ML20004D488
| ML20004D488 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 05/22/1981 |
| From: | Justin Fuller PUBLIC SERVICE CO. OF COLORADO |
| To: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| IEB-81-03, IEB-81-3, P-81151, NUDOCS 8106090457 | |
| Download: ML20004D488 (7) | |
Text
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Public service company ce ceascio 12015 East 46th Avenue, Nite 440; Denver, CO 80239 May 22, 1981 Fort St. Vrain Unit No.1 P-81151 gC3 3\4 40 4 e
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Mr. Karl V. Seyfrit, Director h.9' i y%
Region IV 'f
- JC: wem 0 31981 * ;l U.S. Nuclear Regulatory Commission .,i nwcu l-611 Ryan Plaza Drive, Suite 1000
,d Arlington, Texas 75011 '_;s.-
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Docket No. 50-257
Subject:
Response to IE Sulletin 31-03
Reference:
NRC lettar K.V. Seyfrit to C.K. Millen (G-81069) dated April 10, 1981
Dear Mr. Seyfrit:
This letter is in response to IE Sulletin 81-03 " Flow Block-age of Cooling Water to Safety System Components by Corbic-ula Sp. ( Asiatic Citn) and Mytilus Sp. (Mussel)" dated April 10, 1981. Public Service Company of Colorado's (PSC) response to IE Sulletin 81-03 " Actions to be taken by Licensees" items 1 through 5 are contained in Attachment A.
Very truly yours, M
J. K. Fuller, Vice President Engineering and Planning JKF/JRJ: pa Attachment cc: Director, Office of Inspection and Enforcement, Nuclear Regulatory Commission, Washington, DC 20555
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8106000 L\51
UNITED STATES OF AMERICA ,
NUCLEAR REGULATORY COMMISSION l In the Matter Public Ser/ ice Company of Colorado ) Docket No. 50-267 Fort St. Vrain Unit No. ) )
AFFIDAVIT J. K. Fuller, being duly sworn, hereby deposes and says that he is Vice President of Public Ser/ ice Company of Colorado; that he is duly authorized to sign and file with the Nuclear Regulatory Commission the attached response to the Notice of Violation identified in NRC Inspection Report 81-03; that he is familiar with the content thereof; and that the matters set forth therein are true and correct to the best of his knowledge, information and belief.
DY V K. Fuller Vice President STATE OF ' s.ud
)
- ) ss COUNTY OF W )
Subscribed and sworn to before me, a Notary Public in and for M WM"W of this .22 4 day of - , 1981.
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LNotary&fn Public i T/ C==!::!:.C::!r::J..- :;,:; 3
, 19_.
My commission expires
'U P-81151 ATTACHMENT A Page 1 of 5 PSC RESPONSES TO IE BULLETIN 81-03 FLOW BLOCKAGE OF COOLING WATER SAFETY SYSTEM COMPONENTS BY CORBICULA SP. (ASIATIC CLAM) AND MYTILUS SP. (MUSSEL)
- 1. The Asiatic clam (Corbicula species) currently does not inhabit either the South Platte River or the St. Vrain River in the vicinity of the Fort St. Vrain Nuclear Gen-erating Station (FSV). The South Platte River is the normal source of makeup water for the Circulating Water System, with the St. Vrain River serving as an alternate makeup source.
The FSV Ecological Monitoring Program was conducted by Thorne Ecological Institute at an intensive level of surveillance from 1972 until the program was disconti-nued (with the NRC's pennission) on December 31, 1979.
The Corbicula species was never identified in semi-monthly river sampling by the Thorne aquatic inverte-brate division.
The FSV Environmental Radation Surveillance Program, conducted for PSC by Colorado State University, began in 1968 and is currently in effect. Aquatic biota are col-lected from the South Platte and St. Vrain Rivers on a monthly basis April through September, and on a quar-terly basis October through liarch. Freshwater clams of the Corbicula species have not been discovered in the course of this sampling effort.
This Environmental Radiation Sur/eillance Program col-1ects fish, benthic organisms, vascular plants, and seston from four sample sites along the South Platte and St. Vrain rivers in the vicinity of FSV. The contractor who performs these sample collection services infonned PSC that although freshwater clams are not specifically searched for, they believe they would have discovered any Asiatic clams inhabiting the four river sampling sites. At PSC's requast Xeeton Rocky Mountain Fisheries Consultant 3 conducted a two day search (tiay 20 & 21, 1981) for Asiatic clams in numerous sites along the l
South Platte and St. Vrain Rivers in the vicinity of rSV. The numerous locations searched included the water intake areas of both rivers, the sides of the Circulat-
- ing Water settling basins (where suspended particulate l matter is precipitated before the water flows to the makeup storage ponds and is pumped to the Circulating Water cooling tower basin), and the river area where cooling tower blowdown discharges into the South Platte
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P-81151 ATTACHMENT A Page 2 of 5 River. This rather exhaustive search uncovered no evi-dence of Asiatic clams.
On April 7,1981, while the Main Condenser Circulating Water side was drained for maintenance, each of the three water boxes (inlet, outlet, and return) was thoroughly inspected, with samples scraped from the sides and subsequently analyzed. There were no clams or clamshells in any of these spaces. Likewise, mainten-ance was performed on the Turbine Generator Lube Oil Heat Exchanger, which is cooled by Service Water, in March 1981. There was no evidence of clams on the cool-ing water side of this heat exchanger. PSC therefore concludes that Asiatic clams are not present in the local environment of FSV.
The Aquatic Biota section of the FSV Environmental Radi-ation Surveillance Program has been upgraded to include nonitoring for Asiatic clams in the South Platte and St.
Vrain Rivers. The four existing river sample sites will be surveyed for Asiatic clams in conjunction with aquatic biota sample collections (monthly April-September, and quarterly October-March). This will in-crease detection probability should Asiatic clams inha-bit these rivers in the future.
- 2. No action required since PSC has confimed that Asiatic clams currently do not inhabit the FSV local environment.
- 3. No action required since PSC has confimed that Asiatic clams currently do not inhabit the local environment.
4.a The South Platte River is the normal source of makeup water for the Circulating Water System, with the St.
Vrain River serving as an alternate source. If Asiatic clams were to inhabit either of these rivers in the future, clams could possibly enter the Circulating Water Makeup System by way of the river intake pumping stations.
4.b Water from either intake source is pumped to one of two settling basins, (each settling basin has a capacity of about 2 million gallons), and from there to one of two makeup storage ponds (each makeuo storage pond has a capacity of about 10 million gallons.) The reactor can-not be operated at power unless the inventory in tha circulating water makeup storage ponds is at least 20 million gallons of water (FSV Technical Specification LC04.3.5). The Circulating Water Makeup System and its connections to the service water pump pit and to the l.
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P-81151 ATTACHMENT A Page 3 of 5 firewater pisnp pit are classified safety related since this system must provide makeup water to the service water punps and to the firewater pumps .following a Safe Shutdown Earthquake or a Maximum Tornado.
The design hold-up time of the makeup water in the set-tling basins is approximately 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br />, to precipitate any suspended particulate matter before water enters the makeup storage ponds. In all likelihood, mature Asiatic clams would settle to the bottom of these settling basins and would not enter the Circulating Water Makeup System. Clam larvae could swim to the suction of the Circulating Water Makeup Pumps, and thereby enter the Circulating Water cooling tower basin. The water in this basin is chemically treated to control corrosion, pH, biological fouling and foaming. The Corbicula lar-vae entering the Circulating Water cooling tower basin would be unable to survive the 0.6 ppm concentration of free residual Chlorine maintained in tnis system. It is not known whether adult clams could sur/ive continuous exposure to this level of chlorination. It is very un-likely that adult clams could reach the Circulating Water cooling tower basin from either the South Platte or St. Vrain Rivers, since they ,would settle to the bot-tom of the settling basings. It is also considered highly un'ikely that clams could enter the Circulating Water cooling tower basin or the Service Water cooling tower basin by moving upstream through the 42 inch di-ameter, 600 foat long Blowdown Line, common to both the Circulating Water and Ser/ ice Water Systems. A minimum flow of 1100 gpm is required to be maintained in this line, which would prevent clams from entering the cool-ing water systems from the downstream drainage ditch.
Thus the design configuration of the settling basins, makeup storage ponds, blowdown line, along with Circu-lating Water Chemistry requirements all canbine to pre-l vent infestation of the Circulating Water Sytem by Asi-atic clams. The Circulating Water System, which cools the main condenser, is not safety related, except for I seven al lines which provide for supplying circulating l water to the Ser/ ice Water System in an emergency.
The Service Water System, which includes the Reactor Plant (.coling Water System is, for the most part, safety relateo. The Service Water System receives its makeup water f om the Domestic Water System (Central Weld County dater District). Water fran six shallow wells ser/es as the backup source of makeup water. In an emerge icy, the Circulating Water Makeup Sytem can be l used t a rupply water to the Service Water cooling tower basin Also, in an emergency, the Circulating Water
P-81151 ATTACHMENT A l Page 4 of 5 1
Makeup pumps can be used to supply flow to the Service Water System. In any event, water entering this system, from either the' Service Watar Pumps, or in an emergency, from the Circulating Water Makeup pumps must pass through a 24 inch, duplex, basket type strainer having 3/16 inch perforations, with provisions for manual backwashing. Thus, if Asiatic clams were to enter the Service Water cooling tower basin (extremely unlikely since it is nomally fed by domestic water or shallow well water), only Corbicula larvae or clams smaller th' an 3/16" diameter could pass through the strainer. These immature Corbiculae will die upon exposure to the conti-nuous 0.6 ppm concentration of free residual chlorine.
Thus the makeup water sources, blowdown line situation, oresence of a strainer, and water chemistry requirements combine to prevent infestation of the Service Water Sys-tem by Asiatic clams.
Assuming Asiatic c1ams could somehow enter the Circulat-ing Water cooling tower basin and survive the chlorine, phosphate, pH, and low oxygen levels maintained in this water, a primary area of concern would be the safety related Firewater System, since the firewater pumps take a suction on water in the Circulating Water cooling tower basin. Piping blockage or partial blockage of flow paths in the Firewater ' System would likely be , ,
discovered during the semi-annual flush of the system required by FSV Technical Specification Surveillance ,
Requirament SR5.2.10. A flow test of this system is requii d to be perfomed at least once every three years by SRS.2.10.
, Nearly all of the Ser/ ice Water System safety.related heat exchangers are normally in operation. Any fouling of heat transfer surfaces or partial blockage of flow paths by Asiatic clams would be detected by the de-creased efficiency of the heat exchangers causing abnor-mally high temperatures of the fluid being cooled by Service Water. If infestation of Ser/ ice Water heat ex-changers and piping by Asiatic clams (previously noted
to be extremely improbable for this system) were not at l a high enough level to be detected by this means then l clams would likely be detected upon system maintenance.
Generally, maintenance is perforned on heat exchangers in the Ser/ ice Water System every three months. Inspec-tions associated with such maintenans vould detect the presence of Asiatic clams. PSC believes these detection methods will be very effective in discovering the pre-sence of Asiatic clams in any safety related systems.
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,, . P-81151 ATTACHMENT A Page 5 of 5 i l
5.a As noted in response to Licensee Action Item 1, PSC has upgraded the Aquatic Biota section of the FSV Environ-mental Radiation Surveillance Program, so that the South Platte and St. Vrain Rivers are surveyed periodically for any evidence of Asiatic clams. This will increase the probability of PSC quickly detecting the presence of these clams should they, in the future, inhabit either of these rivers in the vicinity of FSV. A two-day search of numerous sites in both rivers was conducted on May 21, 22, 1981 exclusively for Asiatic clams. No evi-dence of the existence of Asiatic clans in the vicinity of FSV was discovered.
5.b Not applicable.
5.c Not applicable.
5.d Not applicable.
5.e No. corrective action was necessary since Asiatic clams currently do not inhabit the FSV environment. No addi-tional preventive actions have been taken by PSC resul-ting from IE Bulletin 81-03. PSC believes that the design configuration of makeup water to the Service Water and Circulating Water Systems (which includes makeup to the Firewater System), the 500 foot blowdown piping with minimum 1100 gpm blowdown flowrate, and the Service Water System strainer, will prevent adult Corb-icula from entering these cooling water systems. Corb-icula larvae which enter would be eradicated by the 0.5 ppm free residual chlorine concentration continuously maintained in these sytems.
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