ML20084K420

AO 50-237/1974-48:on 740927,standby Gas Treatment Sys Train a Failed to Start on Spurious Initiation from Fuel Pool High Radiation Monitor.Caused by Faulty Sensor Converter. Converter Replaced

ML20084K420
Person / Time
Site:	Dresden
Issue date:	10/07/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084K421	List: ML20084K420 ML20084K423 ML20084K426
References
734-74, NUDOCS 8305190391
Download: ML20084K420 (3)

Text

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[ adr One Fe*s' ?!-'+pnal Plaza. ChicagC. Illinois Q&'y u AadrEsh to: Post Office Box 767 -

Chicago, kaa)is 60690 h) v BBS Ltr.#734-7h Dresden Nuclear Fower Station R. R. #1 Morris, Illinois 60450 October 7, 1974 , ,d_d /p, Mr. James G. Keppler, Regional Director

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I Directorate of Regulatory Operations-Region III [$,y((f!2;y U. S. Atomic Energy Co::snission (D hat '

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799 Roosevelt Road D 1 Ys>

Glen Ellyn, Illinois 60137 D/ .

SUBJECT:

REPORT OF ATEOR".AL OCCURRENCE PER SECTION 6.6.A 0F THE TECMTICAL SPECIFICATIONS.

FAILURE OF "A" ST/RD3Y GAS TREA'Ii/ENT SYSTH4 TRAIR TO START.

References:

1) Regulatory Guide 1.16 Rev.1 Appendix A

2) Notification of Region III of AEC Regulatory Operations Telephone: Mr. F. Maura, 1620 hours0.0188 days <br />0.45 hours <br />0.00268 weeks <br />6.1641e-4 months <br /> on September 27, 1974  !

Telegram Mr. J. Keppler, 1630 hours0.0189 days <br />0.453 hours <br />0.0027 weeks <br />6.20215e-4 months <br /> on September 27, 1974

3) Drawing Number: M-49 Report Number: 50-237/1974-48 Report Date October 7, 1974 Occurrence Dato: September 27, 1974 Facility: Dresden Nuclear Power Station, Morris, Illinois IDDTPIFICATION OP OCCURRD;CE At 0115 hours0.00133 days <br />0.0319 hours <br />1.901455e-4 weeks <br />4.37575e-5 months <br /> on September 27, 1974 "A" train failed to start on a spurious standby gas -treatment system initiation from a fuel pool high radiation monitor.

CONDITICNS PRIOR TO OCCURRENCE Prior to the occurrence,' Unit 2 and 3 were locked in the shutdown mode with all control rod drives at position "00".-

DESCRIPTION OF CTJRRF2JCE At 0115 hours0.00133 days <br />0.0319 hours <br />1.901455e-4 weeks <br />4.37575e-5 months <br /> on Septc=ber-27, 1974,~ channel A fuel pool radiation monitor experienced a greater than 100 ER cpike of spurious origin which tripped the reactor building ventilation fans and initiated an autc=atic start of 830519'0391 741007 -

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"A" standby gas treatment system train. Subsequent to initiation signal, "A" train did not start. Therefoie, the los;ic circuitry tripped "A" train and started "B" train. "B" train started and came up to design flow. In addition, valve Mo-3-7503 operator, which is the Unit 3 reactor building vent to SBGTS supply damper, was found to be tripped.

DESIGNATION OF APPARENT CAUSE OP OCCURRENCE (Other)

The cause of the failure of "A" train to start initially was thought to be a malfunctioning of the timer (not being reset), but it appears that this may not be the case. At this time, there exists no cause of failure.

Regarding the M.0. valve failure, the motor bolts were found to be sheared off possibly due to the working loose of bolts by the torquing action of the motor.

ANALYSIS OF OCCURRENCE At the time of the occurrence, secondary containment integrity was not required to be in effect due to Unit 2 and 3 being suberitical with reactor water temperature below 212*F. Therefore, neither the safety of the public nor plant personnel was in jeopardy as a result of this occurrence.

CORRECTIVE ACTION The in:nediate action was to simulate the initial failure conditions shortly after the occurrence. The failure could not be duplicated. As a result of this occurrence, uork requests were issued to inspect the timing mech-anism, repair the valve motor, and determine the reason for the spurious spiking on channel A fuel pool radiation monitor.

The inspection of the timing mechanism indicated that it was functioning properly.

The valve motor was repaired, reinstalled, and its' limit switches set.

The valve was functionally tested three times.

The inspection of the radiation monitor revealed a faulty sensor converter which was causing the spurious spiking. The sensor converter was replaced and the old one will be tested to determine rcascn for spiking.

FAILURE DATA A review of station records indicate one previous failure of the SBGTS.

This failure occurred on February 7,1973 in which timer 2/3-7541-30K23

Mr. Jam:;o G. Keppl r -> October 7, 1974 i

malfunctioned. The reason for the failure 1:as that r2 cet cercu which held a gear on the drive shaft of the timer had worked loose. The corrective action taken was to tight,cn the set screw after treating the threads with

" lock-tito".

Sincerely, ,

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N.B.Stephenson Superintendent BBS:RLWido

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