I think that kit came with a little alpha particle source.
Can you imagine carrying that through an airport now?
Yes, it came with 4 Uranium ore samples which are weak alpha sources.
Walking through an airport or anywhere else with Uranium (maybe not a nuclear power plant) should not be a problem. Alpha particles can only be detected with specialized detectors and only at very close distances (an inch or two)
Uranium ore though also usually has small quantities of other radioactive isotopes (radium) that are gamma emitters that would set off radiation monitors.