ML19318D252
| ML19318D252 | |
| Person / Time | |
|---|---|
| Site: | University of Missouri-Columbia |
| Issue date: | 06/04/1980 |
| From: | Brugger R, Mckibben J MISSOURI, UNIV. OF, COLUMBIA, MO |
| To: | |
| References | |
| NUDOCS 8007080260 | |
| Download: ML19318D252 (2) | |
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Research Reactor Facility UNIVERSITY OF MISSOURI Research Park Colurnbia, Missouri 65211 June 4, 1980 Telephone (314) 882-4211 Director of Licensing U. S. Nuclear Regulatory Commission Washington, D. C.
20555
Reference:
Docket 50-186 University of Missouri License No. R-103
Subject:
Failune of the Automatic Regulating Blade Drive Mechanism Description On May 16, 1980 with the reactor operating at full power in the automatic mode, a grinding noise was heard from the automatic regulating blade drive mech-anism. Control Room indication for the blade was observed to be stationary at 12.83 inches. The reactor was immediately shutdown by rod run-in.
The reactor had been operating at full power in automatic control with the regulating blade properly maintaining power for a period of 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> preceding the failure. The reactor was shutdown in accordance with Technical Specifi-cation 3.2.a at the time of failure.
Analysis The regulating blade controls reactor power at a desired level Dy the operating crew. The blade is constructed of stainless steel and drivt..
40 inches per minute.
It controls power by balancing the signal received from one of the nuclear instrument channels to a potentiometer set by the operating This blade is frequently making minor adjustments to maintain power at crew.
the desired power level.
Reviewing the nuclear instrumentation chart recorders showed that the regulating blade had been properly maintaining desired power until the reactor was shut down.
A visual inspection of the gear drive unit mounted on the drive motor shaft revealed a worn spot on a drive gear causing the motor to fail to drive the blade.
This explained the loud grinding noise that was heard when the regulating blade failed.
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o Director of Licensing June 4, 1980 Page 2 Corrective Action The regulating blade gear drive assembly was immediately replaced.
Following replacement, the regulating blade was cycled through its full travel assuring proper operation of the blade and all functions derived from the blade position. The portion of the compliance check associated with rod run-ins initiated by regulating blade position was checked satisfactorily.
Sincerely, J. C. McKibben Reactor Manager Endorsement Reviewed and approved Robert M. Brugger Director JCMK:vs cc: James Keppler, Director Regulatory Operations - Region III Reactor Advisory Committee Reactor Safety Subcommittee
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