ML20084E468

Ro:On 720420,while Plant Being Cooled Down in Preparation for Refueling,Release Rate of Airborne I-131 from Plant Vent Exceeded Tech Spec Limits.Cause Unknown.Charcoal Filters from Plant Vent Iodine Monitor Being Replaced

ML20084E468
Person / Time
Site:	Ginna
Issue date:	04/28/1972
From:	Amish K ROCHESTER GAS & ELECTRIC CORP.
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084E471	List: ML20084E468
References
NUDOCS 8304150081
Download: ML20084E468 (2)

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(:OC;ldhi LR GAS AHD ELECTRIC CORI'ORAT OH 57 EAST AVENUE, ROCHE';TER, fl.y.1--n 14649 s,o--..

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Dr. Peter A. Morris, Director Division of Reactor Licensing

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Subject:

Compliance with Facility Technical Specifications .

R. E. Ginna Nuclear Power Plant Unit No.1 4 g g,' -

j Docket No. 50-244

Dear Dr. Morris:

On April 20, 1972, while Ginna plant was being cooled down in prepar- l ation for refueling and the reactor coolant was being processed to remove I radioactivity, it was determined that the release rate of airborne iodine- i 131 from the plant vent exceeded the limiting value defined in the Technical '

Specifications. This determination was made approximately 09_0_0_odpril -

I 20 when a charcoal filter that had been installed in the plaw vent iodine sampler for approximately 29 hours3.356481e-4 days <br />0.00806 hours <br />4.794974e-5 weeks <br />1.10345e-5 months <br />, from 0125 on April 19 to 0620 on April 20, was counted. The average release rate of I-131 over the 29 hour3.356481e-4 days <br />0.00806 hours <br />4.794974e-5 weeks <br />1.10345e-5 months <br /> i period was 1.3 times the limit of Section 3.9.2.2. cf the Technical Speci- i fications . l Immediately upon making the determination tnat the release limit had been exceeded, steps were taken to reduce the iodine release rate. Flushing of auxiliary building floor drains to the liqu(d waste holdup tank was initiated; activity samples were taken in the auxiliary building with a portable iodine sampler; working personn 11 were evacuated from the auxil-lary building; and upon determination that the iodine source was in the basement area, the E-fan in the building ventilation system was shut down. -

l These steps were completed Sy approximately 1030 on April 20. The E-fan f draws suction from the basement and intermediate floor areas. With the l E-fan shutdown the flow of air from the basement area is exhausted through i , other auxiliary building fans, which are equipped with charcoal filters. As l $ /0 there is no possibility for unfiltered leakage from the basement area of the 5' auxiliary building, it can be concluded that the major portion of the iodine l

! ' ) g' s release was terminated by about 1030 on April 20, 1972. Flushing of the }

ftU/k auxiliary building floor drains continued after the E-fan was shutdown.

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1 At 1615 on April 20 the charcoal filter that had been installed in the plant  !

d f";! vent iodine sampler at 0635 on April 20 was removed for counting. It was '

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9 ! determined that the average release rate of I-131 over the period 0635-1615 had been 2.7 times the limit of Section 3.9.2.2. of the Technical Speci-

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fications . From 1615 on April 20 through this date, the iodine release rate .

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• r[A re April 28,1972 To Dr. Peter A. Morris from the auxiliary building has been about 40% of the Technical Spect-fication limit. The E-fan was restarted at 2025 on April 20 and has been l in operation since that time.

3The source of the iodine release has not been positively identified, but the observed increase in release rate was coincident with processing of reactor coolant from the C-holdup tank through the boric acid evaporator. '

!A small leak on a flange of the boric acid evaporator was found later and corrected, but it is considered doubtful that this was the major source.

At 1255 on April 20 processing of the contents of the C-holdup tank was stopped and the boric acid evaporator was shutdown. f Since April 20 and continuing for the remainder of the refueling outage, '

charcoal filters from the plant vent lodine monitor are being replaced and counted every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. A charcoal filter for the areas in the auxiliary building not presently covered by charcoal has been on order for some time. Delivery and installation are expected to occur towards the end of the current outage. If tha filter had been in place on April 19 and 20, we estimate that the maximum release rate of iodine-131 would have been approximately half of the Technical Specifications limit. Furthermore, twenty-one extra reload fuel assemblies have been procured and it is planned to remove the remaining identified and suspected leaking fuel assemblies from the reactor during the current refueling outage. ,

Very truly yours, E6 ll wk)

Keith W. Amish k,.

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