ML20084R647

RO 50-249/75-03:on 750103,while Placing Sys on-line,inboard Isolation Valve MO-3-1201-1 Failed to Open.Caused by Sheared Mounting Bolts Allowing End Bell to Fall Free

ML20084R647
Person / Time
Site:	Dresden
Issue date:	01/30/1975
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
56-75, RO-50-249-75-03, RO-50-249-75-3, NUDOCS 8306150273
Download: ML20084R647 (2)

Text

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.. Addressi EES Ltr. #56-75 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 60450 January 30, 1975 Mr. James G. Keppler, Regicnal Director Directorate of Regulatory Operations-Region III U. S. Nuclear Regulatory Comnission Glen Ellyn, Illinois 60137

SUBJECT:

REPORT OF C! USUAL EVEC PER SECTION 6.6.C OF THE TECHNICAL SPECIFICATIONS FAILURE OF U3 CLEA';UP SYSTEI II;E0ARD ISOLATICN VALVE M03-1201-1 TO OPEi

References:

1) Regulatory Guide 1.16 Rev. 1 Appendix A

2) Notification of Region III of AEC Regulatory Operations Telephone:

P. Johnson, 1445 hours0.0167 days <br />0.401 hours <br />0.00239 weeks <br />5.498225e-4 months <br /> on January 6, 1975

3) Dresden Station Drawing M-361 Report Number: 50-249/1975-3 Report Date: January 30, 1975 Occurrence Date: January 3, 1975 Facility: Dresden Nuclear Power Station, Morris, Illinois IDEGIFICATION OF OCCURRE!CE Failure of Unit 3 Clean-up Inboard Isolation Valve F03-1201-1 to open.

CONDITICNS PRIOR TO OCCURRDICE Prior to the occurrence the unit was in the"run" mode with ther=al power at about 1173 cegawatts. The unit was operating at an electrical load of 376.

megawatts and the cleanup system was being placed in service.

DESCRIFTICN OF OCCURRENCE On January 3,1975 at about 2340 hours0.0271 days <br />0.65 hours <br />0.00387 weeks <br />8.9037e-4 months <br /> the cleanup system was being placed in service following minor repairs. While placing the system on line the inboard isolation valve MO-3-1201-1 failed to open.

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%ESIG'?ATION OF APPARE:T CAUSE OF OCCURRE!CE (Design Deficiency)

On inspection of the valve it was found that four mounting bolts which holds the motor end bell in place had sheared allcwing the end bell to fall free.

Subsequent torque caused the rotor to break free. The cause of the bolts chcaring was due to a design deficiency in sizing the mounting bolts for this size of motor.

ANALYSIS OF OCCURRE!CE The failure of the 3-1201-1 valve to open did not place the safety of the plant or public in jeopardy. At the time of the failure the outboard, isolation

. valves were operational, and the failure of the 3-1201-1 valve was in the closed or isolation condition. In additica all emergency core cooling systems were operational during the time of the failure.

CORRECTIVE ACTION No ir:r.ediate corrective action was required because the unit was in the process of shu' ting down due to high reactor water chloride content. The motor was replaced with the motor from the unit 2-1201-1 valve as unit 2 was shutdown for a refueling outage. The motor from unit 3-1201-1 valve was returned to the vendor for rewiring. The vendor has been informed of the failure and assistance has been requested. Additional corrective actions will be based on vendor recocmendations.

FAILURE DATA This is the first failure of unit 2 or 31201-1 valves in this manner since 1971.

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