ML17173A336

Forwards LER#77-015/03X-1

ML17173A336
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
ML17173A338	List: ML17173A336 ML20027A284
References
NUDOCS 7811090116
Download: ML17173A336 (3)

Text

CommonweA Edison Dresden NuclearWwer Station R.R. #1 Morris, Illinois 60450 Telephone 815/942-2920 October 27, 1978 BBS Ltr. #78-1447 James G. Keppler, Regional Din:~ctor *

• Directorate of Regulatory Operations - Region III.*

U.S. Nuclear Regulatory Commission 79-9__ Roosevelt Road Glen Ellyn, IL : 60137 .

Reportable Occurrence "Update" Rep~rt 77.,-.015/03X-l, Docket i/050-237 i.s hereby submitted ~o your office to update the cause description and final corr~ctive actions taken to. prevent recurrence . . Th:Ls event was reported* to your office under Dresden Nuclear Power. Stat;ion Techni.cal Specification 6.6.B.2.(b), ~onditions leading to operat~on ~n a.*

degraded mode permitted by a limiting condition for operation or plant shutdown required by a limiting c.ondition for operatiOn.

• ens on Superintendent Presden Nuci~ar Power*Station.

BBS/deo*

Enclosure cc: . Director. of Insp~ction' *& Enforcement ..~.~ ' .; :* ... , .

• • Director* of Management Informad.on & Program Control *,

File/NRC

.REGULATORY DOCI\ET FILE COPY

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• -.,..._ ,. ...... -.*~* LICENSEE EVENT REPORT UPATE REPORT: .

P~OUS REPORT DATE 4/29/77 CONTROL BLOCK: I I If0 L---'-~-'-~'--_._~_._---:!_6\.:./

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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!During routine startup operations, CRD*L-5 uncoupled and overtraveled when withdrawn

@ill. I to pos. 48. L-5 immediately inserted and disarmed; Startup operations resumed after

[QITI_jdeterminai::ion that L-S's pos. and core location did not adversely affect core symmetry~

[ill] jFollowing_startup overtravel check of L-5 proved satisfactory, verifying it was re- l

~ I coupled and operable.* Because uncoupling occurred only when drive was fully with-fOT7l

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! drawn, safety implications were ininimal. CRD uncouplings have occurred previously.

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• ACTION FUTURE EFFECT SHUTDOWN .  !;::;-. .<l.TTACHMENT N;>RD-4 . . Pf31ME C0~1P. COMPONENT TAKEN ,.;CTION . ON PLANT. 'METHOD . . .. HOURS.~ su~~~ITTEO FORM $UB.' SUPPLIE8 MANUFACTURER 1£J@LU 'LJJ@

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44 c1 o1 8 1 ai@r 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS_@

!Unlatched inner filter and abnormally long uncoupling rod resulted in unc0upling of QJJJ I CRD L-5 during startup; Since earlier overhaul" of CRD L-5 on-Jan. 1975. *a i:mll.:test* I_

DTIJ I on inner filter has been inco!'.'porated in overhaul & assembly procedure. Revised **I GJ]J I procedure and improved QA coverage is believed adequate to prevent future CRD un.,.-. I CITIJ I tol,lplings, I ...

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ATTACHMENT TO LICENSEE EVENT REPORT 77-0l5/03X-l

• COMHONWEALTH EDISON COMPANY (CWE)

DRESDEN UNIT-2 (ILDRS-2)

DOCKET ii 050.:...237 During routine start.:...up operations, control rod drive (CRD) t-5 was found to uncouple and overtravel when withdrawn to position 48. L-5 was immediately inserted. and electrically disarmed. Reactor start...:.up operations were resumed after.it had been determined that *the position and core location . of the-L-5 control rod .did not adversely affect core symmetry; At a reactor power level of approximately 30%, L-5 was

. i withdrawn t~ position 48 and checked for overtravel. The overtravel :

check proved s~tisfactory ,' verifying that CRD. L-5 was recoup led and operaole. Control rod drive/blade uncoupling incidents had occurred -'->.

several times *in the past.

Symptom and performance evaluations indicated that: a loosened CRD inner .

filter could have caused the blade and drive to. uncouple at the fully withdrawn position. Loosening of the filter could have resulted from a comoination of improper .installation and latching spring fatique.

It was aiso determined that a. loosened filter could not exert. sufficient

• pres*sure .to uncouple: the olade except when* the drive was fully withdrawn to position 48; upon insertion, the f>lade and drive automatically ..

recoup led, Because the potential for uncoupling the blade existed. only*

• wfi.en tiie drive -t.ras. fully withdrawn, the .saf~ty irp.plications of this

.** event were minimal.

As a precautionary measure, an operating order was. issue.cl to ~nsure that.*

• a coupling check was* performed. whenever drive L-5.was withdrawn to

• position* 48

• On Novemf>er 30, 1977 .CRD L-5 was disassemoled and inspected: p~~ Control

• *: . ."/

Rod Drive Inspection and Maintenance Procedure DMP 209,

• To assure. a.

comprehensive inspection a special operating procedure (SOP 216) was

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 ***.*,: *c**,: ....               Upon inspection it was found that the inner filter was unlatched. *:"tri"' *-*.'

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            ~' ,;!                  addition the* distance between the CRD flange and the end of the fully .
                                  *seated uncoupling rod was af>normally long (173.406 + 0.750").* The abnormai length coupled with an unlatched inne.r filter resulted .in the uncoupling of the CRD.

CRD L-5 had oeen overha.uled in January; 1975. Since May, 1975 a 20 to 30 pound pull test on the inner filter has been incorporated in the overhaul

                                 *and reassembly procedure, Control Rod Drives overhauled and reassembled*
                                 *under this revised procedure have not experienced uncoupling. The revised procedure coupled with improved Quality Control coverage of CRD overhaul and reassembly are believed to be adequate to prevent. future* similar ev*ents.
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