ML20004E988
| ML20004E988 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 05/22/1981 |
| From: | Thies A DUKE POWER CO. |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| IEB-81-03, IEB-81-3, NUDOCS 8106160302 | |
| Download: ML20004E988 (4) | |
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4aa SouTx Carnten STazzt, CHARI.CTTz, N. C. assos dI p.iY 27 A3: II A. C. THIES
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May 22, 1981 senion vie Passionar PRODUCTION AND TRANSMsSS4080
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50-269, -270, -287 IE Bulletin 81-03
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Dear Mr. O'Reilly:
Please find attached Duke Power Company's response to IE Bulletin 81-03 for Oconee Nuclear Station.
I declare under penalty of perjury that the statements set forth herein are true and correct to the best of my knowledge, executed on May 22, 1981.
Very truly yours,,
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A. C. Thies FTP/dj s Enclosure cc: Director Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission Washington, D. C. 20555 JG ll
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m DUKE POWER COMPANY OCONEE NUCLEAR STATION Response to IE Bulletin 81-03 May 22, 1981 I
For the past three years, the Oconee Nuclear Station (ONS) Environmental Monitoring Program has conducted a physical search of selected portions of Lake Keowee to determine the presence of Asiatic clans. Class, Corbicula sp., were. detected for the first time in September 1980 in the ONS intake canal, during the last survey performed at Lake Keowee.
Visual Examination of Potentially Affected Systems Amartap System: Amercap balls are collected and counted on a weekly basis. During the December 22, 1980 inspection on Unit 1, a small number of claa shells were found in the collection baskets. No clama have been found in the Amertap system in other inspections, and the December 22 discovery is the only occasion in which clams have been found anywhere in the station.
Condenser Cooling Water (CCW) System: The condenser waterboxes were No inspected for Unit 2 in November 1980 and Unit 3 in January 1981.
clams were found in the waterboxes.
Subsequent inspections of the CCW pump wells on May 1, 1981, showed clams present at the intake structure.
High Pressure Service Water (HPSW) Pur9 Motor Cooler:.Tne cooler was opened for maintenance in August 1980. No clams were found.
Recirculated Cooling Water (RCW) Hast Exchangers: The RCW Heat Exchangers were opened and cleaned during the Unit 1, Cycle 6 refueling ontage (first quarter of 1980). No clams were found.
Flow Tests of Potentially Affected Systems Fire Hose Stations: During 1980 and early 1981, all fire hose stations were tested for valve operation and fitw. During the test, all stations were flushed thoroughly. No clams were found and no evidence of flow restrictions were noted.
Low Pressure Service Water (LPSW) Pumps: Performance flow tests of the LPSW System through the Low Pressure Injection (LPI) and Decay Heat Coolers are conducted monthly. Also, flow through each of the Reactor Building Cooling Units is monitored continuously by the plant computer, No deviations from which provides an alarm if low flow is detected.
normal flow have been noted in either case.
HPSW Pumps: Performance tests are conducted monthly to ensure power No evidence of flow supply and adequate flow to the HPSW pumps.
restrictions have been recorded.
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M'ay 22, 1981 Pcgs 2 (Cont.)
Potential for Clam Intrusion The Oconee systems which use raw water from Lake Keowee, and therefore are most susceptible to Asiatic clam intrusion, are the Condenser Cir-culating Water (CCW) system, the Low Pressure Service Water (LPSW) system, and the Eigh Pressure Service Water (EPSW) system.
The CCW system provides cooling and service water to all three units through twelve 177,000 gpm CCW pumps. Each unit is furnished with four pumps and a single 186-inch diameter pipe for supplying condenser cooling water.
The potential for intrusion of clams into the CCW intake structure and pipes during low water level of Lake Keowee is no worse than during normal water level. Full pond level is 35.5 feet above the CCW pump suction inlet and, even with maximum lake draw down, a minimum level of 10.5 feet of i
water remains above the pump suction. Furthermore, a 3.5 feet clearance exists between the floor of the intake structure bay and the pump suction.
Therefore, a sufficient volume of water is provided during low lake level to preclude a significant increase in the velocity of inlet water to the pump suction.
The LPSW and HPSW systems receive their make-up watrr from the top of the 42-inch CCW crossover line. The CCW crossover line is connected, in turn, to the top of each unit's 186-inch CCW supply line. A difference in elevation of 24.5 f eet exists between the bottom of the main CCW supply line and the suctions of the service water pumps. Therefore, the possibility of introducing adult clams into the service water systems is considered to be extremely remote.
Asiatic Clam Control Methods Duke Power Company has had more than 10 years experience dealing with The Asiatic fouling caused by Asiatic clams at its generating facilities.
It clam has been present in the Duke service area since the mid 1960s.
became a nuisance at one of the fossil fueled plants in 1970 and a program of remedial actions was initiated to minimize the effects of the class.
As the clans extended their range throughout the Duke system, an ad hoc committee was formed in 1978 to deal with clas related problens at all Duke generating facilities. The committee is reviewing each plant to determine, in general, how best to protect raw water systems from fouling by clams.
If the clams become a nuisance at a plant, specific changes involving piping modification, maintenance procedures, and/or biocide application are developed on a c Se by case basis.
Through this ad hoc cennittee, Duke is assessing various control methods for use at Oconee should the clams become a problem. The methods currently i
under review include continuous or periodic chlorination of systems; installation of strainers at the inlet of components or systems; replace-ment of existing strainers with smaller mesh straining elements; periodic flushing of potentially affected lines; and, installation of flow and/or pressure measuring devices on various components and lines to assure
May 22, 1981 Pega 3 (Cont.)
adequate flow.
Past experience at Oconee has not shown the presence of clams f" Lake Keowee to be an impending problem. As discussed earlier, evidence of clams has not been detected in any Oconee systems except for tSe Amertap system, end no evidence of clam fouling has been detected whatsoever. As a pre-caution, however, maintenance procedures and performance criteria are currently being reviewed and evaluated for inclusion in a formal monitoring program to provide early detection of clam infestation of service water Detection of class may consist of differential pressure readings systems.
across an equipment item, examination of strainers and drainage discharge lines, and visual inspection of inlet heat exchanger heads and piping supply lines. Supply and discharge line flow rates to a piece of equipment may also be monitored. The criteria for the acceptable, minimum flow rate in a specific line are currently being evaluated. Flow monitoring will con-sist of either existing flow meters or manually operated, sonic flow meters.
Duke expects to have this monitoring program developed and implemented by October 1, 1981. The results of this program vill then be used to help Duke determine the need for each of the control methods currently under review and the e-hedule by which these methods should be Dnplemented.
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