PNO-III-88-034, on 880406,up to 68 Workers Received Minor Exposures to Airborne Radioactivity,Principally I-131,during Steam Generator Tube Plugging Activities.Cause Under Investigation.Respirators Required to Enter Containment

PNO-III-88-034:on 880406,up to 68 Workers Received Minor Exposures to Airborne Radioactivity,Principally I-131,during Steam Generator Tube Plugging Activities.Cause Under Investigation.Respirators Required to Enter Containment

ML20151C818
Person / Time
Site:	Byron
Issue date:	04/07/1988
From:	Greger R, Shafer W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
References
PNO-III-88-034, PNO-III-88-34, NUDOCS 8804130197
Download: ML20151C818 (2)

PRElstMIMARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-III-88-34 Date April 7,1968

.] ,

This ' preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially received without verification or evaluation, and is basically all that is known by the Region III ,

staff on this date.

Facility: Comonwealth Edison Company Licensee Emergency Classification: ,

Byron Unit 1 Notification of an Unusual Event -

Byron, IL 61010 Alert Site Area Emergency Docket No. 50-454 General Emergency X Not Applicable l

Subject:

UP TO 68 WORKERS RECEIVE POSSIBLE MINOR AIRBORNE EXPOSURES fs During steam generator tube plugging activities on April 6, 1988, as many as 68 workers received minor exposures to airborne radioactivity, principally iodine-131. The exposures were a small fraction of NRC limits.

fnitially workers were found to have small internal depositions of iodine-131 after they triggered contamination monitors as they left the Unit 1 containment at 10:30 a.m. Control room operators had also observed slowly increasing iodine levels in the Unit 1 containment, but the levels were attributed to the recently opened steam generator. Unit I was shut down l on April 3,1988, to repair a steam generator tube leak. ,

t The containment was then evacuated at 11:46 a.m. because of suspected airborne radioactivity.

The licensee determined the source of the airborne iodine to be a temporary ventilation system for the steam generator manway. The ventilation airflow passed through a HEPA filter, but was discharged to the containment before it passed through the system's charcoal filter. The licensee is still investigating the cause of the ventilation system problem.

According to the licensee, 68 individuals were potentially exposed to the airborne iodine.

Uhole body counts have been performed on 36 persons to determine the level of iodine uptake, i

and the remaining individuals will be tested. The highest internal deposition measured j indicates an iodine uptake level of approximately 14 MPC-hours or about 2% of the regulatory

] limit.

The licensee is restricting access to radiological areas for those indiviouals with greater than 1 percent MPC. All personnel entering the containment are wearing respirators with l charcoal cartridges until decontamination efforts are completed.

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DISTRIBUTION:

, H. St. NMBB Phillips E/W WFN 1

' Chairman Zech AEUU NRR DTA NP3r Com. Roberts ARM OI SLITP

. Com. Bernthal EDO Mail To:

Com. Carr PA Resident Inspector Offices DCS (Original)

Comm. Rogers OGC Resident Inspector DOT (Trans. Only) 4 SECY , A' i OGC-H FAX T0: Nicholson Lane Regions 4 CA INPO A: RE5 Region I dp.

j GPA NSAC 4:o Region II /

' ACRS Licensee 4: O') Region IV O(

PDR HOS, Operations Officer $0$ Region V j 8804130197 880407 Region III E-IsOO-034DCD

PREWMilfARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-III-88-34 Date April 7.1988 4 .

A Region III (Chicago) radiation protection specialist will be sent to the site to review the circumstances of the incident.

The State of Illinois will be informed.

Region III received initial notification of the contamination problem at about 2:30 p.m.,

April 6,1988, from the resident inspector. (The contamination problem was not a reportable incident.) This information is current as of 10 a.m. , April 7,1988.

CONTACT: R.l. eg i,0 hW. Shafer V FTS 388.5644 FTS 388-5656 1

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