UF6 Cylinders

Ruth is correct about UF6 and its "self sealing" properties. She is also correct about 48X cylinders shipped in overpacks. However, 48Y cylinders are *NOT* shipped in overpacks. The difference is that the 48X cylinders (48 inches diameter X 10 feet long) may contain up to 10 tons of solid UF6 at enrichments up to 4.5% U-235. The 48Y cylinders are longer (12 feet) and may contain up to 14 tons of solid UF6 at enrichments up to 1.0% U-235. Because the 48Y cylinders are not permitted to contain uranium above 1.0% U-235 enrichment, the DOT regulations do not require an overpack. In fact, no overpack exists for a 14 ton UF6 cylinder. Both the 48X and 48Y cylinders are made of carbon steel (A-516) at a nominal thickness of 5/8 inch.

The recent accident involved UF6 cylinders that are 30 inches diameter X 7 feet long and contain up to 2.5 tons solid UF6 at up to 4.95% U-235 and are known as 30B cylinders. They were being shipped in their overpacks from the Paducah Gaseous Diffusion Plant to Nuclear Fuel Services in Irwin, TN. These 30B cylinders are the same model cylinders being used world wide in the uranium enrichment industry. All UF6 cylinders are governed by ANSI N14.1 if you are interested in reading up on all the details of these robust shipping containers.

The UF6 cylinders that are to be shipped from Oak Ridge for the DUF6 project are filled with depleted UF6 with maximum enrichments around 0.4% U-235.

Jason Bolling

NCS Manager

USEC, Inc.

Portsmouth Gaseous Diffusion Plant

This message is solely my opinion. I do not speak for USEC, Inc.

-----Original Message-----
From: RuthWeiner@AOL.COM [mailto:RuthWeiner@AOL.COM]
Sent: Wednesday, April 16, 2003 10:40 PM
To: loc@icx.net; radsafe@list.vanderbilt.edu
Cc: obbugg@dmvs.ga.gov
Subject: Re: UF6 Truck crashes in Tenn, USA; nothing happens

Some stuff about UF6:

UF6 is a stable compound when not exposed to air. At ambient temperatures it is a solid, and pinhole leaks in casks tend to seal themselves (not that you want a leaking cask...). Slight warming causes UF6 to sublime to a gas (that's why it's used in gaseous diffusion separations). The 48X and 48Y cylinders are usually shipped in overpacks that act as impact limiters if there is an accident. My guess about shipping by truck is that those were the most readily available cylinders and overpacks, but that's just a guess.

Ruth Weiner, Ph. D.
ruthweiner@aol.com