ML20084R586

AO 50-249/75-09:on 750228,during MSIV Not Full Open Scram Test,Relay 590-102B Failed to Deenergize.Apparently Caused by Faulty Limit Switch on 3-203-2A Msiv.Fuse 590-702B Removed,Placing Sys in Fail Safe Condition

ML20084R586
Person / Time
Site:	Dresden
Issue date:	03/07/1975
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084R588	List: ML20084R586 ML20084R592
References
137-75, AO-50-249-75-09, AO-50-249-75-9, RO-50-249-75-9, NUDOCS 8306150213
Download: ML20084R586 (2)

Text

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') */ Address Fi ly to: Pest Othee Box 767 i./ . . Chicago, llhnois 00600 EBS Ltr. #137-75 Dresden Nuclear Power station..

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Mr. Jaces G. Keppler, Regional Director m,[. ^ /2-Directorate of Regulatory Operations-Region III ,} (f #7

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799 Roosevcit Road  :%y"',%by

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Glen Ellyn,. Illinois 60137

SUBJECT:

REPORT OF AENCRPAL OCCURRD;CE PER SECTION 6.6.A 09 TITE TECHNICA;L SPECIFICATICNS_

2A MSIV NOT FVII, OPM! SCRAM

Reference:

1. Regulatory Guide 1.16 Rev.1 Appendix A

2. Notification of Region III of U. S. Nuclear Regulatory Cont::ission Tclephone: Mr. ". Jchnson,1540 hours0.0178 days <br />0.428 hours <br />0.00255 weeks <br />5.8597e-4 months <br /> en February 28, 1975 Telegram: Mr. J. G. Keppler,1550 hours0.0179 days <br />0.431 hours <br />0.00256 weeks <br />5.89775e-4 months <br /> on February 28, 1975 Report Number 50-249/1975-9 Report Dato: March 7, 1975

. Occurrence Date: . February 28, 1975 Facility: Dresden Nuclear Power Station, Morris, Illinois IDENTIFICATION OF OCCURRENCE During a main steam isolation valve (MSIV) not full open scram test, relay 590-1023 failed to do-energize. This switch represents one of several redundant switches which actuate the reactor Protection System.

_ CONDITIONS PRIOR TO CCCURRD'CE Prior to T,ho failure the unit was in the "Run" mode with a thennal power of 1249 megawatts. The unit electrical load was 392 megawatts and surveillance testing of the IGIV's was in progress.

DESCRIPPIO'i 0F OCCURRFA'CE

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On February 28, 1975, at about 0400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br />, relay 590-102B railed to de-energico during the MSIV not full open scram surveillance of the 3-203-2A valve. q

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8306150213 750307 '

PDR ADDCK 05000249 S PDR N O 1-

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n Mr. James G. Koppler Q March 7, 1p75 DESIGNATION OF AFPARM;T CAUSE OF OCCURRM;0E (Equi; ment Failure)

The apparent cause of the failure appeared to be a faulty limit switch on the 3-203-2A M3IV. The curveillance test requires that the 2A MSIV be closed and verification made to insure that the 590-102A & B relays de-energize. Inspection of the relays showed that the 102A relay de-energized but that the 102B relay did not. No problem was fcund upon inspcetion of the 3-203-2)L valve. The limit cwitch was operated manually coveral times and the limit switch operated correctly. Following manual operation, the valve was tested electrically several times and again no problem was noted.

ANAIXSTS OF OCCURR24CE The failure of the 2A limit switch did not place the cafety of the plant or public in jeopardy. The failure of cno limit switch would not have prevented a reactor scram due to redundant logic. Also, at the time of the failure all other isolation valves and safety syctems were functional.

CORRECTIVE ACTIONS, The imediate corrective action taken was to remove the 590-7023 itse. Fuse 590-7023 is in the feedline to relay 590-102B. Removal of the fuse de-enerCited the 590-102B relay to place the cystem in a fail cafe condition. The 3--203-2A valve was inspected to verify the condition of the valve limit switch. The limit cwitch was operated several times rnenually and electrically uithout a recurrence of the trobica. Durin2 the next ovtanded main +ananan ~ n -a *'w cuitch will be given a thorough inspection.

FATLURE DATA -

The previous failure of a main steam line limit owitch occurred on July 28, 1974 in connection with the 3-203-1B isolation valve. The failure at that time was attributed to the limit switch arm 1ccking nut which had backed off, thereby allcwing the arm to swing free.

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. B. Stephenson

/cb Superintendent BBS:TEL:s=p File /AEC

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