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.
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. 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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