We sent 2 Tiger Moth compasses (P-type) across the Canada/US border to Lockhaven, and they were flagged as radioactive at some shipping nexus in NJ. The compasses were marked for destruction, but fortunately Keystone went to the trouble of driving 2+ hours each way to go rescue them -- which wasn't easy even when they got there. (Then they had them for 8 months rebuilding them, but that's another story....)
Obviously we're not shipping anything with radium across a border again.
Radium also gets you into trouble flying into the USA. At St. Clair County (Mich.) airport, during Oshkosh week, there is a steady flow of arrivals all planning to clear Customs. Many of the vintage or warbird aircraft set off the geiger counter. Then you can expect delays. You'd think commonsense would prevail, and I suppose it eventually does (I haven't heard of a Tiger Moth actually being impounded as a WMD) but your x-country plan needs to allow for the delay.
When I arrived there in 2009 in the P-40, the CWH Lysander had been sitting on the ramp for over 4 hours waiting for some kind of clearance. Ol' Rick R was spitting-mad.

We set it off too, but it only took us an hour in the P-40 after that. Thanks, Rick!
Dave