United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 87-29: Recent Safety-Related Incidents at Large Irradiators

                                                   SSINS No.:  6835 
                                                      IN 87-29 

                                  UNITED STATES
                          NUCLEAR REGULATORY COMMISSION
                             WASHINGTON, D. C. 20555

                                  June 26, 1987

Information Notice No. 87-29:  RECENT SAFETY-RELATED INCIDENTS AT 
                                   LARGE IRRADIATORS 


All NRC licensees authorized to possess and use sealed sources in large 


This notice is being issued to inform recipients of recent safety-related 
incidents at large irradiators, which could have been prevented by proper 
management actions and attention to preventative maintenance programs.  It is 
suggested that recipients review this information and their procedures and 
consider actions, if appropriate, to ensure both proper preventative 
maintenance programs and proper management actions at their facilities.  
However, suggestions contained in this Information Notice do not constitute 
NRC requirements; therefore, no specific action or written response is 

Description of Circumstances: 

A description of each of six events is provided in Attachment 1.  In summary, 
these events included: 

o    hose failure resulting in a leak, failure to report the incident to NRC, 
     and deliberate cover-up of this incident when NRC tried to investigate, 
     leading to company fines and personnel probation;

o    intentional bypass of safety interlocks, resulting in license suspension 
     and other enforcement actions by NRC; 
o    improper pipe routing and inadequate piping material, which broke and 
     caused partial loss of pool water; 

o    source unable to retract to its fully shielded position, due to a frozen 
     solenoid valve;

o    a stuck source plaque, due to failure to promptly replace a frayed lift 
     cable; and

o    a stuck source plaque, due to interference from the product carriers and 

.                                                                 IN 87-29
                                                                 June 26, 1987
                                                                 Page 2 of 2


These incidents illustrate a failure by management to assure that proper 
safety and maintenance procedures are followed.  It is suggested that super-
visory personnel, particularly the Radiation Protection Officer and 
maintenance personnel, be reminded of their responsibilities to assure safe 
operation at their facilities.  The incidents discussed in Attachment 1 
demonstrate the importance of: 

1.   prompt reporting of incidents to the NRC, as required by regulations or 
     license conditions 

2.   safety training and periodic retraining of personnel 

3.   not bypassing interlock systems or other safety systems

4.   attention to proper plumbing installation and use of appropriate piping 

5.   proper maintenance of cables, carrier systems, and other components that 
     could prevent radioactive sources from being retracted to a shielded 

No specific actions or written response is required by this Information 
Notice.  If you have any questions about this matter, please contact the 
Regional Administrator of the appropriate NRC regional office or this office. 

                                   Richard E. Cunningham, Director
                                   Division of Fuel Cycle, Medical, 
                                     Academic, and Commercial Use Safety
                                   Office of Nuclear Material Safety 
                                     and Safeguards 

Technical Contact:  Bruce Carrico, NMSS
                    (301) 427-4280

1.   Events That Occurred at Large Irradiator Facilities
2.   List of Recently Issued NRC Information Notices
.                                                                 Attachment 1 
                                                                 IN 87-29 
                                                                 June 26, 1987


1.   While the licensee was attempting to decontaminate pool water because of 
     a leaking source, a hose on a filtration system ruptured.  Contaminated 
     pool water was then pumped onto the facility floor and leaked outside 
     into the surrounding soil.  The licensee failed to report the incident to 
     NRC, and made deliberate efforts to prevent NRC's discovery of this 
     Subsequently, the licensee was indicted by a Federal Court.  A conviction 
     resulted in a $35,000 fine for the company and two years probation for a 
     management employee.  Licensee failure to make required reports prevents 
     the NRC from performing its radiological health and safety function and 
     from making a timely assessment of the nature and severity of an 
2.   A licensee deliberately bypassed the safety interlock systems.  The NRC 
     subsequently learned that licensee personnel had willfully violated 
     requirements, and that senior licensee management knew, or should have 
     known, of these violations.  When NRC attempted to inspect and 
     investigate these suspected violations, senior licensee management 
     knowingly provided false information to the NRC. Subsequent enforcement 
     action included suspension of the license. 
3.   A water line fractured in the pool circulation system which resulted in 
     the loss of 5 feet of pool water.   The line break led to a loss of 
     shielding water because the intake and outlet pipes were misaligned 
     during maintenance.  The pipe break appears to have occurred because the 
     pipe was made of polyvinyl chloride, designed for cold water, rather than 
     for the heated water temperatures typical for the irradiator. The piping 
     was replaced with polypropylene pipe.

4.   A night shift operator noticed that the travel time for the source to 
     reach the fully unshielded position was excessive.  After completing the 
     next phase of irradiation, the source would not retract to the fully 
     shielded position, even using emergency equipment.  The operator 
     discovered that the solenoid valve, that was supposed to retract the 
     source to a shielded position, was frozen due to weather conditions.  The 
     valve was in a room above the irradiator facility.  The operator went 
     there and turned on a room heater to thaw out the valve so that it would 
     operate.  The operator violated license requirements to (1) notify the 
     Radiation Safety Officer (RSO) that the source had not returned to its 
     shielded position because of the frozen valve, and (2) obtain RSO 
     permission to enter and heat the room housing the valve.

5.   A licensee had identified a frayed lift cable a few days previously, but 
     instead of immediately replacing the cable, the licensee decided to wait 
     for scheduled maintenance.  The cable jammed and froze the source plaque 
     in a less than fully shielded position.  Employees cut the cables and let 
     the source plaque free-fall into the pool.  The incident could have been 
     prevented by replacing the frayed cable immediately, and selecting cable 
     material with fray-resistant qualities. 
.6.   A source plaque became stuck in the exposed position.  Conveyors stopped,
     the source DOWN light came on, but cell radiation levels remained high.  
     Cable slack data indicated that the plaque was stuck about five and a 
     half feet down from its full-up position.  The RSO attempted some raising 
     and lowering maneuvers, but the plaque then stuck in a full-up position.  
     The RSO, able to run the product containers out of the cell, saw some 
     were misaligned on the carrier.  The RSO notified a State Inspector, who 
     arrived in the afternoon.  It was determined that the plaque cable was 
     off its pulley.  The bottom of a splice in the cable was resting on the 
     lip of the tube leading to the cell.  After the cable was set on its 
     pulley, the cable was guided through the tube, and the plaque was 
     lowered, until it caught again. 
     A borrowed radiation-resistant camera arrived the next morning.  An 
     adequate view of the plaque was obtained by midnight.  Apparently the 
     stationary aluminum shroud between product containers and plaque had been 
     deflected and caught on the plaque frame.  The plaque was carefully 
     raised and dropped to break the jam.  On the second try, the plaque broke 
     free and dropped into the pool.  Analysis revealed that a product 
     container had probably tipped onto the shroud, causing interference with 
     the plaque. 
     This incident was apparently caused by inadequate design of the shroud.  
     This led to the shroud deforming, which interfered with plaque motion.  
     Inadequate maintenance contributed to the problem.  The cable should have 
     been replaced instead of spliced.  A few months later, the entire source 
     hoist mechanism failed and had to be replaced.  This failure occurred 
     when the source plaque was submerged.
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