ML17173A366

Forwards Reportable Occurrence 77-054/03X-1 Update

ML17173A366
Person / Time
Site:	Dresden
Issue date:	11/02/1978
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML17173A367	List: ML17173A366 ML20027A332
References
NUDOCS 7811160122
Download: ML17173A366 (3)

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Commonw~ Edison Dresden Nucle~~er Station R.R. #1 Morris, Illinois 60450 Telephone 815/942-2920 BBS Ltr. #78-1444 James G. Keppler, Regional Director November 2, 1978 Directorate of Regulatory Operations - Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137 Reportable Occurrence "Update" Report 77-054/03X-l, Docket 11050-237 is hereby submitted to your office to update the cause description and final corrective actions taken to prevent recurrence.

This event was reported to your office under Dresden Nuclear Power Station Technical Specification 6.6.B.2.(b), conditions leading to operation in a degraded mode permitted by a limiting condition for operation or plant shutdown required by a limiting condition for operation

• BBS/deb Enclosure

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-,O~. st.ephenson

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1 Station Superintendent Dresden Nuclear Power Station cc:

Director of Inspection & Enforcement Director of Management Information & Program Control File/NRC

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.SQ EVENT DESCRIPTION AND PROSASLE CONSEQUENCES@

jDuring Unit 2 refueling outage, control rod drive (CRD) H-S overtraveled indicating

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I uncoupling during functional testing. It was recoupled and coupling verified in ac-

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1cordance with T.S.3.3.B.1.

CRD uncoupling had minimal safety signficance since it

[Q]}] 1occurred only when the rod was withdrawn to position 48.

This was the first uncouplin¥

[QJ}J I of CRD H-S.

Several other CRD's have uncoupled in the past.

Reportable occurrences:

li5T7l I S0-237/77-14, 1s, 22 & 29; so-237/76-68, 72 *

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CAUSE DESCRIPTION AND CORRECTIVE. ACTIONS @

43 44 47 I An unlatched inner filter and abnormally long uncoupling rod resulted in the uncouplin~

[JJJJ I of CRD H-S during functional testing.

Drive had been overhauled in Jan. 197S *. A pullj

[I]}] l test on the inner filter has now been incorporated in the overhaul and reassembly

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Revised procedure and improved QA coverage believed to be adequate to r

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ATTACID*IBNT TO LICENSEE EVENT REPORT 77-054/03X-1 COMMONWEALTH EDISON COMPANY (CWE)

DRESDEN UNIT-2 (ILDRS-2)

DOCKET ft'O 5 0- 2 3 7

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f During Unit 2 refueling outage, control rod drive (CRD) H-5 overtraveled indicating uncoupling when withdrawn to position-48 during functional testing.

CRD H-5 was recoupled and coupling verified in accordance with the requirements of T.S.3.3.B.1.

CRD uncoupling had minimal safety sig-nificance since it occurred only when the rod was withdrawn to position

48.

This was the first uncoupling of CRD H-5.

Five other CRD's had previously uncoupled since the 1975 Unit 2 refueling outage (reportable occurrences:

50-237/1977-14, 15, 22 & 29; 50-237/1976-58, 72).

On November 9, 1977 CRD H~5 was disassembled and inspected per Control Rod Drive Inspection and :!'1aintenance Procedure DMP 209.

To assure a

• comprehensive inspection a special operating procedure (SOP 216) was *'

prepared and followed.

Upon inspection it was found that the inner filter was unlatched *. Iri addition the distance between the CRD flange and the end of the fully*

seated uncoupling rod was abnormally long (173.406 + 0.562").

The aonormal length coupled with an unlatched inner filter resulted in the uncoµpling of the CRD.

As part of the revised reassembly prucedure, C.E.Co. Quality Control personnel performed the inner filter installation and the reduced 20-30 pound pull test.

In Feb., 1978 the Control Rod Drive Inspection and Maintenance procedure DMP 209 was further changed to permit Maintenance Personnel to install the inner filter.

This change occurred due to previously existing Management-Union work agreements.

However, Quality Control Personnel will verify proper installation of the inner filter*

and continue to conduct the 20-30 pound pull test.

The revised pro~edure coupled with improved.Quality Control eoverage of CRD overhaul and reassem~

bly are believed to be adequate to prevent future similar events.

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