ML17303A668

Special Rept 2-SR-87-025:on 871002,radiation Monitoring Unit RU-142 Declared Inoperable for Greater than 72 H.Caused by Intermittent Fluctuations Occurring in Cpu Board Reset Switch.Monitors Declared Operable & Returned to Svc

ML17303A668
Person / Time
Site:	Palo Verde
Issue date:	10/29/1987
From:	Haynes J ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
192-00295-JGH-T, 192-295-JGH-T, 2-SR-87-025, 2-SR-87-25, NUDOCS 8711090345
Download: ML17303A668 (4)

Text

REGULA i ORY INFORMATION DISTR IBUTI . SYSTEM (RIDS)

ACCESSION NBR: 8711090345 DOC. DATE: 87/10/29 NOTARIZED: NO DOCKET ¹ FACIL: STN-50-52'P Palo Verde Nuclear Stationi Unit 2i Arizona Publi 05000529 AUTH. NAME AUTHOR AFFILIATION HAYNES'. G. Arizona Nuclear Power Prospect (formerly Arizona Public Serv REC IP. NAME > RECIPIENT AFFILIATION Document Control Branch (Document Control Desk>

SUBJECT:

Special Rept 2-SR-87-025: on 871002. radiation monitoring unit RU-142 declared inoperable for greater than 72 h. Caused bg intermittent fluctuations occurring in CPU board reset smitch. Monitors declared operable 5 returned to svc.

DISTRIBUTION CODE: IE22D COPIES RECEIVED: LTR TITLE: 50. 73 Licensee Event Report (LER)i Incident Rpti

+ ENCL ~etc.SIZE:

NOTES: Stand ar d i z ed p lant. 05000529 RECIPIENT RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD5 L* 1 1 PD5 PD 1 1 LICITRAiE 1 1 DAVIS' 1 1 INTERNAL: ACRS MICHELSON 1 1 ACRS MOELLER 2 2 AEOD/DOA 1 1 AEOD/DSP/NAS 1 AEOD/DSP/ROAB 2 2 AEOD/DSP/TPAB 1 1 ARM/DCTS/DAB 1 1 DEDRO 1 1 NRR/DEBT/ADS 1 0 NRR/DEST/CEB 1 1 NRR/DEST/ELB 1 NRR/DEST/ICSB 1 1 NRR/DEST/MEB 1 NRR/DEST/MTB 1 NRR/DEBT/PSB NRR/DEST/RSB 1 NOTES'OPIES 1 1 NRR/DEST/SGB 1 1 NRR/DLPG/HFB 1 1 NRR/DLPG/GAB 1 1 NRR/DOEA/EAB 1 NRR/DREP/RAB 1 1 NRR/DREP/RPB 2 2 IS/SIB, 1 1 NRR/PMAS/ILRB 1 1 RE E 02 1 RES DEPY QI 1 S T'E RDt J 1 RES/DE/EIB 1 1 RQN5 F ILE 01 1 1 EXTERNAL: EG8cQ GROH> M 5 5 H ST LOBBY WARD 1 LPDR 1 1 NRC PDR 1 1 NSIC HARRIS' 1 NSIC MAYST G 1 1 TOTAL NUMBER OF COPIES REQUIRED: LTTR 47 ENCL 'b

Arizona Nuclear Power Project P.O. BOX 52034 ~ PHOENIX, ARIZONA 85072-2034 192-00295-JGH-TRB/KCP October 29, 1987 U.S. Nuclear Regulatory Commission NRC Document Control Desk Washington, D.C. 20555

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Unit 2 Docket No. STN 50-529 (License NPF-51)

Special Report 2-SR-87-025 File: 87-020-404 Attached please find Special Report 2-SR-87-025 prepared and submitted pursuant

'ery to Technical Specifications 3.3.3.8 and 6.9.2. This report discusses a radiation monitor that 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 />.

If you have any questions, please contact T. R. Bradish, Compliance Supervisor at (602) 393-3531 tru y yours, O'er J. G. Haynes Vice President Nuclear Production JGH/TRB/KCP/cld Attachment cc: 0. M. DeMichele (all w/a)

E. E. Van Brunt, Jr.

J. B. Martin J. R. Ball E. A. Licitra A. C. Gehr INPO Records Center 8712090345 871029 PDR ADQCN 05000529 S PDR

PALO VERDE NUCLEAR GENERATING STATION RADIATION MONITORING UNIT INOPERABLE FOR GREATER THAN 72 HOURS License No. NPF-51 Docket No. STN 50-529 Special Report No. 2-SR-87-025 This Special Report is being submitted in accordance with Technical Specification (T.S.) 3.3.3.8 ACTION 42(b) and 6.9.2 to report an event in which a high range noble gas monitor (RU-142) 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 />. The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> limit for inoperability was exceeded at approximately 0835'ST on October 5, 1987.

At approximately 0835 MST on October 2, 1987 Palo Verde Unit 2 was in Mode 1 (POWER OPERATION) at 100 percent power when the Condenser Vacuum Pump/Gland Seal Exhaust Low and High Range Monitors (RU-141/142) were declared inoperable to permit surveillance testing under 36ST-9SQ04, "Radiation Monitoring Quarterly Functional Check". Compensatory measures were established in accordance with T.S. 3.3.3.8, ACTIONS 36, 37, 40 and 42, and T.S., 3.11.2.1.

During the surveillance test, the skid-mounted indication and control unit (SMIC) for RU-142 di.splayed several incorrect values, preventing successful completion of the test. An investigation was subsequently conducted under an approved work document to determine the cause of failure and to implement appropriate corrective action. The RU-141/142 monitor pair remained inoperable as noted above.

RU-141 and RU-142 monitor for gaseous activity resulting from primary-to-secondary system leakage by continuously and isokinetically sampling the condenser vacuum pump/gland seal exhaust for airborne radioactive particles, and iodine. These monitors work as a pair, with RU-141 as the low range monitor and RU-142 as the high range monitor. RU-141 provides automatic initiation of filtration of condenser vacuum pump/gland exhaust whenever the monitor is in a HIGH-HIGH alarm condition. Normal configuration consists of RU-141 operating and RU-142 in standby. Since RU-141 and RU-142 work in tandem, RU-142 must be declared inoperable if RU-141 malfunctions. RU-142 contains 5 channels, with Channel 1 as the mid-range channel and Channel 2 as the high range channel.

Channels 3, 4 and 5 are shielded particulate/I-131 cartridges. A small G-M tube determines when a cartridge is sufficiently irradiated and automatically switches flow to the next cartridge. Upon initialization of RU-142, Channel 1 is operating with Channel 2 in standby, and Channel 3 is open with Channels 4 and 5 closed.

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Special Report 2-SR-87-025 The investigation determined that intermittent fluctuations were occurring in the 5.0 VDC initialization voltage across the CPU board reset switch (SWl).

When simulating conditions in which Channel 3 was to be off-line and Channel 4 on-line, these fluctuations caused the monitor to reset, placing Channel 3 on-line and Channel 4 off-line. These fluctuations were due to the CPU board being improperly -seated. Additionally, the SMIC display board was found to contain a faulty LED which would not change value. To correct these conditions, the CPU board was reseated and verified to maintain the correct voltage across the CPU board reset switch, and the SMIC display board was replaced.

At approximately 1520 MST on October 5, 1987, RU-141/142 were declared operable and returned to service after satisfactory completion of surveillance testing under 36ST-9SQ04 and 75ST-9ZZ07, "Effluent Monitoring System Daily Surveillance Testing." The monitors were inoperable for approximately 79 hours9.143519e-4 days <br />0.0219 hours <br />1.306217e-4 weeks <br />3.00595e-5 months <br />.