ML17305A729

Special Rept 3-SR-90-002-01:on 900118,loose Part Detection Sys in Alarm Condition Since Startup.Channels Will Be Reworked & Returned to Svc During Next Scheduled Refueling Outage

ML17305A729
Person / Time
Site:	Palo Verde
Issue date:	05/02/1990
From:	LEVINE J M ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
192-00656-JML-T, 192-656-JML-T, 3-SR-90-002-01, 3-SR-90-2-1, NUDOCS 9005080062
Download: ML17305A729 (6)

Text

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NO DOCKET FACIL:STN-50-530 Palo Verde Nuclear Station, Unit 3, Arizona Publi 05000530 AUTH.NAME AUTHOR AFFILIATION LEVINE,J.M.

Arizona Public Service Co.(formerly Arizona Nuclear Power RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Special Rept 3-SR-90-002-01:on 900118,facility entered Mode 2 following completion of refueling outage.DISTRIBUTION CODE: IE22D COPIES RECEIVED:LTR ENCL J SIZE: TITLE: 50.73/50.9 Licensee Event Report (LER), Inciden&Rpt, etc.NOTES:Standardized plant.05000530 RECIPIENT I D CODE/NAME PD5 LA PETERSON,S.

COPIES RECIPIENT LTTR ENCL ID CODE/NAME 1 1 PD5 PD 1 1 CHAN T COPIES LTTR ENCL 1 1 1 1 INTERNAL'CNW AEOD/DOA AEOD/ROAB/DS P NRR/DET/ECMB 9H NRR/DET/ESGB 8D NRR/DLPQ/LPEB10 NRR/DREP/PRPB11 NRR/DST/SICB 7E NRR/DST/SRXB 8E RES/DSIR/EIB 2 2 1 1 2 2 1 1 1 1 1 1 2" 2 1'1 1 1 1 1 ACRS AEOD/DS P/TPAB DEDRO NRR/DET/EMEB9H3 NRR/DLPQ/LHFB11 NRR/DOEA/OEAB11 NRR/DST/SELB 8D RR/4)SQJ='S LB 8 D 1 REG FILE 02 01 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 EXTERNAL EG&G STUART 1 V~A LPDR NSIC MAYS,G NUDOCS FULL TXT NOTES 4 4 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MURPHY,G.A 1 1 1 1 1 1 1'1 1 NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WAS'ONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT-.20079)TO ELIMINATE YOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEEDt TOTAL NUMBER OF COPIES REQUIRED: LTTR 39 ENCL 39 Arizona Public Service Company PALO VERDE NUCLEAR GENERATING STATION P.O.BOX 52034~PHOENIX.ARIZONA 85072-2034 JAMES M, LEVINE V)CE P<ESIDENT HUCLEAA PRGGUCTIGN 192-00656-JHL/TRB/DAJ May 2, 1990 U.S.Nuclear'egulatory Commission Document Control Desk Washington, DC 20555

Subject:

Palo Verde Nuclear Generating Station (PVNGS)Unit 3 Docket No.STN 50-530 (License No.NPF-74)Special Report 3-SR-90-002-01 File'0-020-404 Attached please find Supplement No.1 to Special submitted pursuant to Technical Specifications This report discusses an inoperable Loose Parts If you have any questions, please contact T.R.(602)393-2521.Report 3-SR-90-002 prepared and 3.3.3.7 ACTION"a" and 6'.2.Detection System.Bradish, Compliance Manager at Very truly yours, JML/TRB/DAJ/tlg Attachment CC: W.F.J.B.E.E.D.H.T.L.A.C.Conway Martin Van Brunt Coe Chan Gehr (all with attachment)-

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f I PALO VERDE NUCLEAR GENERATING STATION UNIT 3 Loose Part Detection Instrumentation License No.NPF-74 Docket No.50-530 Special Report 3-SR-90-002-01 This Special Report is being submitted pursuant to Technical Specification 3.3.3.7, ACTION"a" and Technical Specification 6.9.2 to report the Loose Part Detection System being inoperable for more than thirty (30)days.This specification is applicable in Mode 1 (POWER OPERATION) and Mode 2 (STARTUP).

The 30 day period for returning the channel to an operable status was exceeded at approximately 0002 MST on January 18, 1990.The Palo Verde Unit 3 Loose Part Detection System consists of eight (8)channels..

Each channel consists of a piezoelectric crystal monitor sensor and associated amplification, indication, and recording circuitry.

The sensors are positioned in the following locations:

two (2)mounted on the Reactor Vessel upper head, two (2)mounted on the Reactor Vessel lower incore nozzle, and one (1)on each of the two (2)Steam Generators'nlet and outlet nozzles.The piezoelectric sensors detect loose parts using acoustic signals which are generated when loose parts impact a Reactor Coolant System component or structure.

Signals in excess of the alarm setpoint will result in an alarm condition.

The alarms are the"latch on" type, i.e., the alarm will remain on when the system returns to normal and will not clear until the alarm is manually reset.There is one alarm indicator in the Control Room for the eight channels.In addition to the alarm in the Control Room, a tape recorder will start.There are two tape recorders:

each tape recorder receives input from four system channels.At approximately 0002 MST on January 18, 1990, Palo Verde Unit 3 entered Mode 2 following completion of a refueling outage.Since STARTUP, Loose'arts Detection System Channel 1 (reactor vessel upperhead), Channel 6 (Steam Generator No.1 cold leg nozzle), and Channel 8 (Steam Generator No.2 cold leg nozzle)had been in an alarm condition.

Troubleshooting could not commence until stable conditions at full power had been achieved since APS has observed that, at.different power levels and during different plant transients, RCS excitation energies vary and affect the response of the Loose Parts Detection System.Also, other sources (e.g., flow vortexing, core barrel bypass flow, etc.)can produce energy waves which excite the accelerometers.

In many cases, it takes a significant length of time after a plant transient for the RCS to"stabilize" to the point where spurious alarms do not occur.~~Startup testing and resolution of unrelated problems precluded achieving stable full power operation until February 18, 1990.In the interim, spectral analysis, daily aural analysis, and trend analysis of channels 1, 6, and 8 output determined that no loose parts existed.After stable, full power operations were achieved, troubleshooting and engineering analysis were performed.

Engineering has determined that the Channel 1 alarm is most likely being caused by a sensor operating/monitoring problem (e.g., improper contact between the monitoring surface and sensor;intermittent high resistance short, ground, or open;a Special Report 3-SR-90-002-01 Page 2 loose cable connection to the sensor;the sensor or cable being in contact with an external vibrating surface).Based upon the results of troubleshooting, engineering determined that the Channel 6 alarm is most likely being caused by a loose connection.

Engineering has determined that Channel 8 is operating properly and the alarm is'the result of high background noise.Channels 1 and 6 will be reworked and returned to service during the next scheduled refueling outage.Engineering is continuing to evaluate the response of Channel 8.APS has been evaluating the operation of the Loose Parts Detection System in order to improve system performance.

APS is developing a modification to install an Event Analysis Computer which should enhance the ability of the system to discriminate false alarms.Pending parts availability, installation of the Event Analysis Computer should be complete by the next refueling outage.The Event Analysis Computer should enable Channel 8 to be returned to service.Additionally, APS has experienced a high pitched whistle in Units 1, 2, and 3 which may be affecting the response of Channel 8.In order to address this concern, tape recordings of Channel.output from Units 1, 2, and 3 will be analyzed by Combustion Engineering (CE)following Units 1 and 2 restart.Based on the results of the CE analysis, appropriate modifications to the system (e.g., install additional filters)will be performed if necessary.

In the interim in order to enable the reflash capability for the alarm in the Control Room, Temporary Modifications have been installed to raise the alarm setpoint for Channels 6 and 8, and to disable the alarm capability for Channel 1.Channels 1, 6, and 8 remain inoperable; however, they are capable of being used to monitor for loose parts.During the period qf inoperability, the following enhanced monitoring will be performed.

Vibration Group personnel will perform weekly Preventive Maintenance checks on Channels 1 through 8 (this includes an analysis of'system response to determine if a loose part exists).The STA's and operations personnel will perform twice daily aural ch'ecks on Channels 1 through 8 (i.e., during dayshift and nightshift)".

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