Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS
WASHINGTON, D.C. 20555
March 26, 1991
Information Notice No. 91-23: ACCIDENTAL RADIATION OVEREXPOSURES TO
PERSONNEL DUE TO INDUSTRIAL RADIOGRAPHY
ACCESSORY EQUIPMENT MALFUNCTIONS
Addressees:
All Nuclear Regulatory Commission (NRC) licensees authorized to use sealed
sources for industrial radiography.
Purpose:
This information notice is being issued to alert licensees to recent
radiography incidents involving both extremity and whole body overexposures
of radiographers. These occurred during industrial radiographic operations
as a result of: (1) not surveying a radiographic exposure device and source
guide tube after each exposure; or (2) using either a magnetic or
non-magnetic stand for applications that applied stresses exceeding the
limits of the stand. It is expected that licensees will review this notice,
distribute it to responsible staff, and consider actions, as appropriate, to
avoid similar problems. However, suggestions contained in this information
notice do not constitute any new NRC requirements, and no written response
is required.
Description of Circumstances:
The following cases are recent events reported to NRC that have resulted in
radiation overexposures to radiographers and radiography assistants as a
result of improper handling of radioactive sealed sources and inattention to
radiation safety procedures.
Case 1: A radiographer had been performing exposures of welds at the base
of a 300,000 gallon waste storage tank, with a radiography camera equipped
with a 14-foot guide tube. A tungsten collimator had been positioned on the
end of a guide tube that was clamped to a stand that was magnetically
attached to the tank wall. After cranking out the 80-curie iridium-192
(Ir-192) source for an exposure approximately 10 feet above the base of the
tank, the radiographer heard the collimator fall. After straightening out
the guide tube, the radiographer fully retracted the cable, and consequently
thought that the source was in the shielded position of the camera.
Subsequently, the radiographer removed his dosimetry, picked up a survey
instrument, walked up to the end of the source guide tube and removed the
collimator, without observing the meter reading. As he was unscrewing the
nozzle of the guide tube, the source fell to the ground. The radiographer
immediately left the area, and notified the proper authorities. Exposure
estimates to the radiographer, based on source activity and exposure time
estimates, are 8.9 rem whole body, and 1070 rem to the right hand.
9103200074
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IN 91-23
Page 2 of 3
March 26, 1991
Case 2: A radiographer and his assistant were performing radiographic
exposures of welds on a 48-inch diameter tank. After the sixth exposure,
the radiographer left the immediate area to load film in a belt. While the
radiographer was away, the assistant set up the seventh exposure and cranked
out the source. The assistant had turned the crank about two or three times
when he saw that the magnetically mounted stand, that held the guide tube
near the exterior of the tank, had fallen. When the stand fell, the
assistant's personnel dosimeter (chirper) began to alarm, so he quickly
cranked the source back into the shielded position. Because his chirper
stopped alarming, he thought that the source was in the shielded position,
so he did not survey the area (the licensee later reported that the chirper
was found to be malfunctioning due to a shorted ground wire). Instead, he
walked over to the tank, repositioned the magnetic stand and source guide
tube with his right hand, and returned to the camera to proceed with the
exposure. When he cranked out the 50-curie Ir-192 source, he noted that his
chirper did not alarm, so he looked at his pocket dosimeter and noticed that
it was off scale high. When the radiographer returned, the assistant told
him what had happened and that his pocket dosimeter had gone off scale. The
assistant told the radiographer that he did not think he had received an
overexposure, but that he thought his pocket dosimeter was off-scale because
he had bumped it earlier. The radiographer and his assistant continued to
work and did not inform the Radiation Safety Officer of the incident until
the assistant's hands showed clinical signs of radiation injury. From
reenactments, clinical observations, and calculations, the overexposure to
the assistant radiographer's hand was estimated to be between 1500 and 3000
rem. The attending physician stated that amputation of one or more fingers
could be necessary. The whole body dose to the assistant, as measured by
his TLD, was 365 millirem.
Case 3: This radiographic operation involved the use of an 80-curie Ir-192
source. After completing two radiographs of a pipe weld, an assistant
radiographer disassembled the equipment in order to move the exposure device
to another location. While doing this, he removed the source guide tube and
draped it around his neck so that his hands would be free to carry the
remaining equipment approximately 50 feet. As he removed the guide tube
from around his neck, he noticed that the sealed source fell from the tube
to the ground. The assistant notified the radiographer, who telephoned the
company owner and, following his direction, successfully retrieved the
source to a shielded position within the exposure device. The
radiographer's film badge was immediately sent for processing (the assistant
radiographer was not wearing a dosimeter and was immediately sent to a
hospital for a medical examination). The cytogenetic studies revealed
equivalent whole body doses of 17 rem for the radiographer and 24 rem for
the assistant. The assistant developed an area of redness on the left side
of his neck, which later showed signs of more significant damage to skin
tissue in an area approximately 10 centimeters in diameter. The physician
determined that the observed effect corresponded to an overexposure to the
skin of 5000-7000 rem. There were no medical effects observed for the
radiographer.
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IN 91-23
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March 26, 1991
Discussion:
All licensees are reminded of the importance of ensuring the safe
performance of licensed activities, in accordance with NRC regulations,
requirements of their licenses, and accepted health physics practices. The
aforementioned cases illustrate: the lack of radiation surveys following the
retraction of a sealed source; failure to wear a direct reading pocket
dosimeter and either a film badge or TLD; failure to personally supervise an
assistant radiographer while using radiographic exposure devices; the
improper use of a magnetic or non-magnetic stand that cannot hold the weight
of the intended equipment (such as a 12-pound collimator); the necessity of
consistently following standard operating and, when necessary, emergency
procedures; and the need to understand the significance of radiation doses
that result from the misuse of large radiographic sources. Sealed sources
for radiography are capable of delivering significant unintended exposures
to radiographers, assistants, and members of the general public, when source
management procedures are not followed.
Although it might seem obvious that common sense would prevent radiation
workers from picking up highly radioactive sources or guide tubes that might
inadvertently contain a dislodged radiographic source, the number of
unplanned radiation exposures of this type indicates that "common sense"
cannot be counted on, in such a situation. Licensees are responsible for
ensuring the safe performance of licensed activities in accordance with NRC
regulations and the terms of their licenses. In so doing, licensees should
not only provide adequate training, but should also exercise close
supervision over their employees, to ensure compliance with procedures and
with NRC or any other applicable requirements. All workers should
understand the consequences of improperly handling a radiographic source
containing large quantities of Ir-192. Such improper handling can cause a
significant, undesired, radiation dose to both the whole body and
extremities, and can easily result in the amputation of several fingers, the
development of a tumor, or death.
No written response is required by this information notice. If you have any
questions about this matter, please contact the appropriate regional office
or this office.
Richard E. Cunningham, Director
Division of Industrial and
Medical Nuclear Safety
Office of Nuclear Material Safety
and Safeguards
Technical Contact: Cynthia G. Jones, NMSS
(301) 492-0629
Attachments:
1. List of Recent NMSS Information Notices
2. List of Recent NRR Information Notices
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