ML19347F155
| ML19347F155 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 04/29/1981 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| IEB-81-03, IEB-81-3, NUDOCS 8105150348 | |
| Download: ML19347F155 (2) | |
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SACRAMEt'TO MUfJICIPAL UflLITY DISTRICT O 6201 S Street. Box 15830. Sacramento. Cahfornia 95813; (91f,) 452 3211 gf[pdS, 3
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.O e q Q12"g'4 R H ENGELKEN, DIRECTOR REGION V 0FFICE OF INSPECTION AND ENFORCEMEt U N
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U S NUCLEAR REGULATORY COMMISSION 1990 NORTH CALIFORNIA BLVD WALNUT CREEK PLAZA, SulTE 202 WALNUT CREEK CA 94936 IE BULLETIN 81-03 FLOV BLOCAAGE OF COOLING WATER TO SAFETY SYSTEM COMPONENTS BY CORBICULA SP.
(ASI ATIC CLAM) AND MYTILUS SP. (MUSSEL)
The subject Bulletin ~ requires a determination whether either of the subject organisms are present in the source or receiving water bodies in the vicinity of Rancho Seco.
The response to the basic question is no.
Evidence of Corbicula sp. has not been found in the Folsom South Canal (the plant water source), Rancho Seco Reservoir (an alternate source), cooling towers, condensers, plant cooling water system (including component cooling water coolers), nuclear raw water sys tem (including nuclear service spray ponds and coolers), the plant effluent stream and various other locations which might reasonably provide a groath medium.
Nearly all of these locations have been inspected as recently as February 1981, during the most recent refueling outage.
A major study of biological organisms in water supplies was performed in 1979 as a Fish Impingemen t and Entrainment program required by EPA; in that study, no evidence of Corbicula sp. was found.
In 1974 and 1975, examination of biological growths in the cooling tower circui t was done to develop an adequate algal control technique; there was no indication of clams in that program.
In contrast to these negative findings, the presence of Corbicula sp. is well documented in many of the major California aquaducts (California Aqua duct and Del ta-Mendota Canal in particular) and recently the clam has been observed in Folsom Lake and Natomas Reservoir which are the water source of Folsom South Canal.
in the opinion of biologists associated with the Calif-ornia Water Resources Department, it is only a matter of time for migration of the clam into Folsom South Canal; it is reported that the nutrient supply 8_105150gyg n me
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- l V R.-H.:Engelken ApriI 29, 1981 is very meager under-current flow conditions In the Canal and, therefore,.the clam intrusion will take place very slowly.
in completion of the requirements under Bulletin 81-03, a program for detection of Corbicula sp. will be prepared, it will make use of relatively frequent inspection of screens at the plant supply pump station, and regular in.pections
.of condenser water boxes, spray ponds and heat exchangers which have open circuit cooling.
The particular configuration of water supplies at Rancho Seco is not subject to low water level /high velocity intake conditiont.
When this clam watch detects Corbicula sp. In the plant systems, an increased surveillance. program will be initiated to insure that mitigating measures are ef fective and that all potentially invaded areas are controlled. 'Hethods of reducing any clam population will include chlorination, including heavy shock treatment (which is used now occasionally to remove algal bui ldup), elevated temperatures, mechanical cleaning, and probably blocides, as found acceptable by the California Water Quality Control Board.
L Arca John. Mattamoe Assistant General Manager and Chief Engineer
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