ML20080C074
| ML20080C074 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 07/15/1983 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20080C072 | List: |
| References | |
| NUDOCS 8308190044 | |
| Download: ML20080C074 (3) | |
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 23 TO FACILITY OPERATING LICENSE NO. NPF-8 ALABAMA POWER COMPANY JOSEPH M. FARLEY NUCLEAR PLINT, UNIT NO. 2 DOCKET NO. 50-364 Introduction Farley Unit 2 Technical Specification 3/4.3.4, Turbine Overspeed Protection, specifies periodic surveillance testing of turbine valves to demonstrate valve operability. The surveillance requirements necessitate all turbine stop, governor, reheat stop and reheat intercept valves to be stroked through their complete cycle from their operational position on a weekly basis.
Alabama Power Company (APCo) proposed a one-time Technical Specification change by letter dated May 27, 1983, supplemented on July 13 and 15,1983.
By letters of July 13 and July 15, 1983, APCo advised that adherence to the above test schedule would impose significant operational difficulties.
In particular, the power reduction required to perform the test may lead to pressure and temperature transients in the reactor coolant pump seals which could lead to instability in the seal leakage flow rates.
Excessive seal leakage requires plant shutdown and replacement of the seal.
In order to avoid a potential early forced plant shutdown, APCo proposed the one-time change to the Technical Specifications which would exempt testing as required by surveillance requirements 4.3.4.1.2a, b, and c.
APCo requested expedited review of this request because required testing could cause conditions leading to plant shutdown.
Evaluation Steam enters the high pressure turbine through four throttle valves in series with four governor valves. Steam exits the high pressure turbine, flows through the moisture separator reheaters, and enters the low pressure turbines through four reheat stop valves in series with four reheat intercept valves.
The turbine is equipped with an emergency trip system that is designed to close the throttle, governor, reheat stop and reheat intercept valves in the event of turbine overspeed, low bearing oil pressure, low vacuum, or thrust bearing failure. An electric solenoid trip is provided for remote manual trips and various other trips. Turbine trip is effected by three overspeed sensors. The primary overspeed controls is provided by the Digital Electro-Hydraulic Control System which is set to produce a turbine trip at 103% of rated shaft speed.
The first backup overspeed protection is provided by a mechanical overspeed mechanism and trips the turbine at 111% of rated shaft speed. The secondary backup overspeed protection is provided by the electro-hydraulic control system if the rated shaft speed exceeds 111.5%. This redundancy in both valves and overspeed protection controls provides high assurance that turbine speed control will be maintained.
8308190044 830715 PDR ADOCK 05000364 P
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~As the reactor core nears end-of-life, cycling of the nuclear steam supply system imposes operational difficulties in maintaining the axial flux difference within the Technical Specification target band limitation.
The return to full power following turbine valve tests performed near the end of t
reactor core life necessitates the processing of significant amounts of l
In returning to full power, additional operational diffi-culties occur from overcoming negative reactivity due to xenon transients.
Recently the plant has experienced a brief increase in pump leakage in one of the reactor coolant pump (RCP) seals. The temperature transient associated with operations required for the turbine valve tests could cause additional instability in the sensitive seal. This situation is the reason for reducing the valve testing frequency on a more urgent basis than planned.
Such increases of leakage flow in a RCP seal are not uncomon for a seal near the end of its life. APCo has comitted to monitor the seal carefully during the remainder of the cycle. Should excessive first stage seal leakage occur the licensee has-comitted to shut the plant down and replace the seal, in accordance with plant procedures.
These power transients and the potential for delays in the return to power from the turbine valve tests on a weekly basis are unnecessary as the turbine valves and overspeed protection system have been demonstrated as highly reliable in the past. Based on relia,bility evaluations of the turbine valves presented by Westinghouse and APCo,. the staff concluded in our April 21, 1983 " Supplementary Safety Evaluation Report - Testing of Turbine Valves - Farley Unit 2" that there is not.a sufficient basis for totally deleting all turbine valve testing require-ments. However, the staff stated that an extension of the turbine valve testing interval from weekly to monthly is acceptable.
Based on this position, the staff now states that one turbine valve test must be run midway in the approximate two month period remaining until the next scheduled refueling outage due to comence in mid-September 1983.
By letter dated July 15, 1983, APCo has modified their earlier recommendation for the turbine valve test frequency of Technical Specifications 4.3.4.1.2a, b and c.
APCo proposed, and we agree, that only one test should be run between now and mid-September 1983, and that the test shall be run in the month of August.
We find that such a testing frequency approximates a monthly-test schedule, and hence does not constitute a reduction in any safety margin.
Summary The licensee proposed to reduce the turbine valve testing on a one-time basis from weekly to approximately monthly. Since this proposal does not involve any reduction of safety margin and is compatible with the previous staff evaluation, it is acceptable.
,. Final No Significant Hazards Consideration Determination On June 29, 1983, the Comission published a notice in the Federal Register (48 FR 29978) seeking public coments on its proposed determination that this amendment involves no significant hazards consideration. No public coments were received to date. However, at this time the licensee has identified additional operational circumstances which necesitate early issuance of the amendment. These circumstances, described in licensee letters dated July 13, and July 15, 1983, and discussed above justify this expedited action by the Comission. Without issuance of the amendment at this time weekly tests of turbine valves would be likely to jeopardize reactor coolant pump operation and to require a plant shutdown.
Since the next required turbine valve cycling must be accomplished by July 18, 1983, and unless we take this action in a timely way a plant shutdown would be likely next week. The State of Alabama was consulted on this matter and had no coments on the proposed determination. As discussed above, the reduction in turbine valve testing on a one-time basis from weekly to approximately monthly until mid-September 1983 would not constitute a reduction in safety margins.
The change does not involve a significant increase in the probability or consequences of an accident previously evaluated; or create the possibility of a new or different kind of accident from any accident previously evaluated; or involve a significant reduction in a margin of safety. Therefore, the Comission has made a final determination that the amendment does not involve a significant hazards consideration.
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 impact.
Having made this determination, we have further concluded that the amendment involves an action which is insig-nificant from the standpoint of environmental impact and, pursuant to 10 CFR 551.5(d)(4), that an environmental impact statement or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of this amendment.
Conclusion We have concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Comission's regulations and the issuar.ce of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Date:
1 5 1933 Principal Contributors:
M. Caruso J. T. Beard E. A. Reeves
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