Information Notice No. 83-09: Safety and Security of Irradiators

                                                             SSINS NO: 6870 
                                                             Accession No: 
                                                             IN 83-09      

                                UNITED STATES
                           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. 



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. 


                                                             IN 83-09     
                                                             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. 


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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