Information Notice No. 83-09: Safety and Security of Irradiators
SSINS NO: 6870
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
March 9, 1983
Information Notice No. 83-09: SAFETY AND SECURITY OF IRRADIATORS
All irradiator licensees.
The purpose of this notice is to bring to the attention of all persons
involved in the administration and operation of irradiation facilities two
recent incidents which point out the importance of safety and security
procedures for all irradiators.
Case 1: FATAL RADIATION DOSE AT AN IRRADIATOR FACILITY IN NORWAY
In September of 1982, a worker entered the exposure room of a large,
drystorage irradiator. The source was in an unshielded position, and the
worker received a fatal radiation dose. The NRC has not yet received a
written report, but has obtained information on the accident by telephone.
The accident occurred at a 64,000-curie, cobalt-60, dry-storage irradiator
in Norway. The irradiator is a conveyor belt, continuous-mode type,
operating 24 hours a day, unattended at night. In this incident, the
conveyor belt jammed at night (mechanical failure #1) and the cobalt sources
failed to automatically retract into the shielded position (mechanical
failure #2). The first person arriving at work in the morning found a green
indicator light and an unlocked door interlock (mechanical failure #3). He
entered the maze and exposure room while the source was in an unshielded
position. A radiation monitor normally located in the maze was out for
repair. He left the exposure room after an undetermined period of time. He
became ill soon afterwards, and went to the hospital. He did not provide any
information to the hospital to indicate that he may have been exposed to
A second person arrived at the irradiator facility after the victim had
left, immediately recognized from the control console that the source was in
an exposed position, and that mechanical failures had occurred. Upon hearing
that an employee had been hospitalized, he notified the hospital that the
cause of illness might be an acute radiation overexposure. The victim
acknowledged that he had been in the exposure room, but did not provide a
clear explanation as to why he had entered the room, or how long he had been
exposed. He died later of radiation injuries. The final estimate of
radiation dose has not yet been completed.
March 9, 1983
Page 2 of 2
The irradiator control panel had indicators which correctly showed the
cobalt-60 sources to be exposed. Also, a portable radiation monitor was
available to the victim, but was not used. Therefore, the cause of the
accident appears to be a combination of (1) multiple mechanical failures and
(2) human error.
All irradiator licensees are reminded that mechanical failures or human
errors can result in serious, even fatal overexposure. Licensees should
remind their employees of the potential seriousness of an overexposure.
Furthermore, it should be emphasized that individual safety features should
not be relied upon to the exclusion of other safety features. All available
information related to the position of the source should be checked before
entering the exposure room.
CASE 2: SECURITY OF CONTROLS PANELS AND MECHANISMS
NRC recently received a report concerning security of the control an
interlock system at a large irradiator facility. The report noted that the
electro-pneumatic valve control panel was located on the roof of the
facility, and that this area could be reached by anyone climbing onto the
roof. Thus, an unauthorized person could conceivably tamper with the
electro-pneumatic controls of the irradiator, disabling safety interlocks,
or even raising the source itself into an unshielded position.
All irradiator licensees are reminded that their facilities should be
secured against unauthorized access at all times. For small, self-shielded
irradiators, the storage locations should be kept locked at all times when
authorized users are not present. For large irradiators, all areas
associated with irradiator operations, particularly control and interlock
systems, should be locked and secured against unauthorized access. Licensees
should review their facilities and security programs to ensure that adequate
security is being provided.
No written response to this Information Notice if necessary. If you need
additional information regarding these subjects, you should contact the
Administrator of the appropriate Regional Office.
James M. Taylor, Director
Division of Quality Assurance, Safeguards,
and Inspection Programs
Office of Inspection and Enforcement
Technical Contact: R. J. Meyer
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