ML17173A357

Forwards LER#77-029/03X-1 Update

ML17173A357
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
ML17173A358	List: ML17173A357 ML20027A320
References
NUDOCS 7811140203
Download: ML17173A357 (3)

Text

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Comr.i'lnwec9Edison Dresden Nuclear Power Station R.R. #1 Morris, Illinois 60450 Telephone 815/942-2920

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• • • November 2, 197s-----

BBS Ltr. #78-1441 James G. Kepple::r, Regional Director Directorate of Regulatory Operations - Region III U.S. Nuclear Regulatory Connnission 799 Roosevelt Road Glen Ellyn, IL 60137 Reportable Occurrence "Update" Report 77-029/03Xl, 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~(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.

enson Station Superintendent

' Dresden Nuclear Power Station BBS/deb Enclosure cc: Director of Inspection & Enforcement Director of Management Information & Program Control File/NRC

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P . OUS REPORT DATE 9/1/77 CONTROL BLOCK: '----'---'-----'---'---'-""'.!j 6

0) (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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> 60 61 . DOCKET NUMBER 68 69 EVENT DATE 74 75 REPORT DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES@

I During one-haJ..i core scram testing, CRD's F-5 & H-7 uncoupled when withdrawn to po-___J C£m I sition 48. Event has little safety significance since uncoupling occurred only at

~ IPOS. 48 and CRD's retain capability to scram as before uncoupling. Event occurred

[Q]]J I previously with CRD F-5 as ref in R.O. 50-237/1976-68. CRD's F-5 & H-7 were recoupledj

[QJ]J I according to procedure and rec~upling verified by observing no overtravel indication

!o 11 I I when each CRD was twice wichdrawn to position 48.

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a ti  ::i il 12 13 lB 19 20 SEQUENTIAL OCCURRENCE REPORT REVISION

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jAn unlatched inner filter and abnormally long uncoupling rod resulted .in the un-

! 1 11 I I coupling of CRD F-5 and H-7. Drives had been overhauled in Jan. 1975. A pull test ITm ion inner filter has now been incorporated in the overhaul and reassembly procedure.

[JJ]J I Revised procedure and improved QA coverage believed adequate to prevent future CRD

~ I uncouplings.

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STATUS  % POWER OTHER STATUS DISCOVERY DISCOVERY DESCRIPTION ~

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. I o ATTACHMENT TO LICENSEE EVENT REPORT 77-029/03X-1 COM110I\11../EALTH EDISON COMPANY (CWE)

DRESDEN UNIT-2 (ILDRS-2)

DOCKET 1!050-237-During routine one-half core scram testing, control rod drives (CRD's)

F-5 & H-7 uncoupled and overtraveled when withdrawn to position 48 following testing. This event has little safety significance since uncoupled CRD's still retain the same capability to scram as before uncoupling and uncoupling only occurs at µosition 48. This event had occurred previously with CRD F-5 on December 12, 1976 (Reportable Occurrence #50-237/1976-68).

CRD's F-5 & H-7 were recoupled according to procedure and recoupling verified by observing no overtravel indication when each CRD was twice withdrawn to position 48.

On October 6, 1977 and September 30, 1977 -CRDs F-5 and H-7 were 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 in both cases the inner filter was un-latched. In addition the distance between the CRD flange and the end of the fully seated uncoupling rod on both rods was abnormally long (173.406

+ 0.562). The abnormal length coupled with an unlatched inner filter resulted in the uncoupling of the CRD's during normal operating conditions.

As part of the reassembly procedure, C.E.Co, Quality Control persennel performed the inner filter installation and the required 20-30 pound pull test. In Feb., 1978 the Control Rod Drive In~pection and maintenance procedure DMP 209 was changed to permit maintenance personnel to install the inner filter. This change occurred due.to 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 procedure coupled with improved Quality Control coverage of CRD overhaul and reassembly are be-lieved to be adequate to prevent future CRD uncouplings *

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