ML20009D876
| ML20009D876 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 07/09/1981 |
| From: | Parker W DUKE POWER CO. |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| IEB-81-03, IEB-81-3, NUDOCS 8107240454 | |
| Download: ML20009D876 (4) | |
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Vicr Pats 40tMT TcL t pwon t:Anta 704 27 -'o82 src.- Paoouctio" July 9, 1981 Mr. James P. O'Reilly U. S. Nuclear Regulatorv Commission
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9 Region II
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101 Marietta Street, Suite 3100 I $( U L.l L
Atlanta, Georgia 30303 Re: RII:JPO M
Oconee Nuclear Station u.5 %s'sY
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Docket Nos. 50-269, -270, -287 7
f6 S. E.Bulletin 81-03 9
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Dear Mr. O'Reilly:
Duke Power Company's initial response to S. E.Bulletin 81-03, submitted to your office by Mr. A. C. Thies's letter of May 22, 1981, inadvertently did not address the fire protection system at the Keowee Hydro Station.
However, on May 26, 1981, during a fire hydrant test at the Keowee Hydro Station, Asiatic clams were discovered in the fire protection system.
Please' find attached Revision 1 of Duke Power Company's response to the subject bulletin.
I declare under penalty of perjury that the statements set forth herein are true and correct to the best of my knowledge, executed-on July 9, 1981.
.Very ruly yours,
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William O. Parker, Jr JLJ/php Attachment cc: Director Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission 3
Washington, D. C. 20555
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~4 DUKE POWER COMPANY OCONEE NUCLEAR STATION Response to IE Bulletin 81-03 Revision 1 For the past three years, the Oconee Nuclear Station (ONS) Environmental Monitoring Program has conducted a physical search of selee =d portions of Lake Keowee to determine the presence of Asiatic clams.
Clams, 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 Asertap System: Amertap balls are collected and counted on a weekly basis.- During the December 22, 1980 inspection on Unit 1, a small number of clam shells were found in the collection baskets. No clams 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) Systen: The condenser waterboxes were inspected.for Unit 2 in November 1980 and Unit 3 in January 1981. No 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) Pump Motor Cooler:
The cooler was opened for maintenance in August 1980. No clams were found.
Recirculated Cooling Water (RCW) Heat Exchangers: Tha RCW Heat Exchangers were opened and cleaned during the Unit 1, L cle 6 refuel-ing ontage (first quarter of 1980). No clams were found.
Fire Protection System at Keowee Hydro Station:
On May 26, 1981, during a fire hydrant test at Keowee, clams were discovered in the i
fire protection system.
Flow Tests of Potettially Affected Systems Fire Hose Stations: During 1910 and early 1981, all fire hose stations were tested for valve operation and flow.
During the test, all stations were flushed thoroughly. No clams were found and no evidence of flow restrictions re noted.
Low Pressure Service Water (LPSW) Pumps: Performance flow tests of the LPSW System through the Low Pressura 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, which provides an alarm if low flow is detected. No deviations from normal flow have been noted in either case.
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DUKE POWER COMPANY-Response to IE Bulletin 81-03 Revision 1 July 9, 1981 Page 2 - Cont.
HPSW Pumps. Performance tests are conducted monthly to ensure power supply and adequate flow to the HPSW pumps. No evidence of flow restrictions have been recorded.
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 Circulating Water-(CCW) system, the Low Pressure Service Water (LPSW) system, and the High Pressure Service :fater (HPSW) 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 structare 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 water remains above the pump suction. Furthermore, a 3.5 feet clearance exists
-between the floor of the intake structure bi/ and the pump suction. There-fore, a sufficient volume of water is provided during low lake level to tre-clude a significant increase in the velocity of inlet water to the pump suction.
The'LPSW and HPSW systems receive their make-up water 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 eleva-tion of 24.5 feet 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 fouling caused by Asiatic clams at its generating facilities. The Asiatic clam has been present in the Duke service area since the mid 1960s.
It 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 clams. As the clams extended their range throughout the Duke system, an ad hoc committee was formed in 1978 to deal with clam related problems 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 case by case basis.
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DUKE POWER COMPANY Response to IE Eulletin 81-03 Revision 1
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July 9, 1981 Page 3 - Cont.
Through this ad hoc committee, Duke is assessing various control methods for l
use at Oconee and Keowee should the clams become a problem. The methods 1
currently under review include continuous or periodic chlorination of systems; installation of strainers at the inlet of components or systems; replacement 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 adequate flow.
Past experience at Oconee has not shown the presence of clams in Lake Keowee to be an impending problem. As discussed earlier, evidence of clams has not been detected in any Oconee systems except for the Amertap system, and no evidence of cism fouling has been detected whatsoever. As a precaution, however, maintenance procedures and performance criteria are currently being reviewed and evaluated for inclusion in a formal monitoring program to pro-vide early detection of clam infestation of service water systems. Detection of clams may consist of differential pressure readings across an equipment item, examination of strainers and orainage discharge lines, and visual in-spection 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 fic's rate in a specific line are currently being evaluated. Flow monitoring will consist of either existing flow meters or manually operated, sonic floi meters.
Duke expects to have this monitoring program developed and implemented by
-October 1, 1981. The results of this program will then be used to help Duke determine the need. for each of the control methods currently under review and the schedu_e by which these methods should be implemented. The actions required to insure adequate component flow rates will be accomplished 1
by August 15, 1981 on the Keowee Hydro Station fire protection system.
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