicability to their facilities and 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

Haddam Neck Plant

On February 12, 1994, a through-wall leak developed in the service water

system supply piping to the "A" emergency diesel generator. The leak occurred

in a weld in an area of low flow, where the licensee was doing light surface

grinding to prepare for ultrasonic test (UT) inspection.

Previously, in March

1993, the licensee had found a similar leak associated with the "B" emergency

diesel generator. After removing the leaking section and examining the pipe, the licensee determined that the leak was caused by poor initial weld quality

and microbiologically influenced corrosion. Lack of penetration of some welds

created a crevice condition.

Radiographic tests (RT) of additional emergency

diesel generator service water system piping revealed three additional welds

that could form similar leaks.

It was during preparation of one of these

welds 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 in

1993 by radiography. Though based on a uniform wall loss instead of a sharp

,disruption, the licensee had at that time concluded that the worst-case

degraded cross-section of the as-found pipe welds, located in the unisolable

portions of the emergency diesel generator supply piping, met the Generic

Letter 90-05 acceptance criteria for structural integrity and that the

degraded piping would have sufficient mechanical and structural integrity to

remain operable.

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94170C

9411170039 towzl +2ji

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IN 94-79 November 23, 1994 Beaver Valley Power Station. Unit I

On 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 the

emergency diesel generators. The leak developed on the below-grade portion of

the 15-cm [6-inch] diameter A106 Grade B carbon steel piping.

The licensee

excavated the "A" and 'B" train headers, ultrasonically examined them using

the "autoscan" area mapping technique, and found localized pitting to less

than minimum required wall thickness in three additional locations along the

"A" train piping.

The pits were not clustered or closely spaced, but were

located 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] and

minimum code wall thickness is 1.5 mm [0.06 inch].

The licensee evaluated the pitting in accordance with the American Society of

Mechanical Engineers (ASME) Code of record.

The basis for the localized

thinning evaluation was conducted in accordance with industry guidance, EPRI

NP-59IISP, "Acceptance Criteria for Structural Evaluation of Erosion-Corrosion

Thinning in Carbon Steel Piping." This evaluation was reviewed by personnel

in NRR and deemed as an acceptable conservative means of demonstrating ASME

Code conformance. The licensee determined microbiologically influenced

corrosion to be the cause of the pitting and through-wall leak. The licensee

removed a 0.61 m [24 inch] long section of piping to culture and characterize

the microbial activity and perform additional ultrasonic testing.

The general inside surface of the piping was moderately corroded, with

localized pits and tubercles. Cultures from the pits contained sulfur- reducing bacteria and the anaerobic bacteria Clostridium. The tubercle

formation was the result of the growth of the iron-oxidizing bacteria

Gallionella. Ultrasonic examinations of a heat-affected zone indicated that

the weld examined was not subject to preferential microbiologically influenced

corrosion attack.

Discussion

Stagnant or intermittent-flow conditions, as in the case of emergency diesel

service water supply headers, are conducive to the growth of microorganisms

that can accelerate corrosion rates. Service water supply lines to emergency

diesel generators are stagnant because motor-operated isolation valves are

normally maintained shut (except during monthly surveillance testing).

Crevices such as those in piping welds that lack penetration can enhance

microbiologically influenced corrosion attack by giving a place for deposits

and, therefore, for the bacteria to collect. Microbial films form when

aerobic species, such as iron-oxidizing bacteria, create anaerobic conditions

underneath them for microorganisms, such as sulfate-reducing bacteria, to

accumulate at the metal surface.

Sulfate-reducing bacteria attack the metal

surface, produce corrosive chemicals, and cause deep pitting.

K>J

IN 94-79 November 23, 1994 Microbiologically influenced corrosion on carbon steel will increase general

corrosion, through-wall pitting, and the formation of tubercles. Tubercles

consist of corrosion products, microbes, and debris. Tubercle growth could

restrict cooling water flow to equipment.

Stainless steel piping is not immune to microbiologically influenced corrosion

because microbes can attack at the weld heat affected zone (HAZ) in stainless

steels when this zone becomes sensitized. Microbiologically influenced

corrosion can also damage metals lined with polymeric materials, typically at

coating imperfections.

Once microbial films are established on metal surfaces, they are extremely

difficult to eliminate because of the resiliency of the individual

microorganisms. Biocides are applied by some licensees in areas where

continuous flow conditions cannot be maintained. However, biocide treatments

are not always effective against established microorganism colonies because

the biocide cannot penetrate through the tubercles or aerobic biofilms.

Treatment against established colonies involves a combination of mechanical or

chemical pipe cleaning, continued water treatment and regular maintenance.

Continuous flow conditions have been found to prevent the attachment and

growth of microbial films.

It may be necessary to replace materials if microbiologically influenced

corrosion severely damages them or where mitigation measures cannot bring the

system condition under control.

Possible alternatives include replacing

carbon steel with stainless steel or replacing stainless steel with more

resistant materials, such as 6-percent molybdenum stainless steels, nickel

base alloys, titanium, or nonmetallic materials.

The licensee did not regularly treat the Beaver Valley River water supply

lines to the diesel with biocide or corrosion inhibitors. The chlorination

injection point for the main river water headers is downstream of the branch

lines to the emergency diesel generators. It also appears that the existing

program at Haddam Neck of hypochlorite injection was not successful in

mitigating the microbiologically influenced corrosion problems in stagnant

dead-end lines at such locations as the emergency diesel generator supply.

IN 94-79 November 23, 1994 This information notice requires no specific action or written response. If

you have any questions 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.

Vv BaD

D ision f Project Support

Office of Nuclear Reactor Regulation

Technical contacts: Michael Modes, RI

James A. Davis, NRR

(215) 337-5198

(301) 504-2713 Peter P. Sena, RI

Vern Hodge, NRR

(412) 643-2000

(301) 504-1861 Attachment:

List of Recently ssued NRC Information Notices

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Attachment

IN 94-79

November 23, 1994 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information

Date of

Notice No.

Subject

Issuance

Issued to

94-78

94-77

94-76

93-60,

Supp. 1

94-75

94-74

94-73

94-72

94-71

Electrical Component

Failure due to Degrada- tion of Polyvinyl Chloride

Wire Insulation

Malfunction in Main Gen- erator Voltage Regulator

Causing Overvoltage at

Safety-Related Electrical

Equipment

Recent Failures of Charging/

Safety Injection Pump Shafts

Reporting Fuel Cycle

and Materials Events to

the NRC Operations Center

Minimum Temperature

for Criticality

Facility Management

Responsibilities for

Purchased or Contracted

Services for Radiation

Therapy Programs

Clarification of Critical- ity Reporting Criteria

Increased Control Rod

Drop Time from Crud

Buildup

Degradation of Scram

Solenoid Pilot Valve

Pressure and Exhaust

Diaphragms

11/21/94

11/17/94

10/26/94

10/20/94

10/14/94

10/13/94

10/12/94

10/05/94

10/04/94

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for pressurized water

reactors.

All 10 CFR Part 70

fuel cycle licensees.

All holders of OLs or CPs

pressurized-water reactors

(PWRs).

All U.S. Nuclear Regulatory

Commission Medical

Licensees.

All fuel fabrication

facilities.

All holders of OLs or CPs

for pressurized water

reactors.

All holders of OLs or CPs

for boiling water reactors

(BWRs).

OL - Operating License

CP = Construction Permit

-

1/4<>

A~-'

IN 94-79 November 23, 1994 The licensee did not regularly treat the Beaver Valley River water supply

lines to the diesel with biocide or corrosion inhibitors. The chlorination

injection point for the main river water headers is downstream of the branch

lines to the emergency diesel generators.

It also appears that the existing

program at Haddam Neck of hypochlorite injection was not successful in

mitigating the microbiologically influenced corrosion problems in stagnant

dead-end lines at such locations as the emergency diesel generator supply.

This information notice requires no specific action or written response.

If

you have any questions 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.

Original signed by B.D. Liaw for

Brian K. Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts:

Michael Modes,

(215) 337-5198 RI

James A. Davis, NRR

(301) 504-2713

Peter P. Sena, RI

(412) 643-2000

Vern Hodge, NRR

(301) 504-1861 Attachment:

List of Recently Issued NRC Information Notices

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DOCUMENT NAME:

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IN 94-XX

October xx, 1994 inhibitors.

The chlorination injection point for the main river

water headers is downstream of the branch lines to the emergency

diesel generators.

It also appears that the existing program at

Haddam Neck of hypochlorite injection was not successful in

mitigating the microbiologically influenced corrosion problems in

stagnant dead-end lines to such locations as the emergency diesel

generator supply.

This information notice requires no specific action or written

response.

If you have any questions 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.

Brian K. Grimes, Director

Division of Operating Reactor

Support

Office of Nuclear Reactor

Regulation

Technical contacts:

Michael Modes, Region I

(215) 337-5198

Peter P. Sena, Region I

(412) 643-2000

James A.Davis, NRR

(301) 504-2713 Attachment:

List of Recently Issued NRC Information Notices

  • SEE PREVIOUS CONCURRENCE

OFFICE

  • OGCB/DORS
  • REGION I
  • REGION I

NAME

CVHodge

JDMain

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-

IN 94-XX

September xx, 1994 stagnant dead-end lines to such locations as the emergency diesel

generator supply.

This information notice requires no specific action or written

response.

If you have any questions 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.

Brian K. Grimes, Director

Division of Operating Reactor

Support

Office of Nuclear Reactor

Regulation

Technical contacts:

Michael Modes, Region I

(215) 337-5198

Peter P. Sena, Region I

(412) 643-2000

James A. Davis, NRR

(301) 504-2713 Attachment:

List of Recently Issued NRC Information Notices

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IN 94-XX

September xx, 1994 This information notice requires no specific action or written

response.

If you have any questions 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.

Brian K. Grimes, Director

Division of Operating Reactor

Support

Office of Nuclear Reactor

Regulation

Technical contacts:

Michael Modes, Region I

(215) 337-5198

Peter P. Sena, Region I

(412) 643-2000

James A. Davis, NRR

(301) 504-2713 Attachment:

List of Recently Issued NRC Information Notices

  • SEE PREVIOUS CONCURRENCE

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NECK-MIC.INF


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