ML20085J960

Telecopy Ro:On 740429,actual Torus Level Found Approx 2 Inches Below Low Level Limit.Caused by Faulty Indication. Indication Corrected

ML20085J960
Person / Time
Site:	Dresden
Issue date:	04/29/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085J954	List: ML20085J951 ML20085J957 ML20085J960
References
NUDOCS 8310190241
Download: ML20085J960 (1)

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.' " E]'ir' oys!yyt_rnigtfy meno.pnps Docket No. 50-237 Address Haply to. I c mco Box 767 Chicago. Ulinois 00590 BBS Ltr.0318-74 Dresden R. R. 't!1 Nucicar Power 'Station i -

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U. S. Atomic Energy Ccenission 'n.

Washington, D. C. 20545 /m(3nM SUIUECT: _LICP!:SE DPR-19, D 'ESDW NUCLEAR PO"ER. U"TT_f 2, REPORT OF AEMOPPAL OCCim""NCS P;'Ti 5 CTIF! 6.6.M. l .a C' T.lM 7"CM;IC.*.L SP.tC7FICAT:: CMS.

Fall.UPI 07 U::IT 2 /3 fmCX C.'.S SA!MLING Pl'JPS.

References:

1) Notification of Region III of AEC Regulatory Operations Telephor.e: Mr. F. Maura , 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br /> on April 25, 1974 Telegram: Mr. J. Reppler, 1455 hours0.0168 days <br />0.404 hours <br />0.00241 weeks <br />5.536275e-4 months <br /> on April 25, 1974

2) Dwg: 12E2485

Dear Mr. O' Leary:

This letter is to report a condition relating to the operation of Dresden Units 2/3 at about 0720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> on April 25, 1974. At this time, the control room stack gas scmpic flow / pressure abnornal annunciator and alarm signaled. 2/3 "A" stack gas sample pump was found to be tripped. 2/3 "B" stack gas sample pump was placed in service and it tripped at 0855 hours0.0099 days <br />0.238 hours <br />0.00141 weeks <br />3.253275e-4 months <br /> en April 25,1974. This ualfunction is contrary to section 3.8 A.1. of the Technical Specifications which requires that radicactive gases released frc,n the plant chimney shcIl be continuously monitored. To accomplish this, at least one plant chimney monitoring system shall be operable at all times.

PROBLEM On April 25, 1974 Dresden Unit 2 was operating at 2290 int and 764 IGo, Dresden Unit 3 was shutdown for refueling. The off-gas reicase rate from Unit 2, frca grab scepic data collected at 0435 hours0.00503 days <br />0.121 hours <br />7.19246e-4 weeks <br />1.655175e-4 months <br />, was 9.06 millicuries per second. At approximately 0720, the control room stack gas campic flow / pressure abnormal annunciator and alarm cignaled. At approxirately 0740, en operator arrived at the sample pump arca and found 2/3 "A" stack gas scrapic pump tripped. At approxiinately 0600 the operator placed 2/3 "B" stack gas sacple pump in service. 2/3 "E" stack gas supple pump tripped at 0555. At this time, station naintenance was notified to initiate repairs, the linit 2 control room operator was instructed not to 78 ,

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'ltr. J. F. O' Leary ay 3, 1974 increace power on the unit and to increase curveillance on the off-pas ion chamber monitors, and Radiation Protection personnel were requested to supply and install a temporary rample pump. This temporary scepic pump was installed and collecting iodine and particulates at 1033 a.m. lia in t enance repaired 2/3 "A" stack gas scaple pump and this pump vao placed back in service at 1125 a.m. This action corr ected the condition and brought the station into complete ccepliance with Technical Specifications. 2/3 "3" stack gas sampic pump was repaired at approximately 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br /> for standby service.

I!NESTICATION The cause of failure for both "A" and "B" stack gas sample pumps was the breaking of the pump vanes. Simultaneous failure of both pump vancs has not occurred previously.

gRRECTIVE ACTIO!y The corrective actions initiated at the time of the incident vare to provide a temporary sarnple pump and to initiate repairs on 2/3 "A" and 2/3 "B" stack gas sanple pumps. 2/3 "A" pump was repaired and placed in servica at 1125, 2/3 "B" pump was repaired at approximately 1300. Both pumps are functional at this tice.

AVALUAT10fd The amount of time that the total plant chimney monitoring system was not in service was approximately 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> and 15 rainutes. During this period, the Unit 2 reactor was in steady state operation. Unit 2 off-gas icn chamber monitor records during thin period did not indicate any increases or decreases. As previously stated, grab scaple data indicated a neble gas relcace rate prior to the incident of 9.06 nil 11 curies per second which is 1.29 percent of the single unit operation Technical Specification limit.

Iodine and particulate camples prior to and af ter the incident indicated a total release rate of 0.062 microcuries per second (1.8 parcent of the single unit operation Technical Specification limit) and 0.095 microcuries per second (2.7 percent of the single unit operation Technical Specification limit), respectively. Due to the steady state operation of the unit and static response of the off-gas ion chambers, we conclude that no noble gas or iodine and particulate releases above previously stated values occurred during the period when the stack gas sampling pumps were out of service.

Thus, neither the safe operation of the station nor the safety of the general public ucre changed during this period.

The corrective actions taken immediately following the loss of the atack gas sample pumps included: holding the unit at steady state operation, increasing surveillance of the off-gas ion chambers, it:nediate action to

'ltr. 5 F. O' Leary !ay 3, 1974

repair the failed snaple pu=ps, and initiation of a temporary cat

ple pump.

We conclude that theec actions were appropriate and brought the condition safely and quickly into co.mpliance with Technical Specificaticus. Since sinultaneous stack r,as cenple pump failures have not occurred previoucly, the inctalled redundant snaple pu::p systen is adequate and does not impair the cafe operation of the station.

Sincerely, s

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$ B. Stephencon Superin to'ndent BBS:DAA:do e

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