ML20027A332

RO 77-054/03X-1 on 771102:CRD H-5 Uncoupled During Functional Testing Caused by Unlatched Inner Filter & Abnormally Long Uncoupling Rod.Inner Filter Pull Test in Reassembly Procedure & Improved QA Coverage Incorporated

ML20027A332
Person / Time
Site:	Dresden
Issue date:	10/27/1978
From:	Wujciga J COMMONWEALTH EDISON CO.
To:
Shared Package
ML17173A367	List: ML17173A366 ML20027A332
References
NUDOCS 7811160125
Download: ML20027A332 (2)

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L!ChNSEE EVENT REPORT UPDATE REPORT:

' 775 PREVIOUS REPORT DATE 12/2/7)

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le 75 RE8CRT C ATE 80 64 63 EVENT OATE oJ 68 COCKET NU'. 6 ge EVENT CESC.*LIPTION AND PRQ9 A6.'.5 CONSEOUENCES h (During Unit 2 refueling outage, control rod drive"(CRD) H-5 overtraveled indicating ai:]

It was recoupled and coupling verified in ac-g j ufcoupiih:t,uring -functional testing.

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CRD uncoupling had minimal safety signficance since it l

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[ occurred cniv when the rod war withdrawn to position. 48.

This was the first uncoupling

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Several other CRD's have uncoupled in the past. Reportable occurrences: ;

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wa OALSE CESCRIPTICN AND CL',4RECTIVE ACTICNS 2s g;g ] An unlatched inner filter and abnormally long uncoupling rod resulted in the uncoupling functional testing. Drive had been overhauled in Jan. 1975..A pull; gg j of CRD H-5 durin::

.7,,) ; test en the inner filter has now been incorporated in the overhaul and reassembly

,ri I il I procedure. Revised procedute and improved QA coverage believed to be adequate to l

,a..,; prevent future similar events.

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ATTACHMENT TO LICENSEE EVENT REPORT 77-054 /03X-1 i

C0lt!ONWEALTH EDISON COMPANY (CWEl J-DRESDEN UNIT-2 (ILDRS-2) 3 DOCKET f/050-237 i

During Unit 2 refueling outage, control rod drive (CRD H-5 overtraveled indicating uncoupling when withdrawn to posit'on'48 during functional i

testing.

CRD H-5 was recoupled and coupling verified in accordance with )

the requirements of T.S.3.3.B.I.

CRD uncoupling had minimal safety sig-i nificance since it occurred only when the rod was withdrawn to position 48.

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This was the first uncoupling of CRD H-5.

Five other CRD's had previously uncoupled since the 1975 Unit 2 refueling outage (reportable 50-237/1977-14, 15, 22 & 29; 50-237/1976-68, 72).

occurrences:

On November 9, 1977 CRD H-5 was disassembled and inspected per Control Rod Drive Inspection and Maintenance 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.

In addition the distance between the CRD flange and the end of the fully seated uncoupling rod was abnormally long (173.406 + 0.562").

The abnormal length coupled with an unlatched inner filter resulted in the uncoupling of the CRD.

As part of the revised reassembly procedure, C.E.Co. Quality Control

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personnel performed the inner filter installation and the reduced 20-30 l

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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 prohedure coupled with improved Quality Control coverage of CRD overhaul and reassem-bly are believed to be adequate to prevent future similar events.

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