ML20084N691

AO 50-249/75-41:on 750908,intermediate Range Monitors 11, 12,14,16 & 18 Failed to Respond During Plant Startup. Apparently Caused by Personnel Accidentally Loosening Cables.Cables Replaced

ML20084N691
Person / Time
Site:	Dresden
Issue date:	09/16/1975
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084N693	List: ML20084N691 ML20084N703
References
611-75, NUDOCS 8306080428
Download: ML20084N691 (2)

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d Comm:n Ith Edison n () b

/r' a One First National Plaza. Chicago. Ilknois

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' /l Address Reply to: Post Office Box 767 '

(QC Chicago, Illinois 60690 BBS Ltr. #611-75 Dresden NUclea:' Power Station R. B. #1 Morris, 2,11nois 60450 September 16, 1975 . . ,

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Mr. James G. Keppler, Regional Director '

f Directorate of ReEulatory Operation-Region DI ' #

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U. S. Nuclear Regulatory Comission '

s 799 Roosevelt Road -

Glen Ellyn, Illinois 60137

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SUBJECT:

REPORT OF AENORMAL OCCURRE!CE PER SETION 6.6.A OF THE TEENICAL SPEC FAILURE OF INTER'GDIATE RA';GE FONITORS TO B SPOND R;ferences: 1) Regulatory Guide 1.16 Rev. 1 Appendix A ,

2) Notification of Region III of U. S. Nuclear Regulatory Corr.tission Telephone P. Johnson.1430 hours0.0166 days <br />0.397 hours <br />0.00236 weeks <br />5.44115e-4 months <br /> on September 8,1975 '

Telegram: J. Keppler,1950 hours0.0226 days <br />0.542 hours <br />0.00322 weeks <br />7.41975e-4 months <br /> on Septcmber 8,1975 i.

R: port Number: 50-249/75-41  :

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Report Date: September 16, 1975 Y 1

Occurrence Dates September 8, 1975 Facility: Dresden Nuclear Power Station, Morris, Illinois .

IDENTIFICATION OF OCCURRENCE Intermediate range monitors (IRM's) 11, 12, f4,16,and18failedtorespondduring s

plant start-up.

.This occurrence represents a failure,to meet limiting ecnditions

• for operation as defined in section 3 1 of the Technical Specificationci

• e CONDITIONS PRIOR TO OCCURRRICE .

Control rod withdrawal Unit-3 was in the start-up mcde at a power level of 4100 IGt.

was in progress.

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DESCRIPTION OF OCCUBRBICE At approxd:::ately 0500 hours0.00579 days <br />0.139 hours <br />8.267196e-4 weeks <br />1.9025e-4 months <br /> on September.8.1975, the Unit-3 reactor was brought critical for plant start-up. As reactor Lower was increased An immediate it was noted that investigation five of the eight IRM's did not appear to be responding.

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indicated that the problem was intrinsic to the IRM's themselves rather than the 1; cal instrumentation, and a reactor shutdown,was commenced. Control rod insertion began at 0510 hours0.0059 days <br />0.142 hours <br />8.43254e-4 weeks <br />1.94055e-4 months <br />, witRall rods "in" by 0559 hours0.00647 days <br />0.155 hours <br />9.242725e-4 weeks <br />2.126995e-4 months <br />.

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DESIGNATION OF APPARF2;P CAUSE OF OCCURRDiCE (Unusual Servicd Conditions)

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Th:; IRM cables appeared to have been inadvertently pulled "open" by personnel working underneath the reactor vessel in cramped quarters. In addition, water was found in come of the cable connecto- c, whi:h undoubtedly contributed to the IRM response proble,1ss i The water probably entered the table connectors during the initial vessel

" hydro" Onen control rod drive flanges were discovered leaking.

ANALYSIS' 0F OCCURRENCF N

Although the IRM's would ha've been incapable of providing scram protection, the 15fo i cvarage power range monitor (APPJ1) scram logic was in effect throughout the start-up mode. Furthermore, the rod worth minimizer was operable, preventing any deviation from the established rod withdrawal sequence. Consequently, plant personnel and th3 public were not. endangered by th n occurrence. l

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l CORRECTIVE ACTION i

The faulty IRM cables were replaced from the junction boxes in the drywell to the IRM connectors. In order to prevent a similar recurrence, the master start-up

. checklist will be revised to include a resistance check on Source Range Monitors

- (SRM's) and IBM's when c:ajor work has been performed under the reactor vessel. This i fins 1 check will be performed prior to start-up, after all work under the vessel l has been complettd.

1 FAILURE DATA s There have been no previous (IRM failures of.this nature at Dresden.

( B. 3. Stephenson I Superintendent BBS:CES:scp J File /NRC q

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