Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
July 27, 1990
Information Notice No. 90-47: UNPLANNED RADIATION EXPOSURES TO
PERSONNEL EXTREMITIES DUE TO IMPROPER
HANDLING OF POTENTIALLY HIGHLY
RADIOACTIVE SOURCES
Addressees:
All holders of operating licenses or construction permits for nuclear power
reactors, holders of licenses for permanently shutdown facilities with fuel
onsite and research and test reactors.
Purpose:
This information notice is intended to alert addressees to the hazards of
unplanned radiation exposures, especially to the extremities, resulting from
improper handling of potentially highly radioactive sources. It is expected
that recipients will review the information for applicability to their
facilities and consider actions, as appropriate, to avoid similar problems.
However, suggestions contained in this information notice do not constitute
NRC requirements; therefore, no specific action or written response is
required.
Description of Circumstances:
FitzPatrick Events
On March 8, 1990, a radiation control technician (RCT) at the James A.
FitzPatrick Nuclear Power Plant contaminated himself with sodium-24 (Na-24),
at a level of at least 120 mR/hr, after picking up a contaminated cap to put
it back on the empty source vial. Instead of using handling tools as
specified in procedures, the RCT used his gloved right hand. Later, during
the removal of his gloves, the RCT contaminated his left hand. This event
occurred after the preparation of approximately 400 mCi of Na-24 radioactive
solution for injection into the reactor primary system as part of a system
flow check. Calculations performed by the licensee showed that the skin of
the left thumb had been exposed to approximately 48.8 rems (using 7 mg/cm 2
as the thickness of the skin as specified in Form NRC-5). The NRC staff has
taken escalated enforcement action against the licensee because of this
event. See NRC Inspection Report 50-333/90-12 for more details.
Aside from the skin exposure, this event is significant because the
corrective actions taken for a similar event that occurred at the same plant
in February 1987 failed to prevent the occurrence of the above event.
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Regarding the February 1987 event at the FitzPatrick plant, NRC Inspection
Report 50-333/87-07 reported that an irradiated instrument dry tube was
inadvertently removed from the spent fuel pool (SFP) and dropped onto the
floor. A worker picked up the tube and threw it into the SFP, thereby
receiving an overexposure to one hand. As a result of a licensee and NRC
review, five violations were identified: (1) failure to control extremity
exposure, (2) failure to instruct individuals as to the radiological hazard,
(3) failure to perform an adequate survey, (4) failure to follow radiation
protection procedures, and (5) failure to follow operating procedures.
As a result of the 1987 event, the licensee issued standing orders requiring
radiation protection supervisory personnel to monitor and review
radiologically sensitive work. In addition, the licensee required that
procedure reviewers use a checklist to address radiological concerns while
reviewing new or temporary procedures. Those actions were appropriate,
however it is necessary for each worker to understand the hazard of
radiation exposure to the extremities that may result from the improper
handling of objects of high potential radioactivity. Listed below are items
from the licensee's checklist which, if properly addressed, would have
emphasized to personnel the hazards associated in working with a highly
radioactive source and could have prevented the 1990 Na-24 event:
- Are personnel qualified and trained to perform the job? - In both
events, a common weakness was that the personnel did not
understand the magnitude of the hazard associated with the work.
Since Na-24 flow testing is not commonly used at nuclear power
plants, better training of workers on the proper handling of
radionuclides for flow testing could help prevent unnecessary
exposures.
- Do the work procedures have radiological hold points to help
initiate proper radiological job coverage/oversight? - In both
events, hold points were not established to request a survey of
unidentified, potentially highly radioactive objects prior to
handling the objects.
- Do all workers understand what controls have been established for
limiting radiation exposure and contamination? - The protective
clothing requirements on the Radiation Work Permit (RWP) did not
reflect the true nature of the contamination hazard associated
with the performance of the Na-24 flow testing. In addition, at
no time during the mock-up training or the pre-job ALARA meeting
was there any specific mention of the disposition of the highly
contaminated Na-24 source vial and cap. This contamination
incident could have been avoided if the worker had treated the
outside of his gloves as contaminated during removal. For the
Na-24 flow test, the absence of more specific contamination
information may have resulted in the RCT being less vigilant in
his contamination control work practices.
Pilgrim Events
Other examples of improper handling of highly radioactive sources occurred
at the Pilgrim plant. In January 1984, during maintenance work on a control
rod drive (CRD), CRD parts and miscellaneous debris from the bottom of the
reactor
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vessel were placed in a five-gallon bucket of water and left unposted in the
area for five days. On the fifth day, after the CRD parts were removed for
decontamination, a RCT identified the bucket as a source of high radiation
and proceeded to survey the objects by picking them up to perform the
measurements.
Subsequent thermoluminescence dosimeter (TLD) measurements of the objects
indicated contact dose rates as high as 2880 R/hr, resulting in an exposure
to the RCT's hand of about 4.5 rem.
Evidently, lessons learned from this event were not effectively communicated
to all workers at the plant. On August 18, 1984, a RCT identified a highly
radioactive chip of metal in a CRD tool tray (later evaluation indicated a
contact dose rate of 1120 R/hr). This information, however, was not
immediately disseminated to all workers in the area, (i.e., the area was not
posted). Later, when a group of workers began to work in the area around
the CRD tool tray, the RCT, while pointing at the chip with the survey
meter, yelled through his respirator for the workers to move away from the
CRD. One worker, believing that he was being directed by the RCT to remove
the chip, picked up the chip and threw it away from the CRD. The extremity
dose to the worker's hand was estimated to be 1.1 rem for the three seconds
he was holding the chip.
The above events indicate that the hazards of extremity exposure are not
well understood by all radiation workers and that lessons learned from the
occurrence of a higher than normal exposure to one worker are not
effectively integrated into the work habits of other workers. Attachment 1
gives additional examples in which unplanned exposures occurred due to
improper handling of potentially highly radioactive sources.
Discussion:
Although it may appear obvious that common sense should prevent radiation
workers from picking up potentially highly radioactive sources, the number
of identified unplanned radiation exposures of this type indicates that
"common sense" has not been effective. Radiation workers have traditionally
been well indoctrinated in the control of radiation exposures to the
whole-body. However, this knowledge is not well translated into the control
of radiation exposures to the extremities (i.e. hands, forearms, feet and
ankles). Because the contact dose rates of radioactive sources can be
extremely high, handling these objects even for a few seconds can result in
very high extremity exposures. The use of remote handling tools can reduce
the magnitude of unplanned exposures without hindering the completion of the
tasks involved. Most licensees evaluate the need for such tools during the
planning for specific aspects of each job; however their use for an
unanticipated situation has not always been effectively communicated to the
workers.
Because an unidentified highly radioactive object can be picked up with
little or no advance notice, the presence of a RCT or a line supervisor may
not prevent an unplanned exposure. In several events, the RCTs themselves
erred by directly handling the objects and receiving unplanned exposures.
Therefore, it is important that all radiation workers understand the hazards
of high extremity exposures associated with unidentified and possibly highly
radioactive objects and be well trained in the proper handling of these
objects. With
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proper training, a worker is more likely to survey or request timely surveys
of suspect objects that could harbor highly radioactive sources. For these
types of localized hot sources, including beta sources, routine general area
radiation survey maps may not be useful in protecting the worker.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate NRR project
manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: Joseph C. Wang, NRR
(301) 492-1848
James E. Wigginton, NRR
(301) 492-1059
Attachments:
1. Summaries of Other Events
2. List of Recently Issued NRC Information Notices
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Attachment 1
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Page 1 of 2
Summaries of Other Events:
TMI-2 (September 1989)
Two workers handled a piece of material believed to be fuel debris. The
radiological controls technician (RCT) monitoring the work was unaware that
the workers had handled the object. After the RCT surveyed the object, it
was returned to the reactor vessel because of its high dose rate. The
licensee initiated an inquiry when the first worker, on the following day,
asked another RCT about the health implications of handling fuel debris.
The calculated skin dose to the left hand of one of the workers was 55 rem.
(NRC Inspection Report 50-320/89-11, February 8, 1990)
Point Beach (April 1989)
An inservice inspection (ISI) engineer received a dose to the hand of 4.7
rem during a closeout inspection of the Unit B steam generator. The
exposure occurred when the engineer picked up an object and passed it
outside the steam generator without knowing that the radiation level of the
object read 200 R/hr at near contact. (NRC Inspection Report 50-266/89-15,
June 21, 1989)
Rancho Seco (July 1984)
After the completion of a tube plugging job, a worker entered the steam
generator to vacuum loose debris. The worker picked up an object that was
too large to be vacuumed and tossed it out of the steam generator. The
object had been earlier identified as part of a high pressure injection
nozzle thermal sleeve. The radiation level of the object read 28 R/hr at
six inches. A licensee radiation protection investigation concluded that no
overexposure had occurred. (NRC Inspection Report 50-312/84-25, October 19,
1984)
Sequoyah (August 1982)
Two flow tests of reactor systems performed in August 1982, using Na-24 as a
tracer, resulted in an extremity exposure to one worker of 10 rem. Because
this exposure was higher than those incurred during past flow tests, the
licensee initiated an investigation to determine the cause of the high
exposure. The licensee concluded that because of the high contact dose-rate
(1.5 R/sec) of the Na-24 source vial, its cap should not be removed by hand
as was the case in previous tests; instead remote handling tools should be
used. The licensee also concluded that, because Na-24 is not commonly used
at nuclear power plants, health physics management should provide better
training and pre-job planning to both RCTs and radiation workers with regard
to the handling of radionuclides, such as Na-24, used in flow testing.
Based on this event, the licensee determined that prior to 1982, extremity
dose evaluations for flow testing had underestimated the actual doses, and
that the extremity monitoring program for the plant should be upgraded.
However, no overexposures have been reported to the NRC as a result of flow
testing at Sequoyah.
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Attachment 1
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Peach Bottom (October 1981)
A maintenance worker received an unplanned exposure to the hand while
visually inspecting the inservice fuel inspection platform at the Unit 2
spent fuel pool (SFP). This exposure occurred when the worker picked up
fuel channel clips from the fuel elevator with his hand. The area radiation
monitors alarmed. A nearby radiation control technician immediately
instructed the maintenance worker to put down the fuel channel clips. The
clips were then placed into a bucket in the spent fuel pool. Subsequent
radiological survey of the fuel channel clips indicated a gamma dose rate of
3.2 R/hr at 1.8 inches. Exposure to the worker's hand was estimated at 527
mrem. (NRC Inspection Report 50-277/82-11, July 13, 1982.)
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