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 Office of Nuclear Reactor Regulation
To:
References
IN-94-079, NUDOCS 9411170039
Download: ML031060426 (9)

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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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 K>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*err DDrFlVT) rnCUriRFNrEN

OFFICE *OGCB/DORS

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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

• 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

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INY

-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.-- "tf A R'lena-*QVV DPRVUSTnT1 CONCURRENCE

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BKGrimes__/__ /94 09/ /94 09/ /94 DOCUMgNT NAME: NECK-MIC.1fir

A-- 016 I 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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TECH ED A REGION I REGION I NAME CVHodge k ^JDMain MCModes PPSena DATE 1 O9/08/94 09/09/94 09/01/94 09/ /94 ADD:DRS/REGION

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BKGrimes 09/ /94 09/ /94 09/ /94 DOCU;MENT

NAME: NECK-MIC.INF