ML17310B362

Special Rept 1-SR-94-001:on 940511,plant Ventilation Sys High Range Effluent Monitors in Units 1 & 2 Inoperable for Periods Greater than 72 H.Caused by High Voltage Failure Alarm.Design Change Package Installed

ML17310B362
Person / Time
Site:	Palo Verde
Issue date:	06/09/1994
From:	James M. Levine ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
1-SR-94-001, 1-SR-94-1, 102-03002-JML-B, 102-3002-JML-B, NUDOCS 9406210193
Download: ML17310B362 (6)

Text

ACCELERATED DISTRIBUTION DEMONSTRATION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)DOCKET 05000528 05000529

SUBJECT:

Special Rept 1-SR-94-001:on 940511,plant ventilation sys hxgh range effluent monitors in Units 1&2 inoperable for periods greater than 72 h.Caused by high voltage failure alarm.Design change package installed.

DISTRIBUTION CODE: IE22D COPIES RECEIVED:LTR ENCL SIZE: TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.ACCESSION NBR:9406210193 DOC.DATE: 94/06/09 NOTARIZED:

NO FACIL:STN-50-528 Palo Verde Nuclear Station, Unit 1, Arizona Publi STN-50-529 Palo Verde Nuclear Station, Unit 2, Arizona Publi AUTH.NAME AUTHOR AFFILIATION LEVINE,J.M.

Arizona Public Service Co.(formerly Arizona Nuclear Power RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)NOTES:STANDARDIZED PLANT Standardized plant.05000528 05000529 RECIPIENT ID CODE/NAME PDIV-3 PD TRAN,L INTERNAL: ACRS AEOD/ROAB/DS P NRR/DE/EMEB NRR/DRCH/HHFB NRR/DRCH/HOLB NRR/DSSA/SPLB NRR/PMAS/IRCB-E RES/DSIR/EIB EXTERNAL: EG&G BRYCE,J.H NRC PDR NSIC POORE,W.COPIES LTTR ENCL 1 1 1 1 1 1 2 2 1 1 1 1 1 1 1 1 1 1 1 1 2 2 1 1 1 1 RECIPIENT ID CODE/NAME HOLIAN, B AEOD/DS P/TPAB NRR/DE/EELB NRR/DORS/OEAB NRR/DRCH/HICB NRR/DRSS/PRPB NR-SSA SRXB EG F LE 02 N ILE 01 L ST LOBBY WARD NSIC MURPHY,G.A NUDOCS FULL TXT COPIES LTTR ENCL 1 1 1.1 1'1 1 1 1 2 2 1 1 1 1 1 1 1 1 1 1 1 1 NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE!CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT.20079)TO ELIMINATE YOUR NAME FROM DISTRIBUTION LIPID FOR DOCUMENTS YOU DON'T NEED!TOTAL NUMBER OF COPIES REQUIRED: LTTR 28 ENCL 28 Arizona Public Service Company PALO VERDE NUCLEAR GENERATING STATION P.O.BOX 52034~PHOENIX, ARIZONA 85072-2034 JAMES M.LEVINE VICE PRESIOB4T NUCLEAR PRODUCTION 102-03002-JML/BAG/P JC June 9, 1994 U.S.Nuclear Regulatory Commission ATTN: Document Control Desk Mail Station P1-37 Washington, D.C.20555

Subject:

Palo Verde Nuclear Generating Station (PVNGS)Units 1 and 2 Docket No.STN 50-528 (License No.NPF-41)Docket No.STN 50-529 (License No.NPF-51)Special Report 1-SR-94-001 File: 94-020-404 Enclosed please find Special Report 1-SR-94-001 prepared and submitted pursuant to the requirements of the PVNGS Qffsite Dose Calculation Manual and Technical Specification 6.9.2.This report discusses the Plant Ventilation System High Range Effluent Monitors (RU-144)in Units 1 and 2 being inoperable for a period greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.If you have any questions, please contact Burton A.Grabo, Supervisor, Nuclear Regulatory Affairs, at (602)393-6492.Sincerely, JML/BAG/P JC Enclosure cc: L.J.Caltan K.E.Perkins K.E.Johnston (all w/enclosure)

A 9406210193 94060'TI PDR ADat:K OS00OS2a S PDR t/~g3 PALO VERDE NUCLEAR GENERATING STATlON UNITS 1 AND 2 PLANT VENTILATlON SYSTEM HlGH RANGE EFFLUENT MONITOR RU-144 INOPERABLE Docket No.STN 50-528 (License No.NPF-41)Docket No.STN 50-529 (License No.NPF-51)Special Report 1-SR-94-001 Initial Conditions On May 11, 1994, Units 1 and 2 were in Mode 1 (POWER OPERATION) operating at approximately 86 percent power.Descri tion of Event This special report is being submitted pursuant to the requirements of the PVNGS Offsite Dose Calculation Manual (ODCM)and Technical Specification 6.9.2 to report an event (three occurrences) in which the Plant Ventilation System High Range Effluent Monitors in Units 1 and 2 were inoperable for periods greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.The 72-hour periods for returning the monitors to service were exceeded in Unit 1 at approximately 0952 MST on May 23, 1993, and at approximately 0745 MST on March 18, 1994.In Unit 2, the 72-hour period for returning the monitor to service was exceeded at approximately 0945 MST on April 23, 1993.Back round Radiation monitors RU-143 (Plant Ventilation System Low Range Effluent Monitor)and RU-144 work as a pair.RU-143 is normally in service and continuously monitors plant ventilation exhaust.RU-144 is automatically started when RU-143 reaches a predetermined setpoint.RU-144 is provided for tracking radioactive effluents during postulated accident scenarios.

Prior to 1993, the low range monitor was required to be operable for the high range monitor to be considered operable.Therefore, if the low range monitor was inoperable, the high range monitor was also inoperable, and ODCM, Table 2.1, Action 42, which requires initiation of the Preplanned Alternate Sampling Program, was applicable.

During the first quarter of 1993, Design Change Package (DCP)13PJ-SQ-066 was installed for the Plant Ventilation System effluent monitoring pairs in Units 1 and 2.The DCP allowed the high range monitor to be operable when the low range monitor was out-of-service by placing the high range monitor in a mode designated as Handover Disable.lf only the low range monitor was out-of-service, the high range monitor could be placed in the handover disable mode, remain operable, and ODCM, Table 2.1, Action 42 would not apply.

Cause of Event On May 11, 1994, plant personnel performing troubleshooting under an approved work document identified that a high voltage failure alarm and a detector failure alarm would not annunciate when the high range monitor was in handover disable mode.Errors that prevented the alarms from annunciating in the handover disable mode were found in the vendor-revised software code.The software errors were associated with the changes made by the DCP in the section of code which controls monitor and channel handover.For the monitor to be considered operable in accordance with the ODCM, control room alarm annunciation must be demonstrated to occur if the instrument indicates a downscale failure (detector failure).Therefore, the high range monitor was not operable, even in the handover disable mode, when the low range monitor was inoperable.

Undetected errors in the vendor-revised software code associated with the DCP were the cause of the condition.

The PVNGS software test plan in the DCP required testing only for those conditions and functions that were known to have changed.The detector failure and high voltage failure alarms were not expected to have changed.Corrective Action The APS investigation determined that the Plant Ventilation high range monitor in Unit 3 and the Fuel Building Ventilation high range monitors (RU-1 46)in all three units were also affected by the software errors;however, the only periods of inoperability that exceeded the 72-hour limit for returning the monitors to service are discussed below.A review of low range monitor inoperability from the time the DCP was installed until the present was performed to determine if there were periods of inoperability in excess of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.Three occurrences of a low range monitor being'inoperable for periods greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> while the high range monitor was believed to be operable in the handover disable mode were identified.

These periods of inoperability were: Unit 2 RU-143/144 0945 MST, 04/20/93 to 1520 MST, 05/05/93 366 Hours Unit 1 RU-143/144 0952 MST, 05/20/93 to 1243 MST, 05/25/93 123 Hours Unit 1 RU-143/144 0745 MST, 03/15/94 to 1230 MST, 03/19/94 101 Hours Although the monitors could not be considered operable during these periods, they were operating normally and were functional with the exception of annunciation capability for a detector failure.Based upon the satisfactory completion of the monthly source checks, there were no detector failures during the periods of high range monitor inoperability.

A Quality Assurance audit in mid-1993 identified deficiencies in the control of plant process software including procurement of contract software and control of vendor problem reporting.

Extensive corrective actions are being developed to resolve concerns associated with the design, installation, and configuration of process software.Such problems as errors in vendor-provided software are being addressed within the overall context of the corrective action plan.Resolution is being tracked by an open Quality l'

Assurance corrective action document.To resolve the specific software problems identified in this report, Setpoint Change Request (SPCR)S13J-SQ-015 has been developed to correct the software errors in the affected monitors.The SPCR contains an extensive Design Validation Test that will test all of the software features, not just those that have been modified, to demonstrate that the software will perform as designed in all modes of operation.

The corrected software will be installed and tested by July 29, 1994.Once the Design Validation Test has been used to verify SPCR S13J-SQ-01 5 and has been established as a thorough software test for the monitors, it will be used as the design retest whenever significant modifications are made to the source codes.In the interim, the affected monitors are operable.Administrative controls which prohibit using the high range monitors in the handover disable mode have been implemented.