ML17306A810

Special Rept 1-SR-92-004:on 920620,loose Part Detection Sys Inoperable for More than 30 Days.Caused by Hardware Problems Associated W/Installation of Loose Part Detection Sys Mods.New Computer Processor Board Installed

ML17306A810
Person / Time
Site:	Palo Verde
Issue date:	06/27/1992
From:	James M. Levine ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
1-SR-92-004, 1-SR-92-4, 192-00793-JML-T, 192-793-JML-T, NUDOCS 9207070310
Download: ML17306A810 (6)

Text

J ACCELERATED DISTIUBUTION DEMONSTRATION SYSIEM REGULA Y INFORMATION DISTRIBUTI SYSTEM (RIDS)

ACCESSION NBR:9207070310 DOC.DATE: 92/06/27 NOTARIZED: NO DOCKET

,j FACIL:STN-50-528 Palo Verde Nuclear Station, Unit 1, Arizona Publi 05000528 AUTH.FRAME 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 1-SR-92-004:on 920620,loose part detection sys inoperable for more than 30 days. Caused by hardware problems associated w/installation of loose part detection sys mods.New computer processor board installed.

DISTRIBUTION CODE: IE22D COPIES RECEIVED:LTR TITLE: 50.73/50.9 Licensee Event Report 0 ENCL (LER), Incident I SIZE:

Rpt, etc.

NOTES:STANDARDIZED PLANT 05000528 RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD5 LA 1 1 PD5 PD 1 1 TRAMMELL,C 1 1 THOMPSON,M 1 1 INTERNAL: ACNW 2 2 ACRS 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DET/EMEB 7E 1 1 NRR/DLPQ/LHFB10 1 1 NRR/DLPQ/LPEB10 1 1 NRR/DOEA/OEAB 1 1 NRR/DREP/PRPB11 2 2

'NRR/DST/SELB 8D 1 1 NRR/DST/SICB8H3 1 1 4D~ PLB8D1 1 1 1

NRR/DST/SRXB 8E RES/DSIR/EIB 1

1 1

1 E 0 1 RGN5 ILE 01 1 1 EXTERNAL'G&G BRYCE g J H ~ 3 3 L ST LOBBY WARD 1 1 1 NSIC MURPHYgG.A 1 1 NRC PDR NSIC POOREPW. 11 1 NUDOCS FULL TXT 1 1 NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

TOTAL NUMBER OF COPIES REQUIRED: LTTR 33 ENCL 33

Arizona Public Service Company PALO VERDE NUCLEAR GENERATING STATION P.O. BOX 52034 ~ PMOENIX. ARIZONA85072-2034 192-00793-JML/TRB/KR=

JAMES M. LEVINE VICE PRESIDENT June 27, 1992 NUCLEAR PRODUCTION U. S. Nuclear Regulatory Commission Attention: Document Control Desk Mail Station Pl-37 Washington, D.C. 20555

Dear Sirs:

Subj ect: Palo Verde Nuclear Generating Station (PVNGS)

Unit 1 Docket No. STN 50-528 (License No. NPF-41)

Special Report 1-SR-92-004 File'2-020-404 Attached please find Special Report 1-SR-92-004 prepared and submitted pursuant to Technical Specification 3.3.3.7 ACTION (a) and Technical Specification 6.9.2. This report discusses the inoperability of the Loose-Part Detection System for more than thirty (30) days. A copy of the Special Report is being forwarded to the Regional Administrator, NRC Region V.

If you have any questions, please contact Thomas R. Bradish, Compliance Manager at (602) 393-5421.

Very truly yours, JML/TRB/KR Attachment cc: W. F. Conway (all with attachment)

J. B. Martin D. H. Coe r

liUUy VI@

9207070310 920627 PDR ADOCK 05000528 S PDR

PALO VERDE NUCLEAR GENERATING STATION UNIT 1 Loose-Part Detection System License No. NPF-41 Docket No. 50-528 Special Report 1-SR-92-004 Initia Conditions This Special Report is being submitted pursuant to Technical Specification (TS) Limiting Condition for Operation (LCO) 3.3.3.7, ACTION (a) and TS Administrative Controls 6.9.2 to report the inoperability of the Loose-Part Detection System (LPDS) for more than thirty (30) days. TS LCO 3.3.3.7 states that the "loose-p'art detection system shall be OPERABLE with all [8] sensors".

and is applicable in Mode 1 (POWER OPERATION) and Mode 2 (STARTUP). The thirty (30) day period for returning the channels to an operable status was exceeded at approximately 0034 MST on June 20, 1992.

S stem Information The Loose-Part Detection System (LPDS) is designed to detect the presence of loose parts within the Reactor Coolant System (RCS). The Palo Verde Unit 1 LPDS consists of eight (8) channels, Each channel consists of a piezoelectric monitor sensor and associated amplification, indication, and recording circuitry. The eight (8) sensors are positioned in the following locations:

two (2) mounted on the Reactor Vessel upper head (Channels 1 and 2), two (2) mounted on the Reactor Vessel lower incore nozzle (Channels 3 and 4), and one (1) on each of the two (2) Steam Generators'nlet and outlet nozzles (Channels 5, 6, 7, and 8). The piezoelectric sensors detect loose parts using acoustic signals which are generated when loose parts impact a RCS 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 (1) alarm indicator in the Control Room for the eight (8) channels.

Actions Taken During the 1992 Unit 1 third refueling outage, APS installed a LPDS modification that replaced an obsolete tape recorder with a 16-channel recording and analysis computer manufactured by Combustion Engineering (ABB-CE). The digital recording system includes a loose part event analysis computer (LPEAC) for analyzing collected data. Signals from all channels are sampled continuously and stored for time intervals, depending on the sampling rate and memory capacity of the analysis computer. Individual channels can be selected by the computer software for subsequent analysis. Signals from the eight (8) LPDS channels and from six (6) reactor core internal channels are monitored by the LPEAC.

Following installation of the LPEAC and during acceptance testing, hardware problems occurred with the LPEAC's computer processor board. The 18 month

I i'

Special. Report 1-SR-91-004 Page 2 CHANNEL CALIBRATION surveillance test was successfully completed on May 19, 1992. However,, LPDS was not declared OPERABLE prior to entry into Mode 2 pending resolution of LPEAC's hardware problems (TSs permit entry into Mode 1 or Mode 2 with LPDS inoperable). Unit 1 entered Mode 2 at approximately 0034 on May 21, 1992, initiated compensatory actions (i.e., daily aural checks),

and entered TS LCO 3.3.3.7 ACTION (a) (i.e., with one or more loose-part detection system channels inoperable for more than 30 days, prepare and submit a Special Report). During the 30 day TS ACTION time period, multiple attempts were made by APS to secure a replacement computer processor board from ABB-CE following the entry into Mode 2. In addition, Channels l. and 5 were found to be spuriously activating.

Cause of the Malfunction Following the installation of modifications (i.e., 16-channel recording and analysis computer) to the 'system during the third refueling outage, a LPEAC's computer processor board failed. The replacement boards supplied by ABB-CE were for an upgraded equipment design and not compatible with the original equipment design installed in Unit 1. The cause of the excessive number of spurious alarms on Channel 1 may be attributed to an "as left" low alarm setpoint that was calculated and reset during the 18 month CHANNEL CALIBRATION surveillance test which was successfully completed on May 19, 1992. The most probable cause of the spurious alarms on Channel 5 is due to the sensitivity of the system as previously discussed in Special Report 1-SR-90-005. The LPDS channel response is reflective of the excitative energy from the RCS (i.e., at different power levels and during different plant transients, RCS excitation energies vary which affect the response of the LPDS).

Plans for Restorin the Channels to OPERABLE Status'PS is pursuing the acquisition of the original designed computer processor board and is considering replacing the original equipment design with the.

upgraded equipment design. In the interim, another computer processor board is installed and LPEAC is functioning. However, the LPDS will remain inoperable due to the high spurious alarm rates from Channels 1 and 5. The inoperable LPDS is scheduled to be reworked and returned to service during the next scheduled refueling outage. Although the LPDS remains inoperable, the channels are capable of being used to monitor for loose parts. During the period of inoperability, the following enhanced monitoring is being 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).

2. The STAs and Operations personnel will perform twice daily aural checks on Channels 1 through 8 (i.e., during dayshift and nightshift).