ML20148E185
| ML20148E185 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 05/19/1997 |
| From: | Stanley H COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-89-13, NUDOCS 9706030008 | |
| Download: ML20148E185 (4) | |
Text
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(nmmonwraith 1.de.on Company liraidw tun! Generaling $tJtion Route a 1, liox 8 4 liracculle, lI. NHo"%I9 e
Tri N 1 %B8-2801 May 19,1997 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555
Subject:
Braidwood Station Units 1 and 2 NRC Dockets 50-456 and 50-457 Commonwealth Edison Company (Comed) Supplemental Response to NRC Generic Letter 89-13, " Service Water System Problems Affecting Safety Related Equipment", dated July 18,1989
Reference:
1.
K. Kaup (Comed) supplemental response to USNRC dated 10/27/94 2.
K. Kaup (Comed) supplemental response to USNRC dated 5/20/94 3.
K. Kofron (Comed) response to USNRC dated 7/25/91 l
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4.
NRC Generic Letter 89-13," Service Water System Problems Affecting Safety Related Equipment",
dated July 18,1989
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The purpose of this letter is to notify the NRC of a change being made to previous commitments by Braidwood f,tation in response to Generic Letter 89-13 (Reference 4).
l In Reference 1, Braidwood Station revised its response to the original GL 89-13 commitment (Reference 3). This revision stated that to ensure no shelled mollusks become permanently established in the essential service water system, a two-step treatment regimen will be followed when the Braidwood cooling lake transitions through 65 F in the spring and in the fall: Braidwood will inject Sodium Hypochlorite for twenty-three hours per day into one Unit's SX (essential service water) system for a two week period. The remaining hour per day will be used to treat WS (nonessential sersice water).
Braidwood will then inject Sodium Hypochimite for twenty-three hours per day into the second unit's SX system for a three week time period. The remaining hour will be used to i
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Document Control Desk Page 2 treat WS. Braidwood will continue with the SX system heat exchanger and cooler inspection program per GL 89-13 Guidelines on Trending Results to judge the performance of the biocide injection and to ensure that clams, corbicula, zebra mussels, or any other shelled mollusk do not become established in the SX system.
Section I of GL 89-13, titled" Surveillance and Control Techniques to Reduce Flow Blockage Problems Due to Biofouling" contains a specific recommended action which states: "For open-cycle service water systems, implement and maintain an ongoing program of surveillance and control techniques to significantly reduce the incidence of flow blockage problems as a result of biofouling." This discussion is limited to the chemical treatment control programs.
In our previous response (Reference 1), due to significant equipment limitations, a detailed two-part treatment scheme for the spring and fall was described to meet the intent of preventing the establishment of Asiatic Clams in the Braidwood Essential Sersice Water System. The following is a discussion of the changes being made to that commitment.
1 Discussion:
i Braidwood has recently installed 'and begun to operate a new biocide feed system which has the following design features: the system is designed to feed each train of the essential service water system (SX) separately and continuously, all year round; the system also treats the non-essential service water system (WS) separately and also continuously. The system will require periodic maintenance, and is not designed or intended to be mservice 10 <
of the time. Performsnce of this system is monitored through the System Engineer.
This system is designed to feed either sodium hypochlorite only or a combination of sodium hypochlorite and sodium bromide (which is a more effective biocide per pound applied). Operation of this system will allow control of flow blockage problems as a result of biofouling (including Asiatic clams) more effectively than any previous treatment scheme.
Braidwood Station Lake does not have any incidences of Zebra mussels, therefore treatment schemes currently do not need to attempt to control Zebra mussels. Asiatic clams, however, do remain a concern. As such, the new biocide feed system is designed to combat Asiatic clams. Should Zebra mussels become a concern, treatment methods to combat them will be developed. Braidwood Station continues to monitor for the presence ofZebra mussels.
Continuous chlorination or continuous chlorination /bromination is accepted industry-wide as the most effective biofouling control scheme available. Various technical publications (which are provided as an attachment to this letter) state that 2-3 weeks of chlorination at 1
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Document Control Desk Page 3 low levels (sl.0 ppm Cl ) are very eiTective at controlling both larvae and adult Asiatic j
2 Clams. The new system is designed to continuously apply sodium hypochlorite (and bromide for increased efTect) in adequate amounts to control even adult Asiatic clams.
Continuous feed at a lower level is all that is needed to maintain control of the larval stage of the Asiatic clam. In the event that Zebra mussels do become an issue at Braidwood Station. this system is designed for chlorination /bromination, which is at least as effective against Zebra mussels.
Therefore, 6:; a response to the chemical treatment portion of the prevention of flow blockage problems as a result of biofouling, Braidwood Station will operate its new biocide feed system as designed. This will significantly reduce the incidence of flow blockage problems as a result of"oiofouling.
If you have any questions concerning this response, please direct them to Terry Simpkin, Regulatory Assurance Supervisor, at (815) 458-2801 x2990.
Sincerely,
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I. Gene Stanley Site Vice Preside Braidwood Nuclear Generating Station Attachment 1
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A. B. Beach, Regional Administrator, Region III, NRC G. F. Dick, Project Manager, NRC C. J. Phillips, Sr. Resident Inspector, Braidwood Office of Nuclear Safety, IDNS oNonfid admasst nrr97102mt.&w l
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ATTACHMENT I
References:
Service Water Chemical Addition Guideline, Electric Power Research Institute, e
i TR-106229, July 1996.
Symposium on Condenser Macrofouling Control Technologies: The State of the Art, Electric Power Research Institute, CS-3343, December 1983.
Zebra Mussel Monitoring and Control Guide,' Electric Power Research Institute, l
4 TR-101782, December,1992.
Power Plant Chlorination-A Biological and Chemical Assessment, EA-1750, f
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l December 1981.
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