ML20041A015
| ML20041A015 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 02/02/1982 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20041A014 | List: |
| References | |
| NUDOCS 8202180477 | |
| Download: ML20041A015 (3) | |
Text
'a tag UNITED STATES o
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.r> ([,j NUCLEAR REGULATORY COMMISSION WASHINGTON. D. C. 205$5 g *-
' /j: p SAFElf EVALUATION BY'THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPCRTING NiENDf1ENT NO. 62 TO FACILITY OPERATING LICENSE NO. DPR-51 ARKANSAS POWER AND LIGHT C0t1PANY ARKANSAS NUCLEAR ONE, UNIT NO. 1 DOCKET NO. 50-313 4
Introduction i
30, 1981, supplemented by letter dated September 22, By lett.er dated January 1981, Arkansas Power and Light Company (AP&L or the licensee) proposed changes to the Technical Specifications (TSs) appended to Facility Operating License No. DPR-51 for Arkansas Nuclear One, Unit No.1 (ANO-1). The pro-posed amendment would provide limited conditions for operation and opera-tional and surveillance requirements for the Reactor Building Cooling Units (RBCUs) and would provide chlorination requirements for the service water l
sys tem.
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Background===
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As a result of discovering an inadequate service water few to the RBCUs for ANO-2 due to an intrusion of Asian Clams, corbicula sp., the licensee j
inspected and discovered a similar situation existed for AN0-1.
i The Asian Clam is a bivalve mollusc found abundantly in the warm, fresh waters of the United States. The Asian Clam is monoecius (_bi-sexuall, incubatory and precocious in reaching sexual maturity. This hardy clam reproduces prolifically when water temperatures range from 62 to 75 degrees 4
i Fahrenheit.
i Larvae discharged from adult clams are about 1/50 of an inch in diameter and are passively carried by water movement. Stagnant, or low flow areas provide suitable conditions for the larvae to grow into valved clams.
Valved larvae are greater than 1/32 inch in size and grow to mature adult i
clams (1.2 inches in si-ze) in approximately 36 to 42 months, At ANO-1, service wate'r suction is taken from Lake Dardanelle and is
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strained before entering the plant. Differential pressere measurements
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are checked onthe intake screens once per shift to prevent buildup of adult clams.
The current TSs only require a surveillance test of the ANO-1 RBCUs once
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every 18 months, and the test does not require a verification of a flow Apparently, during the previous surveillance test of the RSCUs requirement.
1 the Asian Clam larvae present in the service water were pumped with the water into the RBCUs. Upon completion of the surveillance test, some water was left stagnant in the RBCUs. The larvae present matured into 8202180477 e20202 PDR ADOCK 05000313
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PDR l
ANO-1 valved clams inside the heat exchanger tubes, affixing themselves to the tube walls, and thus causing flow blockage in the cooling units. Signifi-cant effort was expended in cleaning the cooling units and, placing them back into service.
We discussed the problem with the licensee's staff at a meeting of October 22, 1980.
During this meeting, the licensee comitted to imple-ment a 14-day surveillance of flow and chlorination of service water through the coolers and a 31-day system operational surveillance until a TS could be implemented similar tn the ANO-2 TS requirements.
The proposed amendment would implement operational and surveillance require-ments for the RBCUs and chlorination requirements of the service water system consistent with the requirements for ANO-2.*
The amendment also would modify the TSs to provide for limiting conditions for plant' operation in the event (1) one or two groups of RBCUs are in-operable, or (2) one group of RBCUs is inoperable and one reactor building spray system is inoperable, or (3) any cooling unit of the required groups is inoperable because its associated fan is inoperable.
Consistent with the Final Safety Analysis Report, this would assure operability of minimum equipment sufficient to provide heat removal capability during reactor operation to maintain reactor building pressure following an accident below the design value at all times.
Evaluation As stated above, the proposed TSs provide for limit'ng conditions for operation which would assure operability of minimum equipment sufficient to provide heat removal capability during reactor operation to be able to maintain accident reactor pressure below the design value at all times.
In addition, the augmented urveillance 'of flow with chlorination will assure mortality for non-valved larvae in the service water system and the detec-tion of valved larvae or other flow clogging mechanisms before rendering the RSCUs incperable.
Although the proposed TS change only deals with the problem of clams in s the containment cooiing units, they have been observed to exist in other portions of the service-water system. However, the potential for clams blocking flow in other portions of the service water piping system is not considered-as great because clams tend to grow best in stagnant or low flow conditions. The containment cooling units provided this stagnant volume of service water.
In any event, the plant operators have been alerted ~to watch for tell-tale signs of clam buildup throughout the plant's service water system.
The proposed TSs do not reduce the margin of safety, and therefore, we find tha proposed TSs acceptable.
Letter dated October 9,1980, Robert A. Clark (DL/NRR/NRC) to William Cavanaugh, III (AP&L).
3-Environmental Consideration We have detennined that the amendment does not authorize a change in effluent types'or total amounts nor.an increase in power level and will not result in any significant environmental impagt. Having made this determination, we have further concluded that the amendment involves an action which is insignificant from the standpoint of environmental impact and, pursuant to 10 CFR 551.5(d)(4), that an environmental impact statement, or negative declaration and environ-mental impact appraisal need not be prepared in connection with the t
issuance of this amendment.
Conclusion We have concluded, based on the considerations discussed above, that:
(1) because the amendment does not involve a significant increase in the probability or consequences of accidents previously considered and does not involve a significant decrease in a safety margin, the amendment does not involve a significant hazards consideration, (2) there is reasonable assurance that the heal.th and safety of the public will not be endangered by operation. in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's
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. regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
i Dated:
February 2,1982 The following NRC staff personnel have contributed to this Safety Evaluation: Guy Vissing.
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