ML18153C487

Discusses Actions Taken to Reduce Biofouling in Svc Water Sys,Per 901219 Discussions W/G Bishop

ML18153C487
Person / Time
Site:	Surry
Issue date:	01/03/1991
From:	Marshall B VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Ronaldo Jenkins VIRGINIA, COMMONWEALTH OF
References
NUDOCS 9101110329
Download: ML18153C487 (3)

Text

Innsbrook Technical Center

. i 5000 Dominion Boulevard Glen Allen, Virginia 23060 January 3, 1991 Mr. R.R. Jenkins VIRGINIA POWER Virginia water Control Board 2201 West Broad Street Richmond, VA 23230 RE: SURRY SERVICE WATER SYSTEM BIOFOULING

Dear Mr. Jenkins:

This serves to confirm your discussions with Mr. Glenn Bishop on December 19, 1990 regarding corrective actions being taken at Surry Power Station to reduce biofouling (primarily hydrozoans and bryozoans) in the service water system. This past October, Unit 2 had to be taken off line at considerable expense due to biofouling problems evident in the recirculation spray heat exchangers (RSHX). These heat exchangers are safety related equipment and would be used for emergency cooling of the reactor if necessary.

In order to remedy the problems, several actions are being taken which are summarized below:

1. Portions of the recirculation spray heat exchanger's service water supply piping for both units are now being maintained in a "wet layup" condition using ammonium hydroxide (pH 9-10), 28% sodium bisulfite (50-100 ppm), and condensate grade make-up water (see attachment). Since. this is a safety related system, it must be tested quarterly, hence we anticipate a release of its contents (approx. 35k gallons per unit) on a quarterly basis. This release will occur either to the cooling water tunnel via its normal once-through flow path or will be alternately drained to a turbine building sump for release to the discharge canal.

2. In conjunction with the above effort, the 48-inch lines (2 per unit) supplying the RSHXs will also be targeted for biofouling control. This will be accomplished by disinfection with sodium hypochlorite (beginning in March 1991) and by alternatinq flows between these sunnlv lines nn "'l wRekly basis. Alternating flows in this manner will deprive the filter feeding animals of the current vel6city necessary to suspend their food source. Chlorine use will be in accordance with the VPDES limits on dosage frequency (2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> per unit per day, non-simultaneous) and effluent residual (.2 ppm) in the discharge canal.

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I *J, Mr. R.R. Jenkins January 3, 1991 Page 2

3. We have also entered into discus_sions with the Virginia Institute of Marine Science regarding the need for a seasonal evaluation of the environmental factors contributing to this problem. They will be tasked with providing input into the final recommendations for service water biofouling control which may include alternatives to chemical injection such as installation of strainers, travelling screen enhancements, anti-fouling coatings, etc.

These aggressive biofouling control efforts are in direct response to inquiries from the Nuclear Regulatory Commission which has requested that evaluations be performed to reduce the incidences of flow blockage in these systems due to biofouling. If you have any questions, please contact Glenn Bishop at 273-2988.

Sincerely, B. M. Marshall, P.E.

Manager Water Quality cc: u.s.N.R.C., Atlanta, Georgia, Docket #50/280-20-281 u.s.N.R.C., Washongton, DC, Docket #50/280-50-281 U.S.N.R.C., Senior Resident Inspector, Surry Power Station

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