ML17173A344

Forwards LER#76-072/03X-1

ML17173A344
Person / Time
Site:	Dresden
Issue date:	10/27/1978
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML17173A345	List: ML17173A344 ML20027A287
References
NUDOCS 7811090138
Download: ML17173A344 (3)

Text

Commonwec9 E_dison Dresden Nuclear Power Station R.R. #1 Morris, Illinois 60450 Telephone .815/942-2920 October 27, 1978 BBS Ltr. #78-1453 James G. Keppler, Regional Director Directorate of Regulatory Operations - Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137 Reportable Occurrence "Update" Report 76-072/03X-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 I.

Technical Specification 6.6.B.2.(b), conditions leading to operation in a degraded mode permitted by a limiting .condition for operation or plant snutdown required by a limiting condition for operation *.

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Staticin Superintendent*

Dresden Nuclear Power Station BBS/def>

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cc: Director of Inspection & Enforcement

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9-tCENSEE EVENT REPORT CONTROL BLOCK: I I 6IQ (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION) 1

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B 60 61 DOCKET NU.\\BER 68 69 EVENT DATE 74 75 REPORT DATE 80 EVE~!T DESCRIPTION AND PROBABLE CONSEQUENCES@

I During routine startup operations, CRD J-11 uncoupled and overtraveled when withdrawn

[Q]}] I to pos. 48. Insertion to pas. 46 and subsequent withdrawalto pos. 48 showed drive CQ:IIJ I and blade recoupled. CRD J-11 again inserted and withdrawn to pos, 48 and again un-

[QJ}] I coupled. J-11 then inserted and withdrawn again to pos, 48 without incident. Re-CIJ]J I coupling verified by cycling the CRD three times. Because the potential for uncouplin&

~ l existed only at pos. 48, the safety implications of event were minimal CRD uncoupling

, 0 1 3 I events had occurred before.

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CAUSE DESCRIPTION AND CORRECTiVE ACTIONS @

OJ)) jAn unlatched inner filter and abnormally long uncoupling rod resuJ.ted in the uncouplinS ITTIJ I of CRD J-11. Since the earlier overhaul of CRD J-11 in Jan. 1975, a pull test en the lJTIJ l inner filter Ii.as been incorporated in the overhaul & assembly procedure. Revised

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ACILITY STATUS  % POWER OTHER STATUS @ METHOD OF DISCOVERY DISCOVERY DESCRIPTION ~,

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'ii ATTACH.i'1ENT TO LICENSEE EVENT REPORT 76-072/03X-1 COMHONWEALTH EDISON COMPANY (CWE)

DRESDEN UNIT-2 (ILDRS-2)

DOCKET II 050-237 During routine startup operations, CRD J-11 was found to uncouple and over-travel when withdrawn to position 48. An insertion to position 46 and sub-sequent withdrawal to position 48 showed the drive and the blade to be recoupled.

CRD J-11 was again inserted and withdrawn to position 48, and again the over-.

travel alarm annunciated, indicating that the blade and drive had uncoupled.

The drive was then inserted and withdrawn a third time to position 48 without incident. Recoupling was verified by cycling the CRD three times; no over-travel alarm or loss of position indication resulted.

On 12/30/76 an on-site review determined that- a loosened (unlatched) inner filter could cause the blade and drive to uncouple at position 48. It was also determined that the loosened filter could not exert sufficient pressure to uncouple the olade except when the drive was fully withdrawn to position 48; upon insertion, the olade and drive automatically recoupled. Since the possioility of uncoupling the olade existed only when the drive was withdrawn to position 48, CRD J-11 was considered to oe operaole. As a precautionary measure, an operating order was issued to ensure that a coupling check was performed whenever drive J-11 was withdrawn to position 48. Should subsequent uncoupling occur, immediate action would oe taken to ensure that* the drive's status complied with Teen Spec section 3,3.B.l.

Because tfte potential for uncoupling the olade existed only at position 48, tiie safety implications of, this event were minimal. Control ".'.'od drive/b1ade uncoupling incidents had occurred several times in the past.

As mentioned, symptom and performance evaluations indicated that a loosened . ~.: ~ . . .. -

• inner filter could cause the olade and drive to uncouple at the fully with-  :,*_*

drawn position, Loosening of the filter could have resulted from a combination

. of improper installation and latching spring fatique.

Upon inspection it was found that the inner filter was latched. However, the *.

inner filter retaining ring was found oowed apart and galled which indicates th.at tfte inner filter was relatched during the recoupling process at power.

In addition the distance f>etween the CRD flange and the end of the fully seated uncoupling rod was aonormally long (173.406 + .0625"). The abnormal length coupled wi.th an unlatched inner filter resulted in the uncoupling of the CRD during normal operating conditions.

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