ML20205J931

RO 86-01:on 860204,temp Recorder Providing LSSS Signal to Scram on High Fuel Temp Malfunctioned.Caused by Defective Motor Bearing.Bearing Replaced & Recorder Calibr

ML20205J931
Person / Time
Site:	05000128
Issue date:	02/18/1986
From:	Feltz D TEXAS A&M UNIV., COLLEGE STATION, TX
To:	Johnson E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
86-01, 86-1, 86-175, R-860218, R0-860218, NUDOCS 8602260682
Download: ML20205J931 (2)

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TEXAS ENGINEERIh G EXPERIM ENT STATION THE TEXAS A&M UNIVERSITY SYSTEM COLLEGE STATION, TEXAS 77843-3575

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M J 18 February 1986 NUCLEAR SCIENCE CENTER 409/845-7551 Mr. Eric Johnson '

ii ~('h $ ]SO M Office of Inspection and Enforcement 9 Region IV id, FEB 2 01986 U.S. Nuclear Regulatory Commission bOl 611 Ryan Plaza Drive, Suite 1000 9 Arlington, Texas 76012 RE: Final Report of Reportable Occurrence of 4 February 1986

Dear Mr. Johnson:

I am forwarding the final report of the reportable occurrence of 4 February 1986 on the failure of a safety measuring channel instrument to perform its intended safety function. This report is being submitted in accordance with NSC Technical Specification Section 6.6.2.(3) for License R-83, Texas A&M University.

Respectfully, f) /)ll

• 6 Donald E. Feltz Director DEF/ym Enclosure cc: Feenan Jennings, Chairman, Reactor Safety Board K. L. Peddicord, Department of Nuclear Engineering i.es Constable, Nuclear Regulatory Commission Bruce Ernst, American Nuclear Insurers 8602260682 860218 PDR S ADOCK 05000128 PDR

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RESEARCH AND DEVELOPMENT FOR MANKIND i

Final Report Reportable Occurrence #86-01, 4 February 1986 Failure of a Safety Measuring Channel Instrument to Perform Its Intended Safety Function Description of Occurrence On 4 February 1986 at 18:26 hours during pulsing of the NSCR the operator observed that the temperature recorder which provides the LSSS signal to scram on high fuel temperature was not responding properly. Failure of the temperature recorder to respond would result in loss of the high temperature scram trip which is activated by the resistance slide wire mechanism of the recorder. Three pulses were executed with the first pulse indicating normal temperature and a slight reduction of indicated fuel temperature being observed on the recorder for the second pulse and a significant reduction of indicated temperature on the third pulse. The digital temperature meter which is also a monitor of pulse temperature indicated normal temperatures for all three pulses.

The reactor was shutdown and pulse operations terminated for checkout of the temperature recorder to determine the problem.

Corrective Action The temperature recorder motor was found to be dragging due to a bad motor bearing. This resulted in the recorder not tracking the input signal from the

, thermocouple. The bearings in the motor were replaced, recorder maintenance and

< calibration of the LSSS scram signal was perfered and the system returned te service at 11:10 hrs. on 5 February 1986.

Safety Evaluation and Measures Planned to Prevent Reoccurrence Malfunction of the tenperature recorder did not result in operation of the reactor in an unsafe manner as the backup temperature indication was normal.

The performance of the reactor was determined to be normal. There are no recommendations for measures to prevent a recurrence as failure was unexpected and maintenance of the recorder had been performed on routine schedules.