I see these shipping casks on the highway at least once a month. This time I had a Canon with me (Powershot A470, you know, a camera). While sitting at the off-ramp stop light next to this container I began to wonder how much activity shines through the shielding. I began to daydream … if I could see in the gamma spectrum, would this thing be bright or dim?
Then, in the blink of an eye the spell was broken. The light turned green and I parted company with this hot little number.
Lamentations on Chemistry 
I suggest you mount a geiger counter on the tip of your car hood. This will no doubt ensure you hours of high quality, low cost entertainment. 🙂
You’ll discover the large quantities of radioactive material which are disposed of on roadsides daily (no joke).
How long do these things stay there?
You could drop off a little unexposed roll of film next to it and pick it up the next day… take it to Walmart for $2 processing and see how fogged it is!
Hi Jordan,
These things are always in motion. I think the driver had to take a potty break at the local Micky-D’s on this occasion.