PNO-V-87-066, on 871006,while Performing Periodic Surveillance Testing of Control Rods at 100% Power,Rod Control Urgent Failure Alarm Received on Shutdown Bank A. Caused by Blown Fuses.Fuses Replaced & Alarm Cleared

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PNO-V-87-066:on 871006,while Performing Periodic Surveillance Testing of Control Rods at 100% Power,Rod Control Urgent Failure Alarm Received on Shutdown Bank A. Caused by Blown Fuses.Fuses Replaced & Alarm Cleared
ML20235W980
Person / Time
Site: Diablo Canyon Pacific Gas & Electric icon.png
Issue date: 10/06/1987
From: Mendonca M, Narbut P
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:
References
PNO-V-87-066, PNO-V-87-66, NUDOCS 8710190149
Download: ML20235W980 (1)


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{ $E_L_I INARY; NOTIFICATION OF EVENT OR UNUSUAL'0CCURRENCE--PNO-V-87-66 Date 10/06/ g

This[ preliminary notification constitutes'EARLY _ notice of events of POSSIBLE safety publiciinterest significance. The information presented is as initially received. .f <

Gwithout? verification or evaluation and .is basically all that is known by Region V staff i.fon thisJdate. ,

j FACIL!TY: . PACIFIC GAS &' ELECTRIC COMPANY  : Emergency Classification

..DIABLO CANYON UNIT 1 X Notification of Unusual Event 3 DOCKET NO. 50-275 .

Alert. '

SAN LUIS'0BISPD. COUNTY, CA Site Area Emergency General Emergency-Not Applicable

~ SUBJECT': ~ INITIATION OF PLANT SHUTDOWN REQUIRE BY TS3.0.3 i On October 6,l1987, while performing periodic surveillance' testing of control rods at

,100% power, as required by plant Technical Specifications (TS), a " rod control urgent ifailure" alarm was' received on shutdown bank A. Investigation of the urgent failure

" alarm revealed indicator fuses on power cabinet 2AC had blown. Cause of the fuses blowing was not known at the time of this notification ~ .

\

Group 2, shutdown A rods remained inserted intn the core approximately one step for a I period greater than one hour', which exceeds tne action statement for the~ TS requiring all shutdown rods to be fully withdrawn. Accordingly, the licensee determined the unit to be-in TS 3.0.3, declared an Unusual Event at'0405 PDT, and initiated a slow rampdown of. reactor power by boron addition- to the reactor coolant system. Resident inspectors

. responded to the-site.,

By 0530 all blown fuses were replaced, alarms were cleared, the rods were fully )

Lwithdrawn, and the Unusual Event was terminated. The resident inspectors are following Lthe licensce's root cause analysis and subsequent testing of the rod control system.

Preliminarily, the licensee has determined that the cause of the blown indicator fuses was due'to high resistance on the power supply fuse. This problem has been experienced ,

areviously, and the licensee monitors the fuses through infrared observations for ligh resistance-(hot spots) areas in the control rod power cabinet. The licensee has

'also been working with the NSSS vendor to resolve the problem.

This information'is current as of 10/06/87 at 9:30 am PDT.

CONTACT: M. Mendonca, RV P. Narbut FTS 463-3720 805-595-2354 DISTRIBUTION BY 5520: FAX T0:

Date Chairman Zech Time Date Time  !

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Comm. Roberts AE0D RII NSAC Comm. Bernthal PA0 RIII LICENSEE

  • E N  !

Conin. Carr SLITP RIV RESIDENT INSPECTOR

? l Comm. Rogers

'SECY NRR NNSS HQS. OPERATIONS OFFICER > cs M 1

CA. ARM MAIL T0:

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-PDR OI DCS(Original)

  • OGC OIA D0T:(Trans. Only, Applicable State) l

ACRS RES j GPA f i RV FORM 211 g'

)p'bl Revised: 8/19/87 I 199 99 a71006 PD" Q h h 066

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