ML20084T315

Ro:On 730815,exhaust from Purge Sys Sampled & Excessive Airborne I-131 Noted.Caused by Lack of Proper Action by Personnel Including Failure to Stop Purge Promptly Once High Airborne Condition Realized.Purge Procedure Reviewed

ML20084T315
Person / Time
Site:	Palisades
Issue date:	08/24/1973
From:	Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084T261	List: ML20084T268 ML20084T276 ML20084T284 ML20084T287 ML20084T302 ML20084T315
References
NUDOCS 8306230117
Download: ML20084T315 (3)

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Consumers LA'  ? Power

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Mr. John F. O' Leary, Director A' , + Re: Docket 50-255 Directorate of Licensing T jp f, License DPR-20 United States Atomic Energy Commission Washington, DC 20545

Dear Mr. O' Leary:

At 0530 on August 15, 1973, a purge of the Palisades Plant "B" steam generator primary side with dry air was initiated to dry out the tubes and tube sheet to permit inspection for primary to secondary leakage. The plant had been shut down on August 11,1W3 to investigate and repair a primary to secondary leak in the "B" steam generator and, at the time the purge was started, was in a cold shutdown condition with the primary system dra'ined to the hot leg center line. During this purge radioiodine releases via the plant stack were in excess of license limits.

The purge system utilized included a furnace type filter on the inlet to the supply fan and an HEPA filter on the inlet of the ex-haust fan. The exhaust of the steam generator purge was vented to the containment building atmosphere which in turn is exhausted to the environment via the plant ventilation stack. This arrangement had been successfully utilized during the last tube repair work in February 1973 However, in hindsight, radioiodine concentrations in the primary coolant were lower in February than they were in August.

At 0730 the exhaust from the purge system was sampled and higher than anticipated airborne Iodine 131 noted.

At this point a spare charcoal filter was located and installed (at 1230) on the generator purge system exhaust. The operation of this purge continued until 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br />.

At 2100 on August 15, 1(173 the charcoal and particulate fil-ters in the stack gas monitoring system were removed and analyzed.

These filters had been installed at 0700 on August 11, 1973 Based on analysis of the filters, it was concluded that dur-ing the period between 0700, August 11, 1973 and 2100, August 15, 1973 the Technical Specifications limit for release of Iodine 131 had been exceeded. ,

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! Mr. John F. h .ary, Director 2 August 24, 1973 I

I Since the sampler had beer: in service for a time which wan long compared to the mont probabic period of maximum relcano, it In difficult to estimate any instantaneous release rate. Ilowever, there were other iodine sampling units in service which provided information to enable more precise time periods of release. These samplers were being operated by Allied Chemical, under contract to AEC, for the pur-pose of evaluating generic source term data pertaining to PWR systems.

The additional samplers also permitted correlation of data prior to and after the time of significant release.

For the time period from 0300 on August 11 to 1700 on August 20, the total release of Iodine 131 was 174 millicuries. With release rate data as a function of time interval provided by the various samplers, correlated with corresponding plant meteorological measurements, site boundary radiation doses were calculated. The maximum integrated life-time thyroid dose to a potential site boundary receptor would have been 0 38 mrem.

4 Site boundary environmental iodine samplers were retrieved and analyzed by an independent party. Their quoted minimum limit of sensi-tivityis0.02pCi/m3 One site bgundary sampler indicated Iodine 131 concentration of 0.03 + 0.01 pCi/m . Maximum dose calculation based on that concentration at that point would have been 0.02 mrem. Also, a i milk sample was obtained from the nearest real cow and analyzed. No activity was detected.

, The release was the result of the lack of proper action by per-sonnel in the following areas:

a. Proper attention to the known increase in primary iodine '

levels since the last steam generator repair work.

b. Failure to recognize the potential airborne problem and accomplish adequate sampling and airborne containment.

c. Failure of personnel involved to stop the purge promptly once the high airborne condition was realized.

In addition, the procedure ist.ued to accomplish the steam generator purge was inadequate in that it failed to provide adequate

, operator guidance with regard to sampling.

L The following corrective action has been taken to preclude recurrence of a similar incident:

a. This incident was promptly reviewed with the plant staff i and shortcomings discussed.

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b. The purge procedure was reviewed again and changes approved, including required use of a charcoal filter and specific instructions on sampling requirements prior to continuous purging of the generator.

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, Mr. John F. O' ary, Director 3

. August 24, 1973

c. Enclosure tents will be fabricated to contain residual airborne activity when manways are open if access to the primary side of the steam generators in the future is required.

Yours very truly, Ralph B. Sewell (Signed)

RBS/ds Ralph B. Sewell Nuclear Licensing Administrator CC: BHGrier, USAEC

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