ML20010A737
| ML20010A737 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 07/20/1981 |
| From: | Withers B PORTLAND GENERAL ELECTRIC CO. |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| IEB-81-03, NUDOCS 8108120152 | |
| Download: ML20010A737 (3) | |
Text
- ?'
Docket No. 50-344/81-03 L1 /
s
' D,
/D,Y.,,,q$ -
m m
'3-Pbrtland Genetal BectricCorigxurf og C
' ' of ~
1
- (
futD m m Vce Prow 4 4
July 20, 1981 Trojan Nuclear Plant Docket 50-344 License NPF-1
<I M f Mr. R. H. Engellen, Director e
pr-I L
U. S. Nuclear Regulatory Commission gk 3
Region V fl{yg y *9 7
i Walnut Creek Plaza, Suite 202 1990 N. California Blvd.
bg DJ'groes Walnut Creek, CA 94596 g
Dear Mr. Engelken:
hl' This letter is in response to IE Bulletin 81-03 of April 10, 1981 concerning flow blockage of cooling water to safety system components by Corbicula sp. (Asiatic Clam) and Mytilus sp. (Mussel). The Mytilus sp., being a salt-water marine bivalve, is not found at the Trojan Nuclear Plant.
Since 1976, the Corbicula sp. have been known to be present in the l
Intake Structure of the Trojan Nuclear Plant. Their presence is indi-cared by frequent appearances in the weekly traveling screen wash water collections. The most recent sample was collected from the screen washings on July 15, 1981 and confirmed their presence.
In February 1981 a routine inspection of the off-line Bearing Cooling Water Heat Exchanger (6 in. diameter piping) revealed the. presence of Corbicula sp. in sediment deposited on the service water side of the heat exchanger. The clams were not large enough to cause any flow blockage of the system and were mechanically removed.
Prior to the inspection the heat exchanger had been off-line for about 1 year with optimal conditions for intrusion and growth of the clams due to low flow (approximately 1 gpm) and sediment deposition. The low flow was the result of a leaking valve on the outlet side of the heat exchanger. The parallel heat exchanger in this system, which had been in operation, was inspected and had no trace of clams or sediment. In light of these inspection results and in response to the requirements of IE Bulletin 81-03, inspections of a Component Cooling Water lleat Exchanger (30 in. diameter piping) and an Emergency Diesel Generator Lube Oil Cooler (6 in. diameter piping) were conducted.
These heat exchangers have either low flow or previously identified sediment problems. No trace of clams or sediment were found in either 0108120L 910720' PDR ADOCK
- )OO344 '
O PDR:
ll 121 S W Samon SPeet. Poant1 Oregon 97204 g
p.e.
j Podlarid Getual Electric Cai,xuif Mr. R. H. Engelken July 20, 1981 Page two inspection. An inspection of the Cooling Tower Basin during the 1981 refueling outage also revealed no trace of the Corbicula sp.
The Trojan Nuclear Plant Technical Specifications require periodic surveillance testing and inspection of the Fire Proteccion System to detect any flow blockage and to flush debris from the system. Hydrant flushing is required annually, spray headers and nozzles are inspected every 18 months, hose station flushing occurs every 3 years and a system flow test is performed every 3 years.
In March of this year the 3-year flow test commenced using calibrated flow and pressure instrumentation. The results available from this test indicate no flow degradation has occurred. Annual system flushing was completed on April 28, 1981 with no clams or debris consisting of their shells found. To date, there has been no evidence of the presence of the Corbicula sp.
in the Fire Protection System.
In addition to the methods of detection presented above for the Fire Protection System, routine maintenance and chemistry inspections are conducted of components in the Service Water and Circulating Water Systems. These inspections are scheduled on a rotating basis such that all heat exchangers are inspected in a 2-to 3-year period. Annual inspections are conducted of the Intake Structure with cleaning performed as necessary.
The greatest potential for intrusion of the Corbicula sp. into the Trojan Nuclear Plant cooling water systems occurs during clam spawning System strainers and screens prevent intrusion of adult seasons.
clams and shells, but allow larvae to enter the systems. The clam larvae require sediment for growth since they do not have the ability l
to attach to the surfaces of piping or heat exchangers. Effective prevention methods, therefore, are the elimination of sediment from the systems and chlorination to kill the larvae.
Inspection, testing and flushing methods mentioned above effectively eliminate sediment deposition.
Weekly Service Water and Circulating Water System chlorination to a concentration of 1 to 2 ppm for 30 minutes is used to kill clam larvae.
These methods have proven effective for control of the Corbicela sp.
I at the Trojan Nuclear Plant and will be continued.
1 W M M C 0tT4 Mbef j
7 Mr. R.11. Engelken July 20, 1981 Page three No further action is necessary in response to this issue.
If you should have any questions, please do not hesitate to contact me.
Sincerely, W2 Bart D. Withers Vice President Nuclear Subscribed and sworn to before me this 20th day of July 1981.
ALdo 4
w a
Notary Public of Oreg4n My commission expires: August 9, 1983 c:
Mr. Lynn Frank, Director State of Oregon Department of Energy Director Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission Washington, DC 20555