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Information Notice No. 87-29: Recent Safety-Related Incidents at Large Irradiators
SSINS No.: 6835 IN 87-29 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS WASHINGTON, D. C. 20555 June 26, 1987 Information Notice No. 87-29: RECENT SAFETY-RELATED INCIDENTS AT LARGE IRRADIATORS Addressees: All NRC licensees authorized to possess and use sealed sources in large irradiators. Purpose: 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 required. 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 shroud. 8706220303 . IN 87-29 June 26, 1987 Page 2 of 2 Discussion: 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 material 5. proper maintenance of cables, carrier systems, and other components that could prevent radioactive sources from being retracted to a shielded position. 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 Attachments: 1. Events That Occurred at Large Irradiator Facilities 2. List of Recently Issued NRC Information Notices . Attachment 1 IN 87-29 June 26, 1987 EVENTS THAT OCCURRED AT LARGE IRRADIATOR FACILITIES 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 incident. 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 incident. 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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