ML17173A342

Forwards LER#77-022/03X-1

ML17173A342
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
ML17173A343	List: ML17173A342 ML20027A285
References
78-1445, NUDOCS 7811090129
Download: ML17173A342 (3)

Text

Commonwec9 Edison Dresden Nuclear Power Station R.R. #1 Morris, Illinois 60450 Telephone 815/942-2920 October 27, 1978 BBS Ltr. #78-1445 James G. Keppler, Regional Director Directorate of Regulatory Operations - Region III U.S. Nuclear Regulatory Connnission 799 Roosevelt Road Glen Ellyn, IL 60137 Reportable Occurrence "Update" Report 77-022/03X-l, Docket #050-237 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.(o), conditions leading to operation in a degraded mode permitted by a limiting condition for operation or plant shut<lown required by a limiting condition for operation.

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.- ~.-. Director of Management Information & Program Control File/NRC REGULATORY DOCllET FILE COPY _,

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-~ -. -LICENSEE EVENT REPORT UPJ:8: REPORT:

PR~US REPORT DATE 7/1/77 CONTRO~.BLOCK: ~~--'--~-~~-..... 18 b

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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!During routine startup operations, CRD L-5 was found to uncouple and overtravel when

[QJ2J jwithdrawn to pos. 48. CRD L-5 was inserted and disarmed. Rx startup operations re-

~ 1surned after it was determined that L-S's pos. and core location did not adversely

[QJ}] 1affect core symmetry. Following start-up an. overtravel check of L-5 proved satis-

~ I factory, verifying that CRD L-5 was recoupled and operable. This event occurred

~!previously with this rod as ref. in R.O. #50-237/1977-15.

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33 34 35 36 37 40 41 42 43 44 47 CAUSE DESCRIPTION ANO CORRECTIVE ACTIONS @ .

~ jAn unlatched inner filter and abnormally long uncoupling rod resulted in the uncoupling QJJJ 1of CRD L-5 during nonnal operating conditions. Since the last overhaul of CRD L-5 in

... [!]2] I Jan. 1975, a pull test on the inner filter has been incorporated in the overhaul & ,,*.

CIIIJ I assernoly procedure. The revised procedure and improved OA coverage is believed

,.LIJTI I adequate to prevent future similar events*

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ATTACHMENT TO LICENSEE EVENT REPORT 77-022/03X-l COMliOl'll-iEALTH EDISON COMPANY (CWE)

DRESDEN UNIT-2 (ILDRS-2)

DOCKET ilOS0-237 During routine startup operations, control rod drive (CRD) L-5 became uncoupled and overtraveled when withdrawn to position 48. This event occurred previously with this control rod on April 2, 1977 (Reportable Occurrence Number 50-237/1977-15). CRD L-5 was inserted and electrically disarmed, Reactor startup operations were resumed since the position and core location of control rod L-5 did not adversely affect core symmetry. At a reactor power above 20%, L-5 was recoupled and with-drawn to position 48 and checked for overtravel. The overtravel check verified CRD .L-5 to be recoupled and operable.

This was the twelfth Control Rod Drive (CR.D) uncoupling event at Dresden Unit 2 during the preceeding four years. The inspection of CRD's which had previously experienced this event indicated that improper inner filter installation was probably responsible for the uncoupling. If the inner filter becomes unlatched, full withdrawal of the control rod to position 48 could result in CRD uncoupling. Symptoms of this event indicated that

.the same inner filter problem probably existed with CRD L-5.

On November 30, 1977 CRD L-5 was disassembled and inspected per Control Rod Drive Inspection and Maintenance Procedure DMP 209. To assure a com-prehensive inspection a special operating procedure (SOP 216) was pre-pared and followed.

• upon inspection it was found that the inner filter was unlatched. In addition the distance between the CRD flange and the end of the fully seated uncoupling rod was abnormally long (173.406 + 0.750"). The abnormal length coupled with an unlatched inner filter resulted in the uncoupling of the CRD.

As part of the reassembly procedure~*** C. E. Co. *Quality >Control. *~*~r:sohn~]:*~(~'~:i;*~;i.*~~~J};*~~i~;~~~

performed the inner filter installation and a required 20-30 peiund pull**:.::* c:*::"**'*

test. In Feb., 1978 the Control Rod Drive Inspection and Maintenance Procedure DMP 209 was further changed to permit Maintenanc~ Personnel to install the inner filter, This change occurred due to existing Managemerit-Union Work Agreements. However, Quality Control Personnel will continue**

to conduct the 20-30 pound pull test. The revised procedure coupled wi~h improved Quality Control coverage of CRD overhaul and reassembly are believed to be adequate to prevent future similar events.

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