ML20080F241
| ML20080F241 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 01/27/1984 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20080F239 | List: |
| References | |
| TAC-48973, TAC-52539, TAC-52540, TAC-53434, NUDOCS 8402100401 | |
| Download: ML20080F241 (6) | |
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[j NUCLEAR REGULATORY COMMISSION UNITED STATES x-y, x.
MNGTON. D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 41 TO FACILITY OPERATING LICENSE NO. ?!PF-2 AND Af'ENDMENT N0.
32 TO FACILITY OPERATING LICENSE NO. NPF-8 ALABAMA POWER COMDANY JOSEPH M. FARLEY NUCLEAP PLANT, UNIT NOS. 1 AND 2 DOCKET NOS. 50-3a8 AND 50-364
- '!TRCDUCTION In letters dated October 8,1982 (with attachment) and January 18, 1983 Alabama Power Company (APCo) requested a license amendment to delete, in its entirety, that portion of the Standard
- Technical Specification (STS) 3/4.3.4 " Turbine Overspeed Protection," that requires testing of turbine valves from F&rley Nuclear Plant Unit 2 Technical Specifications'.
Subsequent discussions and correspondence with the staff resulted in two appeal meetings one in March 23, 1983 and the other on August 16, 1983.
The conclusion of the August 16, 1983 appeal meeting resulted in a staff agreement to consider deletion of turbine valve testing reouirements from the Unit 2 turbine overspeed protection technical specifications proviced that APCo submit a detailed description of the cemorehensive turbine valve maintenance, calibration, test and inspection program discussed at the two appeal meetings for staff review and concurrence and a technical specification change to reference this program.
The description of their proprietary comprehensive turbine valve testing program entitled " Turbine Overspeed Reliability Assurance Program" and the revised technical specifications were submitted with the APCo letter dated October 6,1983.
In this submittal APCo also provided revised
. Technical Specifications to implement this program'on Farley Unit 1.
APCo management requested an Assistant Director Level Aopeal Meeting for March 23, 1983.
At this meeting representatives of APCo and Westinghouse's Nuclear Energy Systems and Steam Turbine Design Divisions made nresentations to the staff to support the APCo reouested STS deletion. Westinghouse presented results of a study WCAP-10162
" Evaluation of Reduced Testing of Turbine Valves" on the generation of turb.ine missiles prepared specifically for the Farley Turoines and preliminary results of an ongoing generic study on the generation of turoine missiles being conducted on behalf of some licensees and applicants.
Both of these studies include consideration of the testing requirements for the tur2 ne overspeed protection valves on turbine valve arrangements as installed at Farley Unit 2.
Although the results of the generic study were not final, both studies indicate that turoine 8402100401 840127 PDR ADOCK 05000348 P
valve operability and reliability would not be significantly affected by increasing the periodic valve testing from the cresent weekly to a much longer interval.
In Westinghouse's judgement, lack of significant number of valve failures, good operating experience, and a well planned maintenance calibration test and inspection program provide reasonaDie bases to increase the periodic test interval for turoine with steam chest and valve arrangements as installed at Farley Unit 2 from weekly to a substantially greater interval.
However, Westinghouse stated that althougn both studies indicate that turbine valve testing can be extended (up to several months) with minimal effect on the probability of turbine missile generation, for various other reasons and for protection of equipment and personnel, it is their recommendation to extend testing of turbine valves from weekly to monthly on nuclear turoines of the type installed at Farley.
Westinchouse was to make a for al recommendation to their customers who have turbines employing turbine valves and steam chest arrangements as installed at Farley Unit 2, to change from periodic weekly to monthly valve testing.
Since the March 23, 1983 meeting Westinghouse has issued this foAnal recommendation to their customers who have these types of turbines.
At this meeting APCo also presented their arguments for totally deleting turbine valve testing and inspection requirements from the plant Technical Soecifications for Farley Unit 2.
APCo believes their turbine valve maintenance, calibration, testing and inspection program, carried out at some sce'cified interval (greater than one month) is sufficient to orovide assurance of valve operation on demand.
Their program encompasses an intensive and effective turbine valve. maintenance program to preemot valve failures coupled with a periodic testing, calibration and a thorough inspecticn of valve internals by valve disassembly on alternate refuelling outages.
The internal inspection would cover one of each valve type installed on the Farley Unit 2 turbine.
In the event a valve problem is discovered, a.ll turbine valves of that tyce would be disassemoled and the problem Corrected.
DISCUSSION AND EVALUATION The staff's current position which recuires weekly testing of turoine valves as stated in Standard Review Plan Section 10.2 " Steam Turbines" was established several year,s ago only after extensive discussions with major steam turbine manufacturers, and was based largely on operating experience at fossil fueled plants, engineering jucgement and the recommendations of these manufacturers.
Consicering the status of the information presented by APCo and Westinghouse at the March 23, 1983 meeting, and the staff's original basis for the STS, the staff concluded, at the time, that there was insufficient basis for deleting the turbine valve testing and maintenance reouirements from the plant technical specifications.
However, based on the infonnation presented by Westinghouse and the comprehensive turbine valve testing program discussed by APCo, the staff concurs that the interval between periodic turbine valve testing could be increased without materially affecting tne probability of turbine missile generation.
The staff proposed an increase in the cericdic turoine valves test interval for Farley Unit 2 from weekly to monthly, en an interim basis, pending ccmuletion of a staff review cf the Westingnouse generic report on the suoject, without significantly affecting the caoability of the turbine valves to function on cemand.
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Ensuing discussions with the staff on the subject resulted in APCo requesting a director level appeal meeting that was held on August 16, 1983. At this meeting APCo presented further detailed information of their comprehensive turbine valve maintenance, calibration, testing and' inspection program and Westinghouse discussed in further detail the conclusion of their generic study on the imoact of reduced testing of turbine valves on the probability of turbine missile gene ation.
Westinghouse reiterated that the study shows that reduced turbine valve testing on the type of turbine installed at Farley 1 and 2 has little or no etfect on the probability of turbine missile generation.
On the basis of the additional information and data presented to the director!, the staff agreed to consider deletion of the turbine valve testing requirement for the Farley Unit 2 from the plant technical specifications provided that APCo submit a detailed description of their comprehensive turbine valve mainteriance and inspection program for review by the staff and a technical specification change referencing this program described at the.two appeal meetings.
Revised technical specifications for Farley 1 and 2 and a copy of their proprietary comprehensive program entitled " Turbine Overspeed Reliability Assurance Progr3m" (TORAP) were submitted as enclosures to the APCo letter dated '
October 6, 1983, and supblemented by letter dated,Novemoer 28, 1983.
The AEco TORAP includes a comprehensive program of maintenance, calibration and testing of the turbine overspeed protection system.
This program is designed to provide assurance that flaws or cbmponent failures in the overspeed sensing and tripping subsystems, in the main steam throttle, governor, reheat stop, intercept, and extraction steam nonreturn valves that mightJ1ead to an overspeed concition above the oesign overspeed will be detected.
The program is based on reconnendations by Westinghouse regarding' valve maintenance and on operating experience at the Farley Nuclear Plant.
The overall objective of this program is to maintain the high reliability of the turbine overspeed protection system.
The maintenance prog-am includes inspection and maintenance of the throttle, governor, reheat stop, intercept valves and nonreturn 4xtraction steam valves.
l The calibration program includes calibration of' the turbine overspeed protection system.
Calibration is performed during each refueling outage or following major maintenance on the turbine generator or the overspeed protecticn system.
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The testing program includes testing of,the turbine valves and the l
turbine overspeed protection system. Testing is performed during each turbine startup, unless tested within the previous seven (7) days, including startup after each refueling outage.
The testing program '
includes a complete test of all turbine valves on an approximate interval of four (a) months.
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. In the October 6, 1983 submittal APCo states that the proposed revision l
to the Technical Specification 3/4.3.4 " Turbine Guerspeed Protection" for Units 1 and 2 does not involve a significant hazards consideration' as defined in 10 CFR 50.92. The proposed change may result in some increase to.the probability of a previously analyzed accident but the results of the change are clearly within all acceptable criteria specified in the Standard Review Plan.
(10.2.3, " Turbine Disk Integrity").
The staff. concurs with the licensee in the above statements.
In addition APCo has cemitted to add the governor, throttle, intercept, and reheat stoo valves to the Nuclear Plant Reliability Data System (NPRDS).
Deficiencies will be reported and included in the data bank, and reviewed so that appropriate changes may be made in the Farley
' Nuclear Plant program based on reliability infomation.
In sumary, the basis for deleting the testing recuirements for all turbine valves from the Technical Specification at Farley Unit 2 was:
1.
Up to now the test frequency of nuclear service turbine valves has been largely based on experience with turbine generators installed in fossi.1 plants.
The requirement to test and inspect nuclear turbine valves on a weekly basis was originally included in the Standarc TechnicaC Specifications (STS) cased on this experience and to assure functional operability on demand to avert a potential turbine overspeed condition that could result in the generation of turbine missiles..The objective of the valve testing was to assure high valve operability and reliab,ility in order to minimize the '
probability of generating destructive missiles that could damage safety related eouipment and thereby orevent safe shutdown of the plant.
The turbine control and oversceed protection system is designed to control turbine action under.all ncrmal and abnormal conditions to assure that a turbine. trip from full load will not cause the' turbine to overspeed beyond acceptable limits, thus minimizing the probabiltty of generating turbine missiles.
Although the turbine control and overspeed protection system is not relied on to perform a safety function, it controls a piant process that has ootential to imoact plant safety.
The results of WCAP-10162 analysis as submitted by APCo for the Farley 1 and 2 turbine units and the Westinghouse generic turbine missile study show that reduced turbine valve testing frequency on nuclear units of the type installed at Farley has mini ~ mal effect on the probabflity of turbine missile generation.
2.
Nuclear turbine valves have proven to be extremely reliable in.
service as evidenced by the lack of failures over the.many years of nuclear plant operation.
This proven reliability can also be attributed to the all velatile chemical treatment of feedwater which minimizes steam generator carry over and essentially eliminates valve failure due to scale builduo on the alve moving parts.
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The APCo turbine valves and turbir.e overspeed protection system maintenance, ca!ibrstion, test ar:d inspection program described at the March 23 ano August 16, 1.983 meetings and detailed in their proprietary TORAP document is satisfactory to the staff.
4 The data and rationa!e presented by PCo and Westinghouse at the March 23 and August 16, 1983 and other previous meetings with the staff and the staff's, understanding of the data presented.
5.
Testing of turbine control valves on base loaded machines necessitates reduction of generator output for a period of several hours.
The valve testing secuence during turbire operation requires placing the turbine on manual control and repositioning all turbine control valves in the steam chest to permit individual full valve stroking.
All valves are aligned to equal position.
Repositioning of the control valves (on a base load machine) results in reduced steam flow to the turbine with a consecusnt reduction in generator output of' about 5"..
Testing of all turbine control valves is accomplished in a relatively short time (about 35 to 40 minutes).
The bulk of the time consumed (approximately 2 1/2 to 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />) is in slowly icwering reactor output to corresoond with the reduceo turbine generator output to permit control valve testing.
On comoletion of valve tests a similar time period is consumed in slowly in. creasing reactor power to pe'rmit full load operation of the turbine generator.
The icwering and increasing of reactor' output must be accomplished sicwly to. minimize xenon spiking.
The potential for xenon spiking exists when subjecting the nuclear steam supply system to cyclical power transients and this was factored in the staff action.
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6 The proposed revision to Technical Specification 3/4.3.4, dTurbine Overspeed Protection," does not involve a significant hazards consideration.
7 The proposed APC0 turbine valve maintenance and inscection program coupled with installed turbine generator protective features and an inplace inspection program of the low pressure turbine discs provides reasonable assurance of a low design oversceed missile generation orobability, d.
Farley Units 1 and 2 employ -edundant '4SIVs on eacn steam generat:-
steam line.
This added protection 'urther cecreases Oc probability for turbine mi,ssile generation.
1 APCo has proposed to add the same technical specification recuirements for testing all turbine valves on Unit 1 for which none such requirements now exist.
The staff believes that an increase' in overall plant operating safety will result from the aceition of the APCc 'LRAP tc 'Jnit 1.
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- 4FE'Y SUMMaRI On the basis of the above, tne staff concludes that deletion of the turbine valve testing requirements from the farley Unit 2 Technical l
Specifications is acceptable subject to incorporation of the following conditions:
1.
All turbine valves and turbine overspeec protection syst,em for Farley Unit 2 shall be maintained, calibrated, tested and inspected as presently stated in the procrietary APCo TORAP docu. Tent submitted with their letter of October 6,.1983, as sucolemented by letter dated November 28, 1983.
This program is also aaproved for Farley Unit 1.
Subsequent cha.nges to the program as presently described in the TORAP document in scope and/or schedule resulting frcm tne on-coino review by APCo sh=11 be reviewed and accrovad aer 1.0 C:o
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50.59.
tNVIRONMENTAL CONSIDERATION We have determined that the amendments do not authorize chances in effluent types or total amounts, nor increases in power levels, and will not result in any significant environmental impact. Havinc made
' this determination, we have further concluded that the amendments involve actions which are insignificant from the standpoint of environ-
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mental impact and, pursuant to 10 CFR 51.5(d)(4), that an environmental impact statement or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance cf these amendments.
CONCLUSION We have concluded, based on the consideration 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 Commission's regulations and the issuance of the amendments will not-be inimical to the common defense and security or to the health and safety of the public.
Dated: January 27, 1984 Principal Contributors:
A. Ungaro E. A. Reeves m_____m m..___.-_
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