ML17229A498

Special Rept:On 970921,discovered That Several Heated Juction Thermocouple Inputs to Channel B of Rvlm Sys Deviating from Normal Temps.Rvlm Sys Will Be Restored to Operability Before End of Next Unit 2 Refueling Outage

ML17229A498
Person / Time
Site:	Saint Lucie
Issue date:	10/17/1997
From:	Stall J FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-97-264, NUDOCS 9710200194
Download: ML17229A498 (4)

Text

CATEGORY REGULA Y INFORMATION DISTRIBUTIO YSTEM (RIDS)

ACCESSION NBR:9710200194 DOC.DATE: 97/10/17 NOTARIZED: NO DOCKET I FACIL:50-389 St. Lucie Plant, Unit 2, Florida Power & Light Co. 05000389 AUTH. NAME AUTHOR AFFILIATION STALL,J.K. Florida Power & Light Co.

REGIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Special rept:on 970921,discovered that several heated juction thermocouple inputs to Channel B of RVLM sys deviating from normal temps.RVLM sys will be restored to operability before end of next Unit 2 refueling outage.

DISTRIBUTION CODE: IE22D COPIES RECEIVED:LTR ENCL SIZE:

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

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-3 PD 1 1 WIENS,L. 1 1 0 INTERNAL: ACRS 1 1 AEOD SPD RAB 2 2 AEOD/SPD/RRAB '1 1 1 1 NRR/DE/ECGB 1 1 NR 1 1 NRR/DE/EMEB 1 1 NRR/DRCH/HHFB 1 1 NRR/DRCH/HICB 1 1 NRR/DRCH/HOLB 1 1 NRR/DRCH/HQMB 1 1 NRR/DRPM/PECB 1 1 NRR/DSSA/SPLB 1 1 NRR/DSSA/SRXB 1 1 RES/DET/EIB 1 1 RGN2 FILE 01 1 1 EXTERNAL: L ST LOBBY WARD 1 1 LITCO BRYCEIJ H 1 1 D; NOAC POORE,W. 1 1 NOAC QUEENER,DS 1 1-NRC PDR 1 1 NUDOCS FULL TXT 1 1 C

U, E

N NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE. TO HAVE YOUR NAME OR ORGANIZATION REMOVED FROM DISTRIBUTION LISTS OR REDUCE THE NUMBER OF COPZES RECEIVED BY YOU OR YOUR ORGANIZATION, CONTACT THE DOCUMENT CONTROL DESK (DCD) ON EXTENSION 415-2083 TOTAL NUMBER OF COPIES REQUIRED: LTTR 25 ENCL 25

Florida Power & Light Company, 6501 South Ocean Drive, Jensen Beach, FL34957 October 17, 1997 FPL L-97-264 10 CFR 50.4 10 CFR 50.36 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Re: St. Lucie Unit 2 Docket No. 50-389 Technical Specification Special Report Date of Event: September 21, 1997 Failure of Channel B of the Reactor Vessel Level Monitorin S stem VLMS The attached Special Report is being submitted pursuant to the requirements of St. Lucie Unit 2 Technical Specification 3.3.3.6, Action c, and Technical Specification 6.9.2. This report provides notification that one channel of the Reactor Vessel Level Monitoring System (RVLMS) was out of service for greater than seven days. The report also addresses the plan for restoring the channel to service.

Should there be any questions on this information, please contact us.

Very truly yours,

. A. Stall

'ice President St. Lucie Plant JAS/jwr Attachment cc: Luis A. Reyes, Regional Administrator, USNRC Region II Senior Resident Inspector, USNRC, St. Lucie Plant 97i0200i94 97i0i7 PDR ADOCK 050003S9 S PDR lllllllllllllllllllllllllllllllll.lllllll an FPL Group company

L-97-264 Attachment Page 1 SPECIAL REPORT I. TITLE Failure of Channel B of the Reactor Vessel Level Monitoring System (RVLMS)

II. EVENT DESCRIPTION On 9/21/97, with St. Lucie Unit 2 at 100% power, plant operators discovered that several Heated Junction Thermocouple (HJTC) inputs to Channel B of the RVLMS were deviating from their normal temperatures. A work order was written and maintenance technicians investigated the condition. The investigation revealed low resistance to ground on multiple cable inputs from the HJTC probe. Resistance measurements from the HJTC heaters to ground were found to be less than 1000 ohms, and resistance measurements from the thermocouples to ground were found to be less than 700 ohms.

The expected resistance, in both cases, was several orders of magnitude greater than measured. Additional testing indicated that the RVLMS cabinet electronics, Sub-Cooling Margin Monitor and Core Exit Thermocouples were operable. Further assessment of the probe assembly and cable connections inside containment is precluded due to high radiation in the area of the probe and cable connections.

-III. CAUSE OF THE EVENT Because access to the probe and cable connections inside containment is precluded during power operations, the cause of the inoperability has not been determined with certainty.

The cause is believed to be either a) structural failure of the HJTC probe causing shorting, or b) a connector failure in the signal path between the probe and the RVLMS electronic cabinet.

IV. ACTIONS TAKEN A. The HJTC temperature deviations were investigated by maintenance technicians.

B. The entire HJTC input to Channel B of the RVLMS was declared out of service.

(Technical Specification 3.3.3.6 allows continued operation with one channel of the RVLMS inoperable.)

L-97-264 Attachment Page 2 C. A condition report (¹97-1790) was issued to document the failure, assess root cause and determine corrective actions.

V. SCHEDULE FOR RESTORING SYSTEM The Channel 8 HJTC inputs to the RVLMS will be restored to operability before the end of the next Unit 2 refueling outage (SL2-11), which is currently scheduled for the Fall of 1998. After completion of repairs, root cause will be determined and generic concerns will be addressed.

Also, FPL is reviewing industry experience on alternate means to monitor vessel level in case the second channel of RVLMS becomes inoperable.