Can the glass on a tube be repaired???

if the vacuum is lost, i would venture that the tube is shot.

No. It is a "vacuum tube". Without the vacuum the tube is destroyed.

Maybe if it's rare enough might be worth searching for this guy:

http://news.cnet.com/8301-13645_3-9843011-47.html

What GMC and Narrod posted is correct, the tube is destroyed unless the glass can be remade and vacuum restored. Unless the tube is so rare it merits that I would keep it as a conversation piece or throw it away.