ML20134A121

Responds to NRC Re Violations Noted in Insp Rept 50-278/85-31.Corrective Actions:Analysis of Exposure of Personnel Entering Recombiner Offgas Pipe Tunnel to Gaseous Radioactivity Provided.No Adjustments Made

ML20134A121
Person / Time
Site:	Peach Bottom
Issue date:	10/25/1985
From:	Cooney M PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Martin T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
NUDOCS 8511040198
Download: ML20134A121 (3)

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[ PHILADELPHIA ELECTRIC COMPANY 23ol M ARKET STREET l

! P.O. BOX 8699 f' PHILADELPHI A. PA.19101 I

(215) 841-5020 wuCLa PaoouC Tton r FLEC TRIC PRODUC TSON D&P ANTMENT October 25, 1985 Docket No. 50-278 Inspection Report No. 50-278/85-31 l

Mr. Thomas T. Martin, Director Division of Engineering and Technical Programs i U.S. Nuclear Regulatory Commission Region I 631 Park Avenuo King of Prussia, PA 19406

Dear Mr. Martin:

Your letter dated September 25, 1985 forwarded Inspection Report No. 50-278/85-31 for Peach Bottom Atomic Power Station. Within the scope of this inspection, no violations were obse rved . However, a concern was identified relative to an incident which involved the exposures to gaseous radioactivity of individuals who entered the Unit 3 recombiner of fgas pipe tunnel on March 1, 1985. As a result of this event, your letter requested that Philadelphia Electric Company provide an analysis of the incident including final beta dose to the individuals, the radiation survey meter response to noble gases, and the resolution of discrepancy report 85-087 regarding the dif ference between the survey meter and the TLD results.

Response

The noble gas release into the Unit 3 of fgas pipe tunnel occurred as a result of a pressure transient in the offgas recombiner system. The pressure transient was a result of a combination of problems involving the main condenser and the recombiner mechanical compressors, as discussed in Peach Bottom LER 3-85-07. The prompt identification of the release and the immediate exit from the area by all personnel resulted in very minimal exposure to the individuals involved.

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TDuring7the event, the: survey meter that was being used by

the individuals in the of f' gas tunnel apparently indicated

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. of f - scale on the 50 : R/hr range with the beta shield open.'

2 if  : Following L the exit from . the tunnel, the instrument reading

(gradually' returned to normal.

! Subsequent analysis of' the L thermoluminescence devices (TLD) worn by the four individuals indicated- no beta exposure for h; , three : individuals,: and 12.5 millirem exposure for the :other l -

individual. One individual expressed concern regarding the

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" difference between- the survey meter readings and the beta result obtained from his dosimetry. An "as found" calibration- showed - the - instrument response to be normal to

-direct radiation. 'After this determination, the

investigation centered on how the noble gas release could "have caused an erratic up scale response. We . suspect that

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the problem was caused ;by noble. gas entering the detection

. l chamber via a defect ~ in the Mylar Window. We consider the dosimetry data to be representative of ' the exposure-

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received by the individuals.

k It-~ is a iknown fact - that an ionization chamber contaminated c ."

with radioactive gas within its chamber will read abnormally high. We are initiating ~ a search for technical references that may quantify .this ef fect. This search n2 , . should be complete by November 22,'1985. If it is J determined that no such experiments have been performed, Philadelphia' Electric Company (PEco) will develop and

, perform in-house, or through a consultant, an experiment to

determine such response.. It is expected that data from -

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such an experiment will resolve the Discrepancy Report 85-4' 087 regarding the dif ference .between the survey meter and the TLD L results.

Recent testing of Eberline and'Harshaw dosimetry indicates 1 - that both of these devices read low,- by a factor ' of about 5, - for beta energies -less than 300 Kev. In the interest of P' conservatism, an assumption was made that 50% of the total b- beta exposure to the individuals involved was due to isotopes having energy levels less than 300 Kev. One of the four individuals involved with the March 1, 1985 event  !

had an Eberline beta reading of zero and a Harshaw beta ~

reading of 12.5 millirem for that date. The 12.5 millirem value has been adjusted conservatively to 38 millirem to account for~ beta energies less than 300 Kev. A value of 0.038 rem"to the skin has been added to this individual's

exposure record.

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The ' remaining three individuals had zero beta exposure

indicated by both their Eberline and Harshaw readings.

Therefore, no adjustments will be made to the exposure

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• ; Mr..Thomac T., Martin

.0ctobar 25, 1985 s, Page 3 records of the latter three individuals. It-is concluded

- that the agreement between the - Eberline and - Harshaw

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. dosimetry confirms the low exposure levels experienced by all':four individuals and supports our belief that the -

survey meter's .of fscale indication was a result of leakage of ' noble _ gas' contamination into . the detection chamber with resultant conservative up scale reading.

Should you have any questions or require additional in formation, please do not he'sitate to contact us.

V ry truly yours, W .,

cc T. P. Johnson, Resident Site Inspector 9'

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