RE: thorium lenses

[<crm@nrc.gov> (Catherine R. Mattsen )]

Thorium "contained in" lenses would be assumed to be well
dispersed, thorium "on" lenses (coatings) are not covered by the
exemption in 40.13(c)(7). Note other restrictions, such as, not
to be used in eyeglasses, contacts, or eyepieces.  
Yes, ORNL is currently reevaluating potential doses from exempt
byproduct and source material including the exemption for
thoriated lenses.  They might be able to use additional info on
current uses of these lenses and will see it if posted on
radsafe.