ML20039B359

Advises That IE Info Notice 81-37, Unnecessary Radiation Exposures to Public & Workers During Events Involving Thickness & Level Measuring Devices, Was Sent to Attached List of Licensees on 811215

ML20039B359
Person / Time
Issue date:	12/15/1981
From:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
NUDOCS 8112220577
Download: ML20039B359 (12)

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,d WALNUT CREEN. CAUFORNIA 94596 December 15, 1981 MEMORANDUM T0: ALL THOSE ON IE INFORMATION NOTICE DISTRIBUTION LIST FROM:

IE - REGION V

SUBJECT:

IE INFORMATION NOTICE N0. 81-37: UNNECESSARY RADIATION EXPOSURES TO THE PUBLIC AND WORKERS DURING EVENTS INVOLVING THICKNESS AND LEVEL MEASURING DEVICES i

The attached IE Information Notice No. 81-37 was issued this date to the attached list of licensees.

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December 15, 1981 Gentlemen:

The enclosed notice is sent for your information. The two cases presented are intended to show the need for caution while handling and using measuring devices, even though they are considered minimally hazardous during normal use conditions.

If you have any questions related to the subject matter, please contact this office.

Sincerely, Ud M Maned LZ' 2

LE. h 7' R. H. Engelken Regional Administrator

Enclosure:

IE Information Notice No. 81-37

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.a SSINS No.: 6835 Accession No.:

8107230042 IN 81 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE 0F INSPECTION AND ENFORCEMENT WASHINGTON, D.C.

20555 December 15, 1981 IE INFORMATION NOTICE NO. 81-37: UNNECESSARY RADIATION EXPOSURES TO THE PUBLIC 3

AND WORKERS DURING EVEHTS INVOLVING THICKNESS AND LEVEL MEASURING DEVICES'

Purpose:

This information notice provides information about radiation hazards associated with the possession and use of measuring devices containing radioactive sources.

These devices are generally considered to present only minirial potential fo,r radiological problems under normal use conditions.

However, two recent events involving measuring devices resulted or may have resulted in unnecessary radiation exposure to members of the public and to maintenance workers. This information should be brought to the. attention of all persons; involved in the administration and operation of' facilities and processes using measuring devices.

Particular attention should be given'to the environment where measuring devices are located and to procedures to assure that the radioactive source is properly shielded and contained.

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Description of Circumstances:

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Case 1: An NRC-licensee was closipg a-facility in Oklahoma City, dklahoma and had sold a trailer containing a mounted measuring device'(Tube Hall Caliper) i for determining pipe wall thick' ness.

Since the device c'ontained a-1.5 curie I

cesium-137 source and the new owner had not yet obtained-a license to possess the radioactive source, the licensee' removed the device from the trailer prior-to the new owner taking possession.

D-ing removal'of the device (which was performed by an unauthorized user), the radioactive source'was inadvertently released from its shielded position in.the device and fell to the trailer floor.

The dismounting of. the device was performed without benefit of a survey meter or personnel monitoring equipment. The. radiation dose to the individual may have been as high as 600 millirems.

Subsequently, the new owner had the trailer towed to Houston, Texas, with an irterim stop;for, tow truck engine repair in Norman, Oklahoma. The driver, who was not aware of the presence of the radio-active source, waited near the trailer for approximately four hours.

He may have received a radiation dose as high as 1.4 rems. The next day, the_ licensee found that the source was missing from the measuring device. Local health authorities performed a search using radiation detection equipment along the highway route between Oklahoma City and Houston. The source was found lodged on a bridge support structure'near Lewisville, Texas.

The major causes of the event were that (1) the licensee failed to employ an authorized user to remove the device, and (2) the unauthorized user failed to t

rde a radiation survey.

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I4 81-37 December 15, 1981 Page 2 of 2 Case 2: A cooler in an iron ore pellet plant was shut down for repairs on March 30, 1981. On that day, the shutter mechanism of a level control device,-

which contained a nominal 10-curie cesium-137 sealed source,'was locked in the closed position.

Radiation surveys performed at that time indicated that the source appeared to be properly sheilded. After a cooldown period, workmen entered the cooler on April 3,1981 to replace refractory material on the cooler walls. On April 7, licensee personnel discovered that there were radiation levels in excess of 100 millirems per hour withi-the cooler (later determined to be as high as 2.2 rems per hour where the radiation beam entered the cooler).

It was determined that several individuals had been exposed to a radiation beam from the source during the working. days between April 3 and 7,1981. The device source holder was removed from its mounting, and licensee personnel found that the lead shielding in the shutter had melted and drained.from the shielded loca-tion. This rendered the shielding integrity of the shutter useless.

Investigation showed that 17 licensee personnel and 14 contractor personnel had entered the cooler between April 3 and 7, 1981. The calculated radiation exposures received ranged from 0.14 to 3 rems. During the repairs, the pellet cooler area was considered an unrestricted area.

It is estimated that 14 of the 31 individuals exposed may have received whole-body exposures in excess of 0.5 rems. No health effects were observed or~would be expected from these exposures.

The event occurred because a hole had been cut in the side of the cooler to reduce shielding and allow more effective operation of the cesium-137 source in the device.

During recent efforts to increase production, the pressure of the air forced into the cooler had been increased as a means of accelerating the cooling of the pellets. As a result, hot gases may have been forced out of the aperture in the cooler wall at the location of the source holder. The temperature of the pellets entering the cooler is about 2400F, considerably higher than the melting point of lead.

The heat reaching the device was suf-ficient to melt the aluminum alloy dust cover over the device shutter mechanism and the lead in the shutter, thereby allowing a radiation beam to escape the device.

In addition, the licensee's survey failed to determine that the radioactive source was not safely shielded.

No written response to this notice isf required.

If you need additional information regarding these subjects, contact the regional administrator of the appropriate NRC Regional Office.

Attachment:

Recently issued IE Information Notices 4

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Attachment IN 81-37 December 15, 1981 RECENTLY ISSUED IE INFORMATION NOTICES Information Date. of Notice No.

Subject Issue Issued to 81-36 Replacement Diaphragms #ce 12/3/81 All oower reactor Robertshaw Valve (Model facilities with an No. VC-210)

OL or CP 81-35 Check Valve Failures 12/2/81 All power reactor facilities with an OL or CP 81-34 Accidental Actuation of 11/16/81 All power reactor Prompt Public Notification facilities with an System OL or CP 81-33 Locking Devices Inadequately 11/9/81 All power reactor Installed on Main Steam facilities with an Isolation Valves OL or CP 81-32 Transfer and/or Disposal of 10/23/81 All medical licensees Spent Generators 81-31 Failure of Safety Injection 10/8/81 All power reactor Valves to Operate Against facilities with an Differential Pressure OL or CP 81-30 Velan Swing Check Valves 9/28/81 All power reactor facilities with an OL or CP 81-29 Equipment Qualification 9/23/81 All power reactor Testing Experience facilities with an OL or CP 81-28 Failure of Rockwell-Edward 9/3/81 All power reactor Main Steam Isolation Valves facilities with an OL or CP 81-27 Flamnable Gas Mixtures 9/3/81 All power reactor in the Waste Gas Decay facilities with an Tanks in PWR Plants OL or CP 81-26 Compilation of Health 9/3/81 All power reactor Physics Related Information facilities with an Items OL or CP OL = Operating License CP = Construction Permit