ML20085L992

Ro:On 740213,11 Workers Exposed to Airborne Radioactivity During Removal of Main Steam Relief Valve.Caused by Flow Disturbance.Procedure for Removal of Valves Revised to Include Addl Safety Features

ML20085L992
Person / Time
Site:	Browns Ferry
Issue date:	03/15/1974
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Knuth D US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085L986	List: ML20085L992
References
NUDOCS 8311070060
Download: ML20085L992 (5)

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TENNESSEE VALLEY A HOAITY CHATTANOOGA, TENNESSEE 3740'l E W

40 March 15, 1974 nNmivEnsany OF PEOPLE IN PARTN E A S HIP Mr. Den Knuth Directorate of Regulatory Operations U.S. Atomic Energy Cc= mission Washington, DC 20545

Dear Mr. Knuth:

On February 13, 1974, eleven individuals at Browns Ferry Nuclear Plant unit 1 were exposed to airborne radicactivity. The indications that no limit was exceeded are circumstantial; therefore, we are submitting the follcwing report in accordance with 10 CFR 20, Section 20.405(a)(1).

The reactor was at atmospheric pressure, water temperature was below the boiling point, and the reactor vessel head vent was open. Maintenance et ployees had removed a main steam relief valve for replacement. A special vork permit which specified working conditions and protective requirements

]b.jyp.y si Lad been issued as required by plant procedures. Radiological conditions

%f in the work area around the relief valves at the start of work were:

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Radiation dose rates 20 mRcm/hr 4 3

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2 Radioactive contamination - less than 1000 dpm/100 cm Jg,q.* ;;

I.y.(.k Airbcrne radioactivity - 1.54 x 10-10 uCi/cc

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A health physics technician was assigned to the drywell area exclusively.

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7. Qk The technician was either in the drywell or at the entrance area. He was monitoring all e=ployees and equipnent exiting the drywell. The drywell W U.,

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constant air monitor (CAM) was nearby. Before 2 p.m., approximately W Y 20 individuals had entered and left the drywell and had been surveyed-

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no contamination had been found.

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y.p.j c At approximately 2:20 p.m., five men left the drywell after having M lg4' worked on anothpr job in an area with levels of contamination up to

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6500 cp:/100 crf. A survey of these employees indicated two pegle

-k%3r that had facial contamination. All five individuals were sent to the kd '

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health physics technician stationed at the drywell accompanied these individuals to the health physics laboratory to assist in decontamination.

3 It should be noted that it was felt at the ciate that the facial contami-nation was due to possible touching of the face with contaminated gloves.

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It was then determined that three individuals had nasal contamination.

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t o pt._ an air cample. Thi: sup' e wac taken near the open relief valve i

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Mr. Don Knuth March 15, 1974 The mobile whole body counter was brought to Browns Ferry on February 14, and all eleven individuals that had nacal contaminations were counted.

Three individuals were found to have detectable internal deposition of radioactive mterial. The mximum total done due to internal deposition was 6.6 mrem.

It is believed that a flew disturbance resulting from an unplanned reactor recirculating water pump trip caused the airboine radioactivity.

To prevent recurrence, the procedure for removal of thece valves was reviced to include additional safety features. VThenever the relief valves are removed such that the reactor primary system is open, the fol3cwing conditicns will be in force:

1.

IIegative pressure will be mintained in the reactor vessel by the mechanical vacuum pumps.

2.

All reactor operations affecting water level or water flow shall be stabiliced.

3.

Direct telephone communications chall be established between the unit control room and personnel in the drywell.

l 4.

Respiratorc, approved by health physics, will be available for each man working in the drywell.

In addition, blank flanges chall be installed to cloce the primary system as rapidly as possible.

VTe are enclosing an informaticn cheet on the employees exposed to ai-borne radioactivity ac described in this report.

Very truly yours, TEIIITESSEE VALIEY AUTHORITY

. F. Thomac Director of Power Product; ion Enclosure CC:

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Mr. Den Knuth March 15, 1974

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CC(Enclosure):

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Mr. Norman C. Moseley, Director x;kji,,

Region II Regulatory Operatienc Office, USAEC l# l9;i,fj 230 Peachtree Street, IM., Suite 818 DE..

Atlanta, Georgia 30303

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s Enclosure to Report Concerning February 13, 1974, Brcwns Ferry Nuclear Plant Exposure to Airborne Radioactivity The follcwing erployees were exposed to airborne radioactivity as described in the report.

Name Social Security No.

Birth Date J. D. Weaver 415-74-8363 7

47 C. M. McPeters 417-46-5050 1

31 R. H. Her:

349-28-4188 8

38 D. B. stanford 421-54-2862 12

/39 J. L. Ridgeway 316 44-7335 12

/46 A. Wood 423-16-9663 6/

21 J. Watson 401-62-9405 5/

45 W. F. Campbell 424-18-1149 9

22 L. F. Bassham 219-20-7728 2

23 H. P. Todd 381-30-5126 5

28 E. Beddingfield 422-20-9987 7/

6 The following t.hree employees were the only individuals that received detectable internal deposition of radioactive material.

Calculated exposure due to Name internal deposition W. F. Ca=pbell 6.6 mBem J. L. Ridgeway 6.5 rRem D. B. Stanford less than 0.1 rRen These exposure records have been placed in the individual's desir.etry record.

ML: CHB 3/7/74