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NFS reports concerns with UF6 cylinders

UF6 cylinders stored at Nuclear Fuel Services for nearly a decade may have the potential to burst, and the area of the plant housing the cylinders is being restricted.
NFS reported its findings to the Nuclear Regulatory Commission Jan. 20, and that report is part of a public document made available. It was a leaking cylinder that caused a small fire in November – one of two incidents that are partly responsible for NFS voluntarily and temporarily shutting down production at the plant.
NFS is entering its second month of the temporary shut down. Salaried employees have had their wages cut, and 150 hourly workers are now in the middle of a three-week lay off.
Lauri Turpin, communications manager for NFS, told The Erwin Record Monday that the cylinders contain a “solid UF6.”
After the fire, which occurred in the new Commercial Development Line, Turpin said the plant “opened an investigation into the incident.”
She stressed that there has been no danger to workers or the environment.
The report to the NRC says the cylinders range in age from the 1950s to the 1980s and warns that the cylinders have the potential to exceed “the service pressure (200 psi) and some exceed the hydrostatic test pressure (400 psi).”
“The potential pressure in the cylinders,” the report said, “is estimated to be by liberation of fluorine gas in the cylinders. … The path forward consists of further analysis, evaluation and understanding of the issue. The cylinders potentially contain fluorine gas.”
The report says “potential consequences are minimal due to restricted access to the areas and the stable condition of the cylinders.”
“Certainly degradation of the UF6 may have occurred,” Turpin said. “It’s important to note that we have done this with calculations. We haven’t opened, moved or processed any more cylinders. This is all based on calculations, and our initial calculations were assuming the more conservative safety measures – the worst potential thing occurring instead of the best.”
The worst-case scenario, Turpin said, would involve the release of a small amount of fluorine gas.
“But the likelihood is that these containers can withstand more pressure,” Turpin said. “What we found was that there is a potential for degradation of the UF6 … that led us down this road to this investigation. So what we did was as soon we discovered this, we isolated the cylinders inside the facility and inside their original shipping containers and implemented safety measures and boundaries to protect our employees.”
Turpin said any incident would most likely stay “well within the NFS boundaries.”
Among precautions include a fire-patrol inspection of the area at least once an hour and a minimum of five members of the fire brigade on each shift. NFS officials have also met with the Erwin Fire Department.
“The concern, I believe, is with the fluorine gas,” Turpin said, “but it would be such a small amount. This is all preliminary. We are verifying this right now, but it would likely not pose a significant impact from a fire. We have a highly trained fire brigade on site at all times that are trained to respond to any fire on the site and with the different materials or chemicals on site.”
Turpin, who noted that NFS officials have conferred with experts to develop a plan forward, said the actions being taken clearly shows “our ability to address the issue safely and appropriately track it to resolution.”
The future of the cylinder is still unknown, Turpin said.
Roger Hannah, senior public affairs officer with the NRC in Atlanta, said the issue doesn’t pose any immediate threat, but “it needs to be evaluated.”
“Irregardless of the situation, we hope that NFS always identifies their own safety issues,” he said, “and this would be an example of that.”
Some fears have been expressed by members of the watchdog group called Erwin Citizens Awareness Network that in case of a fire, water can actually be problematic to fight a fire involving fluorine gas.
“We are,” Hannah said, “aware of that … and I think the NFS technical staff is acutely aware of that chemical reaction. That is something to be considered – if water would be appropriate in certain situations.”
Hannah, though, said the cylinders in question are small and would not pose a threat of a large fire even if they did burst.
“Some of these cylinders are smaller than an oxygen bottle an elderly person might use,” he said. “This would involve a really small amount of material.”