ML17313A991

Special Rept:On 990510,loose-part Detection Sys Channel 2 Was Declared Inoperable.Caused by Malfunction of Mineral Cable Connector to Accelerometer.Licensee Will Implement Modifications Which Will Enhance loose-part Detection Sys

ML17313A991
Person / Time
Site:	Palo Verde
Issue date:	06/18/1999
From:	Overbeck G ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
192-01049-GRO-D, 192-1049-GRO-D, NUDOCS 9906240158
Download: ML17313A991 (10)

Text

~ CATEGORY REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9906240158 DOC.DATE: 99/06/18 NOTARIZED: NO DOCKET FACXL:STN-50-529 Palo Verde Nuclear Station, Unit 2, Arizona Publi 05000529 AUTH. NAME AUTHOR AFFILIATION OVERBECK,G.R. Arizona Public Service Co. (formerly Arizona Nuclear Po~er RECIP.NAME RECIPXENT AFFILIATION Records Management Branch (Document Control Desk)

SUBJECT:

Special rept:on 990510,loose-part detection sys channel 2 was declared inoperable. Caused by malfunction of mineral cable connector to accelerometer. Licensee will implement modifications which will enhance loose-part detection sys.

DISTRIBUTION CODE: IE22D COPIES RECEIVED:LTR I ENCL i SIZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

E NOTES:Standardized plant. 05000529 G

RECIPIENT COPIES RECIPIENT COPXES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL LPD4-2 1 1 FIELDS,M 1 1 INTERNAL: ACRS 1 1 AEOD/SPD/RRAB 1 1 CE 1 1 NRR/DZPM/IOLB 1 1 1 1 NRR/DRIP/REXB 1 1 NRR/DSSA/SPLB RGN4 FILE 01 1, 1 1 1

RES/DET/EIB 1 1 EXTERNAL: L ST LOBBY WARD 1' LMITCO MARSHALL 1 1 NOAC POORE,W. 1 1 NOAC QUEENER, DS 1 1 D NRC PDR 1 1 NUDOCS FULL TXT 1 1 M

E N

NOTE TO ALL 4RIDSN RECIPIENTS: )

PLEASE HELP US TO REDUCE WASTE. TO HAVE YOUR NAME OR ORGANIZATION REMOVED FROM DISTRIBUTION LISTS OR REDUCE THE NUMBER OF COPIES RECEIVED BY YOU OR YOUR ORGANIZATIONI CONTACT THE DOCUMENT CONTROL DESK (DCD) ON EXTENSION 415-2083 TOTAL NUMBER OF COPIES REQUIRED: LTTR 17 ENCL 17

0 r Commitment. /nnmmt/erL &err///

Gregg R. Overbeck Mail Station 7602 Palo Verde Nuclear Vice President TEL 602/393-5i 48 P.O. Box 52034 Generating Station Nuclear Production FAX 602/393-6077 Phoenix, AZ 85072-2034 192-01049-GRO/DGM/dgm June 18, 1999 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Station P1-37 Washington, D.C. 20555-0001

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Unit 2 Docket No. STN 50-529 Special Report 2-SR-99-002 Attached please find Special Report 2-SR-99-002 prepared and submitted pursuant to Technical Requirements Manual Limiting Condition for Operation (TLCO) 3.3.106 Required Action (B.1). This report discusses the inoperability of one (1) Loose-Part Detection System channel for more than thirty (30) days.

This letter includes a commitment that "Modifications which will enhance the Loose-Part Detection System mineral cable connectors and cable routing will be implemented in Unit 2 during the next refueling outage."

If you have any questions, please contact Daniel G. Marks, Section Leader, Regulatory Affairs, at (623) 393-6492.

Sincerely, GRO/DGM/dgm Attachment cc: E. W. Merschoff (all with attachment)

P. H. Harrell M. B. Fields J. H. Moorman 990b240158 995pp0529 PDR ADGCK 0 PDR 8

0 r

(

ATTACHMENT Special Report No. 2-SR-99-002

0 r

r f

h

Palo Verde Nuclear Generating Station Unit 2 Loose-Part Detection Instrumentation Inoperable Docket No. STN 50-529 Special Report No. 2-SR-99-002 Initial Conditions:

At approximately 1900 MST on May 10, 1999, Palo Verde Unit 2 was in Mode 1

{POWER OPERATION) operating at approximately 100 percent power when Loose-Part Detection System channel 2 was declared inoperable. The thirty-day period for returning the channel to an operable status expired at approximately 1900 MST on June 9, 1997. This Special Report is being submitted pursuant to Technical Requirement Manual Limiting Condition for Operation (TLCO) 3.3.106 Required Action (B.1) to report the inoperability of one (1) Loose-Part Detection System channel for more than thirty {30) days. The remaining seven {7) channels continue to function properly. TLCO 3.3.106 is applicable in Mode 1 (power operation) and Mode 2 (startup).

System information:

The Loose-Part Detection System is designed to detect and record signals from loose part impacts occurring within the Reactor Coolant System (RCS). The Loose-Part Detection System has eight (8) channels each using high temperature piezoelectric accelerometers (transducers) which are located in areas where loose parts are most likely to become trapped. The eight accelerometers are positioned on the reactor vessel upper head (channels 1 and 2), the lower reactor vessel (channels 3 and 4),

Steam Generator No. 1 (channels 5 and 6), and Steam Generator No. 2 {channels 7 and 8). High temperature, low noise, radiation hardened, flame-retardant mineral cables connect the accelerometers to coaxial cables that complete the electrical loop to preamplifiers (charge converters) located outside of the primary shield. The accelerometers detect loose parts using acoustic signals which are generated when loose parts impact an RCS component or structure. Signals in excess of the alarm setpoint will result in a "latch on" type alarm (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.

0 I

lg

. U. S. Nuclear Ragutatory Commission Special Report 2-SR-99-002 Page 2 Actions Taken:

On May 10, 1999, during routine daily monitoring as required by surveillance requirement TSR 3.3.106.1, of the Loose-Part Detection System, Operations personnel determined that channel 2 was inoperable due to loss of audio signal from channel 2.

Only limited troubleshooting activities could be performed due to the radiological exposure that would be received because of the accelerometer's location on the reactor vessel upper head. TLCO 3.3.106 Required Action (A.1) was entered and applicable plant corrective action documents were initiated. During this time, the other channels functioned normally.

Cause of the Malfunction:

The apparent failure of channel 2 is due to the malfunction of the mineral cable connector to the accelerometer. The failure determination is based upon past failures of the cable connector to the accelerometer. An equipment root cause of failure analysis will not be performed to verify or rectify the Loose-Part Detection System channel 2 problem due to the radiological exposure which would be received because of the accelerometer's location on the reactor vessel upper head.

Plans for Restoring the Channels to OPERABLE Status:

Modifications which will enhance the Loose-Part Detection System mineral cable connectors and cable routing and may prevent similar malfunctions will be implemented in Unit 2 during the next refueling outage. The remaining seven (7) channels continue to function properly. Shift Technical Advisors and Operations personnel continue to perform shiftly aural checks on the remaining operable channels (i.e., during dayshift and nightshift).

0 1,

'I

(

t li