ML20084N691
| 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: |
| References | |
| 611-75, NUDOCS 8306080428 | |
| Download: ML20084N691 (2) | |
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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 Dresden NUclea:' Power Station BBS Ltr. #611-75 R. B. #1 Morris, 2,11nois 60450 September 16, 1975
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m, Mr. James G. Keppler, Regional Director Directorate of ReEulatory Operation-Region DI f
U. S. Nuclear Regulatory Comission y, -
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799 Roosevelt Road Glen Ellyn, Illinois 60137
'1 REPORT OF AENORMAL OCCURRE!CE PER SETION 6.6.A OF THE TEENICAL SPEC
SUBJECT:
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 P. Johnson.1430 hours0.0166 days <br />0.397 hours <br />0.00236 weeks <br />5.44115e-4 months <br /> on September 8,1975 Telephone 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 Dresden Nuclear Power Station, Morris, Illinois Facility:
IDENTIFICATION OF OCCURRENCE f4,16,and18failedtorespondduring s
Intermediate range monitors (IRM's) 11, 12,
.This occurrence represents a failure,to meet limiting ecnditions plant start-up.
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 As reactor Lower was increased it was noted that An immediate investigation critical for plant start-up.
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.
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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 fins 1 check will be performed prior to start-up, after all work under the vessel has been complettd.
FAILURE DATA There have been no previous (IRM failures of.this nature at Dresden.
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( B. 3. Stephenson I
Superintendent BBS:CES:scp J File /NRC q
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