ML20009D595

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Responds to IE Bulletin 81-03, Flow Blockage of Cooling Water to Safety Sys Components by Corbicula Sp (Asiatic Clam) & Mytilus Sp (Mussel). Util Has Adequate Warning Sys Re Presence of Corbicula Before Plant Safety Is Affected
ML20009D595
Person / Time
Site: Clinton  Constellation icon.png
Issue date: 07/14/1981
From: Wuller G
ILLINOIS POWER CO.
To: Kepple J, James Keppler
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
IEB-81-03, IEB-81-3, U-0256, U-256, NUDOCS 8107240206
Download: ML20009D595 (2)


Text

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ILLINO/S POWER OOMPANY f9 z9y_3gy_g ffy 500 SOUTH 27TH STREET, DECATUR, ILLINOIS 62525 July 14, 1981 O

Mr. James G. Keppler NV~ '$

Director, Region III gy P ,ll y q.

Office of Inspection & Enforcement d( . k Y g) s U.S. Nuclear Regulatory Commission '

799 Roosevelt Road d_. JUL 2 31981 m i Glen Ellyn, Illinois 60137 ( v.5 eu,mgro= ,

Dear Mr. Keppler:

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Clinton Power Station Units 1 & 2 ^

Docket Nos. 50-461 and 50-462 Construction Permits No. CPPR-137 & CPPR-138 This is in reply to IE Bulletin No. 81-03, " Flow Blockage of Cooling Water to Safety System Components by Corbicula Sp. (Asia-tic Clam) and Mytilus Sp. (Mussel)".

Lake Clinton has been sampled quarterly since May 1974 and no evidence of the Corbicula species (Asiatic Clams) has ever been found. Central Labs have extensive firsthand experience in control-ling Asiatic Clams at some of IP's coal-fired plants, and we plan to use their proven control techniques should the clams appear at the Clinton Power Station (CPS). If Asiatic Clams were present at CPS, the major systems affected would be circulating water, plant service water, shutdown service water, and fire protection.

Since the summer of 1978, Central Labs have conducted the quarterly benthos sampling in six locations in and below Lake Clinton. This program is outlined in chapter 6, " Effluent and Environmental Measurements and Monitoring" of the Clinton Power Station Environmental Report - Operating License Stage (ER-OLS).

The most recent sample was taken in May 1981 and revealed no evidence of Asiatic Clams. After work is completed in the pump suction area of the screes house and it is filled with lake water, monitoring will begin inside the screen house. This will be the most likely location to find the clams since it will be free from their natural predators. gl Because of the different types of systems affected, the CPS control program (if Asiatic Clams are found at Lake Clinton) will y,, /

be in two parts. Flow-through systems (circulating water and parts lP of plant service water) would be clogged by large clams which come through the traveling screens as larva (veligers) and mature in the screen house. Static standby systems (fire protection and shutdown c107240206 810714

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. U-0256 L08-81(07-14)-6 Mr. James G. Keppler Page #2 service water) would be additionally threatened by veligers entering the piping and maturing there.

James A. Smithson, Supervisor of Field Biology for IP, presented a paper to the 43rd Annual Meeting of the American Power Conference, April 27-29, 1981 entitled " Control and Treatment of Asiatic Clame in Power Plant Intakes". It outlines a method of periodically killing the clams that have accumulated in the screen house before they grow large enough to cause blockage. This method involves pumping sodium-metabisulfite (Na 9 S, O c ) to the bottom of the screen house which creates an anerobic condtidn that asphyxiates the clams.

Since the process requires the pumps shutdown for approximately three days, this would be done in each section of the screen house separ-ately. Vital components would always have water available. Treat-ment would be performed often enough so the shell sizes would remain small enough to prevent condenser tubes in free-flowing systems from

,Pl ugging.

~The greater threat of small clams getting into the stagnant systems will be handled by using chlorination. Both 'ack-up systems are normally supplied by plant service water which aiready has an automatic chlorination system and 1/16" screens. No additional chlorination system will be needed. When an incident occurs requir-

'ing operation of the fire protection or shutdown service water pumps, unchlorinated water would enter the systems. Therefore, after such an event, operating procedures will require flushing all normally stagnant systems with chlorinated plant service water. Ir normal testing of the pumps, the flow will be bypassed and not enter the main header.

Smithson's' paper reported having killed over 90% of the clams with the anaerobic method when the water temperature is above 75 F and hydrogen sulfide (H S) is also used. It also states chlorine at .5 ppm for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> dill result in 100% mortality of veligers.

Although the plant service water system's chlorine concentration may be less than that, it is felt the lower concentration will be effective since the water will remain stagnant longer than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

Through it's environmental monitoring program, CPS feels it will-be adequately warned of the existence of Corbicula before their presence affects plant safety. Should they be detected, a combina-tion of periodic oxygen depletion in the screen house to kill the adults plus screens and chlorine to kill the veligers in static systems, should keep fouling to a minimum.

S' ere y, 1

G. E. Nblier, Supervisor Licensing Nuclear Station Engineering GEW/em cc: Mr. H. H. Livermore, NRC Resident Inspector

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Director, Office of I & E, NRC, Washington, D. C.