ML20206J784

Ro:On 881104,unscheduled Reactor Shutdown Occurred Due to Failure of Temp Recorder to Indicate Properly.Caused by Failure of Microswitch.Microswitch & Vacuum Tube Replaced & Calibr Check Performed

ML20206J784
Person / Time
Site:	05000083
Issue date:	11/14/1988
From:	Vernetson W FLORIDA, UNIV. OF, GAINESVILLE, FL
To:	Ernst M NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
NUDOCS 8811290120
Download: ML20206J784 (3)

Text

m NUCLEAR ENGINEERIND SCIENCES DEPARTMENT r Nuclear Reactor Facility University of Florida o ei.,

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iiu v e ='ue s 14, 1988 Temperature nonitoring Syst.es Failure Final (14 Day) Report Nuclear Regulatory Commission Suite 2900 101 Marietta Street, N.W.

Atlanta, GA 30323 Attention: Malcolm L. Ernst Acting Regional Administrator, Region II Re t University of Florida Training Reactor Facility License R-56, Docket No. 50-83 Gentiemen:

Pursuant to the reporting requirements of paragraph 6.6.2(3)(c) of the UFTR Technical Specifications, a description of a potential abnormal occurrence as '

defined in the UTTR Technical Specifications Chspter 1 is described in this 14-day report to include NRC nocification, occurrence sceaario, evaluation of coasequences, corrective action and current status. The potential promptly re-portable occurrence involved failure of the temperature monitoring syi. tem re-salting in an unscheduled shutdown.

NRC Notification h members of the Executive Committee of the Reactor Safety Review Subcommit-tee (RSRS) including the Director of the Facility (W.G. Vernetson) w.ere ap-prised of the details of this occurrence individually on November 4,1988 and individually concluded that it is a potential abnormal occurrence as defined in UFTR Technical Specifications, Chapter 1. The wembers recommended NRC noti-fication per Section 6.642 of the UFTR Tech Spessi. This notification was car-ried out by telephone to Mr. David Verre111 on Friday, November 4, 1988 with a following telecopy on November 7,1988 (next working day) as required (see At-tachment I).

The Executive Committee of the RSRS reviewed the full details of this occur-rence at a final meeting on November 8,1988. The Executive Committee also concurred wth management testart approval subject to NRC notification of the status of the corrective action and readiness to restart normal operations.

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f Nuclear Regulatory Commission yovember 14, 1988 Page Two Initial Event Scenario At 1108 on Fridty, Novembec 4,1988 with the reactor operating at 100 kw for an irradiation supporcing neutron activation analysis (with P.M. Whaley as Roactor 9perator), the temperature recLtder failed to indicate properly (i.e.,

stopped tracking). SRO P.M. Whaley noted that reactor power level indicators were functioning normally and, noting that no other abnormal indications existed, commenced an unschedaled shutdown. The reactor was shut down and se-cured without incidtst with all other systems responding properly. Following securing of the reactor and recorder, the temperature recorder readings for all monitored points failed to vaty shen the temperature recorder was manually activated. Manual manipulation of the indicator. print wheel was accomplished asich na resistance by the instrument. The print wheel remained at the indicat-ing point established by manipulation of the print wheel. .

Evaluation of Consoquences Rasetor staff and administration including Director W.G. Vernetson concluded there was no compromise to reactor safety from this event, nor was there as/  ;

impact on personnel radiation doses. This event is considered to be potential- "

ly a reportable occurrence since the temperature recorder would potentially i fail to register the high temperature required to initiate a high primary l coolant system temperature trip. However, all other control and safety systems responded properly.

Based on evaluations of this event, restart was recommended following replace-mont of the degraded microswitch that disables the motor during switching L transients, recalibration of the temperature recorder and completion of a  ;

valid weekly sad daily p*eoperational checkout on the affected portions of the reactor system.  !

Corrective Action i

i Immediate corrective action consisted of securit.g the reactor and putting it [

on administrative shutdown until the problem could be isolated and corrected.  :

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Preliminary investigation indicated a loss of power to drive the servo motor.

Manual manipulatio7 of the indicator met no resistance and the indicator post-tion did not return to normal. These aymptoms indicated the problem to be in one of three (3) areast the amplifier, the drive control circuit, or the con- l stant voltage unit. The amplifier and drive motor were checked to be func- l tional in an out-of-circuit test and t!.e constant voltage unit was measured to  !

be operating properly in place.  :

, r In-circuit measurements of the servo drive motor, however, indicated one set  !

of windings had low resistance. Following the removal (for physical examina-tion) and replacement of the microswiten that disables the motor during  ;

switching transients, system operation was returned to normal. Checks indi-cated the servo drive motor had proper resistance values. All symptoms were ,

duplicated by installing axternal resistance in parallel (simulating contact l resistance) with the microswitch indicating the microswitch as the probable (

cause of the failure. j l

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Nuclear Regulatory Commission Novembe r 14, 1988 Page Theat Prior to returning to normal operations, the microuitch was replaced along with a vacuum tube which had a marginally acceptable gain when tested and a calibration check was performed on the temperature mnitoring system. Finally, '

a valid weekly and daily preoperational check on the affected portions of the reactor systems were completed. A one hour power operation exercising thJ ten-perature monitor over most of its normal range was the first critical opera-tion af ter return to operations based upon RSRS approval and NRC notification to Mr. Robert Carroll on 9 Novembet 1988. After this test operation was suc-cessful on November 9, the reactor was approved for return to full normal op-

erations including running experiments and other normal operational activi-ties.

Current Status All operators have been made cognizant of this problem. Sinct tastart on No-vember 9, 1988, there has been no recurrence of the temperature recorder failure.

I Sincerely, William G. Vernetson Director of Nuclear Facilities I

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Nota 4 cc: P.M. Whaley l

Reactor Scfety Review Subcommittee t

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NUCLEAR ENGINEERIN3 SCIENCES DEPARTMENT Nuclear Reactor Facility University of Florida ,

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• ce.vae,nesw. autt Novsmber 7, 1988 Nuclear Regulatory Commission, Region 11 101 Marietta Street, N.W.

Suite 2900 Atlanta , CA 30323

- Atteation: Malcolm L. Ernst Acting Regions 1 Administrator, Region 11 Re: University of Florida Training Reactoe Facility License: F.-56, Docket No. 50-83 - -

This letter is in followup to our telephone esil of 4 November 1988 notifying Mr. Dave Verre111 of a failure of the temperature record to track proparly and requiring an unscheduled shutdown.

Preliminary contact with the Reactor Safety Review Subcormittee supported conclusion that this event constitutes a potentially reportable occurrence per Technical Specifications 6.6.2(3)(c) and so the NRC .ts hereby notified per Sect.on 6.6.2 of the UFIR Technical Specifications.

The probable cause has now been isolated and the event and subse-quent planned recovery will be revirsed by the Resctor Safety Re-view Subcommittee within the next 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> for permission to re-start with c followup report to follow.

h 4 William G. 'Vernetson Tlf, h Dap '

Director of Nuclear Facilities WGV/ps cc Reactor Safety Review Subcommittee P.M. Whaley

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