TUCSON, AZ -- When it comes to border security the first line of defense is at the port of entry.

Now agents at the border will have a device which can detect radiation.

The goal of such a device is detect a 'dirty bomb.'

At the I-19 checkpoint just south of Tubac, Arizona Border Patrol agents are using a device that acts as an added layer of security.

It's called the Personal Radiation Device.

The agency began using the small black box in 2003. ....