ML17300B026

LER 87-021-00:on 870729,control Room Essential Filtration Actuation Initiated on Channels a & B of Esfas.Caused by Voltage Spike.Monitor Reset,Returning Setpoint to Specified value.W/870826 Ltr

ML17300B026
Person / Time
Site:	Palo Verde
Issue date:	08/26/1987
From:	Bradish T, Haynes J ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
192-00257-JGH-T, 192-257-JGH-T, LER-87-021, LER-87-21, NUDOCS 8709020017
Download: ML17300B026 (10)

Text

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ACCESSION NBR: 870'F020017 DOC. DATE: 87/08/26 NOTARIZED: NO DOCKET 1 FACIL: STN-50-528 Palo Verde Nuclear Station. Unit ii Arizona Pub li 05000528 AUTH. NAME AUTHOR AFFILIATION BRADISH> T. R. Arizona Nuclear PoUJer ProJect (formerly Arizona Public Serv HAYNES'. G. Arizona Nuclear PoUJer ProJect (formerly Arizona Public Serv RECIP. NAME RECIPIENT AFFILIATION

SUBJECT:

LER 87-021-00: on 870729'ontrol room essential f iteration actuation initiated on Channels A B of ESFAS. Caused bg Cc i

voltage spike. Monitor resetireturning setpoint to specified value. W/870826 ltr.

DISTRIBUTION CODE: IE22D COPIES RECEIVED: LTR ENCL SIZE:

TITLE: 50. 73 Licensee Event Report (LER)t Incident Rpti etc.

NOTES: Standard i z ed plant. M. Davis'RR: 1Cg. 05000528 RECIPIENT COPIES REC IP IENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD5 LA 1 1 PDS PD 1 1 LIC ITRAi E 1 DAVIS' 1 1 INTERNAL: ACRS MICHELSON 1 1 ACRS MOELLER 2 2

• EOD/DOA 1 AEOD/DSP/NAS 1 1 AEOD/DSP/ROAB -2 2 AEOD/DSP/TPAB 1 1 DEDRO 1 1 NRR/DEST/ADS 1 0 NRR/DEST/CEB 1 1 NRR/DEST/ELB 1 NRR/DEST/ICSB 1 1 NRR/DEST/MEB 1 1 NRR/DEST/MTB 1 1 NRR/DEST/PSB 1 1 NRR/DEBT/RSB 1 1 NRR/DEST/SQB 1 1 NRR/DLPG/HFB 1 1 NRR/DLPG/GAB 1 NRR/DOEA/E*B 1 1 NRR/DREP/RAB 1 1 NRI3JJ3RE PB 2 2 NRR/PMAS/ILRB 1

~EG FI 02 1 1 RES DEPY QI 1 1 RES TELFORDz J 1 1 RES/DE/EIB 1 RQN5 FILE 01 1 1 EXTERNAL: EGSQ GROHz M 5 5 H ST LOBBY WARD 1 1 LPDR 1 1 NRC PDR 1 NSIC HARRIS' 1 1 NSIC MAYST G 1 NOTES: 1 1 TOTAL NUMBER OF COPIES REQUIRED: LTTR 45 ENCL 44

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NAC Form 245 UA. NUCLEAR REOULATOAY COMMISSION (502)

APPAOVEO OMS NO. 21500104 LICENSEE EVENT REPORT {LER) EXPIRES: SISIISS 4}r FACILITY NAMK (1) DOCKET NUMSEA (2) PA li r '.

Palo Verde Unit 1 0 5 0 0 0 5 2 8 1 OF 0 3 ESP Actuation Caused By A Voltage Spike Concurrent with Low Radiation Moni r Set oint EVENT DATE (5) LER NUMSEA (5) REPORT DATE (7I OTHKA FACILITIES INVOLVED (Sl MONTH OAY YEAR YEAR PrrrrR SKQVKNTIAL , .err.: 5 1 VISIQIC MONTH OAY YEAR FACILITYNAMES OOCKFT NUMSERIS)

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0 7 2 9 8 7 8 7 021 0 0 0 8 2 687 N/A 0 5 0 0 0 OPKRAT INC THIS REPORT IS SUSMITTED PURSUANT 1 0 THE REQUIREMENTS OF 10 CPA ()I IClrecc one or more ol tne followlnpl (11 rrk} I MOOS ( ~ ) 20.402(O) 20.405(c) 50.72N)(21(ir) 72.71(ol

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LEVEL p p p 20.405(c l(1) (5) 50.25(c) (2) 50.72(c l(2) (r5) OTHER (Specify In Aottrect Oelow end ln ye>>L HAC Form 20.405(e) II )(IIII 50.72(c) (2) II) 50.7l(e)12) (rXl)(Al Sddrtl 20.405(c I (I I(I}i 50.72(c)(2)ll) 50.72(c)(2)(r(K) (Sl 20.405(c) III(r) 50.72(c) (2) l)4) 50.7l(c) (2)(el

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Thomas R. Bradish, Compliance Supervisor 6 023 93- 35 31 COMPLETE ONK LINE FOR EACH COMPONENT FAILURE OESCRISKD IN THIS AEPOAT (ll)

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X NO ASSTRACT ILImft to t400 tpecet, IA. eppreelmetely fifteen tlnple tpece typewrftlen line}i (15)

On July 29, 1987 at 0008 MST, Palo Verde Unit 1 was in Mode 3 (Hot Standby) when

F,) a Control Room Essential Filtration Actuation was initiated on Channels A and B Q.~I of the Engineered Safety Features Actuation System.

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r r The root cause of the actuation was a voltage spike, believed to be caused by 3 r equipment noise in the "A" Control Room Ventilation Intake Noble Gas Monitor i (RU-29), compounded by the monitor having been reset to the default alarm/trip setpoint. The reset was attributed to a temporary loss of power to the r associated Remote Indicating Controller during an electrical storm on July 28, 1987. The default alarm/trip setpoint is approximately 1 decade less than the value specified in the technical specifications. Had the setpoint been at the specified value, no actuation signal would have occurred. As corrective action the monitor was reset, returning the setpoint to the 14'rrr specified value. Ongoing corrective action to prevent recurrence involves .'jg j revising the default alarm/trip setpoints to be consistent with the technical specifications.

  "g Other events involving CREFAS actuations have been reported, including LER
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1-87-001 which also resulted from a monitor set at the default value, however, )>> I>>, C these events did not involve the root cause noted above. 870'7)020017 870826 PDR ADOCK 05000528 w 8 PDR

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NAC Form 944A U.S. NUCLEAA AEOULATOAYCOMMISSION 1943) LICENSEE EVENT REPORT HLER) TEXT CONTINUATION AFFAOVEO OM4 NO EIEOW104 EXFIAES: EISIN FACILITY NAME III OOCXET NUMEEA IEI LEA HUMEEA ISI FACE ISI YEAII SSOVCNTrAL grail AIYrsroN NVM EA NVM 41 Palo Verde Unit 1 TEXT N more rooce N eerroerE rrre oHHt'orMI HAC form JALl'41 I ITI 0 s 0 0 o 528 87 021 0 0 02oF 0 3 On July 29, 1987, at 0008 MST, Palo Verde Unit 1 was in Mode 3 (Hot Standby) when a Control Room Essential Filtration Actuation (CREFAS) was initiated on Train "A" of the Engineered Safety Features Actuation System (ESFAS)(JE). The Train "A" CREFAS cross-tripped the Train "B" CREFAS, per design, and all associated equipment operated satisfactorily. The CREFAS was initiated by the "A" Control Room Ventilation Intake Noble Gas Monitor (RU-29)(IL)(RI). This constitutes actuation of the Engineered Safety Features (ESF)(JE). The actuations were identified by the control room operators (utility-licensed) as a result of main control board (MCBD) annunciations. Following the ESF actuations, the control room operators (utility-licensed) verified that there were no actual radiation level increases by comparing the RU-29 results to the "B" Control Room Ventilation Intake Noble Gas Monitor (RU-30)(IL)(RI). A Radiation Protection (RP) technician (contractor non-licensed) then checked the alarm/trip setpoint for RU-29 and found it to be at the default value (2.20 XE-6 micro curies [Ci]/cubic centimeter [cc]). The specified alarm/trip setpoint for RU-29 is 2.0 XE-5 micro Ci/cc, a difference of approximately 1 decade. The peak spike on RU-29 was measured at 2.81 XE-6 micro Ci/cc. Had the alarm/trip setpoint been at the specified value, the actuations would not have occurred. The RU-29 alarm/trip setpoint was reset to the specified value. Based on the above information, the shift supervisor (utility-licensed) determined the alarm/trip to be spurious. At 0019 MST, the control room operators (utility-licensed) placed CREFAS "A" in bypass and declared RU-29 inoperable. The actuated equipment was returned to normal status at 0034 MST. The event lasted approximately 26 minutes. At 0045 .MST a RP technician (contractor non-licensed) was sent to obtain an air sample from the auxiliary building roof (NF) as a followup measure to the CREFAS alarm. Air sample results indicated no detectable activity. A review of alarm typer (PRNT) printouts showed that significant electrical disturbances occurred on the "A" train busses (BU) on July 28, 1987, at approximately 0014 MST, coincident with a fault and trip of Circulating Water Pump Motor "A" (KG)(P) during a severe electrical storm. This incident was followed at 0018 MST by a similar fault and trip of Circulating Water Pump Motor (KG) (P) . NAC FOAM SSSA 19 SSr

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NRC FCNii 34CA US. NUCLEAR REOULATORY COMMICCION IQ83I LICENSEE EVENT REPORT {LERI TEXT CONTINUATION APPROVED OMC NO. 3150WIOI EXPIRES: C/31/IS FACILITY NAME (II DOCKET NUMCER ICI LER NUMEER IC) ~ AOE ICI VCAR NVM Ii:I'5 CCOVCNTIAL ~IP NVM IIC V IC IO N Cll Palo Uerde Unit 1 0 s 0 0 o 5 2 8 8 7 021 00 03OF 0 3 TEXT IJF TROOP CPPCC N IPCvCW. V44 OICWiPW ARC FCNII 3ISA'Fl IITI Based on this information the reset to the default value of the alarm/trip setpoints for the affected monitors has been attributed to a momentary loss of power to the Remote Indicating Controllers (RIC) cabinet, due to the electrical disturbances noted above. Upon restoration of power, the RIC microprocessors download the default alarm/trip setpoint values to the radiation monitor microprocessor. This was substantiated when, folloving the restoration of the actuated equipment, a RP technician (contractor non-licensed) found the alarm/trip setpoint for the Fuel Pool Area Monitor (RU-31)(IL)(RI) to be set at the default value and subsequent investigation identified RU-33, Refueling Machine Area Monitor (IL)(RI), and RU-37, "A" Containment Power Access Purge Area Monitor (IL)(RI), to also be set at the default value. The RICs for RU-295 31, 33 and 37 are located in the same RIC cabinet and share a common power supply. The root cause of the actuation was determined to be a voltage spike, compounded by the monitor having been reset to the default alarm/trip setpoint as a result of a temporary loss of power. The voltage spiking is believed to have been caused by electronic circuit noise. As corrective action, the monitors were reset, returning the setpoints to the specified values. Other events involving CREFAS actuations have been reported including LER 1-87-001, which also resulted from a monitor set at the default value. However, these events did not involve the root cause as noted above. Corrective action to prevent recurrence for previous events included the installation of an isolated grounding system (FC) to reduce electronic circuit noise. Ongoing corrective action consists of a design change, currently in progress, to revise radiation monitoring system default alarm/trip setpoints to be consistent with the specified values. These changes should also prevent recurrence of this type of event, hence, no additional corrective action is deemed necessary. No personnel or procedural errors were identified which contributed to the event. There were no unusual characteristics of the work location, with the exception of the electrical storm, which contributed to the event. No structures, systems or components inoperable prior to the event were identified as contributing factors. Based on the results of the analysis described above which verified no abnormal radiation level existed, there was no effect on the health and safety of the public and no safety impact on the unit. Should other concerns or information pertinent to the event be discovered, a supplement vill be issued. 4 IIC ~ OII M 3444 IC 43i

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Arizona Nuclear Power Project P.O. BOX 52034 ~ PHOENIX, ARIZONA 85072-2034 192-00257-JGH/TRB/KCP August 26, 1987 Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555

Subject:

Palo Verde Nuclear Generating Station (PVNGS) Unit 1 Docket No. 50-528 Licensee Event Report 87-021-00 File: 87-020-404

Dear Sirs:

Attached please find Licensee Event Report (LER) No. 87-021-00 prepared and submitted pursuant to 10CFR 50.73. In accordance with 10CFR 50.73(d), we are herewith forwarding a copy of the LER to the Regional Administrator of the Region V Office. If you have any questions, please contact T. R. Bradish, Compliance Supervisor at (602) 393-3531. Very trul yours, J. G. Hay es Vice President Nuclear Production JGH/KCP/cld Attachment cc: 0. M. DeMichele (all w/a) E. E. Van Brunt, Jr. J. B. Martin R. C. Sorenson E. A. Licitra A. C. Gehr INPO Records Center

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