ML20114C844

Final Deficiency Rept Re Microbiologically Induced Corrosion in Hxs.Initially Reported on 840601.All HXs Utilizing Lake Water for Cooling Medium Eddy Current Inspected for Microbiologically Induced Corrosion

ML20114C844
Person / Time
Site:	Wolf Creek
Issue date:	01/13/1985
From:	Koester G KANSAS GAS & ELECTRIC CO.
To:	Denise R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
KMLNRC-85-022, KMLNRC-85-22, NUDOCS 8501300549
Download: ML20114C844 (2)

Text

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KANSAS GAS AND ELECTRIC COMPANY THE ELFCTAIC COMPANY l

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Mr. R.P. Denise, Director y Wolf Creek Task Force f U.S. Nuclear Regulatory Conmission Region IV 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011 KMLNRC 85-022 Re: Docket No. STN 50-482 Subj : Final 10CFR50.55(e) Report - Microbiologically Induced Corrosion (53564-Kl41)

Dear Mr. Denise:

Wis letter provides the final report subnitted pursuant to 10CFR50.55(e) concerning microbiologically induced corrosion (MIC) in heat exchangers at Wolf Creek Generating Station (NCGS) . 'Ihis matter was initially reported on June 1, 1984 with supplenental information provided in the Reference.

In March,1984 leakage from the Stator Cooling Water System to the Service Water System was discovered. Eddy Current inspections determined that deep pitting characteristic of microbiological 1y induced corrosion were present.

The results of an investigation conducted by the Architect /Ergineer concluded that damage to this cmponent was a result of the activities of sulfate-reducing bacteria (SRB), which are responsible for MIC at Wolf Creek Generating Station.

Subsequently, all heat exchangers which utilize lake water for their cooling medium (i.e. components cooled by Service Water, Circulating Water, Essential Service Water) were eddy current inspected to determine the affects of MIC. MIC was found to be present on carbon steel water boxes and copper-nickel tubing (the strain of bacteria that affects stainless steel was not present at Wolf Creek) . Badly damaged portions of cmponents were replaced and all reaining portions of components were cleaned using a chenical, steam, or mechanical medium, to reove degraded material and destroy any active SRB, before returning the component to service.

Since Wolf Creek Generating Station's main condenser enploys stainless steel tubing, cleaning of the tube side of the condenser was deferred. Plans have been made to hydrolaze the condenser water boxes since they are composed of

! carbon steel. We condenser hot well was filled with water and its tenperature raised above 200 degrees farenheit for approximately fifteen minutes to destroy SRB introduced during the condenser hydrostatic testing which was performed using lake water. I I

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201 N. Market -Woctwta, Kansas - Mail Address: RO. Box 206 ) Wictuta, Kansas 67201 -Telephone: Area Code (316) 261-6451

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'Mr. R.P. Denise Page 2 i All water (Service Water and . Circulating Water) reintroduced into cleaned components was chlorinated to a concentration of 8.2 ppm free available chlorine . (FAC) ' for thirty minutes every eight hours. Essential Service Water was to be flushed with 9.2 ppm FAC periodically.

In September,1984 evidence of MIC was found once again. in Omnponent Cooling Water Heat Exchanger A. At this time,' visual exaninations, chenical/

biological analyses, and reviews of chlorination logs were performed.

Reinfestation had occurred, but was confined to carbon steel cwpsts, primarily water boxes. Carbon steel piping inspections showed no significant pipe wall thinning or pitting.

Virtually the same techniques for removing corrosion were used for a second time on all affected components. After an extensive reevaluation perfouned by Architect / Engineer using water sampling at various chlorine levels, it

was concluded that MIC had reoccurred because of inadequate chlorination e levels.

i As a result of this recurrence of MIC, Service Water System chlorination levels were increased to between 9.22 and 9.35 ppm free available chlorine

twety-two hours per day and Circulating Water System chlorination levels were changed- to 0.2 ppm total residual chlorine for two hours per day. The Essential Service Water System is receiving a separate chlorination systen

capable of providing chlorination equivilant to that of the Service Water System. . A sampling progran is being implemented to determine if control of j- sulfate-reducing bacteria is being maintained and plans for inspections of equignent are being established to assure the long term effectiveness of the j established chlorination program.

'Ihe aforementioned corrective actions will preclude any recurrence of MIC at

, NCGS. If you have any questions concerning this matter please contact me or l Mr. Otto Maynard of my staff.

Yours very truly, A N

! Glenn L. Koester Vice President - Nuclear GLK: dab '

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