ML17305A525

Special Rept 3-SR-90-001:on 900105,plant Vent Sys Radioactive Gaseous Effluent low-range Monitor RU-143 Declared Inoperable & Remained Out of Svc for More than 72 H.Caused by Anomaly in Check Source Circuitry

ML17305A525
Person / Time
Site:	Palo Verde
Issue date:	02/06/1990
From:	James M. Levine ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
192-00628-JML-T, 192-628-JML-T, 3-SR-90-001, 3-SR-90-1, NUDOCS 9002160199
Download: ML17305A525 (10)

Text

ACCELERATED DISTRIBUTION DEMONSTJRATION SYSTEM I

0 REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9002160199 DOC.DATE: 90/02/06 NOTARIZED- NO DOCKET FACIL:STN-50-530 Palo Verde Nuclear Station, Unit 3, Arizona Publi 05000530 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)

SUBJECT:

Special rept:on 900108,radiation monitoring unit inoperable for greater than 72 h.

DISTRIBUTION CODE: IE22D COPIES RECEIVED: LTR ( ENCL I SIZE:

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

NOTES:Standardized plant. 05000530 RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD5 LA 1 1 PD5 PD 1 1 PETERSON,S. 1 1 INTERNAL: ACRS MICHELSON 1 1 ACRS MOELLER 2 2 ACRS WYLIE 1 1 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 DEDRO 1 1 NRR/DET/ECMB 9H 1 1 NRR/DET/EMEB9H3 1 1 NRR/DET/ESGB 8D 1 1 NRR/DLPQ/LHFBll 1 NRR/DLPQ/LPEB10 1 1 NRR/DOEA/OEAB1 1 1 1 NRR/DREP/PRPB11 2 2 NRR/DST/SELB 8D 1 1 NRR/DST/SICB 7E 1 1 1 1 NRR/DST/SRXB 8E 1 1 1 1 RES/DSIR/EIB 1 1 1 1 EXTERNAL: EG&G WILLIAMS,S 4 4 L ST LOBBY WARD 1 1 LPDR 1 1 NRC PDR 1" 1 NSIC MAYS,G 1 1 NSIC MURPHY,G.A 1 1 NUDOCS FULL TXT 1. 1 NOTES 1 1 NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE.DOCUMENf CONTROL DESK, ROOM Pl-37 (EXY. 20079) TO ELIMINATEYOUR NAME FROM DISTRIBUTION TOTAL NUMBER OF COPIES REQUIRED: LTTR 38 ENCL 38

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ArizOna PubliC ServiCe Company PALO VERDE NUCLEAR GENERATING STATION P.O, BOX 52034 ~ PHOENIX, ARIZONA 85072-2034 JAMES M. LEVINE 192-00628-JML/TRB/DAJ VICE PRESIDENT NUCLEC R I'RODUCIIOII February 6, 1990 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Dear Sirs:

Subj ect: Palo Verde Nuclear Generating Station (PVNGS)

Unit 3 Docket No. STN 50=530 (License No. NPF-74)

Special Report 3-SR-90-001 File; 90-020-404 Attached please find Special Report 3-SR-90-001 prepared and submitted pursuant to Technical Specifications 3.3.3.8 and 6.9.2. This report discusses an inoperable radioactive effluent monitor.

If you have any questions, please contact T. R. Bradish, (Acting) Compliance Manager at (602) 393-2521.

Very truly yours, JML/TRB/DAJ/kj Attachment CC: W. F. Conway (all with attachment)

J. B. Martin E. E. Van Brunt D. H. Coe T. L. Chan A. C. Gehr gr 9002160199 ADOCK O 0OO '3O 90020('ua S PDC

PALO VERDE NUCLEAR GENERATING STATION Radiation Monitoring Unit Inoperable for Greater Than 72 Hours License No. NPF-74 Docket No. STN 50-530 Special Report 3-SR-90-001 I. DESCRIPTION OF WHAT OCCURRED:

A. Initial Conditions:

On January 8, 1990; Palo Verde Unit 3 was in Mode 3 (HOT STANDBY).

B. Reportable Event Description (Including Dates and Approximate Times of Major Occurrences):

Event Classification: Special Report required pursuant to Technical Specification 3.3.3.8 ACTION 42 This Special Report is being submitted pursuant to Technical Specification 3.3.3.8 ACTION 42b and Technical Specification 6.9.2 to report a condition wherein the Plant Vent System Radioactive Gaseous Effluent High Range Monitor (RU-144) was inoperable for greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />'he 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> interval for returning the monitor to service elapsed at approximately 1540 MST on January 8, 1990.

At approximately 1540 MST on January 5, 1990, the Plant Vent System Radioactive Gaseous Effluent Low Range Monitor (RU-143) was declared inoperable after it was noted that the gas channel background level had increased without apparent explanation.

Since RU-143 and RU-144 work as a pair, RU-144 was also declared inoperable. Pursuant to Technical Specification 3.3.3.8 ACTION 42a, the Preplanned Alternate Sampling Program was initiated to monitor the Plant Vent System effluent.

Troubleshooting performed in accordance with an approved work authorization document on RU-143 revealed that the cause of the increase in background level was an anomaly in the check source circuitry. The anomaly occurs due to the distance between the control circuitry and check source causing the check source (a Light Emitting Diode) to remain energized even though not in use.

This resulted in incorrect scintillation detector input into the microprocessor. The check source circuitry was modified in accordance with an approved design change document.

Following the modification to the check source circuitry, RU-143 operated properly. However, RU-143 and RU-144 remained inoperable in order to perform scheduled 18-month surveillance testing.

Following completion of the surveillance testing, RU-143 and

Special Report 3-SR-90-001 Page 2 RU-144 will be returned to service. Surveillance testing is expected to be completed by'ebruary 7, 1990.

Status of structures, systems, or components that were inoperable at the start of the event that contributed to the event:

Other than RU-144 being out of service as described in Section I.B, no structures, systems, or components were inoperable which contributed to this event.

D. Cause of each component or system failure, if known:

Not applicable - no component or system failures were involved.

Failure mode, mechanism, and effect of each failed component, if known:

Not applicable - no component fai.lures were involved.

For failures of components with multiple functions, list of systems or secondary functions that were also affected:

Not applicable - no component failures were involved.

For failures that rendered a train of a safety system inoperable, estimated time elapsed from the discovery of the failure until the train was returned to service:

Not applicable - no failures were involved.

H. Method of discovery of each component or system failure or procedural error:

Not applicable - there were no component or system failures or procedural errors.

Cause of Event:

As described in Section I.B, the cause of RU-144 being inoperable for greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> was an anomaly in the check source circuitry on RU-143. The original circuitry which controls the check source is physically located a long distance from the check source. Induced voltage in the wiring to the check source from adjacent circuits can cause the check source to activate. This anomaly was previously experienced on other PVNGS effluent radiation monitors and a design modification was prepared to install a relay in the check source circuitry providing a positive means for controlling activation of the check source. This modification was prepared and was to be implemented in appropriate PVNGS radioactive effluent monitors if the anomaly occurred.

(,

Special Report 3-SR-90-001 Page 3 J. Safety System Response:

Not applicable - no safety system responses occurred and none were necessary.

K. Failed Component Information:

Not applicable - no component failures occurred.

II. ASSESSMENT OF THE SAFETY CONSEQUENCES AND IMPLICATIONS OF THIS EVENT:

There were no safety consequences or implications resulting from this event. The Plant Vent System radioactive gaseous effluent instrumentation is provided to monitor the releases of radioactive materials in gaseous effluents during actual or potential releases of gaseous effluents. There are two separate radioactive gaseous effluent monitoring systems: the low range effluent monitor for normal plant radioactive gaseous effluents and the high range effluent monitor for pose-accident plant radioactive gaseous effluents ~ The low range monitor operates at all times until the concentration of radioactivity in the effluent becomes too high during post-accident conditions. The high range monitor only operates when the concentration of radioactivity in the effluent is above a pre-determined setpoint in the low range monitors.

There were no accident conditions requiring the operation of RU-144. If an accident had occurred, alternative sampling capability existed and could be implemented as described in the Preplanned Alternate Sampling Program.

III. CORRECTIVE ACTIONS:

As corrective action, a design modification was implemented to resolve the problem with the check source circuitry as discussed in Sections I.B and I.I. The design modification is also applicable to some other PVNGS radioactive effluent monitors. The design modification has been installed in the other monitors. Following completion of 18-month surveillance testing, RU-143 and RU-144 will be returned to service as described in Section I.B.