ML17305A977

Forwards Status of Corrective Actions to Min Multiple Control Element Assembly Drop Events at Plant.Insp of Insulation Coils & Replacement of Defective Coils for Units 1 & 2 Completed

ML17305A977
Person / Time
Site:	Palo Verde
Issue date:	07/25/1990
From:	Conway W ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9008070065
Download: ML17305A977 (8)

Text

~ s 6 ACCELERATED D STRIBUTION DEMONSTPA,TION SYSTEM t

REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9008070065 DOC.DATE: 90/07/25 NOTARIZED: NO DOCKET FACIL:STN-50-528 Palo Verde Nuclear Station, Unit 1, Arizona Publi 05000528 STN-50-529 Palo Verde Nuclear Station, Unit 2, Arizona Publi 05000529 STN-50-530 Palo Verde Nuclear Station, Unit 3, Arizona Publi 05000530 AUTH. NAME AUTHOR AFFILIATION CONWAY,W.F. Arizona Public Service Co. (formerly Arizona Nuclear Power RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Forwards status of corrective actions to min multiple D control element assembly drop events at plant.

DISTRIBUTION CODE:

TITLE: OR ADO ID COPIES RECEIVED:LTR Submittal: General Distribution g ENCL Q SIZE:

/

NOTES:STANDARDIZED PLANT 05000528 Standardized plant. 05000529 A Standardized plant. 05000530 D

RECIPIENT COPIES RECIPIENT COPIES D ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD5 LA 1 1 PD5 PD 1 1

'PETERSON,S. 5 5 TRAMMELL,C. 5 5 INTERNAL: ACRS 6 6 NRR/DET/ECMB 9H 1 1 NRR/DOEA/OTSB11 1 1 NRR/DST 8E2 1 1 NRR/DST/SELB 8D 1 1 NRR/DST/SICB 7E 1 1 NRR/DST/SRXB 8E 1 1 NUDOCS-ABSTRACT 1 1 1 0 OGC/HDS1 1 0 REG FILE 01 1 1 RES/DSIR/EIB 1 1 EXTERNAL: LPDR 1 1 NRC PDR NSIC 1 1 NOTES 1 1 D

A D

D NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM P 1-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

TOTAL NUMBER OF COPIES REQUIRED: LTTR 33 ENCL 31

i ~'

)

Arizona Public Service Company P.O. BOX 53999 ~ PHOENIX, ARIZONA850724999 161-03364-WFC/JST WILLIAMF. CONWAY EXECUTIVEVICEPRESIDENT July 25, 1990 NUCLEAR Docket No. STN 50-528/529/530 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Mail Station Pl-37 Washington, D. C. 20555

Reference:

(1) Letter to NRC from W. F. Conway, Dated May 23, 1990;

Subject:

Status of Improvements to Eliminate the Possibility of Multiple CEA Drop Events (2) Letter to NRC from W. F. Conway, Dated October 25, 1989;

Subject:

"Justification for Continued Operation - Control Element Assembly (CEA) Drop Events, Revision 3"

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Units 1, 2, and 3 Status of "Justification for Continued Operation - Control Element Assembly (CEA) Drop Events, Revision 3" File: 90-056-026 Reference (1) provided the status of improvements to minimize the possibility of multiple CEA drop events at PVNGS. These improvements were outlined in the "Justification for Continued Operation - Control Element Assembly (CEA) Drop Events, Revision 3 (JCO)," reference (2). In order to keep you informed of our progress, the attachment to this letter provides an updated status of the corrective actions for your information.

As a result of the corrective actions taken to date on Units 1 and 2, the JCO is no longer required for those Units. The PVNGS Plant Review Board approved the suspension of the JCO from Units 1 and 2 on June 8, 1990 after reviewing the root cause and corrective actions taken to date. The PRB noted that the only outstanding corrective action, reversal of latch coil polarity, will be completed at the next series of refueling outages and is being tracked as a regulatory commitment to ensure completion. The reversal of the latch coil polarity will minimize lift coil motion during CEA movement and improve long term coil The completion of this corrective action is not required for continued operation life.

since without the original manufacturing defect, damaged insulation on the coil lead wires, no grounding would be expected to occur even with coil motion.

tf~ "t 5'008070065 900725 PDR ADOCK 05000528 paoi P PDC l/I

Qi t5 I L ')'

Nuclear Regulatory Commission 161-03364-WFC/JST Document Control Desk July 25, 1990 Page 2 Please contact me if you have any questio'ns.'incerely, WFC/J ST/j le cc: J. B. Martin T. L. Chan D. H. Coe A. H. Gutterman S. R. Peterson E. E. Van Brunt

4+

4i <Q

,1

~, Jf,+

~ ~

Attachment Status, of Corrective Actions Coil Sleevin To inspect coil insulation, replace defective coils, and sleeve all CEDM coil leads:

Units 1 and 2 - This action is complete.

Unit 3 - Inspection program to be performed at the next scheduled refueling outage.

Ground Fault Detection To assure continuous monitoring and annunciation of any future CEDM ground faults:

Units 1 and 2 - Modified ground fault detector installed and tested.

Unit 3 - Ground fault detector modification will be installed during next outage of sufficient duration.

Latch Coil Polarit Reversal Coupling of the lower latch and lift coil magnetic fields by reversing the polarity of the lower latch coil will minimize lower lift coil motion:

Units 1, 2, and 3 - This design change will be completed for implementation during the next series of refueling outages.

Status of Long Term Enhancements In the long term APS has received a proposal from Combustion Engineering to reduce the CEDMCS susceptibility to noise by modifying the Zero Crossing Detector Circuitry in the silicon controlled rectifier firing circuitry. This proposal is currently being evaluated by APS Engineering.

Qi I

~q s ~