UF6

[MCNAUGHT@LANL.GOV (Mike McNaughton)]

I am editing a course on uranium safety.  The draft includes a statement
about UF6 that I would like to clarify.  I hope some Radsafers can help.

The draft says "Uranium can create widespread low-level gamma radiation
fields less than 5 mrem/hr.  ... Larger sources of gamma radiation may exist
from specific processes, including unflushed UF6 cylinders [in which case]
gamma radiation from residual materials can result in radiation fields of
several hundred mrem/hr.  This problem can be controlled by flushing empty
cylinders to remove residual material."

I assume the sentence means that "residual materials" other than UF6 cause
the "several hundred mrem/hr". If it is UF6 emitting the gammas, I am
puzzled how gammas from UF6 could be greater than from other forms of U.  

I would be grateful for any clarification.  Thanks, mike