ML17306B331
| ML17306B331 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 03/08/1993 |
| From: | Conway W ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 102-02440-WFC-J, 102-2440-WFC-J, NUDOCS 9303150155 | |
| Download: ML17306B331 (13) | |
Text
-aecmr.mm XK Ocmvrmm Drsx xrax svSrzm REGULATOR NFORMATION DISTRIBUTION EM (RIDS)ACCESSION NBR:9303150155 DOC.DATE: 93/03/08 NOTARIZED:
NO DOCKET FA("IL:STN-50-528 Palo Verde Nuclear Station, Unit 1, Arizona Publi-05000528 STN-50-529 Palo Verde Nuclear Station, Unit 2, Arizona Publi 05000529 STN-50-530 Palo Verde Nuclear Station, Unit 3, Arizona Publi 05000530 AUTH.NAME AUTHOR AFFILIATION CONWAYiW.F.
Arizona Public Service Co.(formerly Arizona Nuclear Power R=RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)-
SUBJECT:
Responds to NRC comments on period'ic testing of alternate ac sources, delineated in NRC 920211,0728 a 930104 SERs for station backout.Unloaded operability test will be performed on each of two 100%capacity gas turbine generators.
DISTRIBUTION CODE: AOSOD COPIES RECEIVED:LTR ENCL SIZE: TITLE: OR Submittal:
Station Blackout (USI A-44)lOCFR50.63, MPA.A-22 D S NOTES:STANDARDIZED PLANT Standardized plant.Standardized plant.05000528'05000529 05000530 D.RECIPIENT ID CODE/NAME PD5 PD TRAN,L INTERNAL: ACRS NRR/DE/EELB SA SRXB R G FI E 01 COPIES LTTR ENCL 1 1 1 1 1 1 3 3 1 1 1 1 RECIPIENT ID CODE/NAME TRAMMELL,C AEOD/DSP/TPAB NRR/DSSA/SPLB NRR/PD2-4 COPIES LTTR ENCL 1.1 1 1 1 1 1 1 D'EXTERNAL: NRC PDR 1 1 NSIC 1 1 NOTE TO ALL"RIDS" RECIPIENTS:
I'LEASE HELP US TO REDUCE WASTE!CONTACf TIIE DOCUMEN'I'ON'I'ROL DMK, ROOM Pl-37 (EXT.504-2065)TO ELIMINATE YOUR NAME FROM DISTRIDUTIOi4 LISTS FOR DOCUMEN'I'S YOU DON'T NEEDlTOTAL NUMBER OF COPIES REQUIRED: LTTR 14 ENCL 14 i l II>~k~
~'Arizona Public Service Company P.O.BOX 53999~PHOENIX.ARIZONA 85072<999 WILLIAM F.CONWAY EXECUTIVE VICE PRESIDENT NUCLEAR 102-02440-WFC/JNI March 8, 1993 U.S.Nuclear Regulatory Commission ATTN: Document Control Desk Mail Station P1-37 Washington, DC 20555
References:
1)Letter dated February 11, 1992, from C.M.Trammell, NRC, to W.F.Conway, APS,"Station Blackout Safety Evaluation, Palo Verde Nuclear Generating Station" 2)Letter 161-04684-WFC/NLT, dated March 20, 1992, from W.F.Conway, APS, to NRC,"Response to the NRC Station Blackout Safety Evaluation Recommendations" 3)Letter dated July 28, 1992, from C.M.Trammell, NRC, to W.F.Conway, APS,"Supplementary Safety Evaluation for Station Blackout, Palo Verde Nuclear Generating Station (TAC Nos.M68579, M68580, and M68581)" 4)Letter 102-02300-WFC/JNI, dated October 2, 1992, from W.F.Conway, APS, to NRC,"Response to NRC Comments on Periodic Testing of Alternate AC (AAC)Sources (Supplementary Safety Evaluation for Station Blackout)" 5)Letter dated January 4, 1993, from C.M.Trammell, NRC, to W.F.Conway, APS,"Station Blackout Supplemental Safety Evaluation
-Palo Verde Nuclear Generating Station (TAC Nos.M68579, M68580, and M68581)"
Dear Sirs:
Subject:
Palo Verde Nuclear Generating Station (PVNGS)Units 1, 2, and 3 Docket Nos.STN 50-528/529/530 Response to NRC Comments on Periodic Testing of Alternate AC (AAC)Sources (Supplementary Safety Evaluation for Station Blackout)File: 93-001-41 9 93-056-026 The NRC issued a Safety Evaluation Report (Reference 1)based on Arizona Public Service Company's (APS)response to the Station Blackout Rule (10 CFR 50.63).APS responded to the NRC Station Blackout Safety Evaluation recommendations in Reference 2.Subsequent NRC correspondence (Reference 3)indicated that the APS response (Reference 2)was acceptable, except that the operability test at 3-month intervals should include the gas turbine generators 9303i50i55 930308 PDR ADOCK 05000528'P'PDR l
~r U.S.Nuclear Regulatory Commission ATTN: Document Control Desk Periodic Testing of Alternate AC Sources Page 2 being tested under load.APS responded by providing justification for unloaded testing at 3-month intervals (Reference 4).The NRC Supplementary Safety Evaluation for Station Blackout (Reference 5)indicated a concern that load testing of the alternate AC sources on an approximately yearly basis, rather than on a 3-month basis, will not provide a sufficient data base to demonstrate the required 95%reliability of the gas turbine generators under load.APS has addressed NRC's concern in the enclosure to this letter.If you have any questions, please call Thomas R.Bradish at (602)393-5421.Sincerely, WFC/JNI/jni Enclosure cc: J.B.Martin J.A.Sloan C.M.Trammell I I~e ENCLOSURE PERIODIC TESTING OF ALTERNATE AC (AAC)SOURCES PERIODIC TESTING OF ALTERNATE AC AAC SOURCES APS will implement NUMARC 87-00, Appendix B, Criterion B.10, regarding periodic testing of the AAC power source as follows: Criterion B.10: Unless otherwise governed by technical specifications, the AAC source shall be started and brought to operating conditions that are consistent with its function as an AAC source at intervals not longer than three months, following manufacturer's recommendations or in accordance with plant developed procedures.
Once every refueling outage, a timed start (within the time period specified under blackout conditions) and a rated load capacity test shall be performed.
APS Position:~An unloaded operability test will be performed on each of the two 100%capacity Gas Turbine Generators (GTGs)on a monthly basis in accordance with manufacturer's recommendations.
This will include the initiation of a GTG start signal and will be considered successful upon receipt of a"Ready to Load" signal from the GTG control system.~Once per refueling outage, roughly equating to once every six months, each GTG will be tested at load for a sufficient period to achieve stable operating parameters (temperatures, pressures, voltages, etc.).~On approximately an 18-month interval, each GTG will be tested to demonstrate AAC capability.
This test will include a timed start (within the one-hour time period specified for Station Blackout)and operation of each GTG at rated load.
C APS will implement NUMARC 87-00, Appendix B, Criterion B.13 as follows: Criterion B.13 (a)S stems Not Normall 0 crated Standb S stems System reliability should be maintained at or above 0.95 per demand, as determined in accordance with NSAC-108"Reliability of Emergency Diesel Generators at U.S.Nuclear Power Plants" methodology.
APS Position:~Operating Considerations:
During Modes 1, 2, 3, or 4, two independent A.C.power sources are required by Technical Specification 3.8.1.1~During Modes 5 or 6, one A.C.power source is required by Technical Specification 3.8.1.2.The GTGs are electrically connected to, and can only be significantly loaded through, the PVNGS Units 1, 2, and 3 non-safety related switchgear that furnishes normal offsite power to the Train"A" safety related switchgear.
Transients caused by equipment failure or operator error during load testing of the GTGs could affect the reliability of the power source to safety related loads.Therefore, the GTGs will be load tested during each refueling outage (approximately once every six months)in Modes 5 or 6, when both trains of safety related power are not required.~Sufficient Data to Demonstrate 95%Reliability:
PVNGS is installing two redundant, 100%capacity GTGs, either of which will furnish enough power to operate the expected loads required to mitigate a Station Blackout.The 13.8 kV circuit breakers associated with connecting the GTGs to the blacked out unit are all manually operated (closed)in the event of a Station Blackout.These breakers have uncomplicated close circuitry and do not utilize automatic close functions that need to be tested to demonstrate GTG access to the load.The testing described in the APS Position on Criterion B.10 results in 20 unloaded start tests and 4 start-and-load tests per year.This will furnish sufficient data to demonstrate the 95%reliability.
APS considers the unloaded start tests to be an important consideration in the reliability of the GTGs since industry data and experience show that most failures of GTGs occur in the start cycle of the unit, not in its ability to accept load once it is started.This statement is supported by the following.
Table XI of Appendix L to IEEE Standard 493-1990 (IEEE Recommended Practice for the Design of Reliable Industrial and Commercial Power Systems)lists failures per year by subsystem for standby gas turbines, as follows: 0.13 Starting System, 0.04 Generator, 0.04 Fuel System, 0.04 Control 8 Jl v P~~~V Instrumentation, 0.02 Turbine, 0.02 Lube Oil/Hydraulic, and 0.01 Air Intake.This data was for GTGs with ratings smaller than the PVNGS GTGs.However, APS considers the data applicable because of similiar design.In addition, Table III of Appendix L indicates that the Inherent and Operational Availabilities of GTGs in standby service are 0.9959 and 0.9948, respectively.
This generic industry data indicates the high reliability of standby gas turbine generators.
The Millstone Unit 1 Individual Plant Examination for Severe Accident Vulnerabilities, dated March 1992, included data from over 10 years of operating a safety related gas turbine generator.
The data showed 33 start failures in 988 demands and 1 run failure in 759 hours0.00878 days <br />0.211 hours <br />0.00125 weeks <br />2.887995e-4 months <br />.The GTG supplier, Solar Turbines Incorporated, has indicated that to demonstrate availability of the turbine-generator unit, it is only necessary to start the turbine once per month, and to shut it down as soon as possible after indication that it is ready to accept load.~Conclusion:
APS considers the monthly unloaded testing (20 tests per year)and the approximately semi-annual loaded tests (4 tests per year)to be adequate for demonstrating 95%reliability of the PVNGS GTGs.Load testing requires connection to the PVNGS Units 1, 2, and 3 non-safety related switchgear that furnishes normal offsite power to the Train"A" safety related switchgear.
Therefore, the GTGs will be load tested during each refueling outage (approximately once every six months)in Modes 5 or 6, when both trains of safety related power are not required.
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