ML20084P022

Ro:On 680122,control Rod 1 Did Not Drop to Normal Zero Position When Reactor Shut Down by Manual Scram of Control Rods.Probably Caused by Foreign Matl Lodged in Control Rod Drive Mechanism Dashpot

ML20084P022
Person / Time
Site:	Saxton File:GPU Nuclear icon.png
Issue date:	02/23/1968
From:	Cindy Montgomery SAXTON NUCLEAR EXPERIMENTAL CORP.
To:	Skovholt D US ATOMIC ENERGY COMMISSION (AEC)
References
80615, NUDOCS 8306090199
Download: ML20084P022 (2)

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. $XTON NUCLEAR GENERAL PU B LIC EXPER&NTAL CORPORATION .

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[ n,Gri.C,;wc23RusJ0:pTO. Telephone: Area 45 32M331 f, [ P.O. Box 99, Saxton, Pa. 16678 814 635-2937

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February 23, 1968 1

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11r. Donald J. Skovholt Assistant, Director for Reactor Operations Divinicu of Reactar Licensing U.S. Atomic Energy Commission Washington, D.C. 20545

Dear IIr. Skovholt:

) During January 1968, the Saxton reactor was being utilized for reactor

operator start-up training with the primary coolant systera at operating pressure a

and temperature and nomal flow. On January 22, following completion of the day'a training, the reactor was shutdown by manual scram of the control rods.

( Control rod No.1, however, did rot drop to its nomal zero position, stopping

, at '!.98 inenca above zero. A subsequent rod exercise program resolved the difficulty with this rod.

] 'Ine difficulty experienced with No.1 control rod was reported to the Region I Compliance Office and to Division of Reactor Licensing by telephone on January 29, imd 13 herewith reported in writing in compliance with paragraph

{ 3 E(1) of the Saxton Operating License DPR-4.

With the reactor shutdown, an exercise program for No. 1 control rod was initiated to resolve or. further define the problem. Fifteen drops were made 4

from 40 inches; however, on the 16th drop the rod stopped at 3 22 inches above p itu zero position. Following this,14 drops were made from 40 inches, and 34 4 drops were made fron 10 inches without difficulty. On the 35th drop from 10 inchen, the rod stopped at 2.97 inches above its zero position. Rod exercise was continued for an additional 50 drops without further difficulty.

I Rod withdrawal rates and drop times were measured and compared with previous data. All were nomal.

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i The difficulty experienced with this rod was reviewed by the Saxton

• On-Site Safety Carnittee and by the reactor manufacturer. It was concluded that probably a small piece of foreign material was lodged in the control rod drive mechanium dashpot and that it was subsequent.ly removed by the self-flushing action of the dashpot during the rod drops.

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Sincerely, F - .j f

• w C. R. Montgomery -

General Manager y ec: G. F. Trowbridge, Esquire s

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