ML17304B101

Special Rept 1-SR-89-001:on 890306,Channel B Reactor Vessel Water Level Sys Inoperable for Period Greater than 7 Days. Approved Work Document Initiated to Determine Cause of Improper Operation of Sys.Channel Will Be Replaced

ML17304B101
Person / Time
Site:	Palo Verde
Issue date:	04/07/1989
From:	Haynes J ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
1-SR-89-001, 1-SR-89-1, 192-00466-JGH-T, 192-466-JGH-T, NUDOCS 8904190202
Download: ML17304B101 (8)

Text

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ACCESSION NBR:8904190202 DOC.DATE: 89/04/07 NOTARIZED: NO DOCKET FACIL:STN-50-528 Palo Verde Nuclear Station, Unit 1, Arizona Publi 05000528 AUTH. NAME AUTHOR AFFILIATION HAYNES,J.G. Arizona Nuclear Power Project (formerly Arizona Public Serv RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Special Rept 1-SR-89-001:on 890306,Channel B reactor vessel water level sys inoperable for period greater than 7 days.

DISTRIBUTION CODE: IE22D COPIES RECEIVED:LTR ENCL 50.73 Licensee Event Report (LER), Incident Rpt, etc. D SIZE:'ITLE:

NOTES:Standardized plant. 05000528 8 RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL h PD5 LA 1 1 PD5 PD 1 1 CHAN,T 1 1 DAVIS,M 1 1 INTERNAL: ACRS MICHELSON 1 1 ACRS MOELLER 2. 2 D

ACRS WYLIE 1 1 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DS P 2 2 IRM/DCTS/DAB 1 -

1 S DEDRO 1 1 NRR/DEST/ADE 8H 1 1 NRR/DEST/ADS 7E 1 0 NRR/DEST/CEB 8H 1 1 NRR/DEST/ESB 8D 1 1 NRR/DEST/ICSB 7 1 1 NRR/DEST/MEB 9H 1 1 NRR/DEST/MTB 9H 1 1 NRR/DEST/PSB 8D 1 1 NRR/DEST/RSB 8E 1 1 NRR/DEST/SGB 8D 1 1 NRR/DLPQ/HFB 10 1 1 NRR/DLPQ/QAB 10 1 1 NRR/DOEA/EAB 11 1 1 NRR/DREP/RPB 10 2 2 NRR/DM~S. 1 1 NUDOCS-ABSTRACT 1 1 G FILE 02 1 1 RES/DSIR/EIB 1 1 SR/PRKB 1 1 RGN5 FILE 01 1 1 EXTERNAL EGGG WI LLIAMSI S 4 FORD BLDG HOY I A 1 1 R H ST LOBBY WARD 1 1 LPDR 1 1 NRC PDR 1 1' NSIC MAYS,G 1 1 NSIC MURPHY,G.A 1 NOTES 1 1

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TOTAL NUMBER OF COPIES REQUIRED: LTTR 46 ENCL 45

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Arizona Nuclear Power Project P,O. BOX 52034 ~ PHOENIX. ARIZONA85072-2034 192-00466-JGH/TDS/RJR April 7, 1989 U. S. Nuclear Regulatory Commission NRC Document Control Desk Washington,,D.C. 20555

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

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

Special Report 1-'SR-89-001 File: 89-020-404 Attached please find Special Report 1-SR-'89-001 prepared and submitted pursuant to Technical Specifications 3.3.3.6 ACTION 31. This report discusses the inoperability of one channel of the Reactor Vessel Water Level System.

If you have any questions, please contact T. D. Shriver, Compliance Manager, at (602) 393-2521.

Very truly yours, J. G. HayIies Vice President Nuclear Production JGH/TDS/RJR/kj Attachment cc: D, B. Karner (all w/attachments)

E. E. Van Brunt, Jr.

J. B. Martin T. J. Polich M. J. Davis A. C. Gehr INPO Records'enter 9p4 g 9p A

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'alo Channel Verde Nuclear Generating Station Unit "B" Reactor Vessel Water Level System Inoperable License No. NPF-41 1

k Docket No. 50-528 Special Report No. 1-SR-89-001 Pursuant to Post Accident Monitoring Instrumentation Technical Specification 3.3.3.6 Table 3.3-10, ACTION STATEMENT 31, this submittal provides the required Special Report for the inoperability of one channel of the Reactor Vessel Water Level System (RVWLS) for a period of greater than seven (7) d'ays. RVWLS consists of two channels ("A" and "B"). Each channel utilizes eight (8) heated junction thermocouples (HJTC) to generate, the signals for .8 indicated levels. There are four HJTC's in the Reactor Vessel head region and four HJTC's in the Reactor Vessel outlet plenum. In order for each channel to be operable, two or more of. the upper four sensors 'and two or more of the lower four sensors must be functional.

Prior to the conditions. described in this Special Report, HJTC's 5 and 6 had malfunctioned on January 30, 1988 and HJTC's 3 and 4 had malfunctioned on June 9, 1988. ANPP has experienced reliability problems with the RVWLS.in all three units and is currently investigating the root 'cause of failure mechanism.

On March 6, 1989, Palo Verde Unit 1 was in Mode 3 (HOT STANDBY) when, at approximately 1830 MST, a Shift Technical Advisor observed that Channel "A" RVWLS indication for HJTC's 7 and 8 was not operating properly. 'ince HJTC's 5 and 6 had malfunctioned in January 1988 (HJTC's 5, 6, 7, and 8 are the four sensors in the reactor vessel outlet plenum), RVWLS Channel "A" was declared inoperable. An approved work document was initiated to determine the cause of the improper operation and to perform the necessary rework to return'he channel to service. During the troubleshooting, it was discovered that HJTC pair 7 and 8 had malfunctioned and repairs could not be effected until the next refueling outage.

HJTC's are electrically connected in pairs. HJTC's 5 and 6 are in series and HJTC's 7 and 8 are in series. Subsequent investigation has revealed that HJTC's 5 and 8 malfunctioned. Until permanent repairs can be accomplished, a Temporary Modification is being installed prior to unit startup to connect HJTC's 6 and 7 in series. This will return RVWLS Channel "A" to service pursuant to Technical Specification 3.3.3.6 Table 3.3-10.

The bases for the Technical Specification states:

"The Subcooled Margin Monitor (SMM), the 'Heat [sic] Junction Thermocouple (HJTC), and the Core Exit Thermocouples (CET) comprise the Inadequate Core Cooling (ICC) instrumentation required by Item II.F.2 NUREG-0737, the post TMI-2 Action Plan. The function of the ICC instrumentation is to enhance the ability of the plant operator to diagnose the approach to existence of, and recovery from ICC.

Additionally, they aid in tracking reactor coolant inventory. These instruments are included in the Technical Specifications at the request of NRC Generic Letter 83-37. These are not required by the accident analysis, nor to bring the plant*to Cold Shutdown.

Special Report I-SR-89-001 '...

Page 2 In the event more than four sensors in a Reactor Vessel Level channel are inoperable, repairs may only be possible during the next refueling outage. This is because the sensors are accessible only after the m'issile shield and reactor vessel head are removed. It is not feasible to repair a channel except during a refueling outage when the missile shield and reactor head are removed to refuel the core." "If only one channel is inoperable, it is intended that this channel be restored to OPERABLE status in a refueling outage as soon as reasonably possible."

The root cause of failure initiated as a .,result of previous failures will address the failure mechanism for the, malfunctioning HJTC's in Unit 1. This root cause will require removal of the. presently installed HJTC's and is expected to be completed by Harch 1990 by the vendor. The RVWLS Channel "A" is scheduled to be replaced during the next scheduled refueling outage.

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