United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 91-14: Recent Safety-Related Incidents at Large Irradiators

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
              OFFICE OF NUCLEAR MATERIALS SAFETY AND SAFEGUARDS
                           WASHINGTON, D.C.  20555

                               March 5, 1991 


Information Notice No. 91-14:  RECENT SAFETY-RELATED INCIDENTS AT
                                   LARGE IRRADIATORS


Addressees:

All Nuclear Regulatory Commission (NRC) licensees authorized to possess and 
use sealed sources at large irradiators.

Background: 

This issue was previously addressed in Information Notice No. 89-82, 
"Recent Safety-Related Incidents at Large Irradiators" (attached).  Because 
of the significance and frequency of recurrence of these incidents, NRC 
believes this issue should be reiterated. 

Purpose:

This information notice is intended to remind recipients of the potential 
for large irradiators to deliver life-threatening radiation doses when 
safety and security systems are bypassed or preventive maintenance programs 
are ignored.  It is expected that licensees will review this information, 
distribute and review it with all facility workers and radiation staff to 
prevent similar incidents from occurring at their facility.  Licensees are 
also expected to consider actions, if appropriate, to ensure that adequate 
preventative maintenance and proper safety training programs with periodic 
retraining exists.  However, suggestions contained in this notice do not 
constitute any new NRC requirements; therefore, no specific action or 
written response is required. 

Description of Circumstances: 

Several incidents of overexposure, resulting in loss of life, occurred 
outside of the United States as a result of bypassing safety and security 
systems and not following safety and operating procedures.  However, at the 
facility of an Agreement State licensee, a worker avoided overexposure by 
following proper safety and operating instructions and procedures.  In 
another instance, during an inspection of an NRC licensee, violations noted, 
including the bypassing of safety systems and the willful misleading of NRC 
during the subsequent investigations, resulted in proposed civil penalties.  
A more detailed description of these incidents is provided in Attachment 1. 


9102270158 
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                                                            IN 91-14 
                                                            March 5, 1991
                                                            Page 2 of 3 


Discussion: 

As shown in Attachment 1, beliefs such as "no risk because the machine is 
turned off" and actions such as using numerous ways to bypass safety and 
security systems demonstrate a lack of knowledge of the nature of radiation, 
as well as its danger.  All supervisory personnel, particularly the 
radiation safety officer, are reminded of their responsibility to ensure 
safe operation at their facilities.  The incidents described in the 
attachment demonstrate the importance of: 

1.  Not bypassing interlocks and other safety systems 

2.  Following all authorized operating procedures 

3.  Training all involved personnel in safety and operational procedures, 
    with periodic retraining, stressing the need for operators to promptly 
    notify their supervisors when unusual or conflicting signals arise on 
    control systems 

4.  Maintaining all equipment in good working condition and promptly 
    repairing or replacing any defective or nonfunctional equipment 

5.  Complying with all regulatory requirements and license conditions 

This information notice requires no specific action or written response.  If 
you have any questions about the information in this notice, please contact 
the technical contact listed below or the appropriate NRR project manager. 




                                   Richard E. Cunningham, Director
                                      Division of Industrial and 
                                     Medical Nuclear Safety, NMSS


Technical Contact:  Susan L. Greene, NMSS
                    (301) 492-0686


Attachments:
1.  NRC Information Notice 89-82
2.  Attachment 1
3.  List of Recently Issued NMSS Information Notices
4.  List of Recently Issued NRC Information Notices

.

                                                            Attachment 1
                                                            IN 91-14
                                                            March 5, 1991
                                                            Page 1 of 3 


          DESCRIPTION OF INCIDENTS AT LARGE IRRADIATOR FACILITIES 


Case 1.  (340,000 Ci Co-60 Irradiator in Israel)  A transport jam occurred, 
causing the transport mechanism to stop, the "source-down" signal to come 
on, and the gamma alarm to sound.  The sounding of the gamma alarm was 
considered unusual.  Acting against operating and safety instructions, the 
operator did not notify his supervisor and instead handled the situation on 
his own.  He turned the alarm system off by disconnecting the console 
cables, defeated the door interlock by cycling the power switch, unlocked 
the door, and entered the radiation room.  He did not check the Geiger 
counter he carried before entering the radiation room, and consequently was 
unaware that the instrument was not operational.

Seeing torn cartons, but unable to see that the source rack remained up 
because it was resting on the edge of a carton, the operator got a cart and 
began removing the damaged cartons.  After about a minute, he began to feel 
a burning sensation in his eyes and left the room.  Since the operator was 
not wearing his film badge, the whole body dose for the 1 1/2 to 2 minutes 
he was in the radiation room was estimated to be about 1,000 to 1,500 rads.  
The source rack was later released and lowered to the pool under the 
direction of the supplier, and no further overexposures were reported.  The 
operator died from radiation exposure due to acute radiation syndrome 
effects 36 days after the accident.

Case 2.  (18,000 Ci Co-60 Irradiator in El Salvador)  The sounding of the 
source transit alarm alerted the night shift operator (Worker A) that the 
source was neither fully up nor fully down as a result of a fault condition,
which should have caused the source rack to be automatically lowered to the 
pool.  He followed the reset procedure at the control panel, however had no 
success in stopping the alarm and releasing the door.  He tried to free the 
source rack by detaching the normal regulated air supply and applying 
overpressure to force the source rack into the fully raised position (a 
procedure not recommended by the supplier).  This attempt also failed.  The 
worker was eventually able to stop the alarm, but the general failure light 
and the "source-up" light remained on.  He then manipulated the microswitch 
system to produce a "source-down" light. 

Worker A disabled the door interlock system by rapidly cycling the buttons 
on the radiation monitor panel, while turning the key in the door switch 
(another procedure not recommended by the supplier), thus simulating the 
detection of normal background radiation in the radiation room by the fixed 
monitor and succeeded in opening the door.  He then shut off the power 
supply to the facility and entered the radiation room believing that, as 
with unpowered X-ray equipment, there would be no continuing radiation.  
Without first checking the radiation levels with a portable radiation 
instrument, he began to remove the deformed product boxes that had jammed.  
At this point he noticed that the 
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                                                            Attachment 1
                                                            IN 91-14
                                                            March 5, 1991
                                                            Page 2 of 3 


descent of the source rack was prevented by the slack cable of the hoist 
mechanism.  Unable to free the rack by himself, he left the radiation room 
and turned the power back on, noticing that the failure light was "on" and 
the "source-down" light was intermittent, but that no alarm was sounding.  

Worker A then enlisted Workers B and C to help free the source rack.  They 
had no experience or knowledge of the irradiation facility.  After assuring 
Workers B and C that there was no risk as the machine was turned off, the 
three men entered the radiation room and began removing the jammed product 
boxes, while standing directly in front of the source rack.  As the product 
boxes were removed and the source rack was lowered to the surface of the 
water, the workers noticed the blue glow in the pool from Cerenkov 
radiation.  Worker A was surprised at this and after fully lowering the 
source rack, he told the others to exit quickly.  When leaving the radiation 
room, Worker A was questioned by Worker B as to the use of the portable 
radiation monitor that was located some distance from the irradiator.  He 
explained that the instrument was for radiation detection and measurement, 
but that it had not been necessary to use it. 

Worker A became ill minutes after leaving the radiation room and was taken 
to the hospital.  Workers B and C later became ill and also went to the 
hospital.  The company was unaware of the accident for several days because 
the workers were incorrectly diagnosed as having food poisoning.  It was 
later discovered that some of the source pencils had fallen from the source 
rack into the pool and that one of the pencils had fallen into the radiation 
room.  At least four more persons were overexposed before the circumstances 
of the accident were fully realized. 

Worker A was hospitalized for extensive radiation burns to his legs and feet
and gastrointestinal and hematopoietic radiation syndrome.  His right leg 
was amputated and, 197 days after the accident, Worker A died as a result of 
his radiation exposure.

Worker B was treated for symptoms of acute radiation exposure and severe 
burns.  After the amputation of both legs, he was transferred to a 
rehabilitation facility 221 days after the accident.

Worker C suffered less severe symptoms of radiation exposure and remained on 
sick leave from work for 199 days after the accident.  Long term effects to 
these workers may include eye damage from radiation exposure.  A more 
detailed description of the incident can be found in IAEA, Vienna, 1990 
STI/PUB/847. 

             
STI/PUB/847, IAEA Vienna, 1990.  Copies can be obtained for reference and 
training tools from UNIPUB, 4611-F Assembly Drive, Lanham, MD 20706-4391
.

                                                            Attachment 1
                                                            IN 91-14
                                                            March 5, 1991
                                                            Page 3 of 3 


Case 3.  (3.5 million Ci Co-60 Irradiator in an Agreement State)  The 
operator noticed that the product had received an unacceptably low dose.  He 
shut down cell operations and, with the source position monitor indicating 
that the sources were down and the in-cell radiation monitor showing 
radiation levels at zero, he entered the cell with a portable radiation 
survey instrument.  He noticed elevated radiation levels between 1-2 mR/hr 
on the survey instrument and aborted his attempt to enter the cell.  The 
operator restricted the area and notified supervisory personnel.  
Investigation into the cause of the elevated radiation readings revealed 
that one of the source racks was not fully down and that the top of the rack 
was about 1� feet from the top of the pool.  An inspection of the winch 
mechanism indicated that the cable brake had failed to stop the winch 
allowing the cable to completely unwind.  As a result, the source rack was 
raised instead of lowered with the continuing rotation of the winch 
mechanism.  The source rack was then manually lowered into the pool. It was 
determined that deterioration of the wiring in the Geiger-Muller tube of the 
cell monitor due to radiation exposure was the cause of this system failing 
to warn of the elevated radiation levels in the radiation room.  The 
necessary repairs were made to the control panel and the cell monitor and 
procedures instituted to upgrade the safety systems of the facility.  The 
operator followed safety and operating procedures during the incident and 
avoided overexposure by correctly using the portable survey instrument. 

Case 4.  (1.3 million Ci Co-60 Irradiator in NRC Jurisdiction)  During an 
inspection and subsequent investigation at an irradiator facility, NRC 
identified the following violations, including but not limited to: (1) 
failing to promptly and effectively repair the lock on the personnel-access 
door to the irradiator cell; (2) modifying a procedure without first 
obtaining NRC approval (i.e., replacing a safety component in the irradiator 
start-up system), as was required in the license; and (3) the deliberate 
bypassing of administrative procedures and safety interlock and physical 
barriers to gain entry to the irradiator cell by climbing over the 
irradiator cell access door.  An NRC investigation also determined that 
senior licensee management knew of the violations and made incomplete and 
inaccurate statements to the NRC during an enforcement conference and the 
subsequent investigations involving the circumstances of these violations.  
The potential for extremely high radiation exposures and the licensee's lack 
of candor with NRC raised questions about the ability and willingness of the 
licensee to comply with NRC requirements.  NRC considered these violations 
of the safety requirements to be serious and proposed a civil penalty of 
$13,000 be assessed against the licensee.  Senior management involved in 
this incident are no longer associated with the facility. The licensee has 
instituted a Quality Assurance program and additional training requirements.
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