Empty radioactive material shipping packages

[Slaback@micf.nist.gov]

DoT has a specific hazardous material
category for shipping 'empty' shipping
containers.  
If the container is absolutely clean does
this regulation apply?  That is, is it
hazardous material even if it is not
radioactive?  I can make arguements both ways,
and have specific advice to the negative.
If you had a virgin, 20 ton Type B cask tied 
to a truck bed would you would you omit the
empty cask identification and shipping papers?

If the answer to the above is negative, how
contaminated would it have to be to necessitate
labeling as an empty container?

A little risk adds spice to life.
slaback@MICF.NIST.gov