At the ticket counter and the gates, there is a large sign warning you about what you can and cannot take aboard the plane. One of the items allowed is a "small" amount of radioactive material. I asked the GA about it one time and he said (if memory serves me right and it may not) that you could take about 2 pounds of radioactive material onboard the plane. I tried to find the info online and quit after not finding it on 3 web sites.