ML20084M064

AO 4-73-6:on 730608,during RCS Flow Coastdown Measurement Procedure T-0201.23,rod Control Cluster H-8 Stuck at 225 Steps Following Rod Drop Signal.Cause Undetermined.No Corrective Action Taken

ML20084M064
Person / Time
Site:	Turkey Point
Issue date:	06/15/1973
From:	Schmidt A FLORIDA POWER & LIGHT CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084M062	List: ML20084M064
References
AO-4-73-6, NUDOCS 8306010238
Download: ML20084M064 (2)

Text

f~.. P O Box 3100 MIAYl.FL0r.!DA 33101 ]

O O r,av'r:n 2 s\\)I d-463h" J! b' $i ... J FLORIDA PC'.'.1R ts LIGHT CO'.if .W June 15, 1973 s c)'

Mr. John F. O' Leary, Director 2-Directorate of Reactor Licensing m W. <

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U.S. Atomic Energy Commi.ssion '

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Washington, D. C. 20545 ,

'lVRKEY POINf UNIT NO. 4 C A 8/ J g DOCKLT hutBER 50-251

. N" " ')g% M ABNOR4\L OCCURRENCE NQ(4-73-67 Y

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ROD CONTROL CLUSTER T~ ll 8 STUCK ~'

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Dear Mr. O' Leary:

This report is submitted in accordance with Technical Specification 6.6.2 a and in amplification of Mr. J. K. Ilays' verbal notification to Mr. R. L.

Cubitt, Region II, Directorate of Regulatory Operations on June 9, 1973.

On June 8, 1973, Unit No. 4 was in a hot shutdown condition and Preopera-tional Procedure T-0201.23, Reactor Coolant System Flow Coastdown Measurement was being performed as a part of the precritical testing program prior to starting dilution. Control Rod Bank D was withdrawn to 228 steps. At 9:05 PM rod control cluster (RCC) 11-8 stuck at about 225 steps (indicated) following a rod drop signal. The RCC was verified to be stuck at about the fully with-Crawn position by measuring the rod position indication (RPI) voltages for all Bank D rods. The RPI cables of reds M-6 and 11-8 were exchanged and the RH voltages remeasured. Instrument indications were found to be correct. After

• consulting with the vendor and instrumenting the RCC with an oscillograph and microphone, the RCC was freed by stepping out and in a few steps at a time and found to be operable.

The RCC was verified to have moved using a digital voltmeter monitoring the RPI signal and an oscillograph monitoring the control rod drive mechanism coil currents and sound trace. The 11-8 RCC was tested by driving it in to

! q J. five steps and then out to 228 steps while monitoring with an oscillograpn.

1 The RCC was then driven in.again to five steps and out to 228 steps while d monitoring the RPI. Then 11-8 was dropped ten times following Preoperational Procedure T-1600.3, Full Length RCC Drop Test, while monitoring with an

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oscillograph. Then each bank was pulled to 228 steps and dropped to verify pQp j

' -: ...f, all rod banks and associatM instrumentation functioned properly.

yd* OurinvestigationsandmanipulationswiththeRCCandconsultationswiththe(M vendor did not reveal the cause of the incident. There isJ1o_positivey ay a to determino what caused the RCC to become stuck and consequently no specific corrective action will be taken as a result of this occurrence. ,

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PDR ADOCK 05000251 PDR p S 3ab COPY SENf REGION - __

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Mr. John F. O' Leary, Director June 15, 1973 This Abnormal Occurrence in no way affected the health and safety of the public nor was reactor safety affected. Should a similar incident occur during power operation, reactor safety would not be adversely affected because the accident analyses assumes the most reactive red is stuck out.

Very truly yours,

. D. Schmidt

/~ C Director of Power Resources ADS /JRB/m1w cc: Norman C. Moseley,. Director Region II, Directorate of Regulatory Operation U.S. Atomic Energy Commission Suite 818, 230 Peachtree Street, N.W.

Atlanta, Georgia Mr. G. A. Olson Edison Electric Institute 90 Park Avenue New York, N. Y. 10016 Dr. James Coughlin J. W. Williams, Jr.

J. R. Bensen J. B. Olmstead W. II. Rogers, Jr. -S. G. Brain G. E. Liebler Plant Supervisors

- J. K. Ilays Plant Nuclear Safety Committee C. E. Branning Documentary Files D. W. Jones i

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