ML20004F009
| ML20004F009 | |
| Person / Time | |
|---|---|
| Site: | Surry, North Anna  |
| Issue date: | 05/22/1981 |
| From: | Sylvia B VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| 252, IEB-81-03, IEB-81-3, NUDOCS 8106160382 | |
| Download: ML20004F009 (4) | |
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Notary Public , 19_. My Commission expires: .e. s.. SEAL cc: Director, Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission Washington, D. C. 20555 TGil Mr. Steven A. Varga, Chief 3 Operating Reactors Branch No. 1 / Division of Licensing //[ Mr. Robert A. Clark, Chief Operating Reactors Branch No. 3 Division of Licensing h 819616c382 Attechnent Pag 2 1 NORTH ANNA UNITS 1 AND 2 RESPONSE TO I. E. BELLETIN 81-03 1. Mytilus cannot survive in freshwater,. therefore there are none present at North Anna. Corbicula was first identified in Lake Anna in 1979. Since that time, the population has increased rapidly making this, presently, the dominant l benthic organism in terms of biomass. 2. W en notified of the potential for clogging of water systems by Corbicula shells or shell debris, the most likely site for the accumulation of these organisms was visually inspected. The Unit 1 and Unit 2 fire system deluge piping strainers were removed and examined with no evidence of Corbicula shells or shell debris. This site was selected since it is a low velocity, ambient temperature system conductive to the growth I of Corbicula. This inspection was performed on May 5, 1981. l On May 15, 1981 two additional sites were selected for inspection: A. Circulating Water Intake Structure (Unit 2) - No evidence of Corbicula infestation observed. B. Service Water Reservoir (Units 1 and 2) - Corbicula was not obtained on the dredge sample. However, these have been observed by divers while performing inspections on Service Water Reservoir spray piping. In addition to these inspections, recent inspections of service water and behring cooling water system supply and return piping to and from various lubricating oil coolers were conducted in lieu of another problem I and there was no evidence of clan shells or shell debris at these ( locatioca 3. Corbicula, although present in Lake Anna, have not been found in poten-tially affected safety related piping systems. The small accumulation in the Service Water Reservior is not considered to be excessive at this i time. I 4. The potential for blockage caused by clam shells or shell debris is very low based on current inspections results and previous experience. However, to effectively monitor the increased population growth and the possible intrusions of Corbicula into the water systems, a periodic monitoring program is being incorporated into exis_ ting procedures for the inspection of piping components and various heat exchangers. This l program should be completed by September 1, 1981. 5. Corbicula was initially identified in Lake Anna in 1979. Since then, the population in the cooling lagoon areas has incrused rapidly as reflected in the 1980 Nonradiological Environmental Operating Report that submitted to the Nuclear Regulatory Commission on F - 1981. The was most recent substrate survey was obtained on April 20, * ) It is presently believed that the high density of Corbicula in the cooling lagoons is due to the relatively stable temperature throughout the year. The more drastic temperature changes in the general vicinity of the intake structure will limit the Corbicula population growth. ~ Attachment Pegn 2 SURRY POWER STATION l
- 1. E. BUIJ.ETIN 81-03 l
FLOW BLOCKAGE OF COOLING WATER TO SAFETY SYSTEM COMPONENTS Bf CORBICULA SP. AND MYTILUS SP. 1. Mytilus Environmental conditions in the James River in the vicinity of Surry Power Station are not suitable for Mytilus, with salinity being the limiting factor. Mytilus is a polyhaline to euhaline organism found rarely only near the mouth of Chesapeake Bay, more than 30 miles from the station. Corbicula A freshwater clas generally intolerant of salt water, Corbicula is normally found in the James River upstream from its confluence with the Chickahominy River. As a rule, they are not found at Surry except during 1-periods of high rainfall in the James River basin that result in extended2 l periods of fresh water in the area. Densities only as high as 2 per m l have been found on occasion in the Cobham Bay station discharge area, however, this number is not considered to be excessive. The Surry Power Station is located on the reach of the James River where salinities' can vary between fresh water and 15 ppt, during the course of any given year. The station intake is located approximately 6 miles l downstream from the discharge but slightly within one tidal excursion. From the site description provided it is possible that conditions infrequently exist whereby Corbicula can be found in the vicinity of the Surry intake. Such conditions, however, would be entirely dependent on adequate fresh water inflow to that area. I 2. There is good evidence available that neither of these organisms has affected systems at the station. During the current steam generator replacement outage maintenance - of systems and components using service l water have not disclosed shells or shell fragments identifiable as i I Corbicula or Mytilus. Maintenance action on service water sides of component cooling heat exchangers and charging pump service water systems as recent as March 1981 have disclosed some mud or silt accumulation but I no evidence of Corbicula infestation. "As found" inspections of service water piping to the recirculation spray heat exchangers revealed no shell ( fragments. 3. Not applicable. 4. As noted in 1 above, conditions exist infrequently for salinity condi-tions to be favorable for Corbicula survival at the station intakes. Such conditions however would be forecast by periods of extensive rainfall in the James River Basin which in turn would key additional environmental sampling and observations. - i Attachment Page 3 Current findings of the condition of service water piping and heat l exchangers cooled by service water indicate that the station's current practice of visual inspections appear to be sufficient. The station does not plan at this time to alter its practice. ~. The majority of station systems served by service water are either dry or i active. In this respect, the active systems, thru rising test eratures of the cooled fluids would be a first indicator of fouling and thereby would key investigative action. The temperatures of active systems cooled by service water are monitored at least six times per day. The results of thiz monitoring, when appropriate, initiates cleaning opera-tions and this has been the case in the past station operations. 5. The determination of the presence of Corbicula and Mytilus was made based on an " Ecological Study of the Tidal Segment of the James River Encompassing Hog Point" (Virginia Institute of Marine Science 1977) and j spot samples of the river in the vicinity of the station taken in April 1981. The spot river samples confirmed the findings of that report. Systems that have the potential for infestat. ion are component cooling i heat exchangers, charging pump heat exchangers cooled by service water and control room air conditioning systems cooled by service water. No Co'rbicula fouling has been observed at Surry Power Station. Diagnostic actions have*been outlined in paragraph 4 above. 1 l l l I l l l -