ML20084L700

AO 50-237/1974-36:on 740802,during Withdrawal of Control Rod Drive,Crd K-11(38-43) Went Into Overtravel Condition. Caused by Component Failure.Rod Inserted to Position 00, Electrically Disarmed & Removed from Svc

ML20084L700
Person / Time
Site:	Dresden
Issue date:	08/09/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084L690	List: ML20084L700
References
574-74, NUDOCS 8305230625
Download: ML20084L700 (2)

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Dresden Nuc1 car Power Station R. R. #1

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SUBJECT:

_RFPORT C7_ ABt!O'O'AL OCCURRENCE PER SECTION 6.6.B 0F THE TECHNICAL SPECIFICATIONS.

UNCOUPLING OF CONTROL ROD DRIVE K-11 IN UNIT 2.

References:

1) Regulatory Guide 1.16' Rev.1 Appendix A

2) !!otification of Region III of AEC Regulatory Operations Telephone: lir. F. lisura,1545 hours0.0179 days <br />0.429 hours <br />0.00255 weeks <br />5.878725e-4 months <br /> on- August 2, 1974 Telegram: Mr. J. Keppler, 1620 hours0.0188 days <br />0.45 hours <br />0.00268 weeks <br />6.1641e-4 months <br /> on August 2,1974 6

3) Drawing Number: !! Repor't nutiber: su-2J h 19 /4-Jb Report Date: August 9, 1974 Occurrence Date: August 2, 1974 "

Facility: Dresden Nuclear Power Station, Morris, Illinois IDENTIFICATIO!! 07 OCCURRENCE At about 1355 en August 2,1974, CRD K-11 (38-43), while being withdrawn from position '.'42" to "48", went into en overtravel condition.

The overtravel indication ic indicative of an uncoupled CRD.

_ CONDITIONS PRIOR TO OCCURRENCE

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Prior' to' the occurrence, the reactor was increasing power from 408 INe and 1344 int to 460 INc.

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August 9, 1974 DE CRIPTION OF OCCURr. ENC Whi'le CRD K-11 (38-43) was being withdrawn.from position "42" to

'"48", a " rod overtravel" alarm annunciated and both the four rod and full core displays for the rod went blank.

The initial action taken was to attempt to recouple by inserting and withdrawing the rod five (5) times. On four scrica of insert and with-draw, the rod went- into overtravel on the coupling check. The fifth attempt was successful in getting the CRD coupled.

DESTCMATION OF ApFAPI!.T CAUSE OF OCCURRENCE Component Failure .

At this tire, the failure uechanim is not known, therefore, a

- followup ictter will-be issued subsequent to K-ll's overhaul. IlowcVer, prior failurcs of this type were explained as having occurred because of dislocated inner filters. This CRD, as the previous CRD failures, was codified and over-hauled in the Spring 1972 refueling outage.

. Thic drive uncoupling did not endanger public health or safety because the control blade was capable at all ti=es of being inserted into the reactor core.

CORPICTIVE ACTIONS .

The corrective action taken was to insert the rod to position "00",

electrically dinarn it, and remove it from service. This action was ccupleted on August .2, 1974. In addition, the three cyc=atrical rods with respect to K-11 were inserted to position "00" in order-to prevent possible nuclear consequences. .

, The control rod drive will be removed during' a subsequent extended unintenance outage. At that time, a thorough inspection will be cado to l . dctermine the mode of failure and a followup letter submitted to your office.

l FA7I.URE DATA l Control Rod Drive K-ll (38-43) i.'

This uncoupling phenemonon occurred three (3) times before; February 19, 1973 March 14, 1974,.and June 15; 1974. Inspections of the February 1973 and the March 1974 failures showed that in both cases, dislocated inner

-filters were at fault. The CRD that failed in June.1974 is presently posi-tioned at'"00" and electrically disarmed. (See Incident Report 112-2-74-21).

This CRD will also be'rc=oved during the next extended esintenance outage.

- 'Sia: s ly, t Ch b k. B. Stephenson'

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